GTA
All Springer/NP/PCP Air Gun Discussion General => "Bob and Lloyds Workshop" => Topic started by: rsterne on October 12, 2012, 08:43:54 PM
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I started work on the internal parts for my .25 cal Disco Pumper today.... It will use the MRod barrel and Disco breech I mated up the other day, plus an extended Disco valve with a check valve built in just ahead of the gauge port.... The valve extension will include a gauge mount for a 1500 psi gauge.... Here is the piston and the front mounting block to fit a Benjamin 392 linkage into the Disco....
(http://i378.photobucket.com/albums/oo221/rsterne/Millenium%20Pumper/DiscoPumperLinkageClosed.jpg)
There will be a barrel band mounted on the stub of the front block which projects 3/8" ahead of the shortened Disco tube.... The barrel band will be 1/8" behind the muzzle of the MRod barrel....
(http://i378.photobucket.com/albums/oo221/rsterne/Millenium%20Pumper/DiscoPumperLinkageOpen.jpg)
The next step is to cut the Disco tube to length, and machine an 8" slot in the bottom for the linkage.... and drill the hole for the front pivot pin....
Bob
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Nice little project. What is your projected fpe and # of pumps per shot? Are you expecting to get multiple shots per pumping session?
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I'm hoping to get in the 30 FPE range.... I was hoping to do that in about 10 pumps, but I have been told that is unrealistic, it will take more like 14-15.... In addition, I was originally going to use a 24" barrel, but settled on an MRod 20" for this protptype.... Because of this I have adopted the attitude of "que sera sera".... what will be, will be....
I will have the option of adding a 20 cc auxiliary reservoir to the ~5 cc Disco valve so that I can experiment with retained air for either multiple shots, or just a few pumps to top up the pressure.... like a poor man's FX Independence....
Bob
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Sounds like an exciting project. I am exited to follow your progress. The auxiliary reservoir sounds quite promising.
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this is GREAT your on the same line as my idea. i have a love for pumpers, it will be late june before i get back to my shop. by then you'll be shooting this disco pumper. i have allready learned alot from your uber-pumper guns. THANK YOU FOR SHARING!
you are not just some guy with a dream, you also have an understanding of engineering and machine work.
not a common combination.
i just ordered a turbocad software package. lucky thing i got lots of time on my hands it's been a few years since i used a cad-cam system. by june i should have my pumper modeled and detailed. and with what i am learning from you it will be 10x further along on my 1st gun than i could have imagined. r&d is my favorite thing in life.
one more thing, i have an idea for a varriable displacement resevoir. that will increase the pressure for the BACK-UP shot. to keep the feet/sec up. it's a simple idea. a diespring and a piston in the breach w/a very small dia orifice to slow down the replacement air. i plan on a one inch dia full shroud so i will have some room under the barrel in the breach. i have not done any calc's yet but i think it could work.
mark
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Variable displacement reservoirs have been used before in retained air pumpers.... The problem I foresee is that you end up needing two reservoirs, joined as you say, by a small orifice.... In order to get good power, the reservoir feeding the valve has to be a good size, and the air has to be able to get into the valve faster than it can get out.... It becomes the same problem as a regulated PCP, where ideally you need a plenum of about 1 cc per FPE feeding the valve.... If you could figure out the mechanism, and find a place to put it, using a gas ram style die spring could possibly provide a more constant pressure than a coil spring.... Just a thought....
Bob
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wow! shooting for 30fpe in ten pumps.i must be more of a beast to pump that the benji's
still 30fpe in 15 pumps is something not to be overlooked
keep up the good work its great seeing the guns you turn out
many have inspired my builds.
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anyone ever tried this with two tubes, one for the mechanism and one as a reservoir? just curious.
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Very very very cool. Can't wait to see it finished
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anyone ever tried this with two tubes, one for the mechanism and one as a reservoir?
I "think" that is how the FX Independence works but not sure.... If I was going to go that route, I would likely put the pump underneath on a Disco, like Lloyd does with his Disco Double.... The choice of pump would depend on what pressure you wanted to run.... I understand the Benji maxes out at about 1400-1500 psi (so a Disco based pump - 3/4"ID - would be similar).... but if you used a 5/8" ID pump (like on a 13XX/2100/1400) and got the linkage stiff enough, 2000 psi should be possible without going to a multi-stage design.... The problem is that the more power you ask the gun to produce, the more air it needs.... and the more air you have to add per shot.... which means more pumping.... My Benji pump linkage in a Disco tube will deliver about 53 cc per stroke (3.2 CI) but if you shrink the tube down to 5/8" ID and keep the same 7.5" stroke, that drops to only 37 cc (2.3 CI).... Divide your expected power output in FPE by the CI per stroke, and you will get a feel for the number of strokes of the pump.... Then add more to allow for pumping losses.... subtract a bit if you can get the efficiency over 1.0 FPE/CI....
Bob
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wow! shooting for 30fpe in ten pumps.i must be more of a beast to pump that the benji's
If that's the reason that pump-pneumatics are held back, then I say design a mechanical assistance for the pump. A crank mechanism? I don't know. I'm not an engineer, but I do know it's not impossible
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yup! i was hoping you knew what i was talking about, and you do.
a single quick follow up is very humane, i use my pumpers for hunting and i can't count the number of times i needed one before i could pump-up again. that's the number one goal for my build, a large enough reservoir is the simple way. and if it is not too long (taking up pumper volume) that would be the only way to go. even if a second shot required one pump to keep the f.p.s. equal, that would be a big improvement. and a gauge is nessary. to keep track of your pumping with an over sized reservior.
mark
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I machined the Disco tube today.... cut it to length and squared the end and then machined the slot for the pump linkage....
(http://i378.photobucket.com/albums/oo221/rsterne/Millenium%20Pumper/IMG_2723.jpg)
The tube is 1/2" behind the front of the MRod barrel, and the 3/8" barrel band will fit over the stub of the aluminum front plug.... leaving the front of the barrel band 1/8" behind the muzzle.... The pivot pin is 5/8" behind the front of the tube, and the slot is 8.2" long.... The stroke is 7.6" and the piston is 6.7" from the link pin to the compression face.... That leaves the compression face 0.3" ahead of the front of the gauge hole, which leaves room for the O-ring to seal the valve....
The next step will be to make the extended front end for the valve incorporating the gauge mount and check valve.... Incidently, the front of the Disco stock comes to just behind where the spring sticks through the lever (the bump in the photo).... It will be cut just in front of the gauge, with the forestock becoming the pump handle.... Should work perfectly....
Bob
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way to go bob
mark
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Looking good.
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now your getting somehere!!
cant wait to see this finished
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I got the valve front end done today.... Here are the parts....
(http://i378.photobucket.com/albums/oo221/rsterne/Millenium%20Pumper/IMG_2728.jpg)
The extended front end incorporates a shortened check valve from a male Foster fitting.... It is held closed by a 1" long 0.020" wire spring sitting against a washer located on a shoulder inside the valve front.... I opened up the last coil of the spring to 5/16" so that it can't get past the washer.... Behind the washer is a QB hammer spring, and the location of the shoulder for the washer was chosen to provide the same force holding the valve poppet closed as on a stock Disco valve.... This was achieved by drilling progressively deeper, assembling the valve, and pushing the stem against the stem of a stock valve until they opened at the same time....
The rear (spring) chamber of the valve front is drilled to 3/8" and the front portion to 5/16".... and then a 1/8" NPT hole intersects the front part for a gauge mount.... For initial tests, I will be using a simple male to female 1/8" NPT extension to mount the 1500 psi gauge, which is located in the stock position for a Disco.... At the moment the rear portion of the valve is dead stock....The total volume as built, including the gauge mount, is ~5.5 cc.... That gives me a bore/valve volume ratio of 3:1 with the MRod barrel.... I plan on boring out the rear portion of the valve to unshroud the poppet and increase the volume by nearly 1 cc.... and to drill the throat to 1/4", thin the stem, and increase the port diameter and angle it for improved flow.... but I think I'll try it with the stock valve initially.... Then comes the fun part....
(http://i378.photobucket.com/albums/oo221/rsterne/Millenium%20Pumper/IMG_2725.jpg)
I have made a gauge mount that connects a 16 gr. thread CO2 cartridge to the valve.... It has an internal volume of just over 20cc, and is rated at 250 bar MSWP, >500 bar burst.... It installs into the mount with 3/8"-24 threads which will be either glued or soldered to seal them.... The cartridge just clears the main tube, and will live in a hollow in the stock just in front of the gauge.... It will be invisible when the pump arm is closed.... With the cartridge installed, the total valve volume will be ~27cc, and the gun would, of course, be tuned to retain air and operate like a PCP with an onboard pump to top up the pressure between shots....
I'm pretty excited to see all the parts coming together for this project.... It won't be too long before I can install the parts in the tube and try out the pump.... I still have other parts to make before the gun can be fired, however....
Bob
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houston we have lift-off
mark
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I assembled the pump today, using a stock Disco rear valve half.... and a conventional gauge mount.... Valve volume is ~ 5.5 cc and the swept volume is ~ 54 cc.... The following pressures were achieved:
5 pumps - 600 psi
10 pumps - 1100 psi
15 pumps - 1500 psi
After sitting for an hour, the pressure is still 1450 psi, which I would imagine is the effect of cooling.... I can't comment on the pumping effort as I had no stock on the gun, and it's not exactly easy to pump sitting upside down across my knees and pushing on the 1/4" wide metal pump linkage.... I would say the effort is significant but do-able.... and ergonomically shouldn't be a problem once the stock is fitted....
I'm quite pleased with these results.... I have to make the barrel band and the transfer port and a bolt, so initial testing isn't too far away.... I'm not expecting too much with the stock valve and porting, but need those results as a baseline.... I also have to modify the stock before any serious testing can be done....
Bob
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Well I couldn't wait any longer.... I made a new bolt and transfer port and threw the gun together for a few shots.... no stock, harder than heck on the hand to pump and all.... First a string with the Disco hammer spring set just off coil bind.... varying the pump numbers and recording the pressure and velocity.... I used 25.4 gr. JSB Kings....
(http://i378.photobucket.com/albums/oo221/rsterne/Millenium%20Pumper/25DiscoPumperPressure.jpg)
The gun started retaining air at over 10 pumps (1100 psi).... It delivered 490 fps (14 FPE) on 6 pumps (700 psi) and 590 fps (20 FPE) on 10 pumps (1100 psi) and peaked out at 667 fps (25 FPE) at 15 pumps (1500 psi).... To run the gun as a pump and dump, without changing to a heavier hammer spring, the most I can get is ~590 fps with 10 pumps to refill to 1100 psi....
I then started playing with the RVA (power adjuster), to find out how that affected the velocity and the pressure remaining after each shot.... It turns out that I can back the adjuster out about 3 turns and only lose 10 fps but the pressure drop for the shot is about 150 psi less, which means a big gain in efficiency....
(http://i378.photobucket.com/albums/oo221/rsterne/Millenium%20Pumper/25DiscoPumperVelocity.jpg)
At 7 turns out, I can get two shots at 590 fps (20 FPE), and still have ~350 psi remaining.... It takes 12 pumps to refill after the two shots.... or about 5-6 pumps after the first shot.... Compare that with the pump and dump, same power but 10 (easier) pumps to refill.... At 3 turns out, I get one shot at 656 fps and 7-8 pumps to refill to 1500.... with having a gauge, it is a simple matter to know when to stop pumping....
Now remember that these are preliminary results, using a stock Disco rear valve half, stock barrel port, and matching transfer port (all 0.150").... The next step is to bore out the valve and port everything out to 3/16".... While I'm at it, I have to get the stock done, this thing is killing my hand pushing on the 1/4" wide pump lever....
Bob
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Outstanding results, pretty heavy pellet also. Regards, Tom
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ever since i was a kid i wanted a pumper with 2 shots. i've always been happy with 20fpe. and a .22cal, i could see no reason that a 2 shot 20fpe .22cal would be impractical to build. the idea for a 2 shot pumper faded when i got my 1st pcp in the mid 90's. but after having it for some time i begain to realize how much i missed the simplicity of a pumper. grab it some pellets and GO OFF HUNTING no need to remember to top of the gun, no tank or pump to bring along. i'm not one to shoot 50 shots in a session but for those who do i can see your need for a pump or a tank. bob you have shown 2 times now that it is very practical to build the pellet gun i've wanted for 40yrs. THANK YOU VERY MUCH.
MARK
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Two shots at 20 FPE in .22 cal is certainly do-able.... I think my current gun, rebarreled to .22 with a bit of valve work would do it.... If you used a larger reservoir and filled from a tank or stirrup pump through a Foster (using the onboard pump just for topping off in the field) it would defintely be no problem, likely more than 2 shots if needed....
My previous .22 cal Uber-Carbine delivers two shots at about 12 FPE now, at 10 pumps per shot on a 2100/2200 pump....
Bob
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Wow this is a great build, I too am a huge fan of on board pumpers.. I would like to build one myself on the near future, I am tagging along for the ride 8)
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Nice work, really looking forward to seeing the finished product.
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Got the stock modified and fitted today....
(http://i378.photobucket.com/albums/oo221/rsterne/Millenium%20Pumper/IMG_2731.jpg)
Good ergonomics for pumping, total weight 5 lbs. 6 oz., LOA 35.5"....
Bob
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Looks very nice.
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light weight and has some very decent power
cant beat that ;)
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To someone like me with no technical knowlege of such matters I find this fascinating. Awesome job Bob. I hope the AG manufacturers are taking note of work like this. I truly hope that a manufacturer (preferably on this side of the Atlantic) would have the foresight to bring rifles like this to market. An American or Canadian springer of good quality would be a refreshing development as well. Again, thanks for sharing your talent with us Bob. BTW, what critters might you hunt once you get the rifle into hunting trim?
Scotty
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That gun looks great!!!
Great job.
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Outstanding. That thing looks ready to send to manufacturing. Better than the Benjamin 39X.
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Better than the Benjamin 39X.
That was my hope.... No soldered together parts, a steel tube instead of brass, and a breech with dovetails for a scope, for a start.... The addition of a gauge was actually a BIG plus, as now you can pump to the same pressure for each shot, and not have to waste over half the air blowing it out the barrel without it doing useful work (except making noise).... I was sold on pump and dump guns until I built this one....
Bob
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How's she shooting?
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Soon to be harder, I hope.... valve and port mods nearly done.... First tests (above) were 1 shot at 25 FPE with 7-8 pumps to refill to 1500 psi, or 2 shots at 20 FPE with 12 pumps to refill....
Bob
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Wow! Great looking gun. When are you going to start producing them for sale? ;)
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Thanks for the accolades, guys.... For those of you that don't know, I can barely find time for my own projects, so I don't make parts or guns for others.... You wouldn't want to pay for all the time I have in this anyway !!!
Bob
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Soon to be harder, I hope.... valve and port mods nearly done.... First tests (above) were 1 shot at 25 FPE with 7-8 pumps to refill to 1500 psi, or 2 shots at 20 FPE with 12 pumps to refill....
Bob
Amazing results!!!
Do you store the gun at 1500 psi, or at 1-2 pumps that is typical of pumpers?
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if it were to be mass-produced by crosman, what do you think the retail price would be? I would pay up to 400 for it off the shelf, but probably not much more than that
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I hope Crosman is watching. I hope that you get credit for it too. $
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I don't know what a Benjamin 392 sells for, but I see no reason that this gun should cost more in .22 cal.... In .25 cal, the Blue Mountain barrels are more expensive, of course.... I would think that a .22 cal version based on the Disco with a 392 pump linkage and a different piston and valve front half incorporating a check valve (and gauge mount) would be pretty straightforward to produce.... and assembly has to be easier than the soldering used in the 39Xs, IMO.... The parts count is slightly higher than a Disco, and they would have to machine a slot in the tube, and cut and slot the stock.... so I can see it costing them a bit more than a Disco to build, but less than an MRod.... The attraction to Crosman would be that they have 90% of the parts on the shelf, only a few new parts would have to be manufactured.... just the way they do sooooooooooo many of their guns....
Bob
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The last couple of days I got a chance to bore out the valve, enlarge all the ports, and add a male Foster to the gun.... Here are the photos.... First up the shortened Disco tube with the slot cut, holes for the front block, and a new hole on the left side just behind the gauge hole for the male Foster.... Also shown is the 392 linkage mounted into the front section of the Disco stock....
(http://i378.photobucket.com/albums/oo221/rsterne/Millenium%20Pumper/IMG_2738.jpg)
The next photo shows the larger ports in the barrel, breech, and the new transfer port, made from 5/16" teflon.... All the ports are 3/16" ID, up from about 0.150" stock.... Also shown is the new bolt.... Note there is no O-ring groove, it lives in the end of the MRod barrel.... Also in the photo is the piston, which now has a packing groove full of string which will be soaked in oil to keep a thin film of oil in the pump tube.... similar to the felt used in the old Crosman 140s.... I deepened the O-ring groove a few thou and changed to a 90 Durometer O-ring as the previous 70D one was failing from extruding into the slot....
(http://i378.photobucket.com/albums/oo221/rsterne/Millenium%20Pumper/IMG_2741.jpg)
The next photo shows the guts of the valve.... The Disco rear half has been modded with a 1/4" throat, it is bored out to 5/8" ID, and the exhaust port is 3/16" diameter and angled 20* and smoothed with a Dremel.... The stem has been reduced to 0.109" and shortened 0.060" to increase hammer travel.... The extended front end which incorporates a check valve and a gauge mount has now been drilled and tapped on the left side to 1/8" NPT for a male Foster fitting.... The check valve is shortened from a Foster fitting, with a light return spring.... The valve spring is from a local industrial supply, and between the two is a thinwall aluminum sleeve that acts as the spring seats and has a window in the side to clear the valve in the Foster fitting.... Also shown is the 1500 psi gauge with it's extension, the male Foster QD fitting, and the custom front block / barrel band assembly....
(http://i378.photobucket.com/albums/oo221/rsterne/Millenium%20Pumper/IMG_2742.jpg)
The final photo shows the assembled valve.... The Foster isn't necessary until I add the reservoir onto the gauge mount.... but I don't really feel like pumping this thing 70-75 times to fill it, so now I can fill it from a SCUBA tank or a stirrup pump.... I tried the Foster today, and it works great, but you sure have to be careful filling a 6.1 cc valve from a SCUBA tank.... I only did it once....
(http://i378.photobucket.com/albums/oo221/rsterne/Millenium%20Pumper/IMG_2746.jpg)
I put everything together just before dinner and let it sit to check for leaks and there weren't any.... I then remembered I forgot to shorten the back of the bolt to increase the loading room, so had to pull off the breech and do that before I could do any testing.... Results to follow....
Bob
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After a few months of thinking and buying bits, and a few weeks of making parts, I finally got to test my .25 Disco Pumper Carbine built the way I originally envisioned it.... I was hoping to get 30 FPE with a 24" barrel, and I'm pleased to announce that I have achieved more than that with the 20" MRod barrel.... With the Disco hammer spring maxed out and the gun pumped to 1500 psi, it drives 25.4 gr. JSB Kings at 750 fps (31.7 FPE) and just barely dumps all the air.... With a 24" barrel, another 30 fps should be achievable, putting the gun over 34 FPE....
The modded valve is now 6.1 cc, and the 3/16" ports all the way through, along with a bit more hammer travel, allow the gun to dump a lot more air.... It takes a couple more pumps to reach 1500 psi because of the bigger valve volume.... Here is a graph showing what happens with the Disco hammer spring maxed out to nearly coil bind....
(http://i378.photobucket.com/albums/oo221/rsterne/Millenium%20Pumper/25DiscoPumperPressureBored.jpg)
Note that the gun achieves 700 fps on 13 pumps, over 600 on 9, and over 500 on just 6 pumps.... I'm very pleased with the pumping efficiency, and now that I have the stock on the gun it's a lot nicer to pump.... The effort increases after 10 pumps, but it's still not ridiculously hard at 16, which is just shy of 1500 psi.... My .22 Uber-Pumper which used a 1400 tube and linkage was about the same effort at 20 pumps, from what I recall....
The next set of tests involved pumping the gun to 1500 psi and then dialling back the preload on the hammer spring a turn at a time with the RVA, all the way down to 10 turns out from coil bind.... Here is a graph showing the results....
(http://i378.photobucket.com/albums/oo221/rsterne/Millenium%20Pumper/25DiscoPumperVelocityBored.jpg)
The gun started retaining a puff of air at 2 turns out, but at 5 turns out it was still shooting 732 fps (30.2 FPE) with about 420 psi remaining in the valve.... so that works out to 27.7 CI of air used, for an efficiency of 1.09 FPE/CI (15 barcc/FPE).... It takes 13 pumps to get back to 1500 psi, and the pump displaces 54 cc, so based on the amount of air input (702cc) the efficiency is 23 barcc/FPE.... The difference is due to pumping and cooling losses.... If I crank the RVA out about two more turns, the velocity drops to ~690 fps (27 FPE) but now it only takes 10 pumps per shot.... At that setting, the second shot is over 500 fps, and if I turn the preload out to 9.5 turns, the shots are equal velocity at about 610 fps (21 FPE).... The pressure after the first shot is about 960 psi, and the second shot just dumps the air, or leaves a puff....
To summarize, this pumper can do nearly 32 FPE in a dump shot from 1500 psi.... Dropping the power down to 30 FPE saves 4 pumps, and at 27 FPE, you only need 10 pumps per shot.... It can achieve two shots of 21 FPE with the current size valve.... I'm extremely pleased with these results, they exceeded my original hopes for this design.... Now that I have tasted the benefits of retained air, however, there is another step to take.... I will be adding a 16 gr. CO2 cartridge to the valve, hidden in the stock, to increase the valve volume to a total of 27cc.... While this would require 70-75 pumps to reach 1500 psi from zero, I have already installed a Foster fitting so that the initial fill can be done from a SCUBA tank or stirrup pump.... The extra volume will drastically reduce the pressure drop during each shot, which should give either a boost in power, or more shots, depending on how it's tuned.... At that point, I don't know if it's a retained air pumper, or a PCP with an onboard pump.... but it looks like whatever it is, it should be fun finding out....
Bob
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Now my question is,...Why those guys at Crosman with all the resources at their disposal can't even come close to something like this ?,...Pathetic on their part and excellent work on yours, I hope they pay you good money for giving them such an excellent Idea,..well done
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Now my question is,...Why those guys at Crosman with all the resources at their disposal can't even come close to something like this ?,...Pathetic on their part and excellent work on yours, I hope they pay you good money for giving them such an excellent Idea,..well done
Let me quote in jist what my theory teacher always says.. Engineers design ideas that look good on paper, machinists design things that function and are actually machinable.. I think if Crosman had a couple more prototype machinists that knew a little about airguns working for them, and less engineers, their stuff would be WAY beyond what it is now.. Crosman is 15 minutes down the road from me, lets just say im working on it 8)
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Rsterne- this one officially takes you to guru/legend status- at least in my book. I'm green with envy, both for your gun and your skill set, knowledge and experience.
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Today I installed the reservoir.... It is made from a threaded 16 gr. CO2 cartridge mounted on the side of a gauge mount I made for this purpose.... With the mount, it adds nearly 21 cc to the volume of the valve, so the total is now 27 cc....
(http://i378.photobucket.com/albums/oo221/rsterne/Millenium%20Pumper/IMG_2748.jpg)
I modified the stock so that when it is installed it hides the reservoir completely.... I'm very pleased with how it turned out.... You can see the Foster fitting for filling it from a SCUBA tank or stirrup pump, on the side of tjhe tube, just above the gauge.... I'm really glad I added that.... For the initial testing I never even used the pump....
(http://i378.photobucket.com/albums/oo221/rsterne/Millenium%20Pumper/IMG_2753.jpg)
I also installed a Fitco 2-7 x 32 AO scope.... For pumping you can either hold the scope, or the neck of the stock, and I find tucking the butt under my arm works well....
(http://i378.photobucket.com/albums/oo221/rsterne/Millenium%20Pumper/IMG_2756.jpg)
I couldn't stand the suspense, so I cranked the RVA to the max, setting the Disco hammer spring just shy of coil bind, filled the gun to 1500 psi from my tank, loaded a 25.4 gr. JSB King and fired the first shot through the Chrony.... How does 836 fps, for 39.4 FPE sound?.... Yeah, I was pretty pleased too !!! .... Here is a graph of the velocity vs. RVA setting for the first and second shots.... Obviously there is no way the gun can dump 27 cc.... the pressure available for the second shot was 1000 psi with the RVA maxed out, and gradually increased to about 1370 psi with it 10 turns out.... At 2 turns out, I get 820 fps (38 FPE) on 380 psi pressure drop....
(http://i378.photobucket.com/albums/oo221/rsterne/Millenium%20Pumper/25DiscoPumperVelocityReservoir.jpg)
You can see that the curves cross over at about 3.6 turns out on the preload, and at that setting you get two shots of 780 fps, which is 34.3 FPE.... and the pressure after the two shots is about 960 psi.... That works out to about 1.10 FPE/CI, which I am very pleased with.... By backing off the RVA more and reducing the fill pressure, you can reduce that power level.... That will mean fewer, easier pumps to refill.... Filling to 1250 psi, with the RVA about 6 turns out, gives two shots of 30 FPE and requires refilling from about 750 psi.... I shot a series of shot strings at each RVA setting, and graphed all shots that were within 10% of the maximum for each string.... Here are those results....
(http://i378.photobucket.com/albums/oo221/rsterne/Millenium%20Pumper/25DiscoPumperVelocityStrings.jpg)
You can see that as the hammer spring preload is reduced, you get more shots, a flatter curve, and the peak velocity moves to a lower pressure.... In addition, you will notice that the shots at the high pressure end get dropped from the string due to partial valve lock.... These strings aren't ideal for some of the RVA settings because I always started at 1500 psi.... In fact, that is not the way you would use the gun at lower power levels, you would fill to a lower pressure.... As an example, look at the blue curve for 6 turns out on the RVA.... It uses about 250 psi per shot, and the peak of the curve is at ~1150 psi.... If you filled to about 1400, you could get three shots of about 720, 745, and 720 fps, ending at about 650 psi.... That is very close to 3 shots of 30 FPE with an ES of about 3%.... getting 90 FPE on about 85 CI of air, or 1.06 FPE/CI.... That might be the nearly perfect setting for hunting, and you would just top up after 1, 2, or 3 shots depending on what you needed.... The better your first shot, the less pumping you have to do....
I plan on doing a bit more playing around before deciding on a final tune.... but I think I can call this project an unqualified success at this point.... I will also be keeping track of the number of pumps to refill, today I was lazy, using the SCUBA tank.... Oh, I nearly forgot, I tried some other pellets with the RVA maxed out.... Here are the results....
H&N FTT 19.3 gr.... 911 fps.... 35.6 FPE
JSB King 25.4 gr.... 836 fps.... 39.4 FPE
H&N Baracuda 30.9 gr.... 779 fps.... 41.6 FPE
EunJin Dome 35.2 gr.... 737 fps.... 42.5 FPE
EunJin Pointed 41.7 gr.... 678 fps.... 42.6 FPE
So there you have it, a .25 cal pumper that shoots over 42 FPE on 1500 psi.... built with mostly Disco parts, an MRod barrel, and a 392 pump linkage.... with a few custom parts thrown in....
Bob
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Wow a >40fpe pumper (sort of, almost pcp), just amazing. Unfortunately I don't think that Crosman could sell then gun profitably so it will remain a custombut amazing none the less.
You have certainly given us tinkerers something to strive for.
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Fantastic Job, even a Non technical person like me can fully apreciate what you have done.
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I like the way you added volume to the valve.. I think that having a more than one shot pump gun spitting out pellets at 30+ fpe is on every hunters dream list.. I am interested to see how many pumps it takes for you to fill that 27cc "reservoir"
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Great job. It would be very cool to have a .22 version of this. It would also be cool to have the ability to use full co2 carts. You could shoot the co2 down and then use the pump.
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You could shoot the co2 down and then use the pump.
Or even add air on those cold days to bring the pressure back up.... The problem is that when the gun warms back up, the pressure will increase again....
Bob
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It was time today to fix a couple of things that cropped up during building and testing.... I had noticed that there was a problem with the hammer dragging during testing.... If I squeezed off a shot instead of "yanking" it and holding the trigger back, I lost about 40 fps and the velocity was very inconsistent.... For that reason, all the previous testing was done with the "yank and hold" technique.... I pulled out the hammer and found exactly what I had expected.... a dent.... circled in the photo below....
(http://i378.photobucket.com/albums/oo221/rsterne/Millenium%20Pumper/IMG_2757.jpg)
Remember I shortened the valve stem 0.060".... Well that extra hammer travel was allowing the hammer to impact the back side of the sear, if it was still sticking up like it would be if you just squeezed off a shot.... I've seen this before, that is why I knew what was going on.... I had another Disco hammer handy, that had been lightened 20% by removing the front half of the rear portion of the full diameter part, making the "waist" longer.... Therefore, the section where the impact could occur was no longer there.... Since I wasn't going after maximum power, and I had lots of RVA adjustment to play with, I simply dropped in the lighter hammer and that fixed the problem.... You could squeeze off a shot and get exactly the same velocity as if you "yanked" on the trigger....
The other small issue I addressed was the "clacking" of the pump arm lever against the tube on closing.... I took a small piece of 1/8" thick UHMW Polyethylene about 3/4" square and forced it into the end of the pump arm flush with the end and down all the way inside it.... It stuck up about 1/16" above the arm and forestock so that the plastic is what hits the tube.... I drilled through it for the rear pin to retain it, reassembled the forestock, and voila, much quieter on closing.... BTW, somebody asked about holding onto the scope while pumping.... I find it quite comfortable if I put my hand right over the front scope ring.... Holding the gun there I'm pushing straight down right at the ring, and in all the testing I did today I didn't notice any looseness or POI shift.... I don't think it's a problem....
Now it was time to see if the new hammer made any difference.... It wasn't a big difference in weight, but the valve should open slightly faster, have a bit less dwell, and close quicker.... I expected to see a slight loss in velocity , but in fact I gained a little bit at maximum preload, with the 25.4 gr. JSB Kings hitting 845 fps (40.3 FPE).... I guess the faster opening helped a bit, or possibly the stock hammer was just catching the sear before I could yank it out of the way before.... In any case, I'm now getting over 40 FPE with the Kings for one shot.... In addition, each shot is using slightly less air, so the second shots are a bit faster.... I get two shots of equal velocity with the RVA only 3 turns out, and consequently they are more powerful, at 796 fps (35.7 FPE) instead of 780 fps at 3.6 turns out previously....
Now it was time to get to the serious setting up of the gun.... I'll spare you all the tribulations, but I eventually settled on a 1400 psi fill and 6 turns out on the RVA.... Here are the results....
(http://i378.photobucket.com/albums/oo221/rsterne/Millenium%20Pumper/25DiscoPumperShotString.jpg)
The 4th shot is included just for interest, although it could be used for a "coup de gras" if necessary.... The exciting part is that I get 3 shots within a 3% ES, averaging 31 FPE.... I was only testing indoors, but those three shots kept going into one ragged hole.... With a 3% ES, I wouldn't expect any significant POI shift out to about 70-75 yards between those three shots.... I also pumped the gun up after 1, 2, 3, and even 4 shots, and recorded the number of pumps, as follows:
(http://i378.photobucket.com/albums/oo221/rsterne/Millenium%20Pumper/25DiscoPumperPumps.jpg)
It takes 12 pumps to refill after the first shot, another 15 for the second shot, and 18 each for the 3rd and 4th shots.... The pressure drop per shot is 190 psi for the first shot, 230 for the second, 320 for the 3rd, and 410 psi for the 4th shot.... That gives efficiencies of 1.39 FPE/CI for the first shot, 1.23 for the 2nd shot, 0.83 for the 3rd shot, and a dismal 0.49 FPE/CI for the 4th shot, which only leaves 250 psi in the gun.... Like I said, the 4th shot is for emergencies only, at close range, to finish off a wounded animal.... The average efficiency over the first 2 shots is 1.31 FPE/CI, and over the first 3 shots is 1.10 FPE/CI.... I'm pretty darned pleased with that.... It sounds like there is a bit of hammer bounce on the 3rd shot, and it is definitely present on the 4th shot.... but with the good efficiency on the first 2 shots it really can't be an issue....
I think I'll stop here for a while, and do some work on a PCP that has been calling my name.... In conclusion, with 25.4 gr JSB Kings, I have 3 tunes as follows:
Max. @ 1500 psi.... 1 shot at 845 fps.... 40.3 FPE
3 turns out @ 1500 psi.... 2 shots at 796 fps.... 35.7 FPE
6 turns out at 1400 psi.... 3 shots at 739 fps.... 30.8 FPE
One other thing.... When filling from a SCUBA tank, I would strongly suggest using a regulator set to just below where you want to fill (I'm using 1350 psi).... I damaged one gauge by overfilling the small valve by just 200 psi.... It wasn't a safety issue, just a PITA and cost me a gauge.... The regulator prevents that from happening again....
Call it a day, I'm done like dinner....
Bob
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Simply AWESOME ....
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Awesome job Bob! From conception to completion just a wonderful project. Bravo!
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For the techies, here is a graph from Lloyd's spreadsheet showing what's happening inside the gun over those three shots starting from 1400 psi....
(http://i378.photobucket.com/albums/oo221/rsterne/Millenium%20Pumper/25DiscoPumper.jpg)
Note that the third shot is getting close to a dump shot.... the pellet is 3/4 of the way down the barrel when the valve closes.... Regardless of how different the pressure curves are, the results at the muzzle are 3 shots within a 3% ES.... Pretty amazing how well a simple "smack open" hammer and valve can regulate on such a small volume of just 27 cc....
Bob
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I'll send you my address and you can ship it down to me. I'll see how my critters like it. Get a couple kills under its belt for ya. Furbearer season will be here real soon :) . How loud is it? About the same as a stock disco?
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It's similar to a stock Disco, maybe a bit louder.... More power from a shorter barrel means a higher muzzle pressure.... The pressure on the first shot is about like a Disco in the middle of a string, and on the second shot about like a Disco at the end of the string, and I think the report pretty well matches that.... The third shot has a real "boom" to it, quite different than a Disco.... The late closing valve causes a residual muzzle pressure of over 500 psi....
Bob
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I decided that I liked the way this gun responded to a lighter hammer, so I had another one kicking around that weighed only 40 gr. (30% lighter than a Disco hammer).... I installed it, and the gun responded in exactly the way it should.... I lost about 8 fps at the top end (with greater efficiency) with the Kings, and I needed one more turn of preload on the RVA to get back to my "3-shots at 31 FPE" tune.... and they are a bit more consistent, with a whisker less air use.... I got one additional benefit.... With the RVA at maximum, filled to 1500 psi, and shooting 42 gr. EunJin Points, I get two shots at 655 fps (40 FPE) that are only 2 fps apart.... Should I wish to tackle something larger and that requires extra penetration, that combination would be just the ticket....
Bob
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Holy macaroni....
You ever get tired of that one, I promise it a good home. Wonder how dry moly powder would work on the pump o-ring, in the fashion of the o-ring springer pistons. Also, just in case you've never seen it, check out the 392 linkage from Airchanic. Site says it is no longer made, but their pump handle pressure v. angle sure looks nice.
cheers,
Douglas
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Also, just in case you've never seen it, check out the 392 linkage from Airchanic. Site says it is no longer made, but their pump handle pressure v. angle sure looks nice.
cheers,
Douglas
Got a link for that? Google search came up with nothing
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IF that's the one with the extra link and relatively constant force.... they warn against using more than 8 pumps in a 392 or the linkage will buckle....
Bob
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Also, just in case you've never seen it, check out the 392 linkage from Airchanic. Site says it is no longer made, but their pump handle pressure v. angle sure looks nice.
cheers,
Douglas
Got a link for that? Google search came up with nothing
Sorry Bob...just ad a frustrating search on 'airchanic'...all the more frustrating 'cause I remembered finding it quickly before...:) I forgot the 's' at the end...D-Oh!!! http://www.airchanics.com/ (http://www.airchanics.com/)
I saw that one with hopes of setting up my son with a pumper he could manage better than the stocker on the Sheridans. In this case more than 8 pumps will not be an issue for a while...:)
cheers,
Douglas
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one of the reasons crosman is unlikely to put one like this on the market is ALL the statements on the forums of how people hate to pump. we are a lazy world. so those of us who love pumpers are far and few between. look at the new webely rebel it is selling at a dismal rate. the fact that it is only .177 most certianly is not helping their sales. pumper people tend to be hunters and .22 works better on a rabbit than .177. i like the flater shooting of the .177 at 12fpe but the .22 rebel should shoot at 15fpe that will flatten it out pritty good.
the linkage on the airchanic does not have any inherent weekness. theirs may be week but it does not need to be. i used a similar sized 4link system to push 600lb pallets sideways on a roller conveyor with no strength issues. it located 300 pallets per day for a year with no failures.
mark
p.s.
i hope lots of you do similar builds and post them in the next few months. i know when i get back to my shop in june what my 1st project will be.
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that link doesn't work.... and I would like to view a diagram of the pump in an FX Indy.... Let's try this....
http://users.snip.net/mogul/Air/FXIndyPumpRebuild/FxIndyPumpRebuild-2.pdf (http://users.snip.net/mogul/Air/FXIndyPumpRebuild/FxIndyPumpRebuild-2.pdf)
Bob
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http://www.network54.com/Forum/79537/message/1209784256/FX+pump+take+down+---+Keyrigger+or+others+may+be+able+to+help--------- (http://www.network54.com/Forum/79537/message/1209784256/FX+pump+take+down+---+Keyrigger+or+others+may+be+able+to+help---------)
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John.... that second diagram is for an FX Stirrup Pump, not the onboard pump for the FX Independence.... The link in my previous post works....
Bob
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Sorry, I'm confused...snafu... ::)
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OK, so here is what I got from that rebuild article on the FX Indy pump.... It appears to be a 3-stage design.... The 1st and 3rd (high pressure) stages look like they work when the lever is returned to it's stored position.... The second stage appears to work in the opposite direction, ie on the "out" stroke.... I haven't figured out all the details, but that's what I see, anyway.... If anyone figures it differently, please let us know....
Bob
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I had a chance to get outside and sight the rifle in today.... It shoots quite a few pellets well, but prefers JSB Kings and Polymag Predators.... This is the first gun I have that really like the Preds.... Here is a 3-shot group from the bench at 35 yards....
(http://i378.photobucket.com/albums/oo221/rsterne/Millenium%20Pumper/25Pumper35yards.jpg)
The third shot of the three shot string is consistently the lowest of the three, but when the groups are this small, who cares.... At this range the remaining energy is about 22-25 FPE depending on pellet choice.... which combined with the massive whack from a .25 cal pellet should be just the ticket for hunting....
Bob
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Awesome project, great execution, and what a wonderful group! Awesome job Bob!
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Awsome job Bob i would like one in a .20 or .22 cal ;D
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WOW!!!!!
Tommy
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8) Fascinating thread and a completely awesome build. I love pumpers and I cant believe I missed this thread until tonight. :o
Very nice and a great looking rifle.
Bryan
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This is now old news.... Here is what it turned into.... http://www.gatewaytoairguns.org/GTA/index.php?topic=39328. (http://www.gatewaytoairguns.org/GTA/index.php?topic=39328.)
Bob
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That's just awesome 8) and a beautiful rifle.
I hadn't joined the GTA when the first thread started so that's why I missed it but I have no excuse for the second thread. :o
There's no good reason for rifles like the two you designed not to be in production.
Bryan
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This is now old news.... Here is what it turned into.... http://www.gatewaytoairguns.org/GTA/index.php?topic=39328. (http://www.gatewaytoairguns.org/GTA/index.php?topic=39328.)
Bob
Bob it may be old news but is still Inspiring...
And I do not get why they are not building them either, springers sell for about what it would go for, are they afraid of loosing PCP sales?
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It's interesting that the Carbine can be built with nearly all Crosman/Benji parts, and the Millenium Pumper just needs a beefier linkage and a separate check valve.... I suspect the biggest problem is corporate inertia, plus maybe the fact that as a society we are getting lazier and pumping gets old, fast, for many people....
Bob
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It's interesting that the Carbine can be built with nearly all Crosman/Benji parts, and the Millenium Pumper just needs a beefier linkage and a separate check valve.... I suspect the biggest problem is corporate inertia, plus maybe the fact that as a society we are getting lazier and pumping gets old, fast, for many people....
Bob
Bob I'm impressed with your engineering and work involved. You must be an engineer someplace. Love the data plots you've posted too.
Crosman marketing is the obstacle to production of a gun like this in my opinion. Plus it might cut into sales of existing guns in ways they don't want.
I think it sits between the 392 and a Disco and they probably don't see a niche for it even if their engineers were to see it and fall in love with the idea. Perhaps a small vendor here would be willing to work with you and produce limited production of these much like the disco double. Might make a nice bit of revenue for you.
Another idea just came to mind when talking about lazy folks, and that's the other folks who like to exercise.
Not trying to thread jack but here's my idea.
Imagine an exercise machine that's also an airgun pump.
I mean the hand pumps for Disco and Mrod are a pretty decent workout from what I hear anyway, but if they could adapt it to a machine like a Bowflex or something, that would be pretty cool, especially with a reservoir tank option.
Hook your tank or your gun to a hose on the workout machine and start your workout. At the end of the session you have a fully charged gun and/or tank and can enjoy some fruits from your labor beyond improved health and muscle tone!
Maybe this could be your next engineering project Bob?
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" Imagine an exercise machine that's also an airgun pump.
I mean the hand pumps for Disco and Mrod are a pretty decent workout from what I hear anyway, but if they could adapt it to a machine like a Bowflex or something, that would be pretty cool, especially with a reservoir tank option.
Hook your tank or your gun to a hose on the workout machine and start your workout. At the end of the session you have a fully charged gun and/or tank and can enjoy some fruits from your labor beyond improved health and muscle tone!
Maybe this could be your next engineering project Bob? "
I think a stair stepper or stationary bike would be the thing... Call it P-rod X fitness system or Shooting Fit X... ;)
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If Crosman would build it, I wouldn't expect a dime, just my contribution to airgunning....
No time to build an exercise machine, thanks.... even though I need one !!!
Bob
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" Imagine an exercise machine that's also an airgun pump.
I mean the hand pumps for Disco and Mrod are a pretty decent workout from what I hear anyway, but if they could adapt it to a machine like a Bowflex or something, that would be pretty cool, especially with a reservoir tank option.
Hook your tank or your gun to a hose on the workout machine and start your workout. At the end of the session you have a fully charged gun and/or tank and can enjoy some fruits from your labor beyond improved health and muscle tone!
Maybe this could be your next engineering project Bob? "
I think a stair stepper or stationary bike would be the thing... Call it P-rod X fitness system or Shooting Fit X... ;)
Now, that would be awesome. A treadmill that fills your bottles. I would definitely get my half hour of cvardio in, every morning! Even (especially) on weekends!
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HAH!..a pump IS an exercise machine...especially on a BIG res gun...like a BT-65...or a Evanix Tactical .45
like "Ahnold's" bull worker went into hydraulic dampner mode
you maggots wanna SHOOT?.. ya gotta EARN it
don't believe me? TRY IT..i have and I know somebody that DOES...
this has got to be the most excellent reason for getting a PCP or three...
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Mother of god lol.
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I have been wanting to get the fx Independence for a long time now because it stores what you pump and once topped off after you shoot one shot you can pump a few pumps and your back to full power . After you did all the work on this gun do you think the fx is worth the money for what your getting .
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FX build gorgeous airguns, but out of my price range.... That was the reason for this build, to swap my time for the money I don't have....
Bob
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What an awesome build...you are a genius Bob.
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I know it fits a particular niche, but I think to be economically viable it would have to cost under $300. Otherwise, one could buy a disco and pump twice per shot and carry plenty of shots for field work. Nevertheless, the concept is awesome and I am currently trying to build a tamer version of this for $150 plus some parts I had laying around.
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With the stirrup pump supplied with a Disco, it takes more than 2 pumps just to fill the hose to gun pressure and open the check valve.... plus you have to carry a separate pump.... and you are limited to .22 cal.... This gun is NOT for everybody, but Crosman could build it with mostly existing Crosman & Benjamin parts if they CHOSE to do so.... About the only things they would have to make is a gauge / check valve section, a new piston, and the pivot mount.... the rest is off the shelf.... I can't imagine it being much more than a 39X to produce, although they probably could raise the price point some and still sell a whack of them....
Bob
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With the stirrup pump supplied with a Disco, it takes more than 2 pumps just to fill the hose to gun pressure and open the check valve.... plus you have to carry a separate pump.... and you are limited to .22 cal.... This gun is NOT for everybody, but Crosman could build it with mostly existing Crosman & Benjamin parts if they CHOSE to do so.... About the only things they would have to make is a gauge / check valve section, a new piston, and the pivot mount.... the rest is off the shelf.... I can't imagine it being much more than a 39X to produce, although they probably could raise the price point some and still sell a whack of them....
Bob
Bob, back when you did this project, I sent an email to Crosman with a link to your post. I doubt they will ever do it. They seem to be more about reinventing the same things over and over. I agree, if they did do it and priced it around $250-$300 they would sell a boat load of them.
Scotty
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I was never under any illusion Crosman would build these.... The project was more what COULD be done with Crosman parts with minimal changes and additions....
Bob
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Warning old thread, yep.
Too bad Crosman didn't do these and market as a Sheridan "Blue Supreme Evolution" or any other name for that matter.
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If there's a way to make money from it, someone will eventually build and sell it. Can't keep a good idea out of the marketplace forever.
https://www.pyramydair.com/product/seneca-aspen-pcp-air-rifle?m=4715 (https://www.pyramydair.com/product/seneca-aspen-pcp-air-rifle?m=4715)
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I consider Seneca and At I at the leading edge for the prepper community.. A self contained tool that is powerful enough to guarantee meet on the table.. I just wish the reservoir would have more volume... But, that is just me!! >:(