GTA
All Springer/NP/PCP Air Gun Discussion General => "Bob and Lloyds Workshop" => Topic started by: rsterne on March 03, 2011, 06:53:25 PM
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This thread is a copy of one from another forum.... I just wanted to give you guys an idea of what I'm currently working on....
I decided last summer that my winter project this year would be a "Scratch Built" PCP rifle.... Perhaps I should call it a "Custom" since I will be buying some of the parts, such as the barrel, trigger group, tank, and stock.... Regardless of the semantics, this project is a step up from purchasing parts (with a few bits I made thrown in) and assembling them.... Where possible, given my limited skills and machine tools, I will be making most of the metal parts from billet.... I have christened the gun the "Hayabusa" which is the Japanese name for the Peregrine Falcon, the fastest animal on earth....
I plan on building two guns, one this winter and the other next (assuming the first one works).... This year's gun will be interchangeable .22 and .25 cal using 0.630"D x 23.8" long choked Lothar Walther barrels.... and I hope to test a polygonal barrel in .25 cal as well.... The follow-up, next winter, will be interchangeable .30 cal and 9mm, using 28" LW barrels.... The main tube is 1" OD x 0.065" wall 4130 tubing.... It will be fed by a 22ci. 3000 psi tank and Ninja regulator set (initially) for 2000 psi.... The entire main tube is downstream of the regulator, and the plenum volume (ie between the regulator and valve) will be about 7 ci (115 cc).... nearly the size of the entire air reservoir in a Disco.... The valve is larger than a Disco valve at 0.87" OD which allows larger porting, although the poppet is from a Disco.... I really like their over-molded design and it's plenty big enough to allow a 5/16" throat.... although this gun uses 1/4" ID at the valve seat and 3/16" through ports.... plenty big enough for a .25 cal....
(http://i378.photobucket.com/albums/oo221/rsterne/Hayabusa%20PCP/HayabusaLogo.jpg)(http://i378.photobucket.com/albums/oo221/rsterne/Hayabusa%20PCP/HayabusaMockup.jpg)
The valve is only the back end, with the poppet, ports, O-ring and mounting screws.... There will be a spring to hold the poppet closed when the reservoir is empty.... however, there will be basically no restriction between the plenum and the valve.... making the valve volume virtually 115cc.... Even with an air-gulping 9mm I expect the plenum (and therefore valve) internal pressure to stay above 1600 psi (ie average ~1800).... and in the .25 cal the pressure should average around 1950 psi during the shot cycle.... It is this high AVERAGE pressure that I hope will produce some very satisfactory results....
I designed and built the "reversed" tank block so that the tank is turned around, with the regulator at the front and the tank itself becomes the fore-stock.... The tank block (and the valve) will be mounted with three 10-32 (high tensile) low profile SHCSs with the head spreading the bearing load out into the tube.... The calculated safety margins for the various parts under load (at 2000 psi) are as follows: Tube: 4.7:1.... Screw Shear Strength: 3.9:1.... Tube Bearing Area: 3.2:1.... Tear Out: 6.6:1.... In the event of a regulator failure, the lowest common denominator (the tube yielding around the screw heads) will still have a safety margin of over 2:1 at 3000 psi.... The tank block is threaded for the output of the regulator and acts as the front tank mount.... It contains a gauge for the low pressure side so that I know what the pressure is in the plenum.... On the top is a machined shoulder with two tapped holes to mount a barrel band.... on the bottom is a 3-slot Picatinny Rail for mounting a Bi-Pod....
I hate the way Crosman mount their breech with a tiny screw under the bolt.... and I also wanted to eliminate any hole in the tube for the front trigger mount.... I therefore came up with a rather novel assembly which will mount the back of the tank, the front of the trigger, and wrap around the main tube... It will be pulled upwards with two 6-32 SHCSs coming down through he breech either side of the barrel.... There will be a notch in the bottom of the breech (below the barrel) to clear (and locate) the top of this tank band/trigger mount assembly.... Once the bolts are tightened, the entire assembly will become rigid....
(http://i378.photobucket.com/albums/oo221/rsterne/Hayabusa%20PCP/HayabusaLogo.jpg)(http://i378.photobucket.com/albums/oo221/rsterne/Hayabusa%20PCP/HayabusaParts.jpg)
There is still a lot to do.... I have to make a breech, bolt(s), hammer(s), RVA, and do all the machining on the tube.... plus the necessary machining on the barrels when they arrive.... I'm going to try and make an adjustable transfer port as well.... and I may also experiment with an adjustable hammer fall, similar to the one in a Marauder, which adjusts the length of the front striker on the hammer.... I have a Marauder stock coming which will be cut off just in front of the trigger to fit up against the back of the tank.... and then I have to figure out how to mount the back of the receiver to the stock as well.... However, I thought I would give everyone a "sneak peak" at the progress on my latest project....
Bob
PS: When I was trying to come up with a name for the gun.... my wife suggested "the Widowmaker".... because she has hardly seen me over the last couple of weeks....
RBS
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Part 2....
Had a chance to do a bit more machining today.... I made a couple of RVAs and a hammer.... The hammer is machined from 1045 steel which can be hardened once finished.... It weighs nearly 50% more than the hammer in a 22XX.... nearly 90 grams....
(http://i378.photobucket.com/albums/oo221/rsterne/Hayabusa%20PCP/HayabusaLogo.jpg)(http://i378.photobucket.com/albums/oo221/rsterne/Hayabusa%20PCP/HayabusaHammerRVA.jpg)
The hammer has an adjustment for the fall distance.... The 1/4"-28 NF set screw in the front as yet to be machined flat and hardened.... It is located by an 8-32 SHSS in the side with a small piece of plastic under it to act as a brake.... The hammer and the RVA screw are drilled through to allow adjustment of the hammer length without disassembly.... This arrangement is similar to that used in the Marauder.... As you lengthen the screw (by screwing it in clockwise from the back of the RVA) the hammer hits the valve stem sooner.... This gives the hammer less distance to accelerate and limits the valve opening.... As you back the screw out, the hammer accelerates more and has more momentum when it hits the valve.... opening it faster/further.... The hammer is also slightly overlength at the present time.... Once the parts are fitted into the tube I will machine it to length so that it just cocks reliably before hitting the front of the RVA.... The RVA works by adjusting the preload on the hammer spring, of course.... With two variables, there are lots of possibilities to adjust the hammer strike.... They interact, of course.... but it will be interesting to find out how each adjustment affects the performance and the shot to shot consistency....
Bob
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Part 3....
I had a bit of time today to fabricate the mount for the valve spring for my Hayabusa....
(http://i378.photobucket.com/albums/oo221/rsterne/Hayabusa%20PCP/HayabusaLogo.jpg)(http://i378.photobucket.com/albums/oo221/rsterne/Hayabusa%20PCP/HayabusaValveSpringMount.jpg)
It is supported by a piece of 1/4" ready rod mounted in the tank block.... The aluminum spider part has three legs that just barely slide into the main tube to center the spring mount.... The spring is a snug fit over the part of the spring guide nearest the shoulder.... Preload is determined by the length of the threaded rod.... although it could be set with a locknut if desired....
(http://i378.photobucket.com/albums/oo221/rsterne/Hayabusa%20PCP/HayabusaLogo.jpg)(http://i378.photobucket.com/albums/oo221/rsterne/Hayabusa%20PCP/HayabusaSpringMountDetail.jpg)
There is enough volume (over 20cc) between the spider and the valve for even a full house 9mm.... so any turbulence caused by flow around the spider cannot affect flow out of the valve.... The area for flow past the spider is many times the size of the valve port.... so effectively, the valve volume from a pressure drop point of view is well over 100cc.... This will insure the highest possible average pressure at the valve seat throughout the shot cycle.... This is something most regulated PCPs don't address.... and it is the main reason that non-regulated setups have the reputation of being able to deliver more power than regulated ones.... Since the pressure where most non-regulated guns peak is not far from 2000 psi.... I am trying to minimize any performance differences between a non-regulated setup and my Hayabusa which will initially be regulated to 2000 psi....
Bob
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Looks like a great project! Keep us updated!
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Bob, all I can say is WOW! You really know your stuff and it looks like it's going to be a great gun when you're done. You sure have a lot more creativity and talent than I do. I wouldn't know where to begin to design a PCP gun. Keep us updated on your progress. I'm looking forward to seeing you shoot the thing. You should make a video of you and the gun in action.
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VERY IMPRESSIVE Bob! So glad you've joined us, i really look forward to reading your future posts, J
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Better watch out, your wife might not recognize the old,bald guy coming out of the basement when you're done! Great stuff, wish I had the talent, the patience, and a wife that would let me put so much time into this crazy hobby! ;)
pv
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Impressive is the least I can say. But I hate people with talent and skill, mainly because I have so little of either. ;D ;D
And welcome to the GTA.
Bogey
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Very,Very cool. I like to see when people are not afraid to show there work and ideas. again very nice work and look forward to reading more about your build as it comes together keep u'm coming.
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Bob,
Thanks for sharing the details of this with us. You've obviously given this a lot of thought. Do you think you might get this to a shootable point before spring?
Thanks,
Lloyd
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Got the Marauder stock a couple of day ago and I've modified it and the trigger group so that there is an additional bolt behind the trigger (up through the rear guard screw hole) instead of just the one in front of the trigger.... In addition, it is shortened and fitted around the tank/tube/trigger mount assembly.... I'll post a pic when I get it to the stage of being able to do another mockup.... I'm hoping to get the gun shootable before our Motel gets busy in May....
Bob
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This is a great thread, I wish I had his talent for sure he is injoying what he is doing and thats what air gunning is all about. Thanks David
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Very,Very cool. I like to see when people are not afraid to show there work and ideas. again very nice work and look forward to reading more about your build as it comes together keep u'm coming.
When the work is nice, like Bob's here, it's easier to post with confidence.
I look at some of my early stuff ::) , and I think it would make people point and laugh! ??? In fact, I laugh at it myself!
Lloyd
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Ya lloyd i know the feeling. if i were to post some of mine i'm sure we would all get a good laugh. i'm getting better though.
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It must be nice to have such mad skills and creativity.
I can't even visualize this kind of thing, let along fabricate it.
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I think that considering the valve travel and how little stem is remaining at full lift it would be difficult if not impossible to use a spring on the stem (like in a car engine)....
Bob
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Very Ingenious.
I'm looking forward to the finished product.
Thanks
Ray
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I got some needed materials and finally had time to get back to this project over the last couple of days.... The breech is now about 90% done with just the slots for the cocking pin and bolt handle yet needed.... In addition, last week I had the chance to shorten the Marauder stock and fit it around the tank/trigger band.... so I was able to fit the breech/trigger assembly into it today for the first time....
(http://i378.photobucket.com/albums/oo221/rsterne/Hayabusa%20PCP/HayabusaLogo.jpg)(http://i378.photobucket.com/albums/oo221/rsterne/Hayabusa%20PCP/HayabusaBreech.jpg)
The breech is machined from a piece of 1" x 1.3" 6061-T6 aluminum 6.4" long (which is the longest cut I can make on the milling attachment on my Atlas lathe).... It has a standard 3/8" dovetail milled into the top, and the breech cutout is milled to fit a .25 cal MRod 8-shot magazine.... It will also accept a .22 cal 10-shot MRod magazine by using a 0.1" spacer.... The hole in the side just in front of the breech notch is threaded 10-32 for an adjuster for the transfer port.... and the vertical hole above that is for a 6-32 set screw which will press on a plastic rod to act as a brake for the adjuster.... allowing it to hold the selected adjustment.... The notch on the underside at the front fits over the tank/main tube band which also locates the front of the trigger group....
(http://i378.photobucket.com/albums/oo221/rsterne/Hayabusa%20PCP/HayabusaLogo.jpg)(http://i378.photobucket.com/albums/oo221/rsterne/Hayabusa%20PCP/HayabusaBreechTriggerAssy.jpg)
You can see in the above photo how the trigger group mounts at both ends.... at the back to the RVA..... and at the front to the tank band assembly.... When the two top screws are tightened up, the tank and main tube are both drawn up into place and held securely against the bottom of the breech.... The stock mounts with the original 1/4-20 hole near the front of the trigger group.... Since the entire front of the stock was removed to make room for the air tank.... in order to mount the stock securely, it was necessary to add another mount at the rear of the trigger group.... A hole was drilled and tapped 8-32 just behind the trigger box, in front of where the trigger mounts to the RVA.... This lines up with the rear screw location for the trigger guard.... A hole was drillled up through the stock so that a long 8-32 bolt could be used to attach the stock rigidly....
(http://i378.photobucket.com/albums/oo221/rsterne/Hayabusa%20PCP/HayabusaLogo.jpg)(http://i378.photobucket.com/albums/oo221/rsterne/Hayabusa%20PCP/HayabusaStock.jpg)
All in all, I'm pleased with the progress I made this week.... I'm delighted that I was able to figure out how to make the one breech fit both .22 cal and .25 cal Marauder magazines.... The bolt will be made from 3/8" steel with the front portion reduced to 1/4" diameter for the .25 cal setup .... and 7/32" diameter for the .22 cal version.... Those diameters feed properly through the MRod magazines.... and then a conventional extended probe will load the pellet forward of the transfer port.... I need about 1.3" of bolt travel to be able to retract the probe far enough for magazine removal.... and have allowed for that.... The rear breech mounting screw is recessed below the bolt, which allows for a longer bolt, and the bolt handle to be moved further back away from the magazine....
Bob
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Bob,
Lookin' good. Thanks for keeping us posted on the progress. You are doing some fairly complex work for a milling attachment on the old Atlas! Very nice!
Lloyd
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Looking good. Glad to see more chips being made. Can't wait to see it punch some holes.
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I made the spacer for the .22 cal magazines today, slid the stubs in place, and took some pics....
(http://i378.photobucket.com/albums/oo221/rsterne/Hayabusa%20PCP/HayabusaLogo.jpg)(http://i378.photobucket.com/albums/oo221/rsterne/Hayabusa%20PCP/Hayabusa25Magazine.jpg)
The above photo shows the .25 cal magazine and the 1/2" diameter stub that locates it.... You can just see a part of the 1/4" ID O-ring that will seal the bolt.... There are two tiny bumps top and bottom in the groove in the magazine that "clip" onto the stub to hold the magazine in place....
(http://i378.photobucket.com/albums/oo221/rsterne/Hayabusa%20PCP/HayabusaLogo.jpg)(http://i378.photobucket.com/albums/oo221/rsterne/Hayabusa%20PCP/Hayabusa22Magazine.jpg)
Since the .22 cal magazine is narrower, a spacer is required.... and the stub is 0.100" longer (the same as the thickness of the spacer).... Functionally, with the spacer in place, the magazine sees the same 0.060" stub.... although it is 7/16" diameter for the .22 cal magazine and carries a smaller (7/32" ID) O-ring.... The spacer is held in place by a single 6-32 SHCS....
Bob
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Had a chance to get back into the shop today and make the bolts and finish off the breech....
(http://i378.photobucket.com/albums/oo221/rsterne/Hayabusa%20PCP/HayabusaLogo.jpg)(http://i378.photobucket.com/albums/oo221/rsterne/Hayabusa%20PCP/HayabusaBoltsandBreech.jpg)
The two bolts are interchangeable.... the one with the bolt handle in it is the .22 cal and the other one is the .25 cal.... The middle section is the correct size to pass through the Marauder clips and seal in the O-ring between the stub and the end of the barrel.... In order to move the bolt handle back as far as possible, I needed a way to activate the cocking pin in the hammer without having it ride on the end of the bolt.... In the assembled bolt, you can see a 6-32 screw half way between the bolt handle and the front of the 3/8" section.... That rides in the slot in the bottom of the breech and draws the cocking pin backwards with the bolt.... The wide area near the front of the cocking slot allows the head of the screw to rotate opposite the bolt handle when the bolt is closed.... It was a lot of measuring, bit I'm confident it will work perfectly.... By using this system, I was able to move the bolt slot right to the back of the breech.... This allows lots of room between the bolt handle and the magazine....
You can see the 10-32 button head SS screw which will be used to adjust the transfer port.... The end of it will be turned down to remove the threads and shaped as a hemisphere.... It will enter the 3/16" ID transfer port through a close fitting hole in the side of the brass port (yet to be made) and when turned fully in will choke off about 90% of the port area.... It will take 6 turns to fully withdraw it to give 100% flow.... I plan on shaping the head of the screw like an "arrow" to aid in counting turns..... There is a "brake" in a setscrew hole on the top side to keep the adjuster from turning by itself....
It's getting close to the point where I will have to start machining the main tube.... I still have to fit the cocking pin into the hammer.... and harden the hammer and pin.... There are still a few other small jobs to do as well.... but I'm beginning to see the day when it will be assembled for the first time.... ;D
Bob
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Bob, Again, nice work! Good ideas on the bolt, keeping things compact and captive.
How did you machine that long cove in the bottom of the breech? Looks like it will fit the tube nicely.
Lloyd
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I machined it with a 1" diam. ball-nosed mill.... You have to make every cut in the same direction or the channel ends up too wide....
Bob
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Finally got a chance to get back to this project the last couple of days.... I have now done the machinining on the main tube.... The valve and tank block are installed with three 10-32 low-profile SHCSs with the heads set flush into the main tube to spread the load on the tube wall.... The slots for the cocking pin and sear are done, and the rear mounting holes for the breech, trigger group, and RVA.... The tank band supports the rear of the tank, the front of the trigger group, and the front of the breech and everything is rock solid when tightened up....
(http://i378.photobucket.com/albums/oo221/rsterne/Hayabusa%20PCP/HayabusaLogo.jpg)(http://i378.photobucket.com/albums/oo221/rsterne/Hayabusa%20PCP/HayabusaMainTube.jpg)
I have also made the barrel band, which mounts to the top of the tank block.... It uses an O-ring to locate the barrel and yet allow linear expansion and contraction of the barrel and tube relative to each other with changes in temperature and/or pressure.... I purchased a sling swivel that fits on the picatinny rail on the bottom of the tank block and there is still room for a bi-pod in front of that....
I'm getting really close to being able to pressurize the gun to test for leaks.... Stay tuned.... ;D
Bob
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Awsome job and it looks really cool i bet there will be a large shot count per fill and what might your fill pressure be.
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Amazing work Bob.. Please keep us updated as much as possible. We all are learning from you thread bro.
Thanks
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Bob,
The project is coming together very nicely. This thing is going to be very versatile, I bet.
The little section of Picatinny rail up front says a lot about the planning you did before making any chips.
My compliments,
Lloyd
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The tank is a 22ci 3000 psi unit running a Ninja 2000 psi regulator.... The 1" main tube forms a 13" long plenum with a volume of 115 cc.... and no restrictions before the poppet valve.... so effectively the valve volume is 115 cc of 2000 psi air.... The idea is to have the smallest pressure drop possible during the shot cycle and yet have the advantages of a regulated PCP.... I am aiming at an average pressure during the shot of over 1900 psi for a 100 FPE shot.... or 1950 psi for a 50 FPE shot.... With reasonable efficiency, I'm hoping for about 30 shots at 50 FPE per fill.... I currently have .22 and .25 cal Lothar Walther barrels and next year plan on testing their .30 cal and 9mm barrels on the same platform.... If possible, a .410 shotgun version will follow.... ;D
Bob
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Bob you kill it, wish I had the skills
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Looking good.
The pressurization and leak test are always the anxious part for me. Mainly because it means I flubbed something if it leaks although it has always been an easy fix.
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Looking good.
The pressurization and leak test are always the anxious part for me. Mainly because it means I flubbed something if it leaks although it has always been an easy fix.
Rescue35,
You sure have that right, especially on something brand new. .....Starting to fill..... holding my breath..... fiissssssssssss...........darn ! OK, now which o-ring?
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YAHOO !!!.... No leaks.... ;D
Bob
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Bob I knew you had skills based on all your previous threads but now your my hero ;D
maybe you can send me some of that Canadian water you have been drinking lol ;D
Seriously excellent work you are an incredibly talented person and could probably make a lot of money
with your designs. If crosman was smart they would pay you to help them redesign their guns.
Good luck and 1 question are you a former rocket scientist or something along those lines.
Thanks for sharing and inspiring
Dave
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Thanks for the kind words.... I have a B.Sc. in Organic Chemistry (1968) which I used for a whole 10 months.... I then worked for my Dad as a car mechanic (Morgan sports cars).... I then got into R/C Model Yachts, designed a boat that won the World Championships in 1980 and that became my career (one man shop designing and manufacturing) for nearly 30 years.... My designs won the US Nationals 7 out of 9 years (the other 2 years we didn't attend) during the late 80s and early 90s.... The last three years before I retired I took a part time job at a Machine Shop and learned milling (already knew basic lathe work) and ended up being trained on a CNC Mill.... When I retired nearly 4 years ago I took up airguns (after a 40 year hiatus), combined that with my recently acquired machining (on an old Atlas lathe with milling attachment).... and I've been learning ever since....
Bob
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Bob,
I am pretty sure I have never met anyone who designed and built championship R/C model yachts for a career. From you, I can believe it. Very interesting and very cool!
Lloyd
P.S., Congrats on the no-leaks. ;D
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Absolutely fabulous work Bob. I can't wait till you do the .410 ;D
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I got the gun assembled to the point of some tethered test firing today.... but I've still got some work to do.... I did some 2000 psi fills of the main tube and then shot some strings.... The velocity at 2000 psi was down quite a bit from expectations, but I did manage to record a string of 16 shots starting at 1900 psi and ending at 1000 that averaged 947 fps with 18.1 gr. JSB Heavies (36.1 FPE).... It started at 908 fps, peaked at 980 (at only 1400 psi!), and ended at 901.... The total energy was 577 FPE from a 62 Bar drop on the 115 cc main tube (7.0 CI).... Total air used was 434 CI for an efficiency of 1.33 FPE/CI.... That's significantly better than I have ever had at those power levels.... and more power than I have ever seen at 1400 psi as well.... My Disco and regulated 2260 PCPs run about 1.04 FPE/CI at 36 FPE....
I was having trouble cocking the gun, the hammer is a bit too long and barely latches when I pull the bolt all the way back.... After maybe 50 shots, the gun would no longer cock at all, and on disassembly I found the trigger sear was broken in half.... There was a mark on the hammer where it looked like the middle shoulder was impacting the sear and broke it.... That impact was likely stopping or retarding the hammer and preventing it from opening the valve fully.... When I made the hammer, I basically made a larger version of the 22XX hammer.... but the trigger assembly is from a Marauder.... I didn't have a drawing of the MRod hammer when I made mine but now I find out that it is quite different.... It is a cylinder with the sides milled off to reduce the weight.... but the bottom that rides over the sear is smooth.... The "waist" I machined into my hammer was apparently hitting the sear hard enough to shatter it.... I've got Joe at MuzzleMack getting me a couple straight from Crosman because MRod parts in Canada are nearly impossible to get....
So the first tests are both disappointing and encouraging at the same time.... I was expecting great things from the heavier hammer in regards to opening the valve at higher pressures.... So far, that hasn't happened, but if the hammer was indeed hitting the sear as it appears, then the tests were flawed.... On the other hand, I'm already at 36 FPE with 18 gr. pellets at only 1400 psi, with better efficiency than I have ever seen before.... ;D
Things are now on hold until I can get a new sear and make a new hammer....
Bob
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Bob,
Personally, I think the results are great! The only downside is having to wait for the new sears.
Like you say, if there is some kind of interference between the hammer and sear, the tests are for "reference only," and the follow-up tests ought to give very different results.
The power peaked at 1400 psi. He, He. You've got a sleeping beast there.
Lloyd
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You've got a sleeping beast there
My thoughts exactly.... ;D
Bob
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Great project! I can't wait to see more...
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The volume between the regulator and the valve is very important.... Think about it this way.... Let's say your gun takes 20 CI of air at 1 Bar to produce 20 FPE.... ie an efficiency of 1.0 FPE/CI.... Let's further assume that you have a chamber between the regulator and the valve of only 1 CI but it's filled to 100 Bar (1450 psi).... that's 100 CI at 1 Bar.... After one shot, the pressure would have dropped to 80 Bar, and the average pressure would have been 90 Bar (1305 psi) during the shot.... That's not bad, only 10% below what you thought the pressure was....
Let's take the same gun, and ask it to produce 40 FPE.... Chances are the efficiency will be lower, say 0.8 FPE/CI, so now it needs 50 CI of air at 1 Bar.... Same reservoir, same starting pressure, but now at the end of the shot you will only have 50 Bar left.... and the average pressure during the shot will only be 75 Bar (1088 psi).... Now you were working with only 75% of the pressure you thought you had.... Once the shot is over, the regulator will top up the pressure to 100 bar.... but it's response time won't allow it to do that during the shot, so you are only working with the air between the regulator and the valve during the shot.... You can see that the available volume will pretty quickly put an upper limit on the power the gun can produce.... Is it even possible to produce 40 FPE with under 1100 psi?.... I doubt it....
Now increase the volume between the regulator and the valve to what I have at 7 CI.... Same pressure (100 Bar), same air usage per shot.... but now you have 700 CI of air at 1 Bar available.... After a 20 FPE shot (20 CI used), the pressure will be 97.1 Bar.... and after a 40 FPE shot (50 CI used) the pressure will be 92.9 Bar.... The average pressure available during the shot is 98.6 Bar (1430 psi) for the 20 FPE shot and 96.5 Bar (1399 psi) for the 40 FPE shot.... On the higher power shot, you have nearly 29% more potential power available.... That will likely give you an increase in efficiency (due to the higher average pressure) as well....
If you graph out the volume between the regulator and the valve versus the power you want.... you will see that the larger the better, but it's a steep curve at small volume... and there is little to be gained once the volume reaches a certain point.... I feel that you need about 1cc of volume between the regulator and the valve for every FPE you want the gun to produce.... otherwise, you are fighting an uphill battle (literally, given the shape of the curve!).... In the first example I gave (1 CI for a 20 FPE shot), it was pretty close to that value.... 1 CI is 16.4 cc which is pretty close for a 20 FPE gun.... If you stick to my 1cc / FPE rule of thumb.... your average pressure will usually stay within 10% of the regulator setpoint.... depending on what that is, of course.... For me, it's a good starting point anyway....
Bob
PS.... and yes, I designed this gun for only a 10% pressure drop during the shot at 100 FPE.... The average pressure should be about 1900 psi at that power level... ;D
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Glad to hear you are making progress.
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Bob,
Nice explanation of why having a big reservoir between the regulator and the valve is needed if you want to get big power. On this gun, the size of the reservoir is not going to be the limiting factor.
Nice planning....and work!!
Lloyd-ss
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Outstanding! Very, very good innovations.
Can't wait to see the end of the rainbow!
Charles
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I thought a graph showing how the reservoir volume between the regulator and the valve affects the potential FPE output might make it easier to understand than my long post above.... Here is one based on a design for a 50 FPE gun....
(http://i378.photobucket.com/albums/oo221/rsterne/Hayabusa%20PCP/EnergyvsVolume.jpg)
As you can see, above 50cc, the FPE is virtually flat with very little to be gained by going to a larger volume.... However, at 30cc the FPE is down to 47 FPE, a loss of 6%.... and at 20cc it's down to 44 FPE (down 12%).... Then it begins to drop like a stone.... and at 10cc, it's down to 36 FPE, a loss of 28%.... I'm not saying you can't get more power from a smaller reservoir than what is shown on the graph.... just that if all other factors are the same having a good sized reservoir keeps you from fighting an uphill (literally) battle.... ;D
Bob
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Bob,
I've got a slightly different way of showing how the difference in tank size affects the max fpe capability of a pcp. The numbers are very similar to yours and show how having plenty of volume between the reg and the valve is necessary for max power. It also holds true for any type of serious restriction upstream from the valve. The tiny hole through the pressure gauge adapter in the disco is a good example of a choke point that helps keep the velocity even, but starves the fpe.
The graphs show what is happening inside the barrel of the airgun, going from the breech at zero inches to the muzzle at 24".
The top graph is the air-starved gun with a 10 cc air chamber feeding the valve.
Blue is the air pressure on the right hand scale, and it starts at 1400 psi pushing the pellet, and quickly drops to 800 psi when the valve closes. The velocity in green peaks out at 600 fps. The fpe (on the left hand scale) peaks out at about 35fpe.
(http://i226.photobucket.com/albums/dd79/loyd500/image002.jpg)
The second graph shows the difference when the valve chamber is opened up to 115cc. The pressure still starts at 1400psi, but it only drops to 1300psi when the valve closes at the same time as in the first graph. And the max fpe jumps way up to about 52fpe.
(http://i226.photobucket.com/albums/dd79/loyd500/image001.jpg)
There is a lot more info in these graphs, but they show what is happening in the Hyabusa.
Lloyd-ss
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Those are GREAT graphs Lloyd, many thanks.... I am amazed at how close my simple calculations.... based on the average pressure in the reservoir during the shot.... match your much more sophisticated calculations.... I got 52 FPE and 36 FPE and you got 53 FPE and 35 FPE.... AMAZING.... ;D
Bob
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Well guys, i seriously need some help with this gun.... :-[
I made a new hammer that is cylindrical (no notch) and installed the new sear and the hammer no longer strikes the sear on firing.... However, I'm still nowhere near what I was hoping for the power potential of this gun, and I've created another problem.... Not only is the hammer strike nowhere near what it needs to be to dump 2000 psi, let alone more.... but I'm getting hammer bounce at 1700 psi.... and at 1500 psi it bounces enough to completely empty the reservoir.... :o
Here are the practical differences between the Hayabusa and my modded Disco, as far as the valve and hammer are concerned....
1. The valve porting is larger, and the valve throat is 1/4" instead of 7/32".... but it still uses a Disco poppet....
2. The hammer is larger in diameter and heavier, about 100 gr. instead of 60 gr....
3. The hammer spring is the same, set just shy of coil bind....
4. I have an adjustable fall distance on the hammer but it's set for about the same fall as the Disco....
The gun is currently shooting about 700 fps at 2000 psi, and about 850-900 fps at 1500 psi (when it dumps all the air).... With the previous hammer (95 gr. with notch that shattered the sear) I got the following string (18 gr.pellets) from 1900 psi down to 1000:
908
921
933
941
962
966
971
976
977
980
973
966
944
926
913
901
By comparison, with my Disco when maxed out.... I was able to drive the same pellets at 1080 fps at 2400 psi.... I know from past experience that a heavier hammer tends to dump more air and allow higher pressures to be used.... So WTH is going on here?.... Is it possible I have way too much hammer weight and the spring can't accelerate it enough?.... Why is the hammer bouncing?.... and WTH do I try next?.... HELP !!!....
Bob
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I think you nailed it with the hammer is to heavy to reach a velocity that will impact the valve with more force than the other hammer.
You need a stronger spring or less resistance in the valve.
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Bob,
Yup, too much hammer. I think going from 60 gms to 100gms on the hammer, the hammer velocity will only be a third of what it was, all other things being equal.
How much valve stroke do you think you need? Have you ever checked a disco with a chunk of clay or play dough to see how much it opens? I think the fact that it won't open enough at 2000 psi shows the valve stem isn't being impacted hard enough. Then at the lower pressure you might be getting into a resonance situation...hammer bounce.
How far does the valve stem stick out, and how far do you want it to travel?
Lloyd
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Well that's two votes for my WAG about too much hammer weight, so I guess it's lathe time.... I've never checked the stroke on a Disco valve, but that's a good idea with the clay.... The valve stem sticks out "a bunch", much more than what it can/will open I'm sure.... about like a stock 22XX valve... photo on page 1 of this thread....
I guess maybe I got greedy and I'm paying the price.... On my Disco and 22XX mods when I lightened the hammer I got LESS power.... ie the velocity dropped and I needed more hammer spring to make up what I lost.... This cost me in maximum power, of course (when the spring was already near coil bind).... I reasoned that a heavier hammer would be better.... and I know that a Condor uses hammers from 85 to (I think) 100 gr.... so since I had a bigger tube I figured I'd aim for 100 gr.... The first one I made (photo on page 1) was "waisted" like a 22XX hammer but I'm pretty sure that second shoulder was whacking the sear and caused it to shatter.... The new one is just a straight cylinder, so of course heavier.... It's developing a slight scratch on the side from rubbing on the sear but I haven't hardened it yet.... I think what I will do is turn down the side enough to miss the sear completely in the "up" position for as much length as I can (lock screw to cocking pin) and aim for a weight of about 80 gr. and try that.... If I'm on the right track then perhaps I'll just remove 5 gr. at a time to see if I can find the optimum....
Any other thoughts before I start turning down the hammer tomorrow?....
I think going from 60 gms to 100gms on the hammer, the hammer velocity will only be a third of what it was, all other things being equal.
Math please?.... spring constant, travel distance constant, only the weight changing.... When I tried the math a couple years ago I found the momentum (MxV) INCREASED with added weight.... yes, the velocity was less, but I thought the MV product increased.... Is there a way to calculated the optimum hammer weight?.... ie the one that will deliver the most momentum for a given fall distance and spring force?....
Bob
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Bob,
In this case, the energy delivered to the valve stem is 1/2 m v2
so the velocity of the hammer is important.
Lloyd
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I agree, but isn't the momentum more important?.... It's basically a transfer of momentum from the hammer to the valve stem.... Then the valve stem and hammer together are decelerated by the air pressure/flow and the spring....
I figured that the potential energy of the spring was a constant so the kenetic energy of the hammer.... and ultimately the hammer plus valve stem.... would be a constant.... Did I get that wrong?....
My brain hurts.... ;D
Bob
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It takes the spring longer to overcome the inertia and get a heavier hammer moving. Which means the spring doesn't get the hammer up to a velocity that would increase the energy over a lighter hammer. At least that is what I see in my minds eye.
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What I do know for sure is that in a Disco (stock or modded) and my 22XX HPA conversions (heck even in a 1750 on CO2).... that a stock 58-60 gr. hammer produces more power than a 45 gr. which is stronger than a 40 gr. which is better than a 30 gr.... All with the same spring at the same preload and the same hammer travel distance.... Kind of like shooting a springer.... most pellets produce about the same energy but the heavier pellets have more momentum.... Energy = 1/2 MV^2 but Momentum = MV....
Bob
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I copped out and went to Wiki. Check out the "effect of heads mass."
http://en.wikipedia.org/wiki/Hammer (http://en.wikipedia.org/wiki/Hammer)
I think if you carried your disco hammer weight experiment farther in the direction of heavy hammers you would have found a bell curve where adding more weight to the hammer would make the power drop back off.
The reason is (I think) that you are dealing with a fixed spring force, and more importantly, a fixed travel distance. If this were early in the morning I could continue, but right now, my head is hurting too.
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I think if you carried your disco hammer weight experiment farther in the direction of heavy hammers you would have found a bell curve where adding more weight to the hammer would make the power drop back off.
That makes sense.... Now to figure out the optimum weight for a given spring and travel distance.... Trial and error?....
I'm beginning to think a stronger spring may be the answer and leave the weight the same....
I think I've already seen an optimum travel distance because when you extend the striking face on the hammer is reduces the travel but increases the spring preload at the striking point.... More travel distance equals more momentum/energy (longer acceleration).... but the spring is exerting less force when the hammer finally reaches the valve stem (same initial acceleration, less final acceleration).... This changes when you change the free length of the spring and the rate of course....
Bob
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Perfect your method and then I'll let you modify my m-rod bob ;) . That is some nice work man. Wish I had the equipment and training to do stuff like that.
Matt
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Thanks to Al (Gippeto), all it took was one freakin' hole drilled between the hammer and the valve to cure this thing.... ;D
I drilled a 3/16" hole in the side of the tube with the back edge of the hole level with the end of the valve stem.... and VOILA!.... no more problems with runaway hammer bounce.... OBVIOUSLY (now!) there was an air cushion forming between the hammer and the valve, more than likely made worse by a less than stellar fit for the valve stem that was leaking high pressure air during the shot cycle.... This was not only slowing down the hammer and producing the velocity loss.... but causing the hammer to bounce as well.... The previous hammer wasn't as good a fit, and was likely leaking air around the perimeter so didn't exhibit this problem.... This is a case where a poorer fit actually worked better (by masking a potential problem).... :o
The Hayabusa is finally beginning to show its potential.... I fitted a 0.042" wire hammer spring that is only slightly stiffer than the one I had in my Disco and immediately achieved over 50 FPE.... The valve will now open properly at 2000 psi, and while I can hear a bit of hammer bounce at below 1500 psi, there is no "machine-gun Kelly" action taking place even at 1000 psi.... Since this gun will be regulated at 2000 psi eventually, hammer bounce is no longer an issue.... Here is the first decent shot string from this gun, using JSB 18.1 gr. Exact Heavy pellets....
2200 psi fill
1029
1055
1068
1085 - 47.3 FPE @ 2000 psi
1081
1075
1063
1046
1035
1500 psi remaining
The reservoir is only 7 CI (115 cc) and I was filling it directly.... The efficiency works out to 1.34 FPE/CI (12.2 Barcc/FPE for Voltar1), way better than I have ever achieved before at this power level.... I tried some other pellets right around 2000 psi and recorded the highest velocity for each....
15.9 gr. JSB Exact - 1131 fps (nice sonic crack) - 45.2 FPE
21.0 gr. H&N Baracuda - 1018 fps - 48.3 FPE
25.4 gr. JSB Monster - 946 fps - 50.5 FPE
28.4 gr. EunJin Domed - 892 fps - 50.2 FPE
32.4 gr. EunJin Pointed - 832 fps - 49.8 FPE
The heavier pellets were peaking at 1700-1800 psi so there is room for improvement with a heavier hammer spring.... All the power adjustments are now working the way they should.... The hammer travel adjustment (an adjustable length of the front face) will vary the power down to about 700 fps.... The transfer port restrictor can drop the power as low as about 600 fps.... I didn't see how low I can get with the hammer spring preload, but it works normally.... Neither did I try combining the effects of these three adjustments, I just made sure that they worked properly when moved independantly with the others still at maximum....
This rifle will be fitted with a 22CI tank regulated (initially) to 2000 psi.... That will mean that I will have 69 Bar times 22 CI = 1518 CI of air available to the regulator setpoint.... At 1.34 FPE/CI that works out to 2034 FPE.... or about 40 shots at 50 FPE.... I'm thinking this is going to be one heck of a great gun when it's done.... ;D
Thanks again to Al for cracking this one.... I owe you big time, buddy.... ;)
Bob
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As soon as you said the resolution was to drill a hole the light bulb went on and "air cushion" popped in my head. Good catch Al and Im glad to hear you got her working correctly Bob.
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Good news! I'll have to remember that a sloppy fit on a hammer isn't necessarily a bad thing.
Lloyd
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Well you knew I had to try the .25 cal barrel.... but first, a photo.... The 22CI tank will be the forestock.... ;D
(http://i378.photobucket.com/albums/oo221/rsterne/Hayabusa%20PCP/HayabusaLogo.jpg)(http://i378.photobucket.com/albums/oo221/rsterne/Hayabusa%20PCP/HayabusaUnregulatedTesting.jpg)
Here is the first string with 25.3 gr. JSB Exact Kings....
2200 psi start
964
985
1002
1020
1025 - 59 FPE @ 1900 psi
1020
1014
999
984
966
1400 psi remaining
Bigger caliber = more efficidency.... 1.45 FPE/CI (11.3 Barcc/FPE).... 1518 CI x 1.45 = 2201 FPE.... That should work out to about 40 shots at 55 FPE (25.3 gr. Kings at 990 fps).... ;D
It's time to start bluing some parts and install the regulated tank.... I think it's going to stay .25 cal for the initial regulated testing.... :o
Bob
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Lookin' very good Bob ! 8)
Lloyd
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Fantastic workmanship Bob. Wish I had half of what you know and talents. Makes my mouth water...:)
I thank you and Lloyd both, for being so open and fourthcoming with you work.
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Tested a few more pellets today.... Here are the results for the peak velocity recorded....
Beeman Laser 17.3 gr. - 1162 fps - 51.9 FPE (at about 2100 psi)
H&N Field Target Trophy 19.3 gr. - 1133 fps - 55.0 FPE
JSB Exact King 25.4 gr. - 1025 fps - 59.0 FPE (at 1900 psi)
Benjamin Domed 27.8 gr. - 983 fps - 59.7 FPE
H&N Baracuda 30.9 gr. - 949 fps - 61.8 FPE
EunJin Domed 35.2 gr. - 909 fps - 64.4 FPE
EunJin Pointed 43.2 gr. - 830 fps - 66.1 FPE (at only about 1600 psi)
As is typical when you don't change anything except the pellet in a non-regulated PCP the pressure at which the peak velocity is generated drops as the pellet weight increases.... Based on these results, I need a heavier hammer spring to maximize the FPE with the heavier pellets.... I would think that about 880 fps is within reach at 2000 psi with the 43.2 gr. EunJin Pointed.... That would be about 75 FPE.... I have no doubt that this gun will be in the 70-80 FPE catagory with heavy pellets with the right hammer spring.... 8)
Bob
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Very, very cool Bob. Good work.
Richard
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Gotta say Bob your attention to detail in the planning and figuring out department is sure an skill I would like more of, sometimes I operate a little to much from the seat of my pants. Very nice fruit of your labour!!
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Gotta say Bob your attention to detail in the planning and figuring out department is sure an skill I would like more of, sometimes I operate a little to much from the seat of my pants. Very nice fruit of your labour!!
Yes, I agree. Staying on the intended course can be difficult at times, but looks like your upfront planning has paid off. This is going to be a very versatile gun.
Excellent work.
Lloyd
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I got my heavier hammer springs in and tried them out yesterday.... I ended up using one that was 2.00" long and 0.300" OD made from 0.045" wire (instead of the 0.040" wire I use on my modded Discos).... The velocities, as expected, increased, and the velocity now peaks at 2000 psi with the JSB Kings and Baracudas, 2200 psi with light pellets, and 1800 psi with the heaviest pellets.... Here are the results with the hammer spring just shy of coil bind....
Beeman Laser 17.3 gr. - 1201 fps - 55.4 FPE
H&N FTT 19.3 gr. - 1165 fps - 58.2 FPE
JSB King 25.3 gr. - 1061 fps - 63.3 FPE
Benjamin Domed 27.8 gr. - 1024 fps - 64.7 FPE
H&N Baracuda 30.9 gr. - 983 fps - 66.3 FPE
EunJin Domed 35.2 gr. - 939 fps - 68.9 FPE
EunJin Pointed 43.2 gr. - 867 fps - 72.1 FPE
Over 1200 fps in .25 cal, and over 72 FPE is pretty satisfying for a home-brew airgun.... ;D .... The efficiency with the JSB Kings is about 1.06 FPE/CI (not bad, but I wanted better), so I decided to start backing down the hammer spring as I don't want over 1000 fps anyway.... Here is what happens to the peak velocity and efficiency as I do that.... The last number in each line is the projected number of shots from a 22 CI tank regulated to the pressure where the peak velocity occurred....
Maximum - 1061 fps @ 2000 psi - 1.06 FPE/CI - 25 shots
-0.5 Turn - 1043 fps @ 1900 psi - 1.10 FPE/CI - 30 shots
-1.0 Turn - 1030 fps @ 1800 psi - 1.15 FPE/CI - 35 shots
-1.5 Turn - 1010 fps @ 1700 psi - 1.23 FPE/CI - 42 shots
-2.0 Turn - 979 fps @ 1600 psi - 1.31 FPE/CI - 52 shots
Note that by dropping the velocity only 9% the shot count more than doubles.... :o .... At 1800 psi and 2 turns out the velocity is 950 fps (51 FPE) and the efficiency should actually be slightly higher than 1.31 FPE/CI as that was taken over a 10 shot string, and the efficiency is always better in the first half of the string.... I would expect to get about 50 shots with my 22 CI tank regulated to 1800 psi with that state of tune.... and I will have the flexibility to increase the velocity should I choose to.... I will probably test a lighter hammer just to see what happens, but the current plan is to set the regulator to 1800 psi when I assemble the gun for the initial regulated tests.... I had originally planned to use 2000 psi, but this gun breathes so well that I can get the power I want with a lower pressure.... That means I get 20% more air available in the tank above the regulator setpoint.... ;D
Bob
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Very cool Bob !
That last paragraph is so telling. Those very high velocities are so expensive when it comes to air usage. It's like a bad mortgage payment where most of the money goes for interest and only a small portion goes toward the principal.
I've always found that to be true, too..... back it down a little and the shot count goes way up.
Again, nice job!
Lloyd
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I tested the lighter hammer and it was a few fps less, as expected.... so the gun will stay with the heavy (92 gr.) hammer.... I stripped the gun down completely to blue the steel components and then assemble it with the tank for the first time.... I had to rebuild the regulator to reduce the pressure to about 1800 psi.... After cleaning the bolts, barrels, and main tube carefully I blued them using Van's Gun Blue and I was very happy with the nice even, deep colour.... I cleaned the barrels, oiled them, ran a couple patches through them until they came out clean to just leave a preserving film of oil.... and then carefully assembled the gun, using all the appropriate lubes.... I did a pressure test which seems fine, fired it once just to make sure it worked, and then rushed in to get some photos....
(http://i378.photobucket.com/albums/oo221/rsterne/Hayabusa%20PCP/HayabusaLogo.jpg)(http://i378.photobucket.com/albums/oo221/rsterne/Hayabusa%20PCP/HayabusaonBipod.jpg)
As you can see, I have a .22 cal and bolt that will fit, and MRod clips for both calibers.... The BiPod is a Leapers that fits on the short Weaver rail on the tank block, along with a sling stud swivel.... Both barrels are Lothar Walther, standard rifling, choked.... I have some polygonal rifled barrels coming for comparison purposes....
(http://i378.photobucket.com/albums/oo221/rsterne/Hayabusa%20PCP/HayabusaLogo.jpg)(http://i378.photobucket.com/albums/oo221/rsterne/Hayabusa%20PCP/Hayabusa25Cal.jpg)
The final weight came in at right at 8.5 lbs without the bipod and scope.... I will be fitting a Bushnell 5-15X Legend and then I'll be ready for some seriouis testing.... This project was conceived almost a year ago, and machining started the beginning of 2011, so the gun is now about 9 months from the start of making chips to completed.... It's been quite the gestation period.... but all in all, I'm pretty happy with my "first born".... ;D
Bob
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Bob, it is just way way cool for you to have concieved of this idea and see it through to fruition. And all by tour own hand. A big thumbs up to you sir. Congratulations and have fun with it.
Richard
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great gun and info, hope it performs as spected
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Great work Bob!
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Great work, you are a true craftsman, I can aspire to do such as this.
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I finally got back to testing today.... It was a lot of fiddling around with spring and hammer settings, and then using the velocity adjuster to get close to where I want to be.... I tried two springs, the 2.00" long 0.045" wire, and also one that is 1.75" long 0.051" wire.... With each spring set at maximum preload (just shy of coil bind) I then adjusted the hammer fall distance to see if there was a maximum velocity point.... To my surprise, with the short heavy spring I had to reduce the hammer fall by 9 turns (3/8") to get the maximum velocity.... That told me that a 1.75" spring is too short, it's running out of push in the last part of the hammer stroke.... I then did the same thing with the longer, lighter spring, and the best setting was 3 turns (1/8") from maximum fall.... The difference in fall distance was the same as the difference in spring length.... That means that if I had a longer spring (2.25") I could take advantage of all the hammer travel I have available.... if I wanted more power.... I'll be ordering a longer spring for when I try larger calibers at a later date....
I then started playing with the velocity adjuster.... This is a screw on the side of the breech that chokes up the transfer port.... It has 6 turns of travel from fully closed (just two slits for the air to pass through either side of the screw) to fully retracted clear of the port.... Since the end of the screw is hemisperical, when retracted there is a hollow in the side of the transfer port which likely creates some turbulence and increases the volume.... Therefore I was not surprised that the velocity actually increased as the rounded nose of the screw started to enter the transfer port.... What DID surprise me was that the maximum velocity occurred with the screw about 2.5 turns in from full out, ie nearly half closed.... In fact, there was no consistent difference in velocity between 3 turns out (the mid point) and 4 turns out.... I set it at 3.5 turns out and turned my attention to the hammer spring preload, as the velocity was now firmly over 1000 fps with the 25.3 gr. JSB Kings....
I then turned my attention to the hammer spring preload.... I backed it out a turn and the velocity settled in at about 950 fps.... This is less than I was getting in the unregulated version at 1800 psi (the regulator setpoint pressure).... and I was at a loss as to why.... I took out the hammer spring and measured it, and it turns out it has taken a bit of a "set" as it now measures about 1/16" shorter now than when I first installed it.... That would account for the velocity loss.... I still had more power than I needed, so it doesn't matter, of course.... When I started testing velocities through the range of pressures, I found that after the pressure fell below the regulator setpoint the velocity started increasing, up to nearly 1000 fps, before falling back to 950 fps at only 1400 psi.... This is a sure indication that the gun can breathe too well for the hammer spring and regulator pressure.... I cranked the velocity adjuster in another turn, then a half turn more to only 2 turns out, and the velocity fell to the low 900s.... Then I cranked the hammer spring in a half turn, and it bounced back up to about 960 fps.... Now when the pressure dropped below 1800 psi (the setpoint), it only went up to the high 960s, dropping back below 950 at 1500 psi.... Now we're getting somewhere.... ;D
By now I had burned through about 500 pellets and my SCUBA tank was down to 2600 psi.... However, I had collected enough information to figure out that the efficiency was stll close to the previous testing at about 1.3 FPE/CI.... The velocity is between 950 and 960 fps while the pressure in the tank is over 1800 psi.... below that, it rises about 10 fps before falling back down to 950 at 1500 psi.... This give me 1500 psi of usuable air in the 22 CI tank which works out to 2276 CI.... That should translate into roughly 2900 FPE.... The average velocity is about 958 fps which works out to 51.6 FPE.... That should give me over 50 shots per fill....
Bob
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Bob,
The adjustability you've designed into this airgun makes it a serious learning tool for someone with your patience and tenacity. ;) Good design work and planning on your part. Being able to get consistent performance at so many power levels is truly impressive.
You are still using the heavy hammer of about 90 grams, correct? But by comparison, the springs you are using aren't that much heavier than stock. What about the hammer travel? It is adjustable, so how much travel are you using at this time? A stock disco is about .62" or a little less, I believe.
What about the balance between the return spring and the hammer spring in the fired state? Is the valve heavily preloaded by the hammer spring?
Yes, these are leading questions, but I am trying to piggyback off of what you are discovering. ;D
Thanks, Lloyd
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very impressive.
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Lloyd....
I'm still using the 92? gram hammer.... The spring is 0.045" wire and 2.00" long (well, now about 1.95").... I never measured the hammer travel, but IIRC, I installed the valve about 1/4" further forward relative to the sear than a Disco with the hammer adjustment fully collapsed (ie maximum travel).... Basically, as I'm running it at the moment, the travel is probably within 1/8" of a Disco....
RE preload, again, I can't really tell you where I'm at.... other than if I extend the hammer face I have to cock the gun to fill it.... With it retracted I don't think there is much load on the end of the valve stem, especially with the 1.75" spring.... maybe 3/8" ????
I have a drawing of the tube here somewhere, and I can measure the spare hammer I have.... I'll get back to you if I have any useful dimensions.... The return spring is basically stock Disco at nearly stock preload....
Bob
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OK, so I pulled the back of the gun apart and did some measurements.... The hammer fall as currently adjusted is 0.673".... The proload is 0.253".... The published spring rate for the 0.045" x 2.00" spring I am using is 18.5 lbs./in.... so the preload should be about 4.7 lbs.... and the force when cocked should be 17.1 lbs....
BTW, I notice that I am overloading the spring.... They state the maximum deflection as 0.76" and the maximum load as 14.2 lbs.... I'm compressing the spring 0.93".... which is probably why it has taken a permanent set of about 0.06"....
My adjustable hammer can vary the travel over a 1/2" range.... I'm using the striker/adjusting screw from an MRod.... Based on the measurments I made today, I can adjust the fall distance from 0.3" to 0.8".... What I find strange is that with the shorter spring, the velocity peaks with a hammer fall of only 0.55"....
Bob
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Bob,
Thanks for the additional info. It is helpful.
For such a simple device, springs are awfully complicated. I wonder if the shorter .051 x 1.75 spring ends up with similar 4.7 lbs and 17.1 lbs values, given its lesser preload and hammer travel? The coil count is important too. Removing coils increases the spring rate (lbs/in) so if you shorten a spring and set it to the same initial preload in pounds, not inches, and keep the same stroke length, it will have a higher cocked force. That all affects how the hammer accelerates and how quickly it reverses direction after it strikes the valve stem. I haven't dug into that because the trial and error approach seems to be easier right now. Also, the airflow past the valve head that closes the valve is such a big factor, but a real mystery to me.
I usually start with springs that are too long and then gradually shorten them to zero in on what works. Actually, it only kinda works, LOL. ;D
Lloyd
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that thing is awsome. congrates
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The 0.051" wire x 1.75" long spring has over twice the spring rate.... 38.2 lbs/in.... It is rated at 20.2 lbs maximum load at 0.53" compression (max).... I have to screw the adjuster in quite a bit to put it near coil bind because of the shorter length.... It has 18 coils compared to the 0.045" x 2.00" which has 21.... Because it is shorter it would have very little preload unless I lengthen the striker, which of course I had to do to get the highest velocity (by 1/4").... The performance at maximum is very close to the same as the 0.045" x 2.00" spring.... but the gun is harder to cock.... More force but over a shorter travel I guess....
I can get two longer 0.045" wire springs.... 2.25" and 2.50".... They have more travel but a lighter spring rate.... and end up with the same (14.2 lb) maximum recommend load.... If I understand correctly, they would start accelerating the hammer at the same rate, but the preload would be higher.... so the hammer strike would be more?.... or have I got that wrong?....
Like you said, simple device, hard to understand.... Actually, the hammer fall adjuster is pretty strange too, when you think about it.... The force on the hammer when cocked is dependant on the RVA (preload adjuster) only.... When you change the length of the striker on the front of the hammer you are doing two opposing things.... As you lengthen it....
1. You are reducing the distance the hammer travels, therefore giving it less room in which to accelerate and reducing the impact....
2. You are increasing the preload on the spring when the hammer is resting on the closed valve (you are moving the hammer and spring seat back).... which increases the impact....
It's no wonder you get some strange results.... I initially only thought about the first affect.... and figured full "out" (ie maximum travel) would give maximum velocity.... It turned out that was NOT the case and that the maximum velocity occurred part way along the travel.... with less travel being better for the shorter (stiffer) spring....
My brain hurts !!!
Bob
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I got a slightly longer hammer spring to try.... 2.25" long and 0.045" wire.... As you lengthen a spring with the same OD and wire size the spring rate goes down slightly but the maximum load stays about the same, but at more travel.... I made a new velocity adjusting screw with an integral spring guide.... I picked up a bit of velocity, and the combination of the longer spring and the guide made the cocking significantly smoother.... Anyway, after fiddling with all the adjustments to get the maximum I could, I got the following numbers, regulated at 1900 psi....
JSB King 25.3 gr. - 1038 fps - 60.5 FPE
Benj. Domed 27.8 gr. - 998 fps - 61.5 FPE
Baracuda 30.9 gr. - 958 fps - 63.0 FPE
EunJin Dome 35.2 gr. - 922 fps - 66.5 FPE
EunJin Point 43.2 gr. - 857 fps - 70.5 FPE
These figures were more than I want, and the gun was an air hog at maximum setting.... so I tried two routes to detune it.... I tried using only the hammer spring preload (out 2.5 turns), and I got 47 shots averaging 985 fps down to 1500 psi.... However, the velocity below the setpoint climbed to 995 fps, whereas the velocity above the setpoint had a low of 978 fps and a high of 989 fps.... The total spread was 17 fps.... I then tried a combination of hammer spring and restricting the transfer port.... I backed off the hammer spring until the velocity dropped to 1000 fps (1.25 turns).... Then I turned the screw on the transfer port in 2 turns to reduce the velocity to an average of 968 fps (52.7 FPE).... The velocity no longer climbed when the pressure dropped below the setpoint, it stayed in the same (narrow) range down to 1700 psi (200 psi below the setpoint) before dropping.... The lowest velocity was 964 fps and the highest 972 fps (only an 8 fps range).... I got a total of 43 shots starting at 3000 psi and shooting down to 1700.... for a total energy of 2266 FPE.... The pressure drop of 89.7 bar on a 22 CI tank works out to 1973 CI of air used.... for an efficiency of 1.15 FPE/CI (14.3 Barcc/FPE).... I really like this method of tuning as I can easily adjust the velocity from 1000 fps downwards to find the sweet spot with the 25.3 gr. JSB Kings for accuracy.... by simply turnng a screw on the side of the breech....
I'm very happy with the way the Hayabusa is tuned at the present time.... I hope I can get out to our Camp to test the gun at longer ranges, test various pellets for accuracy, and try fine tuning it.... before the snow flies.... :o
Bob
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Bob,
I have to give you the tenacity award. Good work on getting that thing tamed and predictable. Plus, pretty air-efficient at those power levels, too.
Good work.
Lloyd
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Yeah I'm very pleased.... only an 8 fps total spread from 3000 psi down to 1700.... when you consider there is the ineveitable regulator creep to deal with plus I can shoot 200 psi below the setpoint.... I can't wait to find out it the Lothar Walther barrels live up to their reputation....
Bob
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Impressive
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I would love to see how accurate she is. Nice work!!
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I've been busy with other projects, but figured I better drag out the Hayabusa and do some more work on it, based on what I have learned over the past few months.... I pulled the back end of the gun apart, drilled out the hammer to 3/8" ID, drilled out the RVA, and fitted the hammer spring from a QB.... I now have plenty of spring power so I have lots of adjustment instead of running out of room on the RVA with the shorter springs I had been using previously.... The gun doesn't have any more power with the lighter pellets, but it did pick up a bit with the heavier ones.... I'm still running the gun regulated at ~1900 psi, and here are the results at various hammer spring settings....
(http://i378.photobucket.com/albums/oo221/rsterne/Hayabusa%20PCP/HayabusaRegulated.jpg)
I'm now up to 73 FPE with the EunJin Points, and over 60 FPE with the JSB Kings, at maximum power.... However, the gun set up that way is an Air Hog.... I can dial it down 4 full turns on the RVA without losing any velocity and double the shot count, still at 60 FPE with the Kings and 62 FPE with the Baracudas.... Set that way, I would get about 25 shots per fill.... Once again, I found that giving up just a few fps below the plateau works wonders with the air consumption, however.... Backed out one more turn, I only lost 30 fps, and gained another 10 shots or so.... You can see the effect on the Efficiency that the RVA has using the dotted line on the graph above....
This setting (5 turns out on the RVA) formed the basis for additional tests, starting from 1004 fps and an efficiency of 0.96 FPE/CI with the JSB Kings.... The first thing I did was started restricting the transfer port with the adjusting screw on the side of the breech.... You can see the results in the dashed line on the graph.... The first two turns made no difference, I assume because the small protrusion of the ball shaped end on the screw, although restricting the port, was smoothing the flow compared to when it was fully retracted.... At 3 turns in, the velocity dropped to 962 fps and the efficiency jumped to 1.19 FPE/CI.... At that point, I'm getting over 50 shots at 52 FPE per fill, and I can shoot down to 1500 psi before the velocity drops below 950 fps.... Once I get a chance to do some accuracy testing at longer ranges, I can adjust the velocity from 1000 fps down to as low as 600 fps by simply turning a screw in the side of the breech....
When I made the hammer for this gun, I made the throw (hammer travel) adjustable using the adjusting screw from an MRod.... You reach it from the back with a long allen key, by removing the RVA adjusting screw.... With the spring preload at 5 turns out, there is very little static preload on the hammer spring.... As you lengthen the nose of the hammer by turning in the adjusting screw, you reduce the distance the hammer travels, reducing it's momentum.... However, you increase the static preload on the hammer spring because the resting position of the hammer moves back.... These two effects cancel each other out (at the spring preload tested) for about the first 4 turns on the throw adjuster.... and the velocity stays constant.... I did notice, however, that the first shot in the string had a slightly lower velocity, and that difference increased as I reduced the hammer travel (and increased the spring preload).... As I further decreased the hammer travel, the velocity did begin to drop.... By the time I moved the adjustment 10 turns (0.42"), the velocity had dropped to 920 fps, but the first shot was under 900 fps.... I did not check how the efficiency changed as I adjusted the hammer throw, because the inconcsistency of the first shot bothered me.... I ended up backing up the adjuster to go back to the full hammer travel I started with....
My base settings are: Full hammer travel.... 5 turns out on the RVA.... and 3 turns in on the Velocity Adjuster.... That has me sitting at an Efficiency of 1.19 FPE/CI (13.8 Barcc/FPE) giving 50 shots at 52 FPE (962 fps) with the JSB Kings.... With 1 turn on the velocity adjuster either way, I can change from 900 fps to 1000 fps, which should enable me to fine tune the accuracy.... I can't wait until the snow melts and I can do some long range testing....
Bob
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Very interesting about the adjustable hammer Bob. On my project I wanted to do the same thing. Assuming you are using allen head screw with socket end facing to the rear. My issue with it was it moving. I wanted to experiment with the hammer travel as well. I like what you have come up with in your testing. It may not apply to my project but the adjustable hammer throw does have my attention... :) Do you use a second set screw behind the adjustable screw to lock it in position?
Thanks
Gene
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I purchased a hammer stroke adjusting screw from an MRod.... It is a 1/4-28 socket head set screw but with a 3/8" diameter flat where the cup point would usually be.... You drill and tap a hole in the front of the hammer, insert the socket of the screw into the hole, and wind it in from the back using a long allen key through a hole straight through the hammer.... What you are left with is a flat face that can screw in as far as the face of the hammer when full CCW (viewed from the rear) and turning the allen key clockwise moves that face forward, decreasing the hammer travel.... exactly like an MRod....
The adjusting screw is prevented from turning by a "brake" that is nothing more than a piece of plastic pushed against the side of the adjuster by a setscrew.... I drilled and tapped an 8-32 hole in the hammer from the top, right near the front.... inserted a short piece of delrin rod and followed it up with a short 8-32 SHSS.... You tighten the setscrew forcing the end of the delrin rod against the top of the adjusting screw.... It holds the adjustment perfectly.... While it's nice to have all these adjustments, in my case I found the hammer stroke adjustment to be redundant.... I can get all the adjustment I need with the hammer spring preload (RVA) and I'm leaving the stroke adjustment set at maximum travel.... Next time, I don't think I'll bother, and especially so with the big bore versions coming up where I'll need all the hammer travel I can get....
Bob
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This is great information Bob. Will save me the trouble of making and messing with the adjustment screw set up.
I finally finished up the valve today. That was an effort in patients for me... :) After about three attempts with making different style probes I finally bored out the valve and installed a complete new seat. Before pressing it back into the valve I made the saddle with a tapper and the probe tapered to fit into the seat. The taper on the stem only goes back half the distance of the thickness of the stem. Tested and no bubbles and still sitting here with 3000 psi in the tube.
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I have recently learned from a couple of machinists that the best style of seat for a valve on a PCP is to face the valve off completely flat and have a slight concave on the sealing face of the delrin poppet.... You make the OD of the poppet 0.060" larger than the ID of the valve throat, have a 0.020" flat sealing surface, and then a slight concave (about 10 degrees) inside the face of the poppet....
This style poppet apparently take less effort to knock open.... Tapered seats can be particularly tough to open, sucking up hammer energy big time....
Bob
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Another lesson learned... :) If this starts leaking again that will be my next project Bob. Thank you for passing on that information.
Gene
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It's been nearly a year since I worked on my Hayabusa.... During that time I've learned a lot, and I hope to apply some of that knowledge to this project over the next few weeks.... Here is the gun in it's current form.... It's a .25 cal repeater, regulated to 1900 psi, and shooting 25.4 gr. JSB Kings at 960 fps.... It gets about 50 shots per fill.... I also have a .22 cal LW barrel that interchanges with the .25 cal LW in the same breech....
(http://i378.photobucket.com/albums/oo221/rsterne/Hayabusa%20PCP/HayabusaLogo.jpg)(http://i378.photobucket.com/albums/oo221/rsterne/Hayabusa%20PCP/Hayabusa25Cal.jpg)
For a while now, I have had several other barrels for further development, a .30 cal and 9mm Lothar Walther, a .457 liner from TJs, and even a .410 shotgun barrel with polychoke.... but no time to work on them.... A few months ago, I came across some information about new bullets from Holland that are being used in Benchrest competition and doing a spectacular job, with groups at 100 M (110 yards) as small as 12 mm (under 1/2").... They are a .224 cal version of the classic .22LR bullet, are made by RWS, and appear to be very close to their R-50? target bullet.... The barrel required is, of course, slightly larger than the 0.217" airgun barrel, with a faster twist.... They are using a .22 Hornet barrel with a 1 in 14" twist.... SeanMP and I decided to do a pair of guns.... Sean's is going to be a new, scratch built design, while I'm going to use my Hayabusa as a base, but unregulated, and with a new breech, valve, hammer, and other changes.... In fact, about the only parts carried over to the new gun will be the trigger assembly and the stock, plus the ring assembly that holds the back of the tank and the front of the trigger.... The Mark II Hayabusa will look almost identical, but the changes are vast, and won't occur overnight....
I ordered two .224 liners from TJs with a 1/2" OD, and had them shipped direct to Sean.... He ordered 2000 bullets from Holland, plus two pieces of 1/2" ID x 5/8" OD Carbon Fibre tubing to stiffen the barrels.... We each purchased a .22 cal Hatsan Air Stripper, and Sean did all the machine work on the barrels.... He crowned and threaded the muzzle 1/2"-20-NF for the strippers, glued the CF tubes in place with Accraglas, and machined the chambers and barrel ports.... In addition, he lapped and polished the bores to perfectly fit the bullets.... I received my barrel and bullets yesterday, and here are the photos of his work.... GORGEOUS !!!
(http://i378.photobucket.com/albums/oo221/rsterne/Hayabusa%20PCP/IMG_2954_zps7a8cfc91.jpg)
(http://i378.photobucket.com/albums/oo221/rsterne/Hayabusa%20PCP/IMG_2958_zps78e096a7.jpg)
(http://i378.photobucket.com/albums/oo221/rsterne/Hayabusa%20PCP/IMG_2960_zps56f0f75b.jpg)
The barrel port is a bit unusual.... I designed it so that the area was the same as the bore, but the width was only 75% of the bore size, to prevent damaging the bullets on loading.... The transfer port will be 0.219", and the barrel port starts that size and becomes oval, ending up 0.160" x 0.312" at the bore.... The back of the port is vertical, and the front is angled forward about 45*, maintaining a constant area and smoothing the flow to the base of the bullet.... The valve will have matching areas throughout as a lot of flow is needed to get the performance required....
The goal for these rifles is daunting, but we know it's attainable as they are doing it in Holland with the "Sinner" target rifles.... We need to duplicate the performance of .22LR standard velocity target rounds, or nearly so.... The goal is a velocity with the 41.5 gr. bullets of between 950 and 1050 fps.... for an FPE of 83-102 FPE.... and we need to do this with a 3000 psi fill, at least I do, because that is the pressure rating of my 22CI tank.... My onboard air volume will total about 475 cc, and 110-115 cc of that will be "on deck" and available for the shot in the main tube, which is open directly to the valve seat.... That will keep the pressure drop during the shot to a minimum.... I want to achieve a 5 shot string with the onboard air, if possible.... These guns are usually shot while tethered to a SCUBA tank or a regulated SCBA tank....
The next step is to finalize the design and dimensions, and then I can start making chips.... I hope to be able to finish the gun before the Motel gets busy again in the late spring.... My thanks to SeanMP for the beautiful job on the barrel.... I hope to do it justice....
Bob
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Bob (and Sean MP, too),
The project being undertaken will be difficult, the results will be rewarding, and I have no doubt that the two of you will achieve success. Personally, it makes me feel good to be in some small way associated with you, and to be able to watch the progress.
Sean MP, the barrel work is beautiful. Machining the complex barrel port must have required you to come up with some clever set-up tricks. I am impressed. Bob, the valve "system" will obviously be a very critical key to the success of the project, but you are a proven winner in that department. Maybe I missed it, but will this be shrouded? And if so, will the shroud be used in such a way that it imparts additional stiffness into the barrel?
My hat is off to the two of you and I look forward to watching this unfold, and then come together.
To your success!
Lloyd-ss
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Shrouds?.... In Canada?.... The anti-quiet police would be all over it !!!.... Guns are meant to be noisy !!!
The initial valve will be a scratch-built copy of the one I did originally for the Hayabusa, using a Disco poppet, but with larger porting.... The larger ID main tube in this gun allows good flow in from the sides of the poppet, and as the throat gets bigged the large head becomes more in scale with it.... I'm not crazy about the tapered valve I made for the .25 cal Disco, it seems to be wearing/compressing the seat area on the poppet to a significant degree.... There is basially no longer any 5* difference in the angles, the Delrin? of the MRod poppet is conforming to the angle of the throat....
The funny thing about maching the barrel port is that it's easy on the Milling Attachment on my lathe.... much harder to setup on an actual milling machine....
Bob
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Again ... a great project to watch mature ;)
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(http://i378.photobucket.com/albums/oo221/rsterne/Hayabusa%20PCP/HayabusaLogo.jpg)
It's finally time to start making some chips.... I spent a couple of days designing the breech and came up with a design that will work for all four barrels from .224 to .9mm.... The .224 and .257 will share a breech with a 1/4" loading tray and the .308 and 9mm will share a second one with a 3/8" loading tray.... The design for the tank block was done a year ago, so it was just a matter of printing it off, double checking it and making a few detail changes and notes, and then machining it.... Yeah, well it sounds a lot easier than it was.... It took me the entire day just to make the tank block, and I had to finish it after dinner.... Here it is....
(http://i378.photobucket.com/albums/oo221/rsterne/Hayabusa%20PCP/IMG_2961_zps116e2b36.jpg)
(http://i378.photobucket.com/albums/oo221/rsterne/Hayabusa%20PCP/IMG_2963_zps58415a55.jpg)
The tank mount is the threaded portion of a 5/8"-18 NF Grade 8 bolt drilled out to 3/8".... The tank (sans regulator) seals directly to the rear face of the block with an O-ring.... The stub that goes into the 1" OD x 0.065" CrMoly main tube is located by three high tensile 10-32 low profile SHCSs and sealed by two O-rings.... The tank and tube nearly touch.... The larger hole in the stub is the air passage (9/32") which is larger than any of the ports I'll be using so basically all of the 475 cc of air is available to keep the pressure up at the valve seat during a shot.... The 1/4-20 NC tapped hole above it is for a long threaded rod that carries the valve spring.... On the left side of the block is a 3000 psi gauge (upper hole) and a male Foster fitting (lower hole) and on the right side is a 5K burst disc.... The vertical transfer hole is plugged on top with a flush 1/8" pipe plug.... The recess on the top front with the two 6-32 holes is for mounting a barrel band, and on the bottom is a 3-slot Picatinny rail....
Hopefully tomorrow I'll get to start on the breeches....
Bob
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Keep at it. It is amazing the amount of time that one can spend with hands on tools just to get the desired outcome.
As a side note I found out today that NASA has a mission named Hayabusa. If it where not for your project I would not have known it was named after a bird.
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It's finally time to start making some chips.... I spent a couple of days designing the breech and came up with a design that will work for all four barrels from .224 to .9mm.... The .224 and .257 will share a breech with a 1/4" loading tray and the .308 and 9mm will share a second one with a 3/8" loading tray....
Bob,
Caliber and power interchangeability with a family of parts. Excellent.
Lloyd-ss
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(http://i378.photobucket.com/albums/oo221/rsterne/Hayabusa%20PCP/HayabusaLogo.jpg)
Well, it took three days to machine two breeches.... and I still haven't done the bolts or bolt handles.... They did, however, turn out very nice....
(http://i378.photobucket.com/albums/oo221/rsterne/Hayabusa%20PCP/IMG_2969_zps2c4654f1.jpg)
The two breeches are virtually identical, with the following exceptions: The loading tray (and the forward section of the bolt) is 1/4" for the .224 / .257 cal breech (the rear one), but 3/8" for the .308 / 9mm cal breech.... the through hole above the 3/8" transfer port recess is 1/4" for the smaller cal. breech and 9/32" for the larger (with room to go to 5/16" in a 7/16" TP).... and the slot to clear the cocking lever allows for a 1.25" stroke for the .22/.25 cal and 1.5" hammer travel for the .30/.35 cal.... That is where the lower part of the breech is machined away in front of the bolt slot and behind the loading port to clear the cocking handle which will be a piece of 1/4" steel rod threaded into the hammer near the front.... It will stick out through a slot in the side of the main tube at a 40* angle upwards.... When cocked, it will be just ahead of the "closed" bolt handle (angled downwards at 25*), forming an "X".... This idea is borrowed from my DAQ and works very well, "falling readily to hand"....
The barrel is secured with three 8-32 setscrews against the 5/8" OD portion, the rear one on the top and the front two on an angle.... The barrel is sealed into the breech both sides of the transfer port hole with O-rings.... The breech is secured to the main tube with a single 8-32 bolt at the rear and two 6-32 bolts which screw into the tank band / trigger mount at the front, making for a very rigid assembly.... Next up is to make the bolts and handles and then move on to making the valves and hammers.... After that, I still have to do all the machining on 3 of the 4 barrels, including turning to fit the breech, chambering, porting, crowning, and threading to accept a Hatsan Air Stripper.... I takes longer to do multiples of everything, but in the long run it saves setup time on the lathe.... Stay tuned....
Bob
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Secure attachment of the breech block to the air tube; nice large O.D. for the transfer port; availability of a long hammer stroke. Three very nice features seldom found in one package.
Lloyd-ss
P.S., Yes, I can certainly believe three days on the machine to get 2 breechs. You don't need to tell us how many hours you have in the design work, but I bet it's more than you spent on the machining.
Good work.
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(http://i378.photobucket.com/albums/oo221/rsterne/Hayabusa%20PCP/HayabusaLogo.jpg)
I spent more time over the last two days repairing machinery than making parts.... The switch on my lathe burnt out for the umpeenth time (I haven't been able to find anything that will stand up in this hick town).... My local supplier found a 12V 50A switch in stock and told me something interesting.... Apparently UL / CSA removed the AC rating on most switches a while back.... This switch used to be rated at 125V 20A, and they haven't changed the switch.... They use it on a 1 HP motor there, so I figured it can't be any worse than what I've been using.... The problem was that it was too deep to fit in the cavity on the top of the lathe, so I had to make a 3/4" deep plate with a 1/2" deep cavity so that the switch mounts 1/2" higher.... Looks kinda cool, I hope it lasts.... While I was at it I lubed, checked, and adjusted everything on the lathe as well....
The other job was to replace a broken handwheel on my horizontal bandsaw.... It's a Busy Bee Chinese special, and the handwheel that runs the clamping vice was plastic.... Needless to say, the hub split, and the only part that was reusable was the handle to spin it.... I made a new handwheel from a 1.5" cast iron pipe flange with a couple of adapters screwed into it to bush it down to smaller than the shaft.... I drilled it out, drilled and tapped it for a setscrew, and drilled and tapped a (metric) hole for the handle near the perimeter.... I works like a charm, and looks suitably "Coalmont" in nature.... I guess I've finally graduated from Hillbilly repair school....
Anyway, I finally got around to making the bolts for the two breeches, as below....
(http://i378.photobucket.com/albums/oo221/rsterne/Hayabusa%20PCP/IMG_2973_zpsee483783.jpg)
The front one with the handle screwed into it is for the .224 / .257 cal, while the rear one with the longer probe and larger diameter nose is for the .308 / 9mm.... On both bolts, the short smaller diameter nose section fits the smaller bore barrel (.22 cal on the .25 bolt, .30 cal on the .35 cal bolt), and the 60* taper is the transition to the O-ring size.... A matching taper inside the barrel guides the bullet into the chamber.... The shoulder on the bolt where the probe starts is flush with the back of the barrel port, so the chamber starts just behind the port, and the bullets have lots of length to align with the chamber before engaging the rifling.... The front driving band is just engaging the rifling as the rear of the bullet passes the front of the port, so the chamber is the length of the bullet from front driving band to base, plus the barrel port, plus about 0.030".... The O-ring that seals the bolt is captured between the end of the barrel and the breech, and the bullet slides through it on loading.... I really like this system for sealing the breech.... All the bullets are a loose fit through the O-ring except for the .257 cal, which is 0.007" bigger than the bolt at the driving bands on the bullet.... I think that will squeeze through the O-ring just fine, however....
I have ordered a set of 5C Collets and a square and hex mounting block set for them which will be really handy for making the valve and main tube.... Since they haven't arrived yet, I think my next step will be to make the chamber reamers for the .30 and .35 cal barrels and get the machining done on those.... Still a LOT to do on this project....
Bob
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(http://i378.photobucket.com/albums/oo221/rsterne/Hayabusa%20PCP/HayabusaLogo.jpg)
Over the past three days I got all the machining done on the .30 and .35 cal barrels.... The first step was to machine, harden, and temper two chambering reamers, which took me basically one day.... I had made a compromise on the design of the chambers because the 9mm has both pellets and bullets to deal with (and in fact once they become available I want to try the .30 cal JSBs as well).... This resulted in the bullets being seated further forward, which would have either required a long chamber made for the bullets (and the pellets not engaging the rifling when chambered) or a short chamber made for the pellets (and the bullets would be hard to chamber).... My solution was to cut off the probe on the bolt and drill and tap the nose 8-32 and make two probes different in length by the recess in the back of the pellet, which is 0.200".... Here's what the bolt now looks like...
(http://i378.photobucket.com/albums/oo221/rsterne/Hayabusa%20PCP/IMG_2991_zpsa0f0b9d2.jpg)
Now I could optimize the chamber for the bullet and the pellet would also seat against the leade by using the longer probe....The next step was to turn the breech areas to size and chamber the barrels.... I then reversed the barrel in the lathe, crowned it, and threaded the muzzle 1/2"-20 NF to accept a Hatsan air stripper.... I will have to drill out the brass stripper portion for the larger bullets, but there is lots of meat there.... Once the lathe work was done I machined the barrel ports.... Here is a photo of the machining on the barrel ends....
(http://i378.photobucket.com/albums/oo221/rsterne/Hayabusa%20PCP/IMG_2987_zpsa4176da0.jpg)
The main portion of the barrel that fits into the breech is 5/8" diameter, and then it's shouldered down to 1/2" where the port is.... The larger O-ring is captured between the shoulder on the barrel and the internal shoulder in the breech and is under slight compression.... The smaller O-ring is captured between the end of the barrel and the end of the breech bore, also under slight compression, and it also serves to seal on the outside of the bolt, which slides through it.... I've used this arrangement before, and I really like it.... You can vary how hard the O-ring grips the bolt by sliding the barrel back a thou or two.... The barrel port in the 9mm barrel is 0.281", nearly 80% of the bore size.... I couldn't go quite that big on the .308 but I wanted the same area, so the barrel port is oval.... It tapers from a 0.281" circle where it meets the transfer port to 0.250" wide by 0.312" long at the bore line, with the back of the port being vertical and the front angling forward at 20*.... This keeps the same area while avoiding loading problems.... The valve throat and ports will be optimized to work with the 0.281" transfer port.... Here is a photo of the two barrels, with the .35 cal (9mm) in the breech and wearing a Hatsan air stripper....
(http://i378.photobucket.com/albums/oo221/rsterne/Hayabusa%20PCP/IMG_2984_zps51779f48.jpg)
After completing the machining, I lapped both barrels with JB Bore Paste, followed by polishing with JB Bore Bright.... I checked the twist, and they are both 1 turn in 16", which is a little faster than what Lothar Walther had told me.... They told me all their airgun barrels were 450mm twist (17.7").... Both barrels are 28" long, the 9mm is 18mm OD and the .308 is 17mm OD....
Bob
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Major progress! Mind telling how and why you lap and polish the bores?
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Nice work. Looking forward to what comes next.
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I use felt pellets designed for the job (DFG, I think) to work with the JB coarse and fine pastes.... I was told that the bores stay clean much longer once lapped and polished, and accuracy improves.... I haven't been doing this very long, but there does seem to be an accuracy increase on the ones I've done so far.... When you start with a blank and have to machine your own chamber I figure it's a good idea to lap and polish that area anyway just to smooth it out.... so why not do the whole barrel....
I do 100 strokes full length (from the breech) just to the muzzle but not out (lapping with the JB bore paste).... I then shorten up the strokes 1" at a time, doing 3 at each shorter distance..... so you lap (progressively) the breech end more than the muzzle end.... I then do a couple dozen strokes just in the chamber and first few inches..... I clean the bore with solvent and repeat with the JB bore bright polish.... It comes out gleaming....
Bob
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Thanks for that Bob.
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(http://i378.photobucket.com/albums/oo221/rsterne/Hayabusa%20PCP/HayabusaLogo.jpg)
I got a chance to use my new 5C Collet and the square indexing block today when I made the valves.... I turned down a piece of brass stock a bit over 2" long down to 0.862" OD which is a nice slide fit in my main tube.... I drilled one end for a 9/32" throat and a 1/8" stem and the other end for a 5/16" throat and a 5/32" stem, machined grooves for the O-rings, and then mounted one end in a 7/8" collet and machined the other for the three 10-32 mounting screws and the 30* angled port, reversed it and did the other end.... Then I just cut the piece in half and faced the back end to length to allow 1/4" maximum lift on the poppet.... They are in the fully open position in this photo....
(http://i378.photobucket.com/albums/oo221/rsterne/Hayabusa%20PCP/IMG_3004_zps4f4fa9a4.jpg)
The .22/.25 cal valve (right) uses an MRod poppet, which is 0.33" OD, so it overlaps the 0.281" throat with a seat of just 0.025".... That should be nearly perfect width, and the seat is simply flat to flat.... The port is 0.250", and the throat area minus the 1/8" stem area equals that....
The .30/.35 cal valve (left) uses a Disco poppet, which is 0.43" OD and has a 5/32" stem which I have ground down to 0.120" in the portion in the throat.... I raised the seat area 0.010" so that the seat width was only 0.025" wide past the 0.312" throat.... If I had left it flat, the sealing diameter would have been larger, making the valve harder to crack.... If the seat was made flat like in the other valve, the throat could be even larger than 5/16", so a Disco poppet might even be usuable for my .45 cal / .410 shotgun version later on.... As it is, the port is 0.281", and the throat area matches that size....
I'm very pleased with the valves, the new collet and holder system makes it a lot easier to do this job accurately.... even so, it took an entire day.... The transfer port recesses in both valves are 3/8" OD and the transfer ports will be made from 3/8" Teflon rod.... The ports will be 0.219" for the .224 cal, 0.250" for the .257, and 0.281" for the .30 and .35 cal versions.... There is enough material everywhere to go to a 0.312" transfer port with a 7/16" OD for the .35 cal if required....
Bob
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Bob,
Nice work and appropriate sizing, I think. I have tried modifying the OD of the Disco poppet, but you can only remove several thou before you are in danger of cutting thru to the metal nail-head shaped inner part.
The 3/8" transfer port is what I have kinda settled on as a standard, too. For experimenting, I use a PEX plumbing fixture supply tube. The OD is fine as-is and it seems to seal well by itself, and one supply tube will make a pile of experimental tubes. The ID is a little large at .215 for some projects, though. For permanent bushing I like aluminum sealed with M8x1 metric o-rings. The 1mm cross section fits where the 1/16 CS ones won't.
Thanks for posting all this progess!
Lloyd-ss
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Yes, I have two halves of a Disco poppet in my scrap bin, the steel insert in the head is 0.375", so you can't machine it very far.... I've found that the MRod poppet works well where you want a smaller OD, however, and has the benefit of a smaller stem so you don't need to thin it....
I use Teflon rod for making my transfer ports.... It is available in 1/4", 5/16", 3/8", and 1/2" OD (not sure aobut 7/16") and machines beautifully, easier than Delrin.... It is a bit softer (no good for a poppet head, as an example) but that gives it a bit of "squish" for a transfer port.... I make it about 0.010" long and it seems to seal great!.... I did use a thin washer of it to replace a stock seal in a QB poppet, and it worked fine in that application as it is surrounded on 3 sides by metal.... However, it did take a pretty good impression of the seat at 1600 psi.... but at that pressure the stock material doesn't last at all....
Good tip on the 8 x 1 Metric O-rings.... I don't know if they are available locally, I'll have to take a look next time I'm in the big city (Princeton, pop 3,500)....
Bob
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(http://i378.photobucket.com/albums/oo221/rsterne/Hayabusa%20PCP/HayabusaLogo.jpg)
A couple of days ago I started working on two hammers, but set them aside until today when I got a chance to drill the main tube for the valve and rear cap, and slot it for the trigger sear and cocking handle.... Once that was done I was able to lay out the location for the cocking handle on the hammers, drill and tap them, and face them to final length.... Here is the tube and hammers.... The front of the hammers is at the bottom of the photo, near the tube....
(http://i378.photobucket.com/albums/oo221/rsterne/Hayabusa%20PCP/IMG_3011_zpsd54ab2a0.jpg)
I was VERY pleased with the accuracy achieved on the valve port and mounting screws and the matching holes in the main tube.... They lined up perfectly, the advantage of the 5C collet holder.... I laid out the cocking slot from the matching slot in the .30/.35 cal breech and milled it 1/4" wide.... It is long enough to allow the hammer to hit the back of the valve (at 1/4" lift) and pull back far enough to go about 1/16" past the trigger sear for cocking.... I made two hammers, the one on the right is for the .30/.35 cal and has a travel of 1.50" and weighs 113 gr. with handle.... The one on the left is for the .22/.25 cal, has a travel of 1.25", and a weight of 94 gr. with handle.... The handle is made from a 2" long 1/4"-28 NF bolt with the head rounded.... I still have to make the spring guides, which will thread into the hammer and move with it, adding a bit more weight.... The trigger sear engages on the crosswise ledge (cut at 22* to match the sear) just behind the large flat, ie the hammer sticks out ahead of the sear when cocked.... The cocking location is 1/4" further back on the .22/.25 hammer, hence the reduced travel.... The larger hammer has a 1/4" wide slot 0.10" deep milled into the bottom to clear the sear during the shot.... The front part of the slot tapers to meet the bottom of the hammer at a 30* angle, and this allows the hammer to draw back over the MRod trigger sear during cocking.... The taper on the waist of the .22/.25 hammer accomplishes the same thing.... Here are photos showing the breech / hammer / trigger assembly....
(http://i378.photobucket.com/albums/oo221/rsterne/Hayabusa%20PCP/IMG_3006_zpsdab990e9.jpg)
The above photo shows the hammer in the cocked position.... The cocking handle just clears the front of the shaft of the bolt handle.... and is just inboard of the knob....
(http://i378.photobucket.com/albums/oo221/rsterne/Hayabusa%20PCP/IMG_3010_zps60f06ccd.jpg)
In the lower photo, the hammer is shown in the uncocked position (ie sitting against the valve stem).... You can see there is 1/4" of travel remaining to allow for the valve lift.... Both the bolt handle and the cocking handle clear the MRod stock I use just fine.... They seem to feel nice to operate, I'll know better once I put in a hammer spring.... I still have to cut the main tube to length and drill the front to mount the tank block, and then make the holder for the valve spring.... plus make the spring guides, a new, longer RVA, and then I should be ready for initial assembly and leak testing.... I hope to have my .257 barrel any day, I may wait until that is machined to fit before doing any assembly....
One other note.... I got some of the new .30 cal FX 46.3 gr. Pellets (JSB Exacts) in the mail today from AirGunSource.... I slid one through the LW barrel I have, and it was a disappointingly loose fit.... The head of the pellet had virtually no rifling marks on it, although the skirt, of course, did.... I would be surprised if they are accurate.... If they won't work in an LW barrel, JSB may have made a big mistake making a pellet that won't work in the standard size 0.308 groove 0.300 land barrels used by LW and DAQ.... Time will tell....
Bob
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Neat. Never seen anything like that setup.
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Borrowed the idea from my DAQ, I can't take credit for it....
Bob
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(http://i378.photobucket.com/albums/oo221/rsterne/Hayabusa%20PCP/HayabusaLogo.jpg)
I got the last few internal parts done today, assembled the reservoir, and it is currently sitting with 3000 psi of air in it and appears not to leak.... The plenum is shorter than the regulated version by the length of the regulator, so it is now 100 cc, making the air reservoir includng the 22CI tank a total of 460 cc.... Here are photos of the sub-assembly....
(http://i378.photobucket.com/albums/oo221/rsterne/Hayabusa%20PCP/IMG_3023_zps59436bb9.jpg)
(http://i378.photobucket.com/albums/oo221/rsterne/Hayabusa%20PCP/IMG_3021_zps0414e5cd.jpg)
I still have to make the spring guides for the hammers, do a bit of work on the RVA, and make a transfer port from a piece of 3/8" Teflon rod, but otherwise it's very close to being able to be fired.... The first tests will be with the .224 barrel which is designed to shoot the 41.5 gr RWS bullets we purchased from Holland....
Bob
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Good deal there Bob. I like the way you used that support for the big end of the bottle to lock everything together including the breech block to the air tube.
Lloyd-ss
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It also mounts the front of the MRod trigger.... *grin*.... (now 1/32" lower to accomodate the AGL shim).... BTW, the 30* taper on the underside of the hammer seems to slide over the MRod trigger sear while cocking just fine....
Bob
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No photos today, just a brief report of the first firing.... I made a 7/32" diam. spring guide, drilled and tapped into the hammer and travelling with it.... The total weight is now 115 gr. for the .22/.25 cal one.... I measured the hammer travel at 1.20", the shallower sear engagement with the shim decreased it slightly.... I modified the RVA so that the spring guide slides through it, and to reposition the spring seat a bit further forward to allow some preload on the QB hammer spring.... With it adjusted so that the preload is virtually zero, I still have about 0.1" of adjustment before I hit coil bind.... The cocking force is about 20 lbs., similar to my DAQ....
I haven't yet fitted a transfer port or barrel, but I couldn't resist the temptation to see if the gun would at least fire.... With the adjustments as above (and no resistance on the valve outlet), I fired five shots, starting at 2950 psi, and the gun used 100 psi per shot, and MAN was it LOUD.... With the 460 cc total reservoir volume, that works out to about 193 CI of air (at 1 bar) per shot, which is about twice what it should take to achieve the power level I'm hoping for.... I am therefore pretty sure I have enough hammer strike to do the job....
I'm glad I didn't put the barrel on, as I now have to degas the gun and do the first repair.... The cheap 3000 psi Chinese pressure gauge I used (bought on eBay, straight from China) shook itself apart, and will have to be replaced.... It survived 3 shots, on the 4th shot the dial rotated about 20*, and on the 5th shot the glass and dial card removed themselves from the housing.... It still doesn't leak, I guess the vibration of firing just shook it apart.... Anyone know where I can get some quality 3000-3500 psi 1" gauges (1/8" NPT rear mount)?....
Bob
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bob as far as the guage goes try a welding supply store
love the bulid
d
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I've never seen a gauge that small in a welding supply.... 2" minimum, usually 2.5".... and 1/4" NPT threads.... and very often bottom mount.... There is certainly NO hope in the small towns around here....
Bob
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I cant say for sure but I bet someone like Joe Brancato of Tim of Mac1 might be able to source a decent 3000psi gauge.
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(http://i378.photobucket.com/albums/oo221/rsterne/Hayabusa%20PCP/HayabusaLogo.jpg)
I got the transfer port made, installed the barrel, and fired the first shot today.... I had about 2500 psi in the gun, the hammer spring preload was set so the spring was just touching the hammer when uncocked, which puts it about 0.1" from coil bound when cocked.... I loaded one of the 41.3 gr. RWS bullets we got from Holland, cocked it, and fired it through the Chrony.... 989 fps for the bullet, followed by the barrel, which slid to a stop against my backstop 20 feet away!.... I didn't get a Chrony reading on the barrel !!!
After I picked my jaw up off the floor, I carefully set the gun down, made sure I wasn't missing any body parts, and walked across the shop and picked up the barrel.... No damage, but three marks in the carbon fibre where it ripped out of the setscrews that were (supposed to be) holding it into the breech....
(http://i378.photobucket.com/albums/oo221/rsterne/Hayabusa%20PCP/IMG_3025_zps083b164f.jpg)
I was in complete and total shock, but examined what had happened, and realized that the carbon composite simply didn't have enough shear strength to resist the (significant) load on the barrel on firing.... I made three new marks with the setscrews, milled the CF off down to the steel, and then drilled three shallow pockets using a 3/16" drill for the setscrews.... After carefully tightening it back into place, I had no further problems whatsoever.... After an afternoon's testing the setscrews were still perfectly tight....
(http://i378.photobucket.com/albums/oo221/rsterne/Hayabusa%20PCP/IMG_3027_zpsa51e8519.jpg)
Well, after that initial bit of excitement, I was pleased when things settled down, and even more pleased when I filled the gun to 3000 psi and recorded 1077 fps (106.4 FPE) for the first shot at that pressure.... I'm sure I'm not the first person to hit over 100 FPE in .22 cal, but this is certainly a BIG leap for me.... I shot a string (11 shots, using 900 psi) with that hammer setting, screwed the RVA out 4 turns, refilled the gun (to 2950) and fired another string.... This time, I got only 914 fps on the first shot, and rising about 20 fps per shot for the next couple.... I then got 21 shots within a 4% ES, and then the last one just below, for a total of 25 shots using the same 900 psi as the first 11 shots.... NOW we're talking !!! .... After analyzing the first two strings, I wound the RVA in one turn, filled the gun to 2900 psi, and shot a third string.... I got 19 shots averaging 1003 fps (92.2 FPE), all of them within a 4% ES, using only 800 psi, and in fact I would expect 1 or 2 more starting from 3000 psi.... Here are the first three strings from my Hayabusa .224 cal....
(http://i378.photobucket.com/albums/oo221/rsterne/Hayabusa%20PCP/Hayabusa224Velocity_zps1d8bbd35.jpg)
So I apparently can get about 20 shots within a 4% ES without any real tuning.... The sweet spot within that is 13 shots within a 2% ES (ie 20 fps), with performance right on a par with a .22LR target velocity round.... The actual velocity I end up using will depend on long range accuracy testing this summer, but I already have a choice of an average of 1003 fps between 3000 psi and 2100 with an efficiency of 1.13 FPE/CI, or 980 fps between 2850 psi and 2050 with an efficiency of 1.27 FPE/CI.... I assume another turn out on the RVA could cut that back slightly more with even higher efficiency if desired.... I stuck my Bushnell 5-15 x 40 AO Legend scope on it, did a quick sight-in, and shot a 5-shot group, as below....
(http://i378.photobucket.com/albums/oo221/rsterne/Hayabusa%20PCP/IMG_3034_zps21c99087.jpg)
I realize this is only indoors at 20', but it does show promise.... It will be very interesting if this bullet lives up to the reputation it has in Holland for sub-MOA groups at 100M (110 yards).... The best group I have seen with it so far is 12mm (just under 1/2").... so I have high hopes.... I set out to build an airgun that will duplicate the performance of a .22LR subsonic round.... and it looks like I have succeeded.... Now I can't wait for my .257 barrel and bullet molds to arrive.... Here is a photo of the finished Hayabusa .224 cal....
(http://i378.photobucket.com/albums/oo221/rsterne/Hayabusa%20PCP/Hayabusa224_zpsc6671fce.jpg)
Bob
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You VERY WELL may have succeeding in .22 subsonic power ... But I will bet the NOISE made during the shot is NOT even close :P
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It was pretty darn noisy at 1077 fps and 3000 psi, that's for sure.... At 980 fps, not so much.... It's surprising how much less noise there is once the valve closes before the bullet has passed ~40% of the way down the barrel.... but yes, it's a noisy beast....
Bob
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You continue to amaze. Well done sir.
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I'm glad that the initial "barrel range test" resulted in no injury or damage. Surprises like that really get the heart rate going.
She is looking good all dreased up. I look forward to your additional testing. I have flowers blooming here, I'll send some of this spring time weather your way...just don't send me your winter weather.
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Wow! Never heard of that happening with someone before. Glad you weren't hurt Bob. No plans to quieten that loud report?
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congratulations great build
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Fortunately the barrel didn't reach enough velocity to become a spear.... It hit the ground about 15' from me and skidding into my backstop.... just a slight ding in the air stripper.... It didn't scare me so much as W T F !?!?!....
It's been a mild winter here, much less snow than normal, and the roads have been clear for a couple of weeks, even our driveway has nearly melted now.... The snowmobilers are grumbling....
We're not allowed to make quiet airguns here in Canada, unfortunately....
Bob
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(http://i378.photobucket.com/albums/oo221/rsterne/Hayabusa%20PCP/HayabusaLogo.jpg)
I took SeanMP's advice and polished the bore with Bore Brite (red) today, and true to what he said, I picked up a few fps and the groups tightened up.... I tried the RVA at 2.5 turns out as well, with a 3000 psi fill, and got just about what I expected.... Although the first shot wasn't the fastest, the peak of the bell-curve was only at shot 5, and the efficiency was just under 1.0 FPE/CI.... so that's a little too hot.... I retested at 3 and 3.5 turns out, and the results of these three tunes are below.... All started at 3000 psi except the 3.5 turns out, which required only a 2800 psi fill....
(http://i378.photobucket.com/albums/oo221/rsterne/Hayabusa%20PCP/Hayabusa224ShotStrings_zps0f16dc31.jpg)
The best tune is 3 turns out, which allows me to use a full 3000 psi fill and get 20 shots within a 4% ES and 13 within 2%, using an average of 44 psi per shot.... There are 16 shots within 25 fps between 1004 and 1029 fps, so that makes a pretty decent sweet spot using a 2900 psi fill and a 2200 psi refill, which works out to 1.13 FPE/CI at an average of 95 FPE.... If I was running the gun on a tether, I would fill to about 2700 psi, shoot a 5 shot group, and refill at 2500.... or use a regulator set for 2600.... That would give me 5 shots within about a 5 fps ES (0.5%) by running right at the top of the bell-curve....
When I shot the last string after I reset the RVA to 3 turns out after the days testing, I shot four 5-shot groups.... They were all just ragged holes, but one was exceptional.... It is the first time I have ever had a gun pass the "Feinwerkbau Test"....
(http://i378.photobucket.com/albums/oo221/rsterne/Hayabusa%20PCP/IMG_3037_zps56d033f8.jpg)
I realize this was only at 20', but it's still the only time I could put a bullet in the hole made by a 5 shot group and have it remain in the single sheet of target paper.... The testing and tuning on this gun is now complete until I can get it outside to stretch its legs this summer.... The .257 cal barrel and my new bullet molds should be here this week, so the plan is to work on that next....
Bob
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Bob, Very nice progress. I have shot a shroud through a chrony, but never a barrel! Glad the barrel was ok, too!
Lloyd-ss
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Yeah, it's the things you DON'T think of that can turn around and bite you....
Bob
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Bob,
That is a serious amount of power you are getting from a .25 cal. :o I got that kind of power back when I was prototyping my electronic valve but I veered away from that because I was wasting air with basically a bunch of dump shots, and even back then I knew that wasn't very useful.
But you are getting the power at reasonable pressures and efficiencies. If you don't mind, could you please summarize, maybe grouped in order of significance, what the major factors have been in achieving all of these goals in a single gun. And while you are at it, could you maybe be specific on the specs and dimensions, i.e., heavy 40gn bullets, long barrel xx", valve throat 0.xxx" ;)
Much appreciated,
Lloyd
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That is a serious amount of power you are getting from a .25 cal.
It would be pretty good for a .25 cal, but this version is a .22 cal, and I broke 100 FPE.... Here are the pertinent details.... not necessarily in order of importance....
Barrel 29", port to muzzle, 1/2" OD TJ's liner, .224 cal 14" twist, 5/8" OD Carbon stiffening sleeve affixed with Acraglas, with Hatsan air stripper
QB7X hammer spring, 2.3" long (set), 0.33" D x 0.047" wire, 20 coils, goes coil bound at 0.95"
Hammer drilled to 3/8" ID, 7/32" spring guide attached to hammer, Hammer weight 115 gr. including spring guide and cocking handle
Hammer travel 1.20" - however, at 3 turns out, the spring clears the hammer by nearly 0.20", leaving the hammer only being accelerated for ~1.0"
Exhaust Port 0.250", barrel port oval - 0.16" wide by 0.31" long at the bore, tapered to 0.219" at the transfer port which is 0.250" (I intended to use 0.219")
MRod Poppet (stock), head diameter is 0.33", valve seat is "flat to flat" so the seat is 0.281" ID x 0.33" OD, leaving the seat ~0.025" wide
Valve Throat 0.281", Valve Stem 0.125" (stock), Equivalent Diameter 0.252"
Maximum Lift 0.250" (when hammer hits back of valve, never used of course)
Unregulated, Reservoir 28.0 CI, fill pressure 3000 psi, main tube is 1.0" OD 4130 CrMoly 0.065" wall, tank is 22 CI, reversed, used as forestock
Bore Volume 18.73 cc, Bullet Weight 41.3 gr. made by RWS, similar to their R-50 .22LR target bullet, imported from Holland
MRod Trigger with AGL shim under, hammer has 30* slope under to allow cocking when hammer passes sear
If I forgot anything, just ask....
Bob
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Bob,
OK, .224 cal, got it. I got confused with the .257 you had been talking about, but .224 it is.
Not to oversimplify a splendid project, but the things that seem to stand out as being outside the usual PCP bell curve are:
bullet is heavy and long for the caliber; very long barrel; very heavy hammer; long hammer stroke; all air passages are well over 100% of the bore area. A nicely working combination. Solid engineering triumphs again.
Thank you for the information summary on this great project.
Lloyd-ss
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The barrel port is 100% of the bore area, and it was my intention to make the transfer port 0.219" and the valve porting match that.... Then along came the .257 project, and my desire to make one breech and valve do both calibers.... Since the barrel port is the equivalvent of 0.222", I don't think I'd lose anything with a 7/32" transfer port, but I got lazy and just made the 1/4" one for the quarter bore.... I may make a 0.219" one just to see if it makes a difference.... I'm betting not.... If I go slightly smaller (say 3/16") I would expect a slight drop in peak power, an increase in efficiency, and a flattening of the shot string....
The way the gun responds to tuning right now reminds me of my Hatsan .25 cal.... If you back off on the hammer spring, you get less power, but you don't really gain many shots, because you have to fill to a lower pressure.... Choking up the airflow and leaving the hammer spring set for the fill pressure you want to run seems to do the trick.... You get more shots and a flatter string as you back the power down.... I would think the velocity adjuster on an MRod would work the same way, it does on my regulated Hayabusa.... You optimize the hammer strike for the pressure range you want and then adjust the airflow to set the power level....
BTW, Lloyd, I ground out one of the Lee .243 sizing dies to 0.250" today, and it works perfectly.... I used that Dremel tool post grinder setup and a 3/16" chainsaw stone, with the compound rest set at about 2/3* to give the internal taper.... It took a long time and a lot of passes, as the stone kept wearing away at the same rate as the steel, or faster.... but the finish was superb, way better than original.... I'll do the .257" die tomorrow....
Bob
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(http://i378.photobucket.com/albums/oo221/rsterne/Hayabusa%20PCP/HayabusaLogo.jpg)
I got my .257 cal barrel about 10 days ago, did the basic machining on it, and then waited for my bullet molds to get here so that I could cast some bullets, measure them, make a chambering reamer, and finish the barrel off.... That all happened this week, and I got to test the gun for the first time today.... My SCUBA tank was at about 2800 psi, but I did manage to run a few short strings through just to make sure I had enough hammer preload adjustment, which I'm pleased to say I do.... I may not have much extra available once I try a 3000 psi fill, but it looks like it will be enough.... Here are the initial results, using the 73.4 gr. solids I cast from my new Lyman #257420 (65 gr.) mold....
(http://i378.photobucket.com/albums/oo221/rsterne/Hayabusa%20PCP/Hayabusa257Initial_zps9436de08.jpg)
With the preload at my maximum reference point (still shy of coil bind), the maximum velocity I got at 2800 psi was 947 fps (146 FPE), easily over my goal of 130 FPE.... I also tried a few of the 87.6 gr. solids from my RCBS 85 gr. "Cowboy" mold, and they shot 878 fps (150 FPE) at just under 2800 psi.... Even higher peak FPE should be available at 3000 psi, hopefully I'll find out tomorrow after my ShoeBox compressor tops up my SCUBA tank.... The curve at 2 turns out on the hammer spring preload is decent, 7 shots starting from ~2600 psi within 4% ES averaging 890 fps (129 FPE) at an efficiency of over 1.0 FPE/CI.... I shot a few of the 66 gr. hollowpoints made from the Lyman mold, and at less than 2700 psi they hit 965 fps (137 FPE).... I expect I'll need to set the preload somewhere around 1 turn out to handle the 3000 psi fill....
So far, I'm delighted with the results.... This gun should be a long range hammer once tuned up....
Bob
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Bob,
Very nice. Very reasonable efficiency for that caliber and power level. I would have expected it to waste more air.
Lloyd
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(http://i378.photobucket.com/albums/oo221/rsterne/Hayabusa%20PCP/HayabusaLogo.jpg)
Now that my SCUBA tank was topped up, I could complete the testing on the .257 cal version of my Hayabusa.... The first step was to tether the gun to the tank and fill it to 3000 psi.... Using each bullet, and starting with the hammer spring at just shy of coil bind, I shot two shots (returning the gun to 3000 psi for each bullet), and in each case, the second shot was slower.... I reduced the preload in one turn increments, always starting at 3000 psi, until the second shot was faster, and then shot a string until the velocity had fallen 4% below the peak.... That occurred 3 turns out from coil bind, indicating that was the maximum usuable preload with a 3000 psi fill.... I also shot a full string with each bullet at 4 turns out, recording every shot that was within 4% of the peak, and then graphed the results.... Here is how the power settings affect the velocity....
(http://i378.photobucket.com/albums/oo221/rsterne/Hayabusa%20PCP/Hayabusa257PowerSettings_zps7ddf4273.jpg)
Also included on the above graph is an average of the efficiency values at each hammer spring setting.... As is typical, adding preload past a given point (2 turns out) at a set pressure (in this case 3000 psi) only wastes air without any significant increase in velocity.... At 3 turns out, the efficiency averaged just under 1.00 FPE/CI, and at 4 turns out, the average was just over 1.20 FPE/CI, which considering the gun is still putting out about 130 FPE is pretty good, IMO.... The maximum power worked out to just over 160 FPE, with the 87.6 gr. bullets at 908 fps.... I'm extremely pleased with that result.... Here is a graph of the shot strings at 3 and 4 turns out....
(http://i378.photobucket.com/albums/oo221/rsterne/Hayabusa%20PCP/Hayabusa257ShotStrings_zpsabeec113.jpg)
With the lighter bullets, at 3 turns out, the first shot was the fastest, indicating too much preload, however with the 87.6 gr. bullet, a bell-curve was starting to appear.... At that power setting, the gun was averaging about 140-145 FPE, and the efficiency was running just over 1.00 FPE/CI.... With the hammer spring preload backed out one more turn, all the bullets produced a bell-curve, but the lighter ones were still missing the first few shots, producing 11-12 shots between 3000 psi and about 2300, with the peak occurring at about 2600 psi.... With the heaviest bullet, the 4% ES string started at about 2800 psi, and produced 14 shots ending at 2000 psi.... All the bullets averaged about 130 FPE, with the 66.0 gr. bullet having an efficiency of 1.08 FPE/CI, the 73.4 gr. working out to 1.12 FPE/CI, and the 87.6 gr. producing 1.24 FPE/CI....
If I wanted to have the string include all shots within a 4% ES, I would have to reduce the hammer spring preload slightly more with the lighter bullets, and that would lower the velocity a few fps and extend the string to about 13 shots.... Alternately, I can leave the gun the way it is, and have 10 shots within 20 fps.... which considering the long range use the gun is likely to see, is probably the better choice.... Those 10 shots average 907 fps with the 73.4 gr. solid (134 FPE) and 940 fps with the 66.0 gr. hollowpoint (129 FPE), and I would stop shooting at 2400 psi, achieving an efficiency of 1.16 and 1.12 FPE/CI repectively.... I still have to test the 77 gr. hollowpoint from the RCBS mold.... and all bullets have to be tested for accuracy at longer ranges before a decision can be made about final tuning.... Here is a photo of the completed .257 Hayabusa, with the barrel and main tube still "in the white".... I won't be doing any bluing until the .308 and .357 (9mm) versions are assembled and tested....
(http://i378.photobucket.com/albums/oo221/rsterne/Hayabusa%20PCP/257calHayabusa_zps1e2e3a2f.jpg)
Bob
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Bob, thanks for the excellent descriptions of your procedures and the accompanying graphs. You make it very easy to understand and I am learning a lot because of it. And not just on this rifle, but on all of your projects.
Jerry
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Bob, you should be very pleased. You have done a great job planning and executing this build.
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It's been pretty much a labour of love.... The concept came over a year ago for a pretty much scratch-built PCP using only a trigger group, barrels, and things like a tank and fasteners and part of a stock that I didn't want to take the time to make.... The first version was a regulated repeater using MRod clips in .22 and .25 cal, which I built last winter and ran into some unanswered questions, so I left it sit until I learned more from other projects.... That let me complete the regulated repeater version, and laid the groundwork for the unregulated version I'm currently working on.... I already had .308 and 9mm (.357) Lothar Walther barrels sitting here for it, but when news of the 41.5 gr. .224 bullets from Holland broke last summer, SeanMP and I ordered some, plus suitable .22 Hornet liners from TJs, and then I recently decided to get a .257 liner from him as well.... That required a redesign for a pair of breeches, valves, and hammers, one set for the smaller calibers (now pretty much finished) and one set for the larger calibers, which are next to be assembled.... That will pretty much be the end of my winter building blitz, as once the Motel get busy in May, I'm pretty much hooped for shop time until November.... I still have a .457 TJs liner and a .410 shotgun barrel sitting here for the Mark III version next winter....
One thing that has really astounded me is the amount of power you can get out of a quarterbore.... A year ago, my builds were topping out at about 70 FPE, with a usable power level of just over 50 FPE.... Now, I'm at 160 FPE, with a usuable power level of 130 FPE.... It is quickly becoming my favourite caliber....
Bob
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(http://i378.photobucket.com/albums/oo221/rsterne/Hayabusa%20PCP/HayabusaLogo.jpg)
I topped up my SCUBA tank and tested the 77.2 gr. Hollowpoints cast from the 85 gr. RCBS 'Cowboy" mold today and added the data to the graph.... Here are the shot strings starting at 3000 psi for all four bullets.... The hammer spring preload was 4 turns out from coil bind for all of these strings....
(http://i378.photobucket.com/albums/oo221/rsterne/Hayabusa%20PCP/Hayabusa257Velocity_zps36d7b2dd.jpg)
You can see what is typical of what happens as you increase the bullet weight.... the peak of the curve moves to a lower pressure.... I included all shots above 96% of the peak velocity, which resulted in 14 shots for the heaviest two bullets, 12 for the 73 gr. and only 11 for the 66 gr.... but you can see that the reason for the shorter strings is partly because of the 3000 psi fill pressure cutting off the top of the curves.... That may not matter, as I will likely reduce the ES range to around 2% which will drop the strings to about 10 shots anyway....
All these bullets produce an average of about 130 FPE over the shot string, peaking at about 135 FPE.... which is a ton of energy for a quarterbore.... Really all that remains is to do some accuracy testing to determine which is the most accurate at long range.... I plan to strip the gun and reassemble it with the larger breech, valve, and hammer in preparation for the initial testing of the .308 and .357 cal barrels shortly....
Bob
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(http://i378.photobucket.com/albums/oo221/rsterne/Hayabusa%20PCP/HayabusaLogo.jpg)
All these bullets produce an average of about 130 FPE over the shot string, peaking at about 135 FPE.... which is a ton of energy for a quarterbore.... Really all that remains is to do some accuracy testing to determine which is the most accurate at long range....
THAT's what really has me intrigued - raw power that won't hit the side of a barn is irrelevant. If you can get 130 FPE to group on a nickel or dime at 100 yards - that's intriguing! Shucks, even an inch group would be interesting - but accuracy combined with power is the way to go. I'm VERY interested in how this works out for you.
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All these bullets produce an average of about 130 FPE over the shot string, peaking at about 135 FPE....
Bob
I have found (after preliminary testing) the same to be true in my Dragon Slayer. I still get the same amount of energy out of it with the .30 as I did the .50. Even the various weight .30 projectiles deliver roughly the same amount of energy, the speeds just vary accordingly.
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Bob,
Where did you get the dimensions to machine the breech? I want to make my own also.
Great work.
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I designed my own breech, bolt, valve, hammer, main tube, tank block, tank/breech/trigger mount,etc.etc....
Bob
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I've been playing around with the design on my 2250/Discovery and thought a Marauder breech would be nice. I found one with the right radius to fit the smaller tube but didn't want to pay the $130. That's why the request. What I really need to know is the details for the magazine and how it mounts. The rest I can figure out.
I machined the rear of my valve to accept the stem spring to get it on the outside of the valve and the air flow. I put a groove in the stem for an e-clip to retain and compress the spring. I thought you might be able to do the same and eliminate your spider, although it does look pretty elegant.
Just a thought.
Pierre
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Hi there
Interesting build there, i spoke to Douglas AKA PakProtector about the same build. He is busy with a project like this but his is a bit diffident from yours, his bottle is facing the opposite side and almost has the same look as a Daystate Air ranger, I dont know have far he is with the project but i think it would look very cool.
i like the long barrel on your gun
Cheers
Marno
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Bob,
The power levels are pretty astounding in this build. Are you happy with the air efficiencies you are getting at these velocities. I have always found it tough to maintain efficiency when looking for maximum power.
Lloyd-ss
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Yes, I'm quite pleased to be maintaining over 1.1 FPE/CI at these power levels....
Bob
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Bob, I just read through your entire post. You have certainly created a new paradigm for small bore PCPs, achieving all three sides of the triangle.... power, efficiency and accuracy. I especially enjoyed the part about shooting your barrel out of the gun. I'm not sure I'd be able to fess up to such an event :).
Superb engineering and execution. Lets see, the only thing left for you to make from scratch is a trigger group and barrel. There is still time...........
Tom
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Lets see, the only thing left for you to make from scratch is a trigger group and barrel. There is still time...........
Tom
He even posted a how-to video on these things! I'm looking forward to seeing the hand-forged results... :)
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Bob,
1.1 fpe/cuin at these crazy power levels is pretty darn good. I'd be smiling!
Lloyd
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I especially enjoyed the part about shooting your barrel out of the gun. I'm not sure I'd be able to fess up to such an event :).
Tom
Hahahaha Correction...He shot MY barrel outta his gun. ;)
Never send this man your labour born offspring ;D
I almost peed myself I was laughing so hard
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Darn Carbon Fibre.... *LOL*.... Make sure you drill right through the carbon and set the screws against the metal when you do yours, Sean....
Bob
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(http://i378.photobucket.com/albums/oo221/rsterne/Hayabusa%20PCP/HayabusaLogo.jpg)
I've been working on assembling the .308 version of the Hayabusa over the past few days, and I ran into a problem.... I can't get enough hammer strike to make the velocity peak at over about 2300 psi.... This is despite having a heavier hammer with more travel, and a heavier spring than the .257 version.... The new valve has a larger throat, at 0.312" instead of 0.281", and I used a Disco poppet instead of the MRod poppet on the smaller valve.... After fitting an even heavier hammer spring, again with no success (and the gun was so hard to cock it literally took two hands).... I decided I better pull the valve to have a look, and here is what I found....
(http://i378.photobucket.com/albums/oo221/rsterne/Hayabusa%20PCP/IMG_3258_zpse0d81bd4.jpg)
The sealing face of the poppet started out dead flat.... Note that I was using the latest Disco poppet, with a hole in the top....
(http://i378.photobucket.com/albums/oo221/rsterne/Hayabusa%20PCP/IMG_3260_zps7088e92c.jpg)
The face of the poppet was extruded into the throat about 0.040".... The stem had slid back, and I thought that might have been partially due to the hole in the top allowing air pressure to act on the end of the stem.... The face of the poppet had completely taken on the shape of the raised seat, and was sealing on a diameter larger than the outside of that seat, which was 0.375".... The head of the poppet was actually belled out to a diameter of about 0.44", and was sealing on nearly the outer edge.... No wonder I couldn't drive it off the seat.... Under load, it was probalby wedging into the throat as well.... I talked to SeanP on the phone, and he informed me that the molding force required for Delrin was 270 lbs, and my calculated seat force was nearly 300 lbs. at 3000 psi, so that is what we think is happening.... the force is causing the Delrin to flow....
I had one of the older Disco poppets, without the hole, and wanted to try that, so Sean suggested that I try fitting a metal ring around it to keep it from expanding, which I did.... I also chamfered the edge below the ring slightly, hoping to prevent the seal diameter from getting bigger than the OD of the seat on the valve....
(http://i378.photobucket.com/albums/oo221/rsterne/Hayabusa%20PCP/IMG_3256_zpsc647f58e.jpg)
I put the gun back together, and there was no difference.... Upon disassmbly, I found that the face of the second poppet looked basically just like the first, it had a big groove pounded into it, and was extruding into the throat of the valve.... Interesting, the groove on both poppets is deeper and narrower than the shape of the slightly raised seat on the face of the valve.... There is some serious flowing of the Delrin going on.... I will be pulling the gun apart and reinstalling the valve from the .257 cal version.... The throat is a bit smaller, but at least the hammer will open it....
Bob
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Wow! That one extruded too....DANG!
Hehehehe you have managed to find the design limitation of Delrin. After a fair bit of pondering over Strengths of Materials I think there may be a couple of solutions.
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(http://i378.photobucket.com/albums/oo221/rsterne/Hayabusa%20PCP/HayabusaLogo.jpg)
Well, installing the .257 valve at least got the gun working in .308 cal.... At coil bind I got over 200 FPE on the first shot, which makes this rifle more powerful than my DAQ .308 Exile with the same 119 gr. Lee RN bullets.... My SCUBA tank wasn't quite at 3000 psi, and dropped with each fill, so all I could do was some preliminary testing.... but it was quite satisfying....
(http://i378.photobucket.com/albums/oo221/rsterne/Hayabusa%20PCP/Hayabusa308Initial_zps58521432.jpg)
The gun is quite sensitive to hammer spring preload after 2 turns out from coil bound as that is where you start to get "play" in the spring.... so there was a big drop from 2 turns out to 3, and that happens to be right where I need to be.... I have a 131 gr. hammer with 1.45" of travel driven by a 3.0" long spring made of 0.051" wire.... so the gun is quite hard to cock.... I'll do a bit of playing around tomorrow and see what I can get for a shot string....
I know there is more lurking in this gun once I figure out how to get the bigger valve working.... However, I already accomplished my goal of breaking 200 FPE at 3000 psi....
Bob
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I've been pondering the requirements for hammer strike, and this gun has taught me a lot.... A while back I developed a Hammer Strike Database and then graphed the Hammer Energy and Momentum vs. the Force required to knock the poppet off the seat.... That is the seat area times the pressure, plus the valve spring force.... The trends were pretty linear over a large variety of guns, but there is a problem with it.... It doesn't account for the extra hammer strike required to allow for an increase in bore size, and hence the potential FPE, which is ultimately related to the amount of air released by the valve.... As an example, it would predict the same hammer strike required for my Hayabusa in .224, ,257, and .308 cal (and the yet to come .357)....
I had addressed the idea previously, in another thread, that hammer strike must increase with caliber when you change the barrel on a gun.... In an attempt to correlate this, I added a column in my database for the FPE output of the gun, and graphed the Hammer Energy and Momentum vs. FPE.... Once again, the trends are relatively linear over a wide variety of guns.... Using this version of my Hayabusa as an example, although the opening force is still the same (eg. in .224, .257, and .308 cal) the Hammer Energy and Momentum required increases.... Here are the numbers for those three, all at 2600 psi (where the shot string peaks)....
Opening Force (0.33" Poppet OD @ 2600 psi) = 222 lbs. (same for all calibers)
.224 cal @ 95 FPE, bore volume 18.1 cc: Hammer Energy 0.737 FPE, Hammer Momentum 0.108 ft.lb/sec....
.257 cal @ 135 FPE, 22.5 cc: 0.886 FPE, 0.118 ft.lb/sec
.308 cal @ 185 FPE, 34.2 cc: 1.272 FPE, 0.151 ft.lb/sec
As you can see, the required hammer strike is NOT just dependant on the seat area and pressure, although they are the only factor in "cracking" the valve open.... Once it's open, the hammer strike to produce enough dwell to keep the valve open to produce the necessary FPE is related to the bore volume and hence the FPE produced.... not linear, but certainly there is a correlation.... I'm thinking that the two components (opening force and FPE produced) are BOTH part of the criteria needed to determine the amount of hammer strike required.... As yet, I don't know how to "adjust" their relative importance to improve the ability to predict how much hammer strike is required for a given gun.... but I'm working on it....
Bob
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I'd approach it as an increase in valve closing forces. As volume and FPE increase, the increased flow rate also forces the valve closed faster. That has a lot more to do with the internal valve and poppet dimensions, rather than just the seat dimensions.
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I think the largest closing force on the poppet is the air pressure working on the diameter (area) of the valve stem.... At 2600 psi, with a 1/8" stem, that is 32 lbs., plus another 10 or so from the spring for a total of about 42 lbs.... While this is much less than the force required to crack open the valve (in this case 232 lbs.) it is still a very large number.... If the stem is 5/32", that goes up to 50 lbs. plus 10 = about 60 lbs.... I have serious doubts that the aerodynamic drag of the air passing the head of the poppet (the only place it can add significant force) is of that order of magnitude, but that's just a guess.... In addition, since the pressure and port area (and therefore the flow RATE) are a constant (in the Hayabusa), the drag force would be a constant as well, only applied over a longer dwell time.... I think the biggest reason that additional hammer strike is required as the caliber increases is that the dwell must increase so that there is sufficient time for the required volume of air to flow into the barrel....
In all three cases above, the valve, according to Lloyd's spreadsheet, is open until the pellet has travelled 43-46% of the way down the bore.... That means that the volume of HPA required is nearly directly proportional to (43-46%) of the bore volume.... Since the .308 has 89% more bore volume (and coincidently produces 95% more FPE).... and since the efficiency of all three cases is nearly identical (1.11 - 1.15 FPE/CI).... it follows that the amount of air required is also going to follow that trend.... Since the pressure is the same, and the same valve (and hence port size) is used.... the flow rate should be the same, and the only variable left is the dwell.... The bigger bore requires more dwell, which requires a harder hammer strike....
Trying to analyse where all the forces are coming from without the benefit of CFD or a flow bench is pretty tough.... All I can do is try and come up with a theory (and some tools) to support the observations I make.... If I can eventually get a tool that will allow me to predict how much hammer energy and/or momentum is required for a new gun, that will be of huge benefit.... I'm currently working on the idea of a simple sum of the opening force and the muzzle energy for the "x-axis" in the graph.... Since the range of forces (so far) is 80-340 lbs. and the FPE range (so far) is 20-185 lbs. they are of similar order of magnitude (eg. importance).... and although I have limited data at the moment, the trends are more linear when the sum is used than using either quantity on its own.... Perhaps I need to double the FPE (ie Sum = Force + 2 x FPE) which will make the range of values match even better, I don't know.... It will depend on which is the more important factor....
Bob
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Here is a graph showing the Hammer momentum vs. the Sum of (Opening Force plus 2X FPE) for the .224, .257, and .308 versions of my Hayabusa....
(http://i378.photobucket.com/albums/oo221/rsterne/Hayabusa%20PCP/HammerMomentumHayabusa_zps863aafd9.jpg)
The trend is very close to linear as you can see.... However, before this can be used for predictions, there is one big caveat.... All three calibers are tuned in a similar manner.... They all have the valve closing at nearly the same point in the pellet's travel down the barrel (43-46%), and they all have nearly identical efficiencies (1.11-1.15 FPE/CI).... Therefore, the only real variable left is the caliber, hence the bore volume, and the associated FPE.... If any (or all) of these examples were tuned for a different power level, the hammer strike would change.... Whether or not it would stay on the trendline I can't say....
Bob
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Ah, I should read more carefully.......was thinking there were more changes to porting as well when you changed caliber..
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(http://i378.photobucket.com/albums/oo221/rsterne/Hayabusa%20PCP/HayabusaLogo.jpg)
I pulled off the .308 barrel today and installed the .357.... In addition, I added a knob to the cocking handle to make the hammer easier to pull back.... That made a HUGE difference to how easy it is so cock (it no longer digs into your hand).... and it also added another 14 gr. to the hammer, bringing the weight to 145 gr.... Here is a photo of the Hayabusa with the hammer cocking handle installed....
(http://i378.photobucket.com/albums/oo221/rsterne/Hayabusa%20PCP/IMG_3264_zps05617e46.jpg)
It turns out that with the extra hammer weight, the preload adjustment for the .308 cal is almost perfect for the .357 cal with 132 gr. bullets.... I had 2900 psi in my SCUBA tank, and tethered the gun to find out the maximum velocity with the preload at coil bind, with the following results:
90 gr. - 989 fps - 196 FPE
117 gr. - 910 fps - 215 FPE
126 gr. - 888 fps - 221 FPE
132 gr. - 875 fps - 225 FPE
The first shot was the fastest, but the pressure was a bit below 3000, and I had a feeling that if more hammer strike was available that higher FPE numbers could be recorded.... However, the preload has to be dialed back to about 2.5 turns to produce a proper bell-curve.... By the time I determined that, my tank was under 2800 psi, so a graph of the shot string will have to wait until tomorrow after I top up my SCUBA tank with my ShoeBox compressor.... It looks like I should get about 10 shots at 200 FPE with the 132 gr. Lee cast bullets sized to 0.357".... The preliminary efficiency works out to about 1.18 FPE/CI, which I think is pretty darn good at that power level....
I tried a couple of shots with the 78 gr. JSB pellets, still at 2.5 turns out, and it looks like they shoot at about 1000 fps.... I'll do full strings of all the bullets I have once I can fill to 3000 psi.... I also have a mold for a 150 gr. Lee bullet, which I expect will cast at more like 160 gr. in pure lead.... but since I'm still working with the .257 valve they would likely be under 800 fps, so for now the 132 gr. looks like the best choice....
BTW, bstaley.... I added the .357 cal to (my copy) of the graph, and it's RIGHT on the linear trend line.... *grin*....
Bob
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(http://i378.photobucket.com/albums/oo221/rsterne/Hayabusa%20PCP/HayabusaLogo.jpg)
I had a small problem with the hammer sticking, so I fixed that, and then adjusted the RVA for the best shot string starting from 3000 psi with the heaviest bullets and then shot strings to 96% of peak velocity with all the different .357 cal bullets I have.... The results are below....
(http://i378.photobucket.com/albums/oo221/rsterne/Hayabusa%20PCP/Hayabusa357ShotStrings_zps868c6dbe.jpg)
The 67 gr. is a roundball, the 78 gr. is a the JSB pellet, the 90, 117, and 126 gr. are Air Venturi bullets, and the 132 gr. are Lee bullets which I cast and sized to 0.357".... The three heavier bullets all returned a 10 shot string averaging over 200 FPE, with the 132 gr. peaking at 209 FPE, and returning an efficiency of 1.11 FPE/CI, with all three dropping to 2050 psi at the end of the 10 shot string.... The 90 gr. averaged 186 FPE over 9 shots, the 78 gr. JSB pellets averaged 177 FPE over 8 shots, and the 67 gr. roundball averaged 166 FPE over 8 shots, with the first shot being the fastest at 1055 fps.... The efficiency dropped with the weight, and the roundball only managed 0.91 FPE/CI....
Until such time as I figure out how to get the larger valve working, this completes the initial testing of the unregulated version of my Hayabusa with all four barrels.... Here is a summary of the results, all strings to 96% of peak velocity, starting at 3000 psi:
.224 cal - 41.5 gr. - 20 shots at 1012 fps - 94 FPE
.257 cal - 77.2 gr. - 14 shots at 873 fps - 130 FPE
.308 cal - 118 gr. - 10 shots at 833 fps - 182 FPE
.357 cal - 132 gr. - 10 shots at 835 fps - 204 FPE
The .224 and .257 cal share a hammer and breech, and the .308 and .357 cal share another hammer and breech.... At the moment, all are using the same valve, so it only takes a few minutes to change calibers, I don't even have to degas the gun.... This has turned out to be a very successful winter project.... I'm looking forward to getting out into the bush for some long range testing when the rest of the snow is gone....
Bob
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(http://i378.photobucket.com/albums/oo221/rsterne/Hayabusa%20PCP/HayabusaLogo.jpg) (http://s378.photobucket.com/user/rsterne/media/Hayabusa%20PCP/HayabusaLogo.jpg.html)
As shown above, the Disco poppet material wasn't strong enough for the throat diameter and pressure of the .308/.357 valve I made.... Sean got me some PEEK material to make a new poppet, and explained how he made his.... Today I made my first poppet, and I'm VERY pleased with the way ti turned out.... I used a piece of 5/32" Drill Rod for the shaft, and lengthened the spring guide part of the poppet to give more room for the stem.... The PEEK machines nicely, but it's a bit strange to drill, it gets the drill quite hot, so I found it better to use a very low speed.... If the drill was very sharp it may not have had that problem.... In any case, here are the photos of the old and new poppets and the valve....
(http://i378.photobucket.com/albums/oo221/rsterne/Hayabusa%20PCP/b9456bce-a467-43d9-b8fd-e1ecf7bc10b1_zpsa099c42e.jpg) (http://s378.photobucket.com/user/rsterne/media/Hayabusa%20PCP/b9456bce-a467-43d9-b8fd-e1ecf7bc10b1_zpsa099c42e.jpg.html)
The head of the new poppet is smaller on the OD and streamilined into the valve spring for a bit better flow as well.... The stem is cut away to 1/8" the same as I did on the Disco poppet.... The valve throat is 5/16", feeding a huge 9/32" exhaust port....
(http://i378.photobucket.com/albums/oo221/rsterne/Hayabusa%20PCP/IMG_3852_zps2ab4a9c5.jpg) (http://s378.photobucket.com/user/rsterne/media/Hayabusa%20PCP/IMG_3852_zps2ab4a9c5.jpg.html)
I'm really looking forward to trying this valve in the Hayabusa again, as it never really got a chance to show what it could do with the problems of the previous poppet.... The hammer had great difficulty in unseating the very much deformed valve....
Bob
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Looking more like a valve from a LP paintball gun ;)
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Never seen one....
Bob
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Hey that looks awesome Bob
It came up nice. I'm guessing the quick blow test was a success.
I heard back on the other PEEK poppets. They are performing "crisply"
I think your going to be really pleased by how much difference you'll see
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When I pulled the .224/.257 valve out of the Hayabusa this morning to install the new .308/.357 valve I found that the MRod poppet was deformed slightly from the load.... Here is a photo after a few hundred shots....
(http://i378.photobucket.com/albums/oo221/rsterne/Hayabusa%20PCP/IMG_3853_zps6e21540f.jpg) (http://s378.photobucket.com/user/rsterne/media/Hayabusa%20PCP/IMG_3853_zps6e21540f.jpg.html)
The throat of the valve is 0.281", and you can see that the OD of the poppet is no longer a cylinder, it is belled out slightly on the end from the forces involved.... The original OD was 0.330" and it is now 0.350".... At 3000 psi, the force on the poppet was 256 lbs, assuming a 0.33" sealing diameter, and may well now be greater than that, but the fact remains that was too much for the poppet to withstand without distorting....
I know from past experience that a 1/4" throat on an MRod valve works fine, but pushing the throat ID to 9/32" is evidently overstressing the poppet material.... It may stay like this forever, not getting any worse.... or it might not.... Nice to know, anyway....
Bob
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I finally got around to fitting the big valve in the Hayabusa today with a poppet that actually works!.... The new poppet is made from PEEK, which is a much harder material than Delrin.... I had a problem with the original poppet extruding into the large 5/16" valve throat at 3000 psi, which then required huge additional force to knock it off the seat.... The previous testing in .308 and .357 cal had to be done with the valve from my .224/.257 cal version, so the gun barely broke 200 FPE.... With the new valve in place, it now hits almost 240 FPE, and I still have a stronger hammer spring yet to test.... Today's testing was done with a 3" long, 3/8" OD x 0.051" wire spring just shy of coil bind, filling to 3000 psi.... Here are the results....
(http://i378.photobucket.com/albums/oo221/rsterne/Hayabusa%20PCP/Hayabusa357NewValve_zps89e27846.jpg) (http://s378.photobucket.com/user/rsterne/media/Hayabusa%20PCP/Hayabusa357NewValve_zps89e27846.jpg.html)
The gun now drives a 67 gr. roundball over 1100 fps, and the 78 gr. JSB and EunJin pellets at over 1060 fps.... With all three of those, the first shot is the fastest, so hammer preload is too much to produce a proper shot string.... In fact, you have to get up to a 132 gr. bullet to show a first shot that is slower than the peak velocity.... With that bullet, the velocity hits nearly 900 fps (234 FPE), and with a 154 gr. bullet I am starting to get a normal bell curve, peaking at 835 fpe (238 FPE).... One thing that surprised me was the efficiency of the gun at this power level.... The gun is using about 100 psi per shot (460 cc reservoir), which works out to 1.21 FPE/CI with the heaviest bullet, dropping gradually to 1.13 FPE/CI with the 117 gr.... The 90 gr. bullet got 1.01 FPE/CI, and as expected the pellets and roundball were lower, at 0.90 FPE/CI for the pellets and 0.82 FPE/CI for the roundball.... Reducing the hammer spring preload to produce a bell curve would raise that however, even with the lightest rounds....
This version of the Hayabusa has now been developed to the point where pellets are now too light, and in fact even the 90 gr. Air Venturi HollowPoint is really too light.... The gun really needs bullets over 110 gr. to make use of the power available.... I plan to test the heavier bullets with a stronger hammer spring, just to see how far I can push the FPE, but in fact as a useful gun, this hammer spring is just about perfect, and with bullets in the 117-132 gr. range the preload is a bit too much to produce a proper shot string at the best efficiency....
Bob
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That is some big energy...I do appreciate the effort required to get it. Let me wish you the best in getting it to land within MOA out to 100 yards. That particular goal may lead me into a serious rat hole...but I comfort myself with the idea that I can live with a lot less energy if I can accurately place what I do make...lol then, maybe energy is required to place it accurately...and round and round I go. Fortunately the science of pill-form, mood improvement is gathering steam quickly...heh-heh-heh
cheers,
Douglas
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I tried the stronger hammer spring, which is 3" long, 3/8" OD x 0.059" wire, and at coil bind I could barely cock the hammer.... Fortunately, for some reason, the velocity actually increased with a couple of turns less preload.... Here are the best numbers I got at 3000 psi.... This is the first gun I have had that broke 250 FPE....
(http://i378.photobucket.com/albums/oo221/rsterne/Hayabusa%20PCP/Hayabusa357MaximumFPE_zps7ab332a6.jpg) (http://s378.photobucket.com/user/rsterne/media/Hayabusa%20PCP/Hayabusa357MaximumFPE_zps7ab332a6.jpg.html)
The best looking hunting bullet of the ones I have is the 132 gr. Lee 358-125-RF (it's supposed to cast at 125 gr.) which has quite a large meplat.... so I hope it proves to be accurate.... After the flat-out testing I changed back to the other spring and reduced the preload a turn and shot a string with them, starting from 3000 psi and ending at 2200....
856
872
875
876
870
866
862
859
856
Maximum Energy: 225 FPE
Average Velocity: 866 fps
Average Energy: 220 FPE
ES: 20 fps (2.3%) over 9 shots
Efficiency: 1.28 FPE/CI
So, I gave up 9 FPE (4%) to get 50% more shots with extremely good efficiency.... I think that is an excellent trade off.... The next step for the Hayabusa is to install the .308 cal barrel and find out what it does in that caliber with the new valve.... By the time I'm ready to test, hopefully the mold for my new Boattail bullets will be here and I can see how they work....
Bob
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That's pretty cool, Bob.
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I installed the .308 barrel today and tested a few bullets and settings.... Here are the shot strings with the 118 gr. Lee which had previously produced the best accuracy in my DAQ....
(http://i378.photobucket.com/albums/oo221/rsterne/Hayabusa%20PCP/Hayabusa308BigValve_zps41105bd5.jpg) (http://s378.photobucket.com/user/rsterne/media/Hayabusa%20PCP/Hayabusa308BigValve_zps41105bd5.jpg.html)
The gun is very sensitive to small changes in hammer spring preload, those three curves span only one turn of adjustment.... Just shy of coil bind, the first shot is the fastest at 207 FPE, and efficiency over the 6 shots is 1.03 FPE/CI.... At one turn out, I have 11 shots averaging 184 FPE within a 4% ES and the efficiency has increased to 1.22 FPE/CI.... The first 10 of those shots are within a 2.5% ES, and 7 of them are within just 1%, with 3 in a row being identical at 847 fps.... This gun is slightly more powerful than my DAQ, and a lot more efficient at the same pressures.... As a comparison, my DAQ gets only 5 shots averaging 180 FPE at an efficiency of 0.88 FPE/CI, and that was after I tuned it.... The way I got it, it lost nearly 100 fps over the first 3 shots at an efficiency of 0.38 FPE/CI, but with no more power....
For hunting a good tune is 1/2 turn out.... The first 6 shots are within 7 fps ES (0.8%) and average 193 FPE.... The mid-portion of the shot strings with this bullet are the flattest I have ever seen in a big bore.... Just for the heck of it, I fired a few 46 gr. JSB pellets which I had upsized to 0.308" diameter and they shot between 1190-1198 fps, easily supersonic.... Talk about LOUD !!!
Bob
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Very kewl Bob! Nice job!
Bruce
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Bob,
You say this set-up is very sensitive to spring preload, where a single turn makes a big difference. I take it that this is a heavy spring with a short hammer stroke?
Thanks,
Lloyd
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Not that heavy, but not a lightweight either, 0.051" wire, 3/8" OD McMaster Carr you got me a few months back.... and the hammer stroke is 1.45" with a 145 gr. hammer.... However, the spring is operating with very little preload at coil bind, and that one turn removes most if not all of it.... That's the problem with that much hammer travel and only a 3" long spring....
Bob
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Bob,
Thanks for the answer. Yes, that makes perfectly good sense about the sensitivity.
Lloyd
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ok, now I'm lost. I thought when a spring is compressed all the way to coil bind, that is the maximum preload on the spring.
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ok, now I'm lost. I thought when a spring is compressed all the way to coil bind, that is the maximum preload on the spring.
John,
I can understand the confusion. When the 3" spring is not cocked, it barely has any preload on it. Then when it is cocked, it goes almost to coil bind. If Bob adds one turn of preload (I think, approximately), it goes totally to a coil bind situation before the sear will latch. Or something like that. Bob will explain if I messed it up.
Lloyd
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Exactly correct.... The hammer travel is so great that if you start with zero preload on the spring when uncocked, the spring is within about 1 turn of coil bind when cocked.... That leaves you with only about 1 additional turn of preload adjustment.... Actually, that is not strictly true, you can back the preload off further, but you end up with the hammer spring rattling around loose when uncocked.... That has both good and bad to it.... The good is that the hammer is less likely to bounce hard enough to open the valve a second time.... The bad is that you aren't using all of the hammer travel, for the last part the hammer is coasting, without any force from the spring, and actually losing velocity.... You may as well have designed the gun for less hammer travel, you would have ended up with a greater adjustment range on the preload....
The basic problem is that the hammer spring is too short for the designed hammer travel.... Installing a longer one requires adding additional length at the back, behind the hammer, either by using a longer tube, or making a longer rear plug to move the preload adjuster further back.... It then becomes problematic finding the right spring, because as you make it longer the spring rate drops.... Many springs you cannot find in a great enough length, so the answer there is to stack then one behind the other on a long spring guide.... Let's just say that trying to get a long hammer travel is challenging....
My new .410/.457 version of the Hayabusa will have 2.00" of hammer travel using a 200 gr. hammer, and to drive that, a spring that is 4.5" long with a 1/2" OD and made from 0.072" wire.... Increasing the caliber and FPE even further brings a whole new set of challenges....
Bob
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....
.....................The basic problem is that the hammer spring is too short for the designed hammer travel.... Installing a longer one requires adding additional length at the back, behind the hammer, either by using a longer tube, or making a longer rear plug to move the preload adjuster further back.... It then becomes problematic finding the right spring, because as you make it longer the spring rate drops.... Many springs you cannot find in a great enough length, so the answer there is to stack then one behind the other on a long spring guide.... Let's just say that trying to get a long hammer travel is challenging............
Bob
Bob,
That paragraph really sums up a lot of the challenges of modifying PCPs. Changes that seem like they ought to be easy, snowball into having to change several different parts. The farther you deviate from the factory set-up (assuming there is a factory set-up to begin with) the more likely you to run into unforeseen problems. And decisions often are driven by available materials, rather than optimum choices
Lloyd-ss
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My mold for the new Boattail bullets I designed came in a couple of days ago and I cast some yesterday.... Today I had a chance to test them in my .308 Hayabusa.... Here are the results....
(http://i378.photobucket.com/albums/oo221/rsterne/Hayabusa%20PCP/Hayabusa357NewBoattail_zpsb1fb8e3f.jpg) (http://s378.photobucket.com/user/rsterne/media/Hayabusa%20PCP/Hayabusa357NewBoattail_zpsb1fb8e3f.jpg.html)
Peak velocity reached at coil bind was 1022 fps (184 FPE).... I shot strings with the preload at 2 and 3 turns out, shooting 5 shot groups through the Chrony at the same time.... At 20 feet the groups were all ragged holes, most under 1/2" OD, which is decent for cast bullets.... but I noticed there was no resistance loading these very short bullets and pushed one out after chambering it and there were no marks on the bullet from the rifling.... I have a longer bolt probe which I use for pellets and installed that, and then you could feel the bullet engaging the rifling, there is a photo below....
(http://i378.photobucket.com/albums/oo221/rsterne/Hayabusa%20PCP/308cal79gr_zpsb06d31b1.jpg) (http://s378.photobucket.com/user/rsterne/media/Hayabusa%20PCP/308cal79gr_zpsb06d31b1.jpg.html)
The front band is engaged about half way long the leade, and the accuracy immediately improved.... Here is a typical group when chambered deeper....
(http://i378.photobucket.com/albums/oo221/rsterne/Hayabusa%20PCP/308Hayabusa79grBoattail_zpsb3dc8b95.jpg) (http://s378.photobucket.com/user/rsterne/media/Hayabusa%20PCP/308Hayabusa79grBoattail_zpsb3dc8b95.jpg.html)
The group measures 3/8" across the longest point, pretty tight when a single hole is 5/16".... I think these new bullets show a lot of promise.... The velocity dropped a bit when chambered deeper, but I got one extra shot and greater efficiency.... The green string above averaged 965 fps (164 FPE) with 10 shots within 21 fps (2.2% ES), starting from 3000 psi and ending at 2320, for an efficiency of 1.25 FPE/CI.... The string shot at 3 turns out (black) was 15 shots within less than 4% ES at 154 FPE and 1.30 FPE/CI, so the gun is delivering excellent efficiency with what for this gun are pretty light bullets.... I'm delighted with the way my new Boattails performed, it's going to be a frustrating wait until the spring to let them stretch their legs....
Bob
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Bob,
Very nice! I wasn't expecting to see that custom mold that fast. Bummer about having to wait until spring to really try them out for long range accuracy.
I am very curious about the seating. First, have you pushed one all the way through by hand to see how they engrave?
You show a loss of 10-20 fps with the fully seated bullets being slower. I would have expected the opposite because it might have prevented some air leakage at the beginning of the shot. Do you think the bullets like the running start into the rifling to give some extra velocity? Or do you think the air leakage at the beginning of the shot is minimal compared to the power need to free the bullet from the initial partial engagement in the rifling?
Thanks,
Lloyd
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I haven't pushed a bullet right through to look at it.... yet.... It is also possible that the extra volume for the air to expand into with the deeper seated bullet may be causing a pressure drop that is causing the velocity loss.... nawwwww, scratch that your spreadsheet says it's only about 3 fps.... I'm guessing the running start is the important factor for the higher velocity with no pre-engagement.... I think the leakage is minimal because the chamber is fairly close to the OD of the bullet.... I just measured the chamber (parallel) portion of the reamer I used and the bullets are only 0.001"-0.002" smaller than the reamer OD.... I wouldn't think you get a lot of leakage through a 0.001" gap, especially when once the bullet has travelled less than 1/2" it's fully engaged in the rifling past the 2* leade....
Bob
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(http://i378.photobucket.com/albums/oo221/rsterne/Hayabusa%20PCP/HayabusaLogo.jpg) (http://s378.photobucket.com/user/rsterne/media/Hayabusa%20PCP/HayabusaLogo.jpg.html)
Over the last year plus I have been collecting the major parts I needed to continue the development of my Hayabusa.... From the beginning, this project was a test gun, designed to help me learn about PCPs, both regulated and un-regulated, and from .22 cal up to .45 cal.... Originally, I have developed a .22 and .25 cal regulated version, shooting pellets.... I then moved on to an unregulated version, or actually two versions, one set up for .224 cal and .257 cal bullets, and the other set up for .308 and .357 cal bullets.... During the process, the larger one ruined a Disco poppet, which was not up to the task of handling 3000 psi on a 5/16" valve throat, so development was delayed until we found PEEK as a much better material for the higher loads of a big bore airgun....
This allowed me to get to work on the largest version, which will be made as a .410 bore air shotgun, and then as a .457 cal rifle.... In order to deliver greater power, I had to make virtually all the parts from scratch, building the new gun around a 500 cc 3600 psi tank from Best Fittings in England.... The main tube diameter was increased from 1.000" OD to 1.125" OD, still 0.065" wall CrMoly tubing, which pushed the limits of safety to the maximum I am comfortable with.... The yield limit on the tube is 8,200 psi (2.3:1), and 12,600 psi at burst (3.5:1); the shear force on the three 10-32 low profile, 180,000 psi screws is down to a safety margin of 2.1:1, and the yield limit of the tube wall supporting the screw heads is only 1.4:1.... In order to guarantee I never have to worry, I fitted a 5K burst disc in the tank block to prevent the pressure (even on a messed up overfill) ever rising to the point where that became an issue.... NOTE: I am not recommending that anyone ever push safety limits to this extent.... I am very experienced with HPA, and I feel comfortable doing it, but I am working this design to the maximum I would ever do.... You can bet I will be watching the tube cradling the screw heads like a hawk (a Hayabusa?) for any sign of distortion under load during the first fill....
Anyway, I have spent the last couple of weeks machining the custom parts I needed to utilize the larger tank and main tube, and here is the first look at them....
(http://i378.photobucket.com/albums/oo221/rsterne/Hayabusa%20PCP/IMG_4043_zps8ed9401c.jpg) (http://s378.photobucket.com/user/rsterne/media/Hayabusa%20PCP/IMG_4043_zps8ed9401c.jpg.html)
The 250 bar 500 cc tank is about an inch longer than the 22 CI 3000 psi tank that I used on the previous versions, and it's 3/8" larger in diameter.... to accomodate the 64% increase in air crammed into it.... The main tube holds an additional 145 cc of air, bringing the total to 645 cc (39.3 CI) at 3600 psi.... The passages through the tank block are larger than the valve throat, which is 0.406" (with a 1/8" stem), and all the ports are a full 3/8" diameter, which equals the largest hole I can get through the base of a .410 shotshell where the primer used to be and still retain the wad.... and is 82% of the boresize for the .457 cal, at the limits of what can be done with a round barrel port.... I'm using the same Marauder trigger, but I had to mount it on a pad silver-soldered onto the main tube as it needed to be moved forward an inch to accomodate the 2" hammer travel.... The hammer is 2.25" long, and with the cocking handle and 5/16" spring guide (which is 5" long) weighs 225 gr. (8 oz.).... The spring is a McMaster Carr, having 31 coils of 0.072" wire, and it's 4.5" long, and takes over 36 lbs. to cock it at coil bind.... Surprisingly, with the side cocking lever, that isn't that hard to do.... you can see the long slot in the main tube just behind where the valve mounts....
The weird looking part fastened to the trigger is an enlarged version of the trigger/tank/breech mount I used on the previous versions, but all new parts because everything is bigger.... It took me 2 full days to make.... The top of it has two tapped holes to accept the front breech screws, tying everything together rigidly.... The RVA has a 9/16"-18 NF adjusting screw that allows me to change the hammer spring without stripping the back of the gun apart.... It has well over 1/2" of travel outward from coil bind, and as the spring only has 0.2" of preload at coil bind, that should be plenty of adjustment.... The spring guide, incidently, is free floating, but captured between the hammer spring and the hammer by a small conical flange on the front of it.... It travels with the hammer, so becomes part of the mass.... If I want to lighten the hammer, I can replace it with a Delrin one.... The tank block has mounts for the 5K burst disc (visible) and on the other side mounts for the 4,000 psi gauge and male Foster fitting.... The tank mount is made from an 18 mm x 1.5 mm bolt drilled out to 7/16" ID for the airflow, and a vertical air passage through the block of the same size is sealed on the top with a flush fitting 1/4" NPT plug.... When assembled, everything drops into the same stock I used on the previous versions, even though the only shared part is the trigger, everything else is new....
I still have the valve spring mount to make, and then all the parts above can be assembled and pressure tested.... Once that is done, I can get on with the challenge of chambering and porting the barrels and making the breech to hold them.... I'm pretty excited to see this project coming along so nicely, and I'm especially anxious to find out how the .410 shotgun version will work out....
Bob
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I've been curious about PCP scatterguns for some time. The microbores (.22 and .25, etc) really don't interest me. A .410? This should prove interesting!
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Just to put this information into this thread.... I posted this a while back....
(http://i378.photobucket.com/albums/oo221/rsterne/Hayabusa%20PCP/HayabusaLogo.jpg) (http://s378.photobucket.com/user/rsterne/media/Hayabusa%20PCP/HayabusaLogo.jpg.html)
Over this winter I plan to continue with the development of my Hayabusa project gun by building a .457 rifle and a .410 shotgun version.... It is my hope for them to share a common valve, main tube and hammer, and a 500cc 250 bar (3625 psi) tank.... They will, of course, have different breeches.... Here is the ammo for the .410....
(http://i378.photobucket.com/albums/oo221/rsterne/Hayabusa%20PCP/IMG_3814_zps645125e5.jpg) (http://s378.photobucket.com/user/rsterne/media/Hayabusa%20PCP/IMG_3814_zps645125e5.jpg.html)
(http://i378.photobucket.com/albums/oo221/rsterne/Hayabusa%20PCP/IMG_3816_zps96e49b7e.jpg) (http://s378.photobucket.com/user/rsterne/media/Hayabusa%20PCP/IMG_3816_zps96e49b7e.jpg.html).... (http://i378.photobucket.com/albums/oo221/rsterne/Hayabusa%20PCP/IMG_3815_zps6bbda39c.jpg) (http://s378.photobucket.com/user/rsterne/media/Hayabusa%20PCP/IMG_3815_zps6bbda39c.jpg.html)
The shell has been shortened from 2.5" to 1.75" and the primer hole drilled out to 3/8".... The shot cup holds 223 grains of #7.5 shot (0.51 oz) full to the top (about 180 pellets).... My target velocity is 950 fps, but that works out to 450 FPE, which even with 3600 psi may be a stretch....
Bob
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and some more previously posted....
An interesting thought came to me today when I was thinking about how to Chrony the shotshell loads without hittting my Chrony.... I had some OOO Buckshot which measure about 0.36", and found out that they are a perfect fit inside the shotcup.... it still loads normally into the shell....
(http://i378.photobucket.com/albums/oo221/rsterne/Hayabusa%20PCP/IMG_3817_zpsb6577630.jpg) (http://s378.photobucket.com/user/rsterne/media/Hayabusa%20PCP/IMG_3817_zpsb6577630.jpg.html) .... (http://i378.photobucket.com/albums/oo221/rsterne/Hayabusa%20PCP/IMG_3818_zps7ccab9dc.jpg) (http://s378.photobucket.com/user/rsterne/media/Hayabusa%20PCP/IMG_3818_zps7ccab9dc.jpg.html)
They weigh just under 70 gr. each, so the total, is only 5% less than a 1/2 oz. of birdshot.... Just out of curiosity I also tried a .357" bullet and it also nestles nicely in the shotcup.... so if I want to have only a single projectile for Chronying I could get some 220 gr. bullets as an alternative.... However, I would think the dispersion on just three roundballs would be so slight that the chance of hitting my Chrony would be no worse than usual within 10' or so, and that should get it away from the muzzle blast no problem....
Incidently, the retained energy of EACH roundball is 120 FPE at 30 yards starting from 950 fps at the muzzle if I can push them that fast.... Three of them would make a heck of a mess of whatever they hit....
Bob
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Now, what shell WAS that before trimming and boring out the primer pocket?
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Magtech all brass 2.5" .410 shotshell....
Bob
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Magtech all brass 2.5" .410 shotshell....
Bob
Good ol' Companhia Brasileira de Cartuchos. I suspected as much, but didn't know if they were available up north. Are those Boxer primed, or Berdan? (not that it matters for the task at hand, just curious since they only produced Berdan when I was a kid) This build will definitely be followed by yours truly.
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I don't know, I bought them unprimed.... However, I would think they would take the same primers as any .410 sold in the USA.... Ballistics Products carry them....
Bob
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I don't know, I bought them unprimed.... However, I would think they would take the same primers as any .410 sold in the USA.... Ballistics Products carry them....
Bob
The difference between Berdan and Boxer priming is that the Berdan priming system includes an "anvil" in the primer pocket, it's a spike in the center with two holes on either side of it to allow the flash to travel into the powder chamber. The Boxer system has the "anvil" included in the primer itself and there is only one hole in the center of the primer pocket to transmit the flash to the powder chamber. Ironically, Berdan was a US inventor (and military officer - headed up Berdan's sharpshooters during the "recent unpleasantness" as some refer to the US Civil war) but his system did not gain foothold in the US but was used in Europe and (I believe) England. Boxer, on the other hand, was English and his system was widely adapted in the U.S. - probably because of the ease of reloading that the single, central flash hole brings to the system.
Anyway, it really has NOTHING to do with your project other than my idle curiosity on the subject. I learned to reload by reloading full brass 32 gauge shells with the Berdan priming system. A knife point to pierce and remove the primer, the flat of a knife blade to seat the new primer, a measure of powder tamped into place under a jute fiber wad, a measure of lead held in place (preferably) with a simple card wad and you were ready for business.
I've been curious about the use of air power in small bore shotguns for some time. Gamo had (has?) a 22 caliber system, but I've never had the chance to examine it - not even in pics. This looks interesting. We've no access to full brass 410 shells here, but I DO have access to a small amount of brass tubing. The main problem would be finding a way to flange a rim for extraction purposes. The other issue is bore size - the brass is not a "standard" bore, nor do I currently have a barrel of suitable dimensions. But I'll be following this project in the interest of increasing my knowledge of the principles involved in utilizing air power to project a load of shot.
Okeydoke, I took a look at Ballistics Products website, they use a Boxer Large Pistol primer. A much better system than what I grew up with. :-D And, incidentally, easier to drill out than the Berdan system would be, with that anvil projecting from the center of the primer pocket.
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The shells have a single small flash hole, about 1/16"? in the bottom of the primer pocket.... The brass is a loose enough fit in the chamber that it will fall out by holding the muzzle up.... I don't plan on having an extractor as the brass won't expand on firing at 3600 psi, which is my maximum pressure....
Bob
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The shells have a single small flash hole, about 1/16"? in the bottom of the primer pocket.... The brass is a loose enough fit in the chamber that it will fall out by holding the muzzle up.... I don't plan on having an extractor as the brass won't expand on firing at 3600 psi, which is my maximum pressure....
Bob
That will simplify the action, the only caveat being the use of clean cartridges - not allowing anything to get in there beside the shell that would cause it to NOT fall out by gravity. Is this going to be a bolt action, or will you depart from your usual type of platform?
Ok, I'll quit bugging you and let you get some work done on it. Most of my current questions will be answered as your project develops! ;D
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Bolt action single shot.... Separate cocking lever that pulls back the hammer directly, you can see it in the photo of the parts....
Bob
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I got the bottom end assembled and pressure tested overnight....
(http://i378.photobucket.com/albums/oo221/rsterne/Hayabusa%20PCP/IMG_4045_zps29876910.jpg) (http://s378.photobucket.com/user/rsterne/media/Hayabusa%20PCP/IMG_4045_zps29876910.jpg.html)
I filled it to 4000 psi, which is about 10% more than I will ever be using, and no sign of the tube yielding around the heads of the mounting screws for the valve and tank block.... which should be the first place to show any yield problems.... I left it overnight and it lost about 300 psi, there is a very tiny leak in the valve O-ring.... I used a 70D for the first test, replacing it with a 90D will cure that problem.... I was VERY pleased with the PEEK valve, it didn't leak even at only 500 psi....
Bob
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Hello Bob, here is an interesting reading on the 410 shot gun
http://www.hoeningbigboresouth.com/index.html (http://www.hoeningbigboresouth.com/index.html)
I hope you like it
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Interesting, yes, but has nothing to do with airguns.... I somehow doubt I will be approaching 1200 FPE.... in fact more like a third of that....
Bob
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Bob,
This truly is your test mule. The fun never ends ! ;D Swap parts and make new parts and it morphs into something else.
A good shotgun is sorely missing from the airgun market. Good luck on this.
Lloyd
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(http://i378.photobucket.com/albums/oo221/rsterne/Hayabusa%20PCP/HayabusaLogo.jpg) (http://s378.photobucket.com/user/rsterne/media/Hayabusa%20PCP/HayabusaLogo.jpg.html)
I got back to working on the Hayabusa the last couple of days and got the breeches roughed out.... I decided to make two, one for the .410 shotgun and one for the .458 rifle, as there were too many compromises to make to fit the rifle barrel in the shotgun breech.... Sean supplied me with a bar of aluminum long enough for two, so I cut a couple of 9" pieces and set up the mill to reduce then to the proper dimensions and machine the groove along the bottom for the main tube.... Here is a photo of one of them at this point....
(http://i378.photobucket.com/albums/oo221/rsterne/Hayabusa%20PCP/IMG_4250_zpsffef5963.jpg) (http://s378.photobucket.com/user/rsterne/media/Hayabusa%20PCP/IMG_4250_zpsffef5963.jpg.html)
I had a LOT of material to remove, and it took me the better part of two days.... I had to remove 1/8" from the width and 3/8" from the height, and then when I machined the groove I didn't have a 1.125" ball mill, so I used a 1" and then took extra passes off center to get a near perfect fit with three points of contact, the center and both edges.... One of the reasons it took so long was that my milling attachment on the lathe only has 6" of crossfeed and the breech is 9" long, so I had to do the machining in two setups for each dimension.... I then laid out the location of the bore and drilled it from both ends and the 3/8" pilot hole met perfectly in the middle.... The other breech is finished to the same stage except I haven't drilled the through hole yet....
I have machined the chambers in both the shotgun and rifle barrels and sleeved them up to 3/4" OD (they were only 5/8") to make them large enough to accept a 1/2" OD x 3/8" ID transfer port.... More to come soon....
Bob
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Not quite finished the breeches, but I've made quite a bit of progress in the last 10 days....
(http://i378.photobucket.com/albums/oo221/rsterne/Hayabusa%20PCP/IMG_4255_zpsa76661c6.jpg) (http://s378.photobucket.com/user/rsterne/media/Hayabusa%20PCP/IMG_4255_zpsa76661c6.jpg.html)
The longer breech in the background is for the .410 shotgun, capable of loading a 2" long shell.... It is likely that I can use the shell at a length of 1.75" but I left enough length for an extra base wad behind the shot cup in case the seal isn't good enough with just the plastic cup at airgun pressures.... The breech in the foreground is for the .457 rifle version.... I could have shortened the loading port and the breech another half inch, but there was no reason to.... The boss on the front is for a 1" OD shroud to put the barrel in tension to stiffen it.... The long slot in the bottom of the breech, in front of the bolt slot, is for the cocking handle.... Yes, it really does have 2" of hammer travel.... for the 8 oz. hammer....
The next job is to make the bolts and finish machining the barrel ports.... then machine in the scope mounts on the top of the breeches.... The rifle is getting a dovetail as usual, but the shotgun is going to have a Weaver mount for a wide-screen red-dot.... I haven't decided yet if it will be in front of the loading port or behind it.... I may put a Weaver/Picatinny rail both places if I don't get lazy / in a hurry....
Bob
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I understand the temptation to use a bolt on picatinny, I have seen aluminum versions as cheap as $10. It's hard to justify all the necessary setup and machining for 10 bucks! Looking good and amazing progress as always. I curious, why no j-bolts?
Tom
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Actually, I will machine the Weaver/Picatinny mount into the top of the shotgun breech.... 8)
I have to put the breech O-rings on the bolts because of wall thickness issues on the barrel.... To use a "J" bolt you have to have a smooth bolt.... In addition, again because of wall thickness issues, I can only go to a 3/8" ID x 1/2" OD transfer port.... which is as large a hole as I can squeeze into the base of the .410 shell anyway.... The bolts will use a scooped out flow-through design with a 3/8" wide channel to move the air from the barrel port to the hole in the shell, and the rifle, which uses the same valve and tube will share that system.... The compromises are worth it, however, as I can still achieve a barrel port that is 82% of the boresize on the .457 (91% on the .410), which at 3600 psi will move a LOT of air....
Bob
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Have you had time for anymore work on this Bob?
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I hope to get back to it in a couple more weeks.... no time lately....
Bob
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It's been a couple months since the last post. Is this project still in the works? I can't wait to see the finished product.
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Summer is here and the Motel is busy.... I may not get back to it until the winter....
Bob
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I finally got back into the shop to finish off the breeches for the Hayabusa Mk.3.... Here they are with the barrels installed.... The .457 rifle barrel is 30" long, the .410 shotgun barrel is 25" including the poly-choke....
(http://i378.photobucket.com/albums/oo221/rsterne/Hayabusa%20PCP/HayabusaMk3Barrels_zpsc65edfa0.jpg) (http://s378.photobucket.com/user/rsterne/media/Hayabusa%20PCP/HayabusaMk3Barrels_zpsc65edfa0.jpg.html)
In this photo, you can see the basic differences.... The .457 rifle (top) has provision for a shroud, and a shorter loading port, and a dovetail for a scope.... The .410 shotgun (bottom) is longer overall, with a longer loading port to accommodate the shotshell, and a Picatiinny rail forward of the port for mounting a Holosight....
(http://i378.photobucket.com/albums/oo221/rsterne/Hayabusa%20PCP/457and410Breeches_zpsaf1149e4.jpg) (http://s378.photobucket.com/user/rsterne/media/Hayabusa%20PCP/457and410Breeches_zpsaf1149e4.jpg.html)
The third photo shows the bottom and side views, with the monster transfer port visible.... It is 1/2" OD with a 3/8" ID and the flow-though bolts have the same size passage....
(http://i378.photobucket.com/albums/oo221/rsterne/Hayabusa%20PCP/BreechDetails_zps811bd759.jpg) (http://s378.photobucket.com/user/rsterne/media/Hayabusa%20PCP/BreechDetails_zps811bd759.jpg.html)
The next steps are a cocking handle for the hammer (you can see the clearance slot in the breeches, below the loading port), make the transfer ports (from 1/2" Teflon rod), strip the valve out to chase a leak, and it will be ready to assemble and test.... My biggest concern at that point is assuring I have an adequate backstop....
Bob
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Glad to see you back to work on this Bob.Are you still using a milling attachment on your lathe or did you get a milling machine?
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Still using the old Atlas milling attachment.... This breech is so long I have to reposition, so careful adjustment in all 3 axis was critical....
Bob
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Today I took the valve out, replaced the 70D O-ring that had a slow leak with a 90D, filled the gun from my new Great White, took out my hearing aids, put in my earplugs, and fired the first shot.... Yup, it's pretty loud!.... I had the hammer spring preload at maximum, and at 3600 psi it was just under 800 fps with three 000 Buck.... Not as strong as I was hoping for, but nearly 300 FPE, the most powerful shot I have ever had from an airgun.... I fired a few shots and examined the plastic shot cups I found down by the backstop, and they were all split or blown open through the middle of the base.... I wondered if possibly I was getting a lot of blowby, so I used a 1/4" thick fibre wad in the shell first and then the three Buckshot (no shot cup), and got more consistent and higher velocities.... The highest I saw was 817 fps, and that was 7 yards from the muzzle, so that corrects to 833 fps at the muzzle (313 FPE) at just under 3000 psi.... I got 7 shots from 3600 psi down to 2700 within 4% ES....
The disappointing part of the first tests was that I don't have enough hammer strike.... I got a very nice shot string, but I'm maxed out, and the peak is at just under 3000 psi.... This is despite having a 237 gr. hammer with 2" of travel and a spring that takes 36 lbs. to cock.... and a PEEK valve.... Before I make any changes I will try the .457 Rifle barrel with some 220 gr. bullets I have, and some roundball, just to get a baseline.... I have no idea how I could increase the hammer strike if I need to, to get more power....
Bob
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Nice progress Bob. Lloyd suggested a tungsten hammer as a method for more strike in the same space. I did a little research and it's stated to be very machinable.
Tom
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Oh, goody!.... I can increase my hammer to a whole pound from over 8 oz.... *LOL*....
I have one more thing to try on the .410 to see if I'm getting blowby.... I can make the shell casing 2" long instead of 1.75" (I left room in the breech and chamber for that) and put a 1/4" fibre base wad in first and then the shot cup on top of it.... Who knows, that might give me a boost in fps and FPE....
I guess I shouldn't complain, at 3000 psi I'm right where Lloyd's spreadsheet said I would be with 65% efficiency.... I wish I knew what it would do maxed out at 3600 though.... In theory a max. shot should be ~ 920 fps (382 FPE), and about 890 fps with the valve closing at 50% @ 3600 psi....
Bob
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On the bright side I suspect you've eliminated bounce ;)
Space permitting , solenoid or servo actuation may be the way to go.
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It turns out I had another hammer spring here to try, which allowed me to examine what the maximum performance was.... It was actually two 3" long springs of 0.062" wire instead of the single 4.5" long spring of 0.072" wire.... This gave me about the same force when cocked, but instead of having no preload when uncocked it had a preload of about 10 lbs.... That gave more hammer energy, so I was able to find out where the velocity plateau was at 3600 psi.... It turns out the gun maxes out at about 870 fps (340 FPE).... I couldn't back the preload adjuster out far enough with the long spring to get down under 800 fps, but by using the original spring I was able to plot the velocity profile.... Once I established that the best place to tune the gun was with the original spring maxed out, I then shot a string, recording all the shots within 5% of the peak....
(http://i378.photobucket.com/albums/oo221/rsterne/Hayabusa%20PCP/Hayabusa410_zps75a0315b.jpg) (http://s378.photobucket.com/user/rsterne/media/Hayabusa%20PCP/Hayabusa410_zps75a0315b.jpg.html)
The best choice for a hammer spring would be one about 5" long, made of 0.062" wire, and I can get a 10" one from Trakar and then cut it in half, which is the eventual plan.... However, I was able to get 9 shots with 5%, of which 7 shots were within 3% ES.... The average velocity for those 7 shots was 819 fps (302 FPE), and I would refill at about 2500 psi, and the efficiency is 0.76 FPE/CI....
I think this will prove to be an effective short range Grouse gun.... It doesn't have the smack of a powderburner, but if I can get decent patterns with the #8 shot I think it will do the job....
Bob
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(http://i378.photobucket.com/albums/oo221/rsterne/Hayabusa%20PCP/HayabusaLogo.jpg) (http://s378.photobucket.com/user/rsterne/media/Hayabusa%20PCP/HayabusaLogo.jpg.html)
Today was quite a day.... After a couple of years of planning and a year of work, I shot my Hayabusa .457 for the first time today, and saw over 550 FPE.... I tested three kinds of ammo, found the maximum that the gun would do at 3600 psi with all three, and found two great shot strings.... The bullets used were a 143 gr. roundball, and two Lee bullets, a 216 gr. RN and a 336 gr. FN.... In order to find the velocity plateau I had to use the two 3" hammer springs like I did on the .410 shotgun, and here are the maxed out results....
143 gr. RB - 1101 fps (385 FPE)
216 gr. RN - 993 fps (473 FPE)
336 gr. FN - 859 fps (551 FPE)
Needless to say, all the work and frustration has paid off and I've got a pretty big smile right now.... I put the 4.5" long 0.072" wire spring back in and shot the following strings....
(http://i378.photobucket.com/albums/oo221/rsterne/Hayabusa%20PCP/Hayabusa457_zps4c23b7a5.jpg) (http://s378.photobucket.com/user/rsterne/media/Hayabusa%20PCP/Hayabusa457_zps4c23b7a5.jpg.html)
With the spring just shy of coil bind the roundball showed the first shot fastest at 1070 fps.... The 216 gr. RN had the 2nd shot fastest at 960 fps.... Both bullets had 5 shots before falling more than 4% below the peak.... With the 336 gr. FN bullet I got a very nice 7 shot string peaking at 815 fps (496 FPE).... That string averaged 800 fps (477 FPE) with an efficiency of 0.96 FPE/CI.... I then backed the preload down a turn and shot another string with the 216 gr. RN and got 8 shots peaking at 929 fps (414 FPE) and averaging 913 fps (400 FPE) with an efficiency of 0.99 FPE/CI from 3600 psi down to 2400....
To say I'm pleased with this performance is an understatement.... I was hoping this gun would break 500 FPE, I never though it would break 550, nor did I think it would give me 8 shots at 400 FPE on a fill.... Time to just bask in the glow of satisfaction for a while.... I need a break.... and a drink....
Bob
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The 216gn RN looks really sweet :) Earned your drink for sure!
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This will give you an idea of the power.... I taped four clear Cedar 2x4s together and it blew through two of them and imbedded completely in the third....
(http://i378.photobucket.com/albums/oo221/rsterne/Hayabusa%20PCP/Entrance_zpsd5cd125a.jpg) (http://s378.photobucket.com/user/rsterne/media/Hayabusa%20PCP/Entrance_zpsd5cd125a.jpg.html)
This was the 336 gr. Lee FN travelling at 792 fps (468 FPE), which is the first shot of my 7 shot string.... Here are the exit holes and bullet in the third 2x4 (edge view)....
(http://i378.photobucket.com/albums/oo221/rsterne/Hayabusa%20PCP/Exit_zps5be00080.jpg) (http://s378.photobucket.com/user/rsterne/media/Hayabusa%20PCP/Exit_zps5be00080.jpg.html)
The 2x4s were a foot long and taped tightly together at both ends with duct tape, and the 3rd one where the bullet stopped was split from end to end.... They were against a solid backstop to prevent movement....
Bob
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WOW!
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Hi Bob and thanks for all knowledge you share with as.
I was thinking to use (stole) your idea about valve and return spring support with spider from first page and applying to the small tube of samyang 909 dual tube 500cmc.
It is enough space around the valve poppet to obtain same power like an 909 single tube after power tune?
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Not familiar with any of the Korean guns, sorry....
Bob
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Photo of the .410 Shotgun, the .457 rifle is identical except longer barrel and scope....
(http://i378.photobucket.com/albums/oo221/rsterne/Hayabusa%20PCP/Hayabusa410Shotgun_zpsfb2626a8.jpg) (http://s378.photobucket.com/user/rsterne/media/Hayabusa%20PCP/Hayabusa410Shotgun_zpsfb2626a8.jpg.html)
Bob
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I wasn't very happy with the hammer spring I was using, it had no preload and must have required 40 lbs. to cock it, so I searched for a longer spring of smaller wire.... I couldn't find anything ready to use, but I did manage to find a 10" long spring made of 0.062" wire, and when I finally got it in the mail, the first thing I did was "set" it to collapse the coils so that in future during use it wouldn't get even shorter.... It's a good thing I did, because it lost 2" in length, ending up at only 8".... I cut 2" off and tried it, but the preload was too much, I could hardly install it, and it turned out that I didn't need that much, so I cut it down to 5.5" and that worked out great.... I can still max out the gun with the 336 gr. bullet at 855 fps, with a bit of preload left, and even at that setting the gun was much easier to cock.... I tried it with the 216 gr. bullet and it did 979 fps (460 FPE), and I had to back the preload down 6 turns to get a proper string, and at that setting it was MUCH nice to cock.... I shot three strings at different preloads, and the results are below.... The caption on the pressure line is wrong, that was at -8 turns....
(http://i378.photobucket.com/albums/oo221/rsterne/Hayabusa%20PCP/Hayabusa457NewSpring_zpsfa95bb97.jpg) (http://s378.photobucket.com/user/rsterne/media/Hayabusa%20PCP/Hayabusa457NewSpring_zpsfa95bb97.jpg.html)
At 6 turns out I get three shots within 10 fps and two more before the velocity has dropped by 4%.... The first 3 shots average 965 fps (447 FPE) and the 5 shot string works out to 0.86 FPE/CI, not too bad for that much power.... At 7 turns out I got 6 shots averaging 934 fps (419 FPE) at 0.90 FPE/CI, and at 8 turns out I got 7 shots averaging 922 fps (408 FPE) at an efficiency of 0.96 FPE/CI.... Any of the three strings would be fine, but the first one, with 3 nearly equal shots at almost 450 FPE with two more within 4% looks very tempting....This pretty much completes the development of the .457 version, when I get a chance I will test the .410 shotgun with the new spring....
Bob
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Amazing project Bob, enjoyed all 12 pages of information and pictures. I think I'm soon going to be tuning springs for my project too. Might have to bother you for some pointers when the time comes.
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Bob, did you try the .410 with smaller shot? Like #6 or #8 lead? I am curious if this might be a useable bird gun??
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The plan is to use #7 1/2, I have a 25 lb. bag of it.... However, testing will have to wait until the spring, I can't test that inside my shop.... The three OOO buck were just a Chrony load....
Bob
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I picked up some Tungsten rod one ebay very reasonable. I was able to machine it. But it is not my favorite material that's for sure.
Edit: that's odd I guess I was reading a post farther up the thread and thought I was responding to it. Sorry
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The plan is to use #7 1/2, I have a 25 lb. bag of it.... However, testing will have to wait until the spring, I can't test that inside my shop.... The three OOO buck were just a Chrony load....
Bob
I can't wait to see how it does. I have been waiting to see how this comes out for some time.
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Bob, are there and restrictions in Canada regarding lead shot?
Tom
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Not allowed for waterfowl.... not a problem for upland game birds....
Bob
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(http://i378.photobucket.com/albums/oo221/rsterne/Hayabusa%20PCP/HayabusaLogo.jpg) (http://s378.photobucket.com/user/rsterne/media/Hayabusa%20PCP/HayabusaLogo.jpg.html)
My Hayabusa has been hanging on the wall ever since I made the 7mm version.... I just don't have enough time to shoot in the summer when the Motel is busy to really let it stretch its legs.... However, I still have all the versions, and they all share one MRod trigger group and stock, but not much else.... ::) .... Anyways, I have learned a huge amount since 2011 when I built the first one, so I thought it might be interesting to revisit the Mark I version, which is a regulated PCP repeater with interchangeable LW .22 and .25 cal. barrels.... Both versions use MRod mags, and feed from a 23 CI 3000 psi bottle which is reversed under the main tube.... They look like this....
(http://i378.photobucket.com/albums/oo221/rsterne/Hayabusa%20PCP/Hayabusa25Cal.jpg) (http://s378.photobucket.com/user/rsterne/media/Hayabusa%20PCP/Hayabusa25Cal.jpg.html)
The main tube is a piece of 1.00" OD x 0.065" wall CrMoly, and the valve and tank block are both secured with three 10-32 low profile SCHSs, giving me a MSWP of 3400 psi (higher than the bottle).... The regulator is currently set at 1900 psi, feeding a plenum of about 115 cc, plenty big enough for what I need.... If you go back to the first few pages of this thread, you can see how the gun came together, and how it performed.... Anyways, long story short, when I built it, the "best" pellets were the 18.1 gr. JSB Exact Heavy in .22 cal, and the 25.4 gr. King in .25 cal.... so the gun was tuned to shoot them in the mid 900s.... Things have changed now, JSB have a new 34 gr. King Heavy in .25 cal, and have just introduced a "Redesigned" 25.4 g. Monster in .22 cal.... Both pellets are working well in a wide variety of barrels, including the LW, which is what I am using, and have almost identical SDs of 0.077-0.078, which is a LOT higher than the 0.054-0.058 of the older pellets.... I have learned how to drive heavier pellets into the mid 900s, so I figured it was time to update this gun....
The first thing I attacked was the valve.... I changed from a Disco poppet, with it's 5/32" stem, running in a 1/4" throat and feeding 3/16" ports to an MRod poppet, with a 1/8" stem, running in a 17/64" throat, and a 7/32" exhaust port milled at a 20 deg. angle (actually a bit over that, closer to 15/64" once I finished grinding it out to fair it into the throat).... The .22 cal bolt has a 1/8" probe, and the .22 cal probe is 7/64", both of which are going to be slimmed by 1/64".... That will give me a chamber area in the .25 cal equivalent to a 0.225" hole, and in the .22 cal equal to 0.196", which is 90% of the bore area.... I will be machining oblong barrel ports to match that area, and the transfer ports will be that big as well, so I will have the equivalent of 90% bore area porting throughout.... I made a new valve housing from aluminum, with a 1/2" ID, and incorporated a conical valve spring to eliminate the foot long spring seat arrangement I had originally.... I can get away with this because the MRod poppet is so much smaller OD than the Disco one, it will work just fine in a 1/2" ID valve.... This has been proven many times in my BRods and other guns....
Anyways, I've made a start on a major update, with the goal of shooting the new, heavier pellets at the same velocity I had before.... I hope to incorporate an SSG to increase the efficiency, and I'm hoping that the MRod poppet won't be any harder to cock than what I had before, maybe even easier.... I guess we'll find out as the rebuild progresses....
Bob
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Today I worked on the barrels.... I had used a brass thimble with the port in it to provide the mounting stub for the magazine, and there was an adjusting screw in the transfer port (like an MRod) which I am doing away with completely.... Since the transfer ports are going to be much larger, and 3/8" OD, the thimble idea wasn't workable, so I shortened the barrels 1/2" and profiled the outside to fit in the receiver and provide the magazine stub.... Then I used my chamber reamers to deepen the chamber to fit the longer pellets, when loaded past the longer barrel ports required.... I am pleased with the way that went, and a bit lucky that there was enough room for the larger transfer port OD in the receiver.... The next step is to mill out the receiver for the larger port and cut the O-ring grooves inside the barrels and machine the barrel ports and TP sealing fact into them.... We are full in the Motel this weekend, so shop time is getting harder to find.... ::)
Bob
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Dang work going to ruin everything LOl. Are you going to convert the valve in this one also to Art/Sikes?
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I shouldn't need an SS Valve is this regulated version, but we'll see how hard it is to cock.... that will be the governing factor.... but I do plan to fit an SSG....
I got the transfer port passage in the receiver opened up to 3/8" to match the hole in the tube and the new valve....
(http://i378.photobucket.com/albums/oo221/rsterne/Hayabusa%20PCP/Receiver%20and%20Tube%20Ports_zpsvrit1t8q.jpg) (http://s378.photobucket.com/user/rsterne/media/Hayabusa%20PCP/Receiver%20and%20Tube%20Ports_zpsvrit1t8q.jpg.html)
Then I worked on positioning the barrels and marking and machining the barrel ports and the 3/8" flats that the end of the TP will seal against.... I had to rotate the .25 cal barrel because the bolt was binding slightly in it's original orientation (you can see the old set-screw flat on the side of it).... The .25 cal barrel is on top, and the .22 cal on the bottom, in the photo....
(http://i378.photobucket.com/albums/oo221/rsterne/Hayabusa%20PCP/Barrel%20Ports_zpsizv7uhrx.jpg) (http://s378.photobucket.com/user/rsterne/media/Hayabusa%20PCP/Barrel%20Ports_zpsizv7uhrx.jpg.html)
The outside of the barrels is identical, except for the stub that the magazine locates on.... The .25 cal stub is 1/2" OD and sticks out 0.060" into the mag. well in the receiver.... while the .22 cal one is turned down to 7/16" OD and projects 0.160" because the .22 cal mag. is 0.100" thinner.... There is a spacer that bolts into the receiver to take up that extra 0.100" in the front of the mag. well.... I also machined the O-ring grooves inside the barrels for the bolts to seal in.... and I checked the loading depths of the pellets with my existing bolts and the probe length is just fine, so all I have to do is thin the probes down by 0.016" each to give more area around them for flow....
I still have to make the 3/8" OD Teflon transfer ports, the .22 cal will have a slightly smaller ID, and I will probably taper the inside just to avoid a step at the valve end.... The barrel ports are oblong, they are about 77% of caliber wide, so that they won't damage the pellets on loading.... and are more than a caliber long, to have slightly more area than the chamber area around the bolt probe.... Other ports will match in area as well.... about 90% of caliber, which is all you can use unless you make a retracting bolt....
Bob
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I made the .25 cal transfer port today and reassembled the Hayabusa Mk.I with the original QB hammer spring and RVA.... I thought it was regulated at about 1900 psi, BUT IT TURNS OUT IT IS ONLY AT 1750 PSI, and here are the results with the 25.4 gr. JB Kings and 34.0 gr. JSB Heavies....
(http://i378.photobucket.com/albums/oo221/rsterne/Hayabusa%20PCP/Hayabusa%2025%20Plateaus%201_zps89yz9whu.jpg) (http://s378.photobucket.com/user/rsterne/media/Hayabusa%20PCP/Hayabusa%2025%20Plateaus%201_zps89yz9whu.jpg.html)
I gained about 40 fps with the larger porting with the 25.4 gr. pellets, so it was well worth doing.... The QB Spring just touches the inside of the hammer at 3 turns out from maximum, so I should be able to make an effective SSG using that spring on a guide with some preload and a bit of a gap.... That will be the next project.... The cocking force on the knee of the curve is high but acceptable.... with an SSG it will be more constant and "feel" lighter because all the load won't come on at the end of the stroke.... I may use a longer lighter spring, I'll see what I have around that might be even better than the QB spring....
Bob
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I built an SSG for my Hayabusa Mk.I today.... I used a 7/16" x 20 NF hex head bolt 1" long for the gap adjuster, and drilled it out to 13/64" for a 3/16" steel guide rod.... The rod I threaded both ends to 10-32 thread, on the inside I loctited on a nut and turned it down to 0.35" OD with a rounded end to fit inside the hammer, and then slid on a 1/4" plastic tube 1-1/4" long for a spring guide spacer, and at the other end an O-ring bumper and two 10-32 nuts locked against each other for preload adjustment.... The mount was turned from a piece of 1" OD 2024-T2 barstock, drilled and tapped for the adjusting bolt.... The hammer spring is 3.0" long x 0.36"D x 0.049" wire, with a rate of 13 lb/in.... Here is what it looks like....
(http://i378.photobucket.com/albums/oo221/rsterne/Hayabusa%20PCP/SSG%20Cartridge_zpsrgq5dkeu.jpg) (http://s378.photobucket.com/user/rsterne/media/Hayabusa%20PCP/SSG%20Cartridge_zpsrgq5dkeu.jpg.html)
I set the preload to 0.40" (5 lbs.), adjusted the SSG gap so that the end of the guide just cleared the inside of the hammer for my "Zero" gap point, and then shot a 34.1 gr. King through the Chrony at each gap adjustment to 8 turns of gap (0.40").... I then chose three settings on the knee of the curve and shot one 8-shot group at each setting, recording the starting and ending pressure on the 22 CI bottle (using a digital gauge) for each string so that I could calculate the efficiency.... Here are those results....
(http://i378.photobucket.com/albums/oo221/rsterne/Hayabusa%20PCP/Hayabusa%2025%20Plateaus%202_zpsqrejzn6c.jpg) (http://s378.photobucket.com/user/rsterne/media/Hayabusa%20PCP/Hayabusa%2025%20Plateaus%202_zpsqrejzn6c.jpg.html)
I then kept on shooting the gun down until I saw the plenum pressure gauge on the downstream side of the regulator start to move, checked the velocity and it was still the same, and actually shot down another 150 psi without any velocity loss with 5 turns of gap.... By that time I was down to 1600 psi, so I topped up the bottle until I saw no more movement on the plenum gauge, and determined that the regulator setpoint is only about 1750 psi, not the 1900 psi I thought previously.... That explains why the velocity plateau was only 960-970 psi, when I expected a bit more....
You will note that the FPE/CI increases from just 1.01 at 945 fps to 1.23 at 930 fps and 1.48 FPE/CI at 895 fps.... I want to raise that entire range upwards by about 30 fps, so I plan to drain the bottle and reset the regulator to 1900 psi.... I should still have lots of adjustment using this same hammer spring.... and the cocking effort is a bit less than previously without the SSG.... One thing I noticed during the 8-shot strings was that the ES was quite low on the knee.... 12 fps on the 945 fps string and only 6 fps on the 930 fps string, but increased to 18 fps on the 895 fps string.... It is not uncommon to see the ES increase when the SSG gap gets larger, and you start to get down on the downslope part of the velocity curve.... all the more reason to run a regulated PCP right on the knee of the curve....
Bob
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Nice work on the SSG Bob. Gives me an idea why I’m getting inconsistent velocities from one of my .25 builds . I’m going to add a plastic sleeve to the spring guide .😀
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The plastic sleeve only keeps the spring straighter.... You could use a 1/4" diameter steel rod and get the same results.... but the guide would then be 77% heavier.... I made the sleeve about the same length as the spring at coil bind....
The biggest reason for inconsistent shot-to-shot velocities in a PCP is that any small variation in hammer strike can cause a difference in the valve lift and dwell.... especially when the pressure is higher than where the velocity peaks.... This occurs in an unregulated PCP between the fill pressure and the peak velocity.... and in a regulated PCP that is tuned on the downslope of the curve.... The velocity is much more stable, shot-to-shot, on the back half (low pressure side) of the bell curve in an unregulated PCP, which is like a regulated gun tuned up on or near the plateau.... It is unfortunate things work out this way, because it means that efficient tunes tend towards a higher ES.... ::)
Bob
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I confirmed that the setpoint was only 1750 psi, so I bumped up the regulator to 1900 psi today.... I used my "tiny" tank to test for the plateau curve and check for leaks, and here are the results....
(http://i378.photobucket.com/albums/oo221/rsterne/Hayabusa%20PCP/Hayabusa%2025%20Plateaus%203_zpshm7d8kyt.jpg) (http://s378.photobucket.com/user/rsterne/media/Hayabusa%20PCP/Hayabusa%2025%20Plateaus%203_zpshm7d8kyt.jpg.html)
With the higher setpoint, I can barely reach the plateau with zero SSG gap with the 34.1 gr. King Heavies, which is exactly the way I like it.... This places my usable tune at a couple of turns of gap, and I like keeping the gap small for better consistency in the hammer strike.... With the 25.4 gr. Kings, the plateau starts at about 2 turns of gap, with the mid 900s occurring at about 5 turns out.... Using those pellets is only a secondary consideration, the whole point of this series of mods was to increase the power to make the 34.1 gr. Heavies into the mid 900s, which I have now done.... After I replace the 22 CI tank tomorrow, I will do some efficiency testing to compare the higher setpoint to the old one.... I hope to also do some testing with the .22 cal barrel fitted....
Bob
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I put the .22 cal upper on the gun today and plotted out the plateau, knee and downslope curve with the 18.1 gr. JSB Heavies and the 25.4 gr. JSB Redesigned Monsters.... Here are the results....
(http://i378.photobucket.com/albums/oo221/rsterne/Hayabusa%20PCP/Hayabusa%2022%20Plateaus%201_zpslhmpacmf.jpg) (http://s378.photobucket.com/user/rsterne/media/Hayabusa%20PCP/Hayabusa%2022%20Plateaus%201_zpslhmpacmf.jpg.html)
Running wide open the gun is now capable of driving the 18.1 gr. Heavies Supersonic.... :o
I installed the 22 CI bottle (360 cc) and tested some SSG gap settings on the knee of the curve and settled on 5 turns out as the best compromise with the 25.4 gr. Monsters.... I got an average of 940 fps (50 FPE) at an efficiency of 1.04 FPE/CI, and I was able to shoot all the way down to 1600 psi before the velocity dropped below 930 fps.... That is 300 psi below the setpoint, which should give me a total of about 45 shots per fill at 50 FPE.... I think that pretty decent for a .22 cal at that power level which is basically a detuned .25 cal, but I think that using a bit lighter hammer might improve the efficiency even further, while reducing the SSG gap somewhat, which is desireable.... If I wanted to use the 18.1 gr. Heavies I could back out the SSG to about 6.5-7 turns of gap to shoot them in the mid 900s.... but I would get way more shots if I dropped the regulator setpoint to below 1600 psi.... I'll reinstall the .25 cal upper and do a similar test with the 34 gr. King Heavies soon....
Bob
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I reinstalled the .25 cal. barrel on my Hayabusa Mk.I. today, set the SSG at 2 turns of gap, and took 8 shots to check the efficiency.... The average velocity was 953 fps, with a high of 955 and a low of 948 (0.8% ES) for 69 FPE and a drop in the 22 CI tank of 320 psi.... This works out to 1.13 FPE/CI, which is OK for the power level attained.... By comparison my unregulated Hatsan AT-44 S10 Long with the same pellets had the same average velocity, but the ES was twice as great at 1.7%, for 9 shots from 2750 psi down to 2250, an efficiency of 1.25 FPE/CI.... As is typical for a regulated PCP at high power, you give up a bit of efficiency (because of the lower pressure, in this case 1900 psi).... but get a lower ES and gain in shot count.... The gun as configured should be about 27 shots to the setpoint, and possibly about 35 down to 1600 psi, which is where the .22 cal velocity started to drop off.... Relative to the caliber, the tunes are similar, 50 FPE in .22 cal and 70 FPE in .25 cal.... I think this is a good place to leave the Mk.I. until I get a chance to shoot it at distance and see how it likes the new heavier pellets....
Bob
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Now that I have some shop time with no major projects on the go, I decided it was time to revisit the Hayabusa Mk.3 version, which is a .410 shotgun and .457 rifle.... Ever since the SS Valve came on the scene, I have been itching to make one for this big-bore, as it REALLY needs it.... The gun uses a 1/2 lb. hammer with 2" of travel, and it takes over 28 lbs. of cocking force.... If there was ever a gun that needs a reduction in hammer strike and cocking force, this is it.... ::)
I pulled the gun completely apart, had a look at what I was dealing with, and started with the new valve internals.... I scaled up my SS valve to use a PEEK poppet with a 1/2" big end and a 5/16" small end.... The thimble is turned from a piece of 5/8" 1144 Stressproof, and after drilling and then finishing the bores with end mills and sandpaper, I turned the outside down to 9/16" at the back and 3/8" at the front.... I turned the poppet from a piece of 1/2" PEEK rod, drilled it for a 1/8" stem and a 0.040" bypass vent, and pressed it onto the valve stem with some Loctite 638 for good measure.... The last step was to turn the O-ring grooves, working gradually deeper until I had a nice slide fit and the valve spring would reset the poppet.... Here is what it looks like, along with the original parts....
(http://i378.photobucket.com/albums/oo221/rsterne/Hayabusa%20PCP/Huyabusa%20457%20SS%20Valve%20Internals_zps5qpcyigd.jpg) (http://s378.photobucket.com/user/rsterne/media/Hayabusa%20PCP/Huyabusa%20457%20SS%20Valve%20Internals_zps5qpcyigd.jpg.html)
The original valve was just a rear half, there is a long pedestal inside the reservoir for a spring seat.... not an elegant arrangement, but it did unshroud the poppet completely.... I will have to make a complete valve body for the SS Valve, because it has to mount the thimble.... The exhaust port is 3/8" (0.375") and the throat is 13/32" (0.406"), and the original poppet OD was 0.453".... At 3600 psi, the force holding the valve closed was 580 lbs.... With the new SS valve, it will only be 280 lbs., less than half.... I will use either 27/64" (0.422") or a full 7/16" (0.437") for the throat in the new valve, as either will work with the new larger (0.500") poppet.... Next up is to figure out how to make a new valve body to mount everything inside....
Bob
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I continued working on the valve yesterday and today.... I got the body bored out inside, with a shoulder for the thimble mounting wheel, and a groove for the retaining circlip.... Then I made the perforated wheel that mounts the thimble.... Here are those parts....
(http://i378.photobucket.com/albums/oo221/rsterne/Hayabusa%20PCP/457%20Valve%20Front_zpsju5gsbay.jpg) (http://s378.photobucket.com/user/rsterne/media/Hayabusa%20PCP/457%20Valve%20Front_zpsju5gsbay.jpg.html)
The total area of the eight 3/16" holes is twice that of the 3/8" transfer port.... The valve is bored out to nearly 7/8", which gives an annular gap of 0.150" around the thimble, so that area is three times the area of the transfer port.... You can see the 1/16" vent hole in the thimble mounting screw.... As usual for my SS valves, there is a collar on that screw so that I can tighten it against the end of the thimble without having the thimble mounted rigidly to the wheel.... In fact, the hole is oversize, so that the thimble can align itself with the poppet to prevent any binding....
I also drilled and tapped the 10-32 mounting holes, machined the O-ring groove, and milled out the huge exhaust port.... I machined this a bit differently than I have done before, and I really like the way it turned out.... I did a 1/2" flat for the transfer port, and then ran a 3/8" ball end mill in until the center was just past the flat.... I then used a 5/16" end mill, tilted on a 25 deg. angle towards the valve seat, and milled through to the throat.... I moved the mill sideways in the hole until the width of the port was the full 3/8", and fore and aft until it just touched the front and back of the 3/8" hole.... I then removed the valve from the milling attachment, and finished it with a spherical burr on my Dremel.... I recently purchased some adjustable hole gauges, and I set the diameter to 3/8", and after grinding away any steps inside the port, I kept checking it and grinding the restrictions until the exhaust port was at least 3/8" everywhere.... Here is a photo of the valve with the gauge in place, and the thimble mounted in the perforated wheel....
(http://i378.photobucket.com/albums/oo221/rsterne/Hayabusa%20PCP/457%20Valve%20Parts_zps60rcwahp.jpg) (http://s378.photobucket.com/user/rsterne/media/Hayabusa%20PCP/457%20Valve%20Parts_zps60rcwahp.jpg.html)
This photo shows how massive the exhaust port is, with the adjustable gauge beside the valve, for those of you that have never seen one....
(http://i378.photobucket.com/albums/oo221/rsterne/Hayabusa%20PCP/457%20Valve%20Port_zpsdpqizakg.jpg) (http://s378.photobucket.com/user/rsterne/media/Hayabusa%20PCP/457%20Valve%20Port_zpsdpqizakg.jpg.html)
The main tube had a bit of rust on it, so I polished it down and re-blued it with Van's Cold Blue.... I then lapped the poppet to the seat until it appeared to seal, and then reassembled the main tube, using my "mini-tank" instead of the 500 cc bottle, in case there are any leaks.... I filled it to 3000 psi, and it appears to be holding.... I will leave it overnight before working on a new hammer and spring, because I think (hope) the old one will be way to much for this replacement SS valve....
Bob
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I made an SSG assembly yesterday, using two 2.5" long x 0.48" diam. springs made from 0.051" wire.... They have a rate of 10 lb/in, but when you stack two inline that drops in half, to just 5 lb/in.... I had to make a spacer that runs on the guide rod to keep the ends aligned, and after the springs were set, they lost 0.1", but the spacer replaced that, so the total spring length was 5.0".... I set the preload to only 1/2" (2.5 lbs.) and assembled the gun, with the adjuster backed off all the way, so the 2" hammer stroke was reduced to only about 1.25".... The resulting roar brought my wife out to the shop to see if I was OK, and I just explained to her that the machine gun she heard was an example of runaway hammer bounce.... :o
Step two was to make an MDS hammer to the same dimensions as the steel one, which reduced the weight from 165 gr (237 gr. with the original guide and cocking handle) to just 24gr. plus the cocking handle, so the hammer dropped to 48 gr. or just 20% of its original weight.... At zero gap the gun fired with an anemic "pop", so I knew I was going to have to end up some place in the middle.... So much for yesterday.... ::) …. The really exciting part is that the cocking force is a fraction of what it used to be.... This SS Valve REALLY works.... 8)
This morning I machined away as much of the original steel hammer as I could, and at the same time moved the cocking notch back 1/2" to reduce the hammer stroke to 1.5".... The hammer was down to 82 gr. (half what it started out) plus the cocking handle, for a total of 106 gr.... The gun was beginning to show that it had a chance of being tuned, and I obtained velocity readings just under 820 fps with the 336 gr. Lee FN bullet, which works out to 500 FPE, using a 3600 psi fill of the main tube and mini-tank, which is about 145 cc (less than 0.3 cc/FPE).... That is a pretty anemic plenum volume for a 500 FPE gun, but shows I am likely on track to match the 550 FPE I had before, when I have the 500 cc bottle in place, with 640 cc available to keep the pressure up during the shot cycle....
I ran into a problem when I dropped the action into the stock, the end of the SSG, while cocking, hit the cheekpiece, and wouldn't allow me to cock the gun.... I pulled it out and shortened the guide rod, increasing the preload to 1", and moved the sear notch back on the hammer another 1/4", so I now only had 1.25" of hammer stroke.... This allowed the end of the guide to JUST clear the stock.... Here are the new parts at this stage....
(http://i378.photobucket.com/albums/oo221/rsterne/Hayabusa%20PCP/457%20Modified%20Hammer%20and%20SSG_zpsij0e90y5.jpg) (http://s378.photobucket.com/user/rsterne/media/Hayabusa%20PCP/457%20Modified%20Hammer%20and%20SSG_zpsij0e90y5.jpg.html)
With this set of parts, I was still getting machine-gunning with 1/4" of gap in the SSG, really loud inefficient shots with 3/8" of gap, and workable shots with 1/2" of gap.... The velocity was around 815 fps, with stellar efficiency of about 1.35 FPE/CI.... pretty remarkable at just under 500 FPE.... With the 216 gr. Lee bullet the gun was shooting just over 950 fps at that tune.... Now remember that I had 1" of preload on the spring, and with 1/2" of gap that means the spring was only being compressed a total of 1.75" when fully cocked.... That works out to about 9 lbs. of force, with a 3/4" effective hammer stroke on a 106 gr. hammer.... Yet I was getting similar power (other than the undersized plenum, which was costing me about 10% in FPE) to what I had originally with a 2" stroke on a 237 gr. hammer that took 28 lbs. to cock it.... WOW !!! you can really see what an SS valve can do to reduce the cocking force, even on a big-bore.... 8)
I wasn't happy with the 1/2" of gap in the SSG, so I decided to try the MDS hammer again, with the full 2" of stroke and 1" of preload in the SSG.... With the gap set to 1/4" I got the gun to fire properly, but the SSG rod was hitting the stock again.... So, I moved the cocking notch back 1/2" (1.5" stroke) and increased the preload to 1.25", and I got just one "proper" shot, with 1/2 turn of gap on the SSG.... I am learning that this particular SS Valve is acting like a Cothran valve, it is either working or not, with no bell curve.... at least that is how it appears right now.... Then things went south.... The poppet failed, the stem started sliding back in the PEEK, so my testing is over for today, and I have to rebuild the valve.... >:(
I am delighted with how easy the valve is to open, perhaps too easy.... I am not happy with the cycling, which appears to have no bell-curve, not the best for an unregulated PCP, as I won't be able to tune it for a bell-curve.... I think the only solution is that when I rebuild the valve to increase the diameter of the front portion of the poppet.... This will make the valve harder to open, but hopefully will make it tuneable.... I just hope that my current hammer can be made to work after I change the valve.... Plus, I have to figure out why the stem backed out, I think it is likely because of the air pressure in the center chamber, between the O-rings, may have worked its way around and be pushing on the front end of the stem (with a force of about 40 lbs. at 3600 psi).... The autopsy showed the stem had slid back about 1/4".... ::)
Bob
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Wish to stop the jack hammering bounce ? ...... Jet DOWN the cobra chamber & get the free flight gap under .100"
JMO of course
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but first of all, I have to get in the ballpark with the hammer strike.... Way too light or way too heavy won't cut it, just like with a conventional valve.... except the margin of error is less with a valve that is this easy to open, yet expected to deliver over 500 FPE....
Incidently, the jack hammering bounce was far worse with a smaller SSG gap, and reduced as I increased the gap.... indicative of too much hammer strike, IMO....
Bob
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Incidently, the jack hammering bounce was far worse with a smaller SSG gap, and reduced as I increased the gap.... indicative of too much hammer strike, IMO....
Bob
Or the balance of valves calibration has it "too easy to open" :o
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Yep, I agree, as I stated above, the plan is to increase the diameter of the front of the poppet to 11/32" or even 3/8" from the 5/16" it is currently.... The rear is, of course, 1/2".... All the previous SS Valves I built (from scratch) use a 1/4" front end on a 3/8" back end (67%) and work great.... This valve is only 63%.... I favoured "easy to open" because of the HUGE cocking force required on the conventional version.... I certainly got my wish.... ::)
It may now be a case of "two steps forward, then one step back".... ;)
Bob
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Well, it has been an interesting few days.... I rebuilt the SS valve with a 3/8" small end on the poppet instead of 5/16".... I bored out the thimble, and made a new PEEK poppet.... I used a 0.040" vent parallel to the stem, and still the 0.062" vent at the front.... The poppet looks the same as before, just a larger front end....
I tested it with the 107 gr. hammer, which has 1.25" of stroke, and it popped, but that is about all.... Now remember, that with the 5/16" front end on the SS valve, I needed to have 12 turns of gap with this setup.... :o …. That shows how much the diameter of the balance chamber changes the required hammer strike.... I changed the 0.051" wire spring to a 0.055", and eventually to a 0.059", and with 1.25" of preload and zero gap on the SSG I managed to get into the 700's with a 336 gr. bullet.... The valve was stable and showed a pretty linear response to SSG gap, so I knew it could be made to work, but I needed more hammer strike....
I made a new hammer with 1.5" of stroke, that weighed 140 gr. with the cocking handle.... With the two 0.059" springs, set at 1" of preload, I hit 810 fps with just the plenum and tiny tank, a total volume of 155 cc (less than 1/3 cc per FPE)…. As the gun was finally working properly, I stripped it down and installed the 500 cc, 250 bar tank, topped up my SCBA tank, and filled the gun.... Yay, no leaks.... 8)
I now hit 842 fps (529 FPE), which was close to the highest I have ever had, and faster than I knew I could get with any kind of efficiency and without a Korean Cliff for a shot string.... It is pretty interesting that the extra volume gained me over 30 fps and 40 FPE.... That really shows how much a small plenum hurts performance.... I backed out the SSG gap a turn at a time, and at 4 turns out I got three shots of 827, 820 and 810 fps with the 336 gr. Lee FN, which works out to an average of 819 fps (501 FPE), using 500 psi of air from a 3600 psi fill.... The total volume of air in this gun is 640 cc (bottle plus plenum), and the ports between them are larger than the exhaust port, so it all can feed the valve.... That works out to 1.12 FPE/CI.... which is pretty incredible for a 500 FPE gun.... 8)
I dropped back to the 0.055" springs, but couldn't get over 800 fps, so I settled on the two 0.059" wire springs, but reduced the preload to 0.8".... That required 2 turns less gap to get exactly the same velocity as before.... I am running out of bullets to shoot full strings, but here are the results, tuned like this.... Basically, the first 3 shots are right at the top of the bell curve, and I couldn't be happier....
336 gr. Lee FN.... 3 shots using 500 psi total.... 824, 819 and 814, average = 819 fps (501 FPE) at an ES of just 10 fps (1.2%) at 1.12 FPE/CI....
216 gr. Lee RN.... I tried just one shot, it was 965 fps (447 FPE)….
I had one other modification I needed to make.... When I built this gun, 4 years or so ago, the bolt slot ended with a thin web at the back of the receiver.... A couple of years ago, when chatting with Lloyd, he mentioned that the gun fired accidently with the bolt open could break through such an arrangement, because the bolt, being accelerated backwards, acts like a hammer, and can exert incredible force if it stops suddenly.... I made up a circle of 1/4" aluminum, and retained it on the back of the receiver with three SHCSs tapped into the back.... I also added an O-ring at the back of the bolt channel, to provide a bit of a cushion for the bolt, should the gun ever be fired with the bolt not locked down.... I feel confident that this accident waiting to happen (and one I missed the potential of) is now a non-issue.... Here is a photo of the Action showing the new rear bolt stop and the new SSG....
(http://i378.photobucket.com/albums/oo221/rsterne/Hayabusa%20PCP/457%20Hayabusa%20SSG%20Bolt%20Stop_zpssu2kjion.jpg) (http://s378.photobucket.com/user/rsterne/media/Hayabusa%20PCP/457%20Hayabusa%20SSG%20Bolt%20Stop_zpssu2kjion.jpg.html)
Although I don't know what a full string would be, tuned the way it is, three shots at 500 FPE within a 10 fps ES will certainly suffice for any deer hunting.... My son has applied for a Limited Entry Permit for our area, and I hope that someday he will have a chance to give this PCP the ultimate test.... I checked the trajectory using ChairGun, and sighted at 50 yards, the POI is within 1" out to 60 yards.... or I can sight it in at 64 yards and have a 4" KZ out to 75 yards.... I think the 50 yd. zero makes the most sense....
Here is a summary of the hammer cocking force with the three arrangements I have used on this gun....
Conventional Valve.... 237 gr. hammer with 2.0" stroke, cocking force over 28 lbs.... ie almost impossible to cock....
SS Valve with 3/8" front chamber.... 140 gr. hammer with 1.4" stroke, cocking force under 19 lbs.... quite comfortable and linear....
SS Valve with 5/16" front chamber.... 107 gr. hammer with 0.7" stroke, cocking force about 9 lbs.... but nearly impossible to control the hammer bounce....
If anyone has any doubts about what the SS Valve can do to reduce the cocking force.... you can put those doubts to rest.... ::)
Additional Note: I let the gun sit, filled with air for 3 weeks (pressure still 3200 psi), topped it up to 3600, and tested the velocity to see if there was any "stiction" problem with the SS Valve.... I shot 4 shots using the 216 gr. bullet (topping up between shots), and the velocities were 962, 973, 978 and 973 fps.... With less than a 2% loss on the first shot, it would appear there is no significant stiction problem with this SS Valve.... 8)
Bob
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Bob
That sounds like a BIG BOOMER, I hope you have lots of lead handy, as you are going to need it @ 336gr per shot. ;) LoL,
I got a dumb question, I am going to throw out at you,
What do you mean via this phrase, "without a Korean Cliff for a shot string".
I don't have a clue what it means, Sorry. ::)
Thanks,
Don
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A lot of the Korean PCPs are tuned so that the first shot is the fastest, and every shot after that drops in velocity as the pressure falls.... It also wastes a lot of air.... It was so common that a PCP tuned that way was said to have the "Korean Cliff" tune, because it was like falling off a cliff.... Unfortunately, more and more PCPs are tuned that way now, so that the manufacturer can claim the highest possible velocity, even if it's only for one shot.... Crosman ruined the Discovery by fitting a stronger hammer spring a few years ago to increase the velocity, at the expense of about half the shot count, and a declining shot string.... It is very common amongst Big Bore airguns, even though you only have to give up a few fps to get 2 equal shots or a short bell curve with a very small ES....
Bob
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Thanks Bob
You have educated me some more, ;)
Thank you,
Don
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Well, I dragged out all the parts for the Hayabusa Mk.II today.... Wow, do I have a lot of parts for that gun!.... I have three receivers that all fit the same lower.... One accepts both .224 cal and .257 cal TJ barrels, and I have the bolts to go with them.... One has a 7 mm TJ's barrel, set up to tension and index it, with a thimble.... I have a third receiver set up for .308 and .357 cal LW barrels, again with interchangeable bolts for the two calibers.... I have two complete sets of valves, hammers and springs that all fit the same lower tube.... The .224 and .257 use a 115 gr. hammer with 1.2" of stroke, and the valve has a 0.281" throat and 0.250" ports, and both barrels have oblong porting to full bore area.... The 7 mm, .308 and .357 use a 145 gr. hammer with 1.45" of travel, and the valve has a 0.328" throat and 0.281" ports.... The 7 mm has an oblong barrel port giving full area, the .308 has a slightly oblong one, and the .357 is just drilled, so all three have a port size of 0.281"....
The lower consists of a 1" OD x 0.065" wall 4130 CrMoly tube, with a reversed tank block, and a 3000 psi, 22CI bottle mounted under it.... It uses the same MRod trigger assembly and stock as the Mk.I and Mk.III Hayabusas…. Yes, I only have one trigger and stock to cover a total of 9 barrels and three versions.... ::) …. My plan is to make an SS Valve of appropriate size for the .357 cal, and then step down the transfer ports for all the other calibers.... That way, I can have 5 different calibers without having to degas and pull the valve.... It should only require changing the hammer spring / SSG guide assembly.... or at most the hammer as well.... when I swap out the various uppers.... With a bit of luck, it may only require readjustment of the SSG gap.... ;)
With what I have learned from my previous SS valve, I plan to make this one with a 7/16" poppet with a 5/16" front section.... At 71%, that is halfway between the 67% of the valves that fit my 6 mm & .257 PCPs I built last year, and the 75% of the .457 I just finished.... I think that should be about perfect.... I will have to make a slightly scaled down version of the valve I just made for the .457, which fit in a 0.990" ID tube.... as this tube is 0.870" ID.... It will be a challenge to fit a 1/2" OD thimble in there, but I think I can do it.... If so, I can use a valve with a 0.375" throat, which is large enough to feed nearly caliber sized porting on the .357.... :o
Bob
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Now that I have my backstop rebuilt, I decided to finish up the tuning on the .457 Hayabusa with the new SS Valve.... I connected it up to my SCBA tank, with a digital gauge in between, so that I could monitor the fill pressure and pressure drop per shot accurately.... I then tried various SSG Gap settings with both the 336 gr. Lee FN and the 216 gr. Lee RN, plus a couple of shots with a their 143 gr. Roundball…. Here are the results....
(http://i378.photobucket.com/albums/oo221/rsterne/Hayabusa%20PCP/Hayabusa%20457%20SSG%20Velocity_zpsm1viicla.jpg) (http://s378.photobucket.com/user/rsterne/media/Hayabusa%20PCP/Hayabusa%20457%20SSG%20Velocity_zpsm1viicla.jpg.html)
I then tried a few shot strings at various settings, stopping the string when it fell 4% below the peak velocity....
(http://i378.photobucket.com/albums/oo221/rsterne/Hayabusa%20PCP/Hayabusa%20457%20SSG%20Strings_zpsbfwaguwg.jpg) (http://s378.photobucket.com/user/rsterne/media/Hayabusa%20PCP/Hayabusa%20457%20SSG%20Strings_zpsbfwaguwg.jpg.html)
The velocity with the roundball was 1092 fps (379 FPE), at 2 turns of gap on the SSG.... With the same adjustment I got 956 fps (438 FPE) with the 216 gr. at 0.96 FPE/CI.... The 336 gr. hit 819 fps (501 FPE) at 1.06 FPE/CI.... Tuned that way, I got a 4-shot string with the first 3 shots within a 1% ES (8 fps)…. When I turned down the power the efficiency hit levels I have never seen before in a Big Bore.... At 8 turns of gap with the 216 gr. I got a 4-shot string averaging 919 fps (405 FPE) at 1.19 FPE/CI.... At 6 turns of gap with the 336 gr. I got 6 shots averaging 770 fps (443 FPE) at 1.27 FPE/CI, and the first 5 shots were within a 7 fps (1%) ES....
I am extremely pleased with the way this gun turned out.... I lost a few fps at the top end, but I never tune my guns that way because they are super loud and complete air hogs when you do.... I have mounted a Fitco 2-7 x 32 Scope on it, and I plan to sight it in at 50 yards.... Now if my son gets drawn for a Limited Entry Doe Tag, we'll be all set.... We see plenty of does close up when Grouse hunting, but rarely see a buck and when we do they are never in airgun range.... I hope we'll find out what she will do this fall, using the 336 gr. at 500 FPE....
Bob
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Here is the completed .457 rifle, along with the .410 shotgun upper which fits the same lower assembly....
(http://i378.photobucket.com/albums/oo221/rsterne/Hayabusa%20PCP/Hayabusa%20410%20amp%20457%20SS%20amp%20SSG_zpsq6h4zmf5.jpg) (http://s378.photobucket.com/user/rsterne/media/Hayabusa%20PCP/Hayabusa%20410%20amp%20457%20SS%20amp%20SSG_zpsq6h4zmf5.jpg.html)
The rifle weighs 10.5 lbs. including the scope.... Tank is a 500 cc, 250 bar tank from England, total reservoir capacity is 640 cc (39 CI)….
Bob
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I mounted the .410 shotgun upper on the Hayabusa today to see what it does with the new SS Valve.... Here is the test load, three 36 cal roundball that weighs a total of 204 gr.... The wad is intended for 1/2 oz. of lead shot (219 gr.), so it should give a pretty good indication of the velocity.... The case is a shortened 2.5" all brass case with the primer pocket drilled out to 3/8", the same size as all the other ports....
(http://i378.photobucket.com/albums/oo221/rsterne/Hayabusa%20PCP/410%20Test%20Load_zpss1vtp7se.jpg) (http://s378.photobucket.com/user/rsterne/media/Hayabusa%20PCP/410%20Test%20Load_zpss1vtp7se.jpg.html)
The Chrony is a bit reluctant to measure the velocity, throwing low velocity errors (eg. 550 fps) if the wad cup separates early, but discarding the obviously wrong readings I got a three shot average of 850 fps (846, 849, 856)…. That is actually a bit better than I got before, so I'm very pleased.... It works out to 327 FPE, just about what I expected, based on the ratio of bore volumes of the .410 shotgun and .457 rifle....
Bob
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Thanks Bob
I also love the 410 bore for quail/rabbitshooting, 8)
What does it do with shot loads, enough power for Quail/Cottontails etc.
Tia,
Don
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No idea, haven't yet hunted with it.... In fact, so far I haven't even loaded a shell with shot, although I have a bag of # 7.5's here for it....
Bob
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I’m really impressed with the shotgun Bob . Here in Ontario we can only hunt turkey with shotgun . I’m really contemplating converting one of my Cothran valved guns . Finding the right barrel is going to be tough .
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I don't know if a 1/4" port would deliver enough air, even for a .410.... My valve and ports are 3/8"....
Bob