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All Springer/NP/PCP Air Gun Discussion General => Machine Shop Talk & AG Parts Machining => Show Off Your Air Guns With Mods (SHOW and TELL) => Topic started by: michaelthomas on July 25, 2013, 03:37:50 PM
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I have always loved the look of the Air Arms EV2 Mk(any), and finally got going on my own project that will try to retain the EV's good looks and implement some other features and ideas that I like.
I have finished the 250cc air tube, the valve block, valve and solenoid hammer.
I am typically bad at posting progress on any projects I do because I put it off until I have way too much done, then it seems like too much work to catch it up.
I'm starting early, and I plan to keep up this time. :D
I am shooting for a 16fpe .177 gun that will have at least 50 good shots per fill. If I get 12-20fpe.....that's fine. The gun is gonna be for target shooting at longer distances than my 753 is effective at.
Valve is .200", throat is .140", and transfer port is .100.....stem is .078". Concave seat with delrin valve.
I like the pellet loading into the rear of the barrel like the Mac1 guns......so that is the idea I'm going with.
I also like the idea of possibly being able to tune electronically.....so that's why I went with the solenoid. It will be a capacitive discharge arrangement like the Daystate.
I ran across a picture of a USFT/EV2 hybrid that somebody made, and I really liked it. http://airgundevelopment.com/custombuild/karlcaron.html (http://airgundevelopment.com/custombuild/karlcaron.html)
Here are some pictures of my beginning.
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I have only done some preliminary testing of the solenoid operated valve.
I had an extra spring and hammer from my Avanti 753 for comparison.
I set up a pinball type setup that would shoot a small 55 gram cylinder with the spring and hammer. I allowed it .5" to accelerate and compressed the spring almost fully. It would shoot the cylinder 38 inches from a height of 33 inches.
I then set up the solenoid to do the same thing. at 60v and 300 microfarads......I was able to get the same distance. Increasing the capacitance lengthened the discharge time, and would shoot the cylinder further, but it was actually powering the solenoid after hitting it's fixed stop in the body. I have up to 100volts to play with the dc to dc boost converter I currently have. Its small and light, and will work from 2 9v batteries in series. If 60v is all I need, I can get away with 1 9v battery and a different boost converter. I want the solenoid to have exhausted all (or most) of the capacitors energy just before striking the valve.....so just momentum is in play.
Calculating backwards, I was able to determine that the 40gram plunger took about 5 milliseconds to strike the cylinder with the .5" approach.
One interesting thing I noted was that shortening the approach to .25" on the solenoid, made no measurable effect on the distance that the cylinder was shot. I think this is because the solenoid becomes more powerful the deeper the plunger goes in. I made a screw cap for the back of the solenoid housing that can be used to adjust the approach distance easily. It may end up being an important tuning feature along with the capacitance and voltage adjustment.
Until my barrels and pump get here, I suppose that's all I can do.
I bought the Lothar Walther .177 standard rifling barrels.....I making two of these at the same time.
Mike
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Very cool project !! .... love fabrication but lack advanced electronic skills :P
projects like this can only sit back and watch in amazement ;D
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Awesome project.. :D
Please share some more detail of the electronics... I would really like to build my own solenoid gun in the future, but I'm more a mechanical guy than electrician..
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Thanks, Scott......you might want to hold off on any amazement until I actually get it firing some pellets. ;)
Bent.......A simple capacitive discharge circuit is just a capacitor and a resistor in series to do the charging. The value of the resistor sets the charging rate.
After the cap is charged, you just have to put the load (solenoid in this case) across the cap. The charge and discharge rates can be calculated easily......but it's easier, yet, to just use a calculator. http://hyperphysics.phy-astr.gsu.edu/hbase/electric/capdis.html (http://hyperphysics.phy-astr.gsu.edu/hbase/electric/capdis.html)
A micro switch that has a normally open and a normally closed set of contacts can do both operation for you. Charge with the normally closed, and then discharge with the normally open (button press). When you release the button the charging cycle will begin again. I'm using a SCR in conjunction with a micro switch to keep the higher current out of the micro switch for longevity.
Fool around with the discharge calculator for a bit and you will begin to see the discharge characteristics of different capacitance and voltage values. Higher capacitance values will put more power through the circuit......but at a longer time frame. There probably isn't much use is discharging beyond 10ms for 1 time constant, or maybe less......because the plunger has already come into contact with the valve, and can no longer supply any more forward momentum. To get more power in a shorter amount of time (MORE KICK), the voltage will need to be increased......or the resistance of the solenoid must be reduced (meaning get a different solenoid).
I'm using photo flash capacitors that are rated at 360v......meaning they can be charged to 360v. Photo caps are capable of very high current flow without heating up as much. Probably doesn't really matter for this, but I had them on hand.
Don't bother with any solenoids that have high resistance......they probably won't get you where you want to go without a lot of voltage.
Don't worry too much about the rated voltage of a solenoid (mine is 12v), because for the few milliseconds that you will be pumping some amps through it.....it's not really indicative of what it can tolerate. I can trigger mine 50 times in a row with 80 plus volts and detect zero heat from the solenoid. I can't really tell how much a particular solenoid can tolerate.......but it's a lot more than one would think because of the tiny duty cycle.
I have scoured the net for info about the specifics needed to do what i want, but was unable to find anything definitive. So it's trial and error, really.
I'll just keep upping the voltage until I get what I need for starters.
Mike
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Beautiful work! I'm very familiar with how much work is involved when you custom build every part of gun, then add some electronics to boot, A trying task to say the least.
I'm curious why CD and not direct drive? A simple regulated boost topology could give you the power you need with out the discharce curves, temp and tolerance issues associated with HV caps. You could also control the current in the winding via PWM. Just thoughts :).
Tom
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Beautiful work! I'm very familiar with how much work is involved when you custom build every part of gun, then add some electronics to boot, A trying task to say the least.
I'm curious why CD and not direct drive? A simple regulated boost topology could give you the power you need with out the discharce curves, temp and tolerance issues associated with HV caps. You could also control the current in the winding via PWM. Just thoughts :).
Tom
Stop speaking GREEK !!!
Lol ... had too
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Sorry 8) Just had to. LOL
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Tom,
The main reason for CD is the ability to extract the energy needed in a few milliseconds. The boost convertor itself would not be capable of producing the instantaneous current needed.
The simplicity of the CD arrangement is nice, too.
The discharge voltage of a cap is easily controlled by the amount of time a given voltage is applied over a given resistance......making it very easy to charge a cap to any voltage up to the max output of the boost converter just by changing the charge time. That would be a simple task for a any micro controller.......and if I get into altering the shot string without a pressure regulator, that will be the first method I will try.
I don't expect any heat or tolerance issues with capacitive discharge.
The discharge curve is very repeatable, too.
Mike
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I agree with the simplicity of the CD. A driven or hard switched circuit would still require a bulk cap to store energy, the difference is you modulate thew buss voltage in a more controlled manner allowing for programmable discharge curve. I use this type of circuit to control the strike voltage on UVc lighting ballasts.
I do understand keeping it simple. Embedded systems is my bread and butter so I'm always look for way to have more control. :)
Tom
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Let me be the first to say that my knowledge of electronics is far from comprehensive. I build and service cnc equipment for my living. Most of the electronics for me is implementation......not design.
My initial plan is to put the gun on a regulator and just find a solitary discharge voltage to fire the solenoid and open the valve for the appropriate time......and when I'm off the reg, it will be time to pressure up. I really don't have any grand plans to monitor or compensate on the fly. I don't think valve bounce will be any issue with the solenoid, and I'm hoping that will help to find some extra efficiency.
I also like the flexibility that the solenoid can provide. It could be adapted to a ton of different platforms with relative ease.
That's my plan, anyway.
If it morphs into some thing more complex than this, I may have to pick your brain. :D
Mike
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A plan is a good thing :) If you have any questions that I can help with just shoot me a pm.
Just curious if you don't mind..... Are you planning on charging the cap on trigger pull or maintaining the voltage when the system is activated? What voltage do you plan to boost to?
Sorry, can't help my self.
Tom
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I'm planning to maintain voltage while activated. The on/off switch being the "safety".
Voltage will be the least I can get away with. :D
Mike
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This a very interesting project. When you turn to switch off will the voltage be dumped ?
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Great project you have going on here Mike! I love working with control circuits.
Starting with regulated air will make it much easier and eliminate a whole bunch of variables. If you have some success with this then I am sure others will be able to jump in and expand the knowledge base for everyone. It would also make a great foundation for the dwell experiments.
Really jonesing for the machine shop equipment I used to have access to though.
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This a very interesting project. When you turn to switch off will the voltage be dumped ?
No, I wasn't planning to dump the cap. The SCR will be dead and not allow an accidental trigger when the "safety" is on. I'm guessing that was why you asked......maybe not.
Jesse,
If you are CNC control repair capable.....and can be patient, you can find some great deals on broken CNC equipment. The manual stuff always holds it's price, but a CNC with a dead control will often go for scrap value.
Here is a pic of my last summers' project. It's a Mazak QT20n that I got for $800.00. It was control dead and looked like a steaming $)((# when I got it......but was mechanically sound. I originally intended to do a control retrofit, but ended up repairing the original. It will hold a few tenths all day after its warmed up. It's a really nice machine. I probably have $3000.00 into it as it sits now......not including tooling.
Mike
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I've been trying all week to get a response back from Lothar Walther so I can get my barrels on the way. I have finally found out that I now have to send them a check, as they don't take credit cards.
That seems odd for this day and age.....It's like I'm back in the 70's and ordering from the Sears catalog. Maybe they will come by way of the Wells Fargo wagon?
Mike
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Yes, good luck getting what you actually ordered. WW at LW is hit or miss with accuracy and replies. I ordered 1 poly and one conventional, sent check with a hard copy PO and received 2 conventional ??? Send an email to WW at LW and never received a response. Not a big deal, I used both anyway.
Tom
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I'm beginning to draw the stock while I'm waiting for the rest of my stuff to show up I'm no wood carver, so I'm going to use a 3 axis router with a ballnose bit. I want to get the basic 2d outline right.....then I'll have to work it all out in 3d to do the toolpathing. I don't really enjoy drawing freeform stuff in 3d.
I was going to lay up a laminated stock blank......but I recently learned how inexpensive the pre-made ones are from Boyd's. ($40.00) That's definitely not worth me messing with it. I chose the pepper laminate.
Mike
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Got my Hill pump earlier today.
I charged the (naked) gun up to 1500psi, and tested the solenoid hammer out. I have no barrel on the gun, so it was just an open transfer port.
I was able to get anything from a small pop to a seriously loud bang depending on the voltage the cap was charged to......which ranged from 20 to 60v.
That seems initially promising.
Mike
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So question begs to be asked HOW STABLE the cap voltage is while guns cocked and sitting there in a charged up state ready to fire ?
Secondly as battery Voltage & Current diminish from a full charge on down .... How do you control or alter the caps voltage set point to cycle the solenoid the same independent of batteries state of charge ?
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Well..... cap voltage will always be what the dc to dc boost converter is putting out.
The boost converter is regulated, and should maintain consistent output as long as the input stays between 3v and 34v. I plan on using a plain old 9v battery.
So, the voltage set point should not change until the 9v is really, really dead. As long as the voltage to charge the cap is consistent.....the amperage from the charged cap will be consistent, too.
I'm sure there will be some tolerance.....but it's hard to say (for me anyway) until it's actually in a complete unit and able to evaluate.
I conservatively came up with a shot count for the 9v battery......and it's a ridiculous 10,000 shots. That seems like a lot to me, but I cannot find the hole in my math if there is one.
I don't know.......time will tell.
For now, I'm happy with the big bang. ;D
Mike
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Oh man! Just waiting to see what the rig will do with back pressure on it. Keeping my fingers crossed and hoping you are really on to something here Mike.
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I tried it out at 2000 psi today, just a bigger bang.
Screwing in the endcap actually produce a bigger bang (shortening travel) than unscrewing......not what I would have originally guessed. I'm sure it has to do with the solenoid being more powerful with the plunger deeper to start with. Screwed in fully has 1/4" of travel to valve stem.....fully out is 1/2".
Here is s a pic of the ultra sophisticated (lol) test circuit. Just a 9v battery going to the dc to dc booster......then splitting off the spst center off switch as the charge side and the discharge side. Charge has a 2.2k resistor in series, and discharge has a big diode to protect the boost convertor after the collapse of the solenoid coil. 2 200 microfarad photo caps in parallel. It seems to do just fine on 300 mf, too.
Takes about 2 seconds to charge with this resistor.
I rested a pellet on top of the transfer port pointing up......and it shot through the drywall ceiling in my kitchen......oops.
My wife didn't like that.
I suspect that the back pressure of the barrel will extend the opening of the valve at any given setting.
Mike
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I forgot to mention that I tried a new 9v( read 8.99) vs a substantially weaker 9v (7.86). Both output 60.1v on the booster.
Mike
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For a given hammer strike energy, as you increase the backpressure the valve lift will increase, and therefore the time required to complete the round trip (the dwell) also increases.... I recently measured the lift on a .30 cal running on 3000 psi, and with no pellet, the lift was 0.06", with 46 gr. pellet it was 0.07", and with the barrel blocked about 95% (call it a VERY heavy pellet) it was 0.08".... Since the pressure inside the valve is the same, and the valve spring is the same, in all cases, the difference must be due to a higher pressure in the exhaust port section of the valve (ie downstream of the seat) because of the pellet.... This means a smaller DIFFERENTIAL in pressure across the head pf the poppet, and hence less closing force during the shot.... It is that reduction in closing force that resullts in increased lift and dwell.... Since the third case, although interesting, is not a "real world" situation, the difference between the first two is the significant one.... and that is about 17% more lift and dwell with a pellet compared to open bore.... call it 15-20% depending on pellet weight....
You should note that once you open a poppet valve 1/4 of the throat diameter, the flow rate can no longer increase as the "curtain area" (circumferential area above the valve seat) equals the throat area at that lift.... and at higher lift, the throat area becomes the limiting factor.... That seems to happen at the high pressure end of the shot string in many unregulated PCPs, and as the pressure drops, the lift and dwell increase, becoming roughly double at the bottom end of the string.... However, only the dwell increase is significant, the additional lift sees any flow rate increase "clipped" by the throat restriction....
Bob
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Thanks for that info, Bob. Nice to have all of your testing information.
I went to find a 004 o ring today to put over my valve stem so I could get an idea of how far it was opening, but didn't have any luck with that itty bitty size locally. I guess I'll have to order some......and pay 500 times the cost of them to be shipped. >:(
I'm excited to get a barrel on this thing and get it in front of the chrony.
Mike
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Smallest I have is an 006 or I'd just mail you one....
Bob
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Thanks for the offer, Bob......006 is the smallest available around here, too.
I'm just going to poke a hole in some rubber sheet and shove it over the stem and see what happens. If I can make it snug, it should work. My valve stem has only a few tenths clearance, so I'm hoping there won't be enough air coming past the stem to artificially move the sheet.
Thanks,
Mike
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I tried out the rubber sheet dealio. I drilled a hole in the rubber then used a paper punch to make a donut around it.
It's difficult for me to measure very precisely, but it's between .025" to .030". I really don't know what that means to me right now.....other than the valve is not opening greater than 1/4 of my .140" throat.
Mike
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Gaps that small are easiest to measure using a set of feeler gauges.... Your lift measurements sound feasible for a valve that small.... and incidently efficiency should be good as a results.... The amount of FPE generated will be the question, as that's not a lot of "area under the (lift) curve"....
Bob
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I had read in quite a few places that a .100" transfer port was plenty of area for a 20fpe .177. That is what I based my .100" transfer port, and .140" throat with .078" valve stem. It will be .100" all the way to the barrel.
I'll be satisfied with less than 20fpe.....but not less than 12fpe.
I don't know.....hopefully I will sometime soon, though. :D
Mike
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At 0.035" or more lift (to maximumize the flow of the 0.140" throat) I would think you should be OK for your 20 FPE goal.... At your measured 0.025" lift I'm not so sure, that was all I meant.... However, getting more lift is just a matter of more hammer strike....
Bob
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At 0.035" or more lift (to maximumize the flow of the 0.140" throat) I would think you should be OK for your 20 FPE goal.... At your measured 0.025" lift I'm not so sure, that was all I meant.... However, getting more lift is just a matter of more hammer strike....
Bob
........maybe the 24" barrel will get me closer. This test was done with 2000 psi in the reservoir. I wasn't planning on regulating any higher than that.
I have a boost convertor that is capable of up to 100v on the way. Right now, 60v is all I have with the current one. That will allow me some more striking power to play with.
I suppose I will use the 100v, even if the 60 is adequate for power. I will be able to use less capacitance with the higher voltage to get the same kick.......and get a quicker lock time.
I cycled the cap through the solenoid 2500 times today on the original 9v battery. It's still charging the cap to 60.1v. I'll try to see if I can wear the battery out tomorrow. :D Resting voltage of the "9v" is now 7.6v. I checked the cap voltage throughout, and never found it to be anything but 60.1v......so that's a good sign.
Mike
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I did some more clicking this morning while drinking my coffee.......and at 3500 shots, there are still no signs of any fluctuation of the cap charge voltage (still 60.1). Battery is still over 7 volts. This is an enercell from Radio Shack......which seems to be rated about 310mah. I'm betting I could still get another 1000 shots from it......but I honestly don't care anymore. 3500 is plenty for me.
I had considered a 11.1v 850mah 3s lipoly. That would easily get me well over 10,000 shots based on what I am seeing so far. Pack weight is 54grams compared to the 45 grams of the standard 9v. Footprint is slightly larger. Doesn't really seem worth worrying about at this point, as it will probably take me months to wear out a cheap 9v.
Mike
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I got some more done this past weekend. Scope rail, swing breech, barrel block and other little things.
I'm really pleased with the way the swing breech feels......it's very tight and smooth. I have to make a handle for it , now.
I should be ready to go when (if) the barrels from LW show up......aside from machining them.
Maybe this week?
Mike
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Looks gorgeous! And fantastic progress too!
Tom
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Thanks Tom.......thankfully it's just a little less complicated than your project. ;)
Mike
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Still no barrels yet......big surprise, there.
I spent some time today (actually most of the evening) trying to get the stock in 3d so I can cut it.
I think it's a good start, anyway. I really struggle with freeform drawing. I think someone proficient could have knocked it out pretty quick. Still have to put the cheek rest in, too.
Mike
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You're doing some great work. Thanks for letting us tag along.
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Thanks Mike.
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Will the stock have to have a slot cut into it for the swing breech? Just from your drawings it looks like the stock will limit how much you can move the swing/bolt.
Looks awesome though 8)
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Yes.....There's a whole lot more tweaking left. ;D I will have to make some room for the electronics, too.
I'm probably just going to cut a stock from Poplar to see how it feels, first.
It's gonna be slow......I decided to cut it on the small mill that I have at home. It only has a 2000rpm spindle......so I won't be breaking any speed records.
I suspect there may be some adjustments I will want to do before the final.
Thanks for the encouragement.
Mike
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I picked up a 6" 4 jaw chuck to help with small items and second operations. Bored a set of soft jaws to put the 4 jaw in the hydraulic chuck.....this will make the barrel machining easier for me.
I have been wanting to do this for a long time.
I still have to grind a tiny boring bar to cut the crown and leade.
Mike
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Little more progress......
I cut a stock from some maple.....and I'm pretty happy with it, except for the gouge in the grip.
I tried to crank up the speed a little too much, and ended up with a following error. I forgot to raise the Z after clearing the error, and that was the result. Gotta love it......lol.
This stock wasn't intended to be the final anyways, as I was going to use a laminate blank. I may try some king of cool paint job on this one, though.
It's taking shape......It looks like a grenade launcher right now. ;D
Mike
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Got some more done this afternoon.
I hollowed out some of the grip to fit the electronics into, relieved the stock for the swing breech (I guess that's what it's called), thread milled a few holes to fasten the stock to the valve chamber and solenoid housing, and whittled and sanded a bit to make the stock grip feel nice to me.
Weighs 5 lbs right now. I'm figuring another 1.75lbs for the barrel.....a scope is another 1.5-2.0lbs......hamster, cheek rest, and butt...?
Probably 10-10.5lbs all together, I'm guessing.
If I ever get the barrels that I ordered, I just might actually get to fire this thing. ;)
Mike
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If I ever get the barrels that I ordered, I just might actually get to fire this thing. ;)
Don't wait too long. It's about a 2 week process to get barrels from LW. At your pace you are going to need one soon :)
Tom
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They have been ordered since July 26th. WW said they would ship the same day that they got the cashiers check.....that was the 30th. He can't (or won't) tell me when they will ship.
Mike
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I finished the trigger this afternoon and got it all mounted up.
It's pretty much just a blade with a lever that operates the micro switch that bolts to the main tube.
Currently the pull is a shade over 3oz. I can adjust the tension by rotating the switch to less angle......which will make it softer. It can also be adjusted to take up the slack. It's a single stager, but could easily be set up for 2 stage.
I honestly could not imagine anything with a cleaner "break". I would guess that the blade had to travel between .005 to .010". The micro switch has an audible click to it as well.
It's pretty simple, but it feels awesome.
No worry of balk firing with a setup like this, either.
Mike
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I got my LW barrels today.......so I spent a little time on the lathe to get one fitted up.
Earlier today, I took a 20" barrel off of an old Crosman pumper to try and get some chrony results to see if I was in the neighborhood that I wanted to be in. About the time that I got that finished, the UPS guy showed up with the LW barrels....lol.
I was getting a max of 926 fps with the 7.9gr Crosman wadcutters, and about 850 with JSB Exact 10.34's, and 910 with the Exact 8.44's.
After getting the LW barrel on, which is 24"ish, I was getting 875 with the 10.34's and 925 with the 8.44's. I no longer care about the Crosmans, I was just using them up since they were not very good in my other gun. Probably a little faster than the JSB 8.44's, though.
I did a shot string earlier with the 20" Crosman, but I haven't had any real time with the new barrel, yet. Efficiency was around 1.45 FPE/CI per shot and 14.7FPE with the 7.9 Crosmans and the makeshift barrel.
Looks like the 10.34s are around 17.5FPE, and the 8.44's at 16FPE with the Lothar Walther......so I'm sure the efficiency number has changed, too.
I'll try to check that tomorrow.
I'm pretty happy with things so far.
Mike
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Sounds like it's doing good so far.
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Thanks Ricky
I'm feeling pretty happy about it all.
I did some shot strings today with the 10.34 JSB Exact Heavies. They seem to be more efficient. The gun is speeding up a bit as I go.
Starting pressure 2000
Ending 1750
Hi 888
Lo 872
ES 16
Shot count 20
17.8 AVE FPE
1.35 FPE/CI per shot
I was able to repeat this many times over, so it seems valid.
I brought out some targets and went to my buddies shop and shot some 30 yarders.
Despite no cheek rest or butt stock, 5/16" 10 shot groups were pretty repeatable with no fliers (Exact Heavies).....until I shot some wadcutters, lol. Those were terrible. 2" groups.
He has been trying to thin out the squirrel population there, so he asked if he could borrow the gun for a shot since he had a visual on one sitting on a woodpile at about 30yards. One chest shot clean through.....puffs of fur, and a quick drop. I was surprised at the apparent power, since I have never owned anything stronger than 3 FPE.....lol.
I'm partial to paper shooting, but if he wants to knock off squirrels......that's his business. I was happy to furnish him with the tool to do so. He wants a gun like this now, which is funny because he had absolutely no interest in it the whole time I have been building it.
It's reading 92 db outdoors......it doesn't seem too obnoxious. I think I'm going to shroud it anyway, though.
Pic as it is for now.....lots to do yet, but good to have it shooting.
Regulator is next. What would be the ideal pressure based on the above results?
Mike
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What would be the ideal pressure based on the above results?
What was the shot string like?... high at the beginning, middle, or end?....
Bob
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Hi Bob,
The shot string was a bell curve, and it is the sweet spot for 2% ES.
At 2000psi, it begins at around 872, by 1900 it has peaked near 888 and then begins to decline back to around 872......finishing at 1750.
The pressure numbers are the best I can determine from the gauge on my Hill pump.
Mike
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Wow that is some sweet gun you have build....
A regulator and it looks as you will be shooting a flatline string.
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Thanks Bent,
I cant wait to get a decent scope and a cheek/butt rest on it.
That avatar cracks me up every time I see it.
Mike
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Since you know that the top of your cell curve is at about 1900 psi, I would try and set the regulator for 2000.... Because you will lose some on the average pressure, even that may not be quite enough.... The reason I say that is this....
If you set the reg. to 1800, your velocity would be about 872 (minus the loss for the plenum) and the velocity would fall immediately that you go past the setpoint.... Your efficiency would be lower as you are operating on the "plateau" of the velocity vs. hammer strike curve....
If you set the reg. to 1900, your velocity would be about 888 (minus the plenum loss) and the velocity would still fall immediately below 1900.... Your efficiency would be slightly better as you are operating right where the "plateau" starts....
If you set the reg. to 2000, your velocity would be about 872 (minus the plenum loss) and as the pressure drops below 2000, the velocity would first creep up to 888 before dropping.... You will be operating on the "knee" of the velocity vs. hammer strike curve, which is where you find the best balance between power and efficiency....
Since you are using a capacitor instead of a hammer spring, it would seem to me that it's a bit harder to get small changes in hammer strike.... Therefore, you have to get the regulator pressure just right.... In case you haven't seen it, here is the graph I'm talking about....
(http://i378.photobucket.com/albums/oo221/rsterne/QB%20on%20HPA/QB79NinjaDelrin1200_zps999456be.jpg) (http://s378.photobucket.com/user/rsterne/media/QB%20on%20HPA/QB79NinjaDelrin1200_zps999456be.jpg.html)
I'm not sure of how sensitive your gun is to the relationship between hammer strike and pressure.... but over 100 psi you have a change of velocity of about 16 fps.... That MIGHT put you at about 3 turns on the above curve at 1800 psi and and 5 turns at 2000 psi.... In your case, at 2000 psi the velocity is falling again, but if the gun was regulated at 1900, it would be roughly on that curve at the 3 turn point.... Look at the difference in efficiency between 3 and 5 turns out.... it's substantial (35+%)....
Bob
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Thanks again for the detailed reply.
I see what your saying about the efficiency.
I will shoot for making a regulator that can be adjusted from 1700 to 2100 or so. Before I had any idea of what I was going to need , I designed the reg for this gun to function around 1200-1400. I have not looked at it since, but I will obviously need to add some more spring, or change the surface areas. I'm going to look for a coil spring that might fit my needs. The original design used bellevilles, but some of the other types of work I have done with bellevilles suggest that they are not as repeatable in spring performance as a standard coil.....especially when in the "series" arrangement. I suppose that is because of excessive friction when they are stacked like that.
Pretty much all of the information that I acquired to build this rifle has come from this forum, and the vast majority of that information was submitted by you. I really appreciate you putting this stuff out for all to see. It has been a tremendous help to me, for sure. I'm certain that I would not have been able to get this rifle so close to where I wanted it on the first try without it.
BTW, the capacitors in my system are kind of a rough tuning measure. I can vary the charge voltage from the boost convertor in extremely small increments.... which, in turn, controls the amount of stored energy in the cap. It's a much finer means of adjustment.
Mike
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If its easy to fine tune the hammer strike, then pick whatever regulator setpoint you want and tune the gun conventionally.... The higher the pressure you choose, the more power, but the shorter the shot count.... It's really that simple.... For whatever pressure you pick, start with enough hammer strike that you are well up on the "plateau" and then reduce it until you see the velocity starting to drop.... I run that QB in the graph above at 4.5 turns out, and that is where I tune virtually ALL of my regulated guns, just on the "knee" of the curve.... That way you get good efficiency, and you can shoot 100-200 psi below the setpoint before the velocity drops, giving you a few more good shots....
Bob
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This is a most interesting project. Let me suggest a safety implementation that has a switch between the power cap and the solenoid. Perhaps another pole on the switch you're using to cut the main power. The thing can still fire as long as your HV cap is charged.
cheers,
Douglas
--I have use those photo flash caps for energy storage too. I get the camera bodies from the developers and salvage them. The last project I built with them is still in service and I built it a decade ago...:) IFF you get them that way, be aware that some may still be charged up...lol
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Douglas,
That's a good idea, but in this case it is probably not needed.
With the small amount of shooting that I have done so far, I have already become accustomed to just leaving the breach slightly open until ready to shoot. It's in a very convenient location, and it's a good habit to get into. With the breech open the transfer port hole no longer lines up, and pulling the trigger amounts to nothing but a light tapping on metal sound. Rotating the breech to the firing position right after a misfire seems to result in nothing as well.
The cap in this setup holds it full charge for about 1/4 second after the battery power is removed. After about 3 seconds, the remaining power is not enough to fire at all. There won't be any surprises after extended storage.
I think you may be referring to the disposable camera flash units. This is just a photo cap and a DC to DC boost converter. A regular cap would probably have worked fine in this setup, too. I'm only using 60 volts.....those disposable units are closer to 300, with a much smaller photo cap. (10uf)
Mike
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Douglas,
That's a good idea, but in this case it is probably not needed.
With the small amount of shooting that I have done so far, I have already become accustomed to just leaving the breach slightly open until ready to shoot. It's in a very convenient location, and it's a good habit to get into. With the breech open the transfer port hole no longer lines up, and pulling the trigger amounts to nothing but a light tapping on metal sound. Rotating the breech to the firing position right after a misfire seems to result in nothing as well.
The cap in this setup holds it full charge for about 1/4 second after the battery power is removed. After about 3 seconds, the remaining power is not enough to fire at all. There won't be any surprises after extended storage.
I think you may be referring to the disposable camera flash units. This is just a photo cap and a DC to DC boost converter. A regular cap would probably have worked fine in this setup, too. I'm only using 60 volts.....those disposable units are closer to 300, with a much smaller photo cap. (10uf)
Mike
I read the whole thread :-), cool :-).
Two questions, do you get the cool "whine" when you charge the cap ??
Also I thought about using a solenoid to just cock a coil spring, and or work a bolt, with a little work it could make a Marauder into a sort of semi or even full auto :-).
I never really thought about how much "work" a single 9 volt battery will do, but it sounds like the answer is "quite a bit".
A friend shared some of the cap boosted solenoid stuff with me when I was looking at using a solenoid to open a damper on a meat smoker, it is a good way to get a low hold current (so the solenoid does not heat up) but still move some mass to position, effectively allowing you to use a lot smaller solenoid.
Curious about the LW barrels, I had talked to that guy via email and never knew that if/when I do order I will have no idea if I actually GET what I order :-).
Bill
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It has been a while, but the disposable flash cameras I had ran 80-160 uF/330V caps. If you've got room I bet you can tune hammer energy with the cap size. Boost the voltage and you'll be able to run smaller caps...and I can't help wondering what metalized mylar in the 150 V range would do for you...
cheers,
Douglas
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Hi Bill,
There is no detectable noise on my gun.......bummer, eh?
The gun is completely silent throughout the whole cycle except for the actual firing. No cocking noises, etc. If I was a hunter, I suppose that would be a cool side benefit of this solenoid and rotating breech.
You have to submit an order via email, and wait for them to respond with a PO. It took roughly a week and a half to get a response from them with a PO. It took several calls during that time as a reminder.
When I ordered my barrels from LW, I was assured that they would ship the same day that they received the funds, since they were in stock.
They do not take credit cards, so you must send a cashiers check or money order. I paid extra to send my funds quickly. I waited a week, then called to check on the shipping. They said that they had not yet shipped, but were going out that day. I waited another week, and made another phone call. They, then, told me that they didn't think they had shipped, but there was no real way they could be sure. They told me to send them an email with the PO again, and they would get back to me. They were not very nice, and they seemed to want me to feel bad for them because they were so busy. I never received a response, but the barrels showed up a week and a half later. When I order from them again, I will factor in 6 weeks for delivery....at least.
Things happen to people that disrupt their normal expected functioning. Some folks are frank about circumstances and apologetic when things fall short on their end......others try to make the customer feel bad when they don't do what they said they were going to do. My dealing with LW has been of the latter category. Whether it's true or not......I feel that if I had not followed up with them repeatedly......I may not have any barrels today. If they told me they were real busy and it would take 6 weeks.......and it did.......nobody would be upset.
That said, I'm pleased with the barrels. I really don't know what other options are available, either.
Mike
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Hi Bill,
There is no detectable noise on my gun.......bummer, eh?
The gun is completely silent throughout the whole cycle except for the actual firing. No cocking noises, etc. If I was a hunter, I suppose that would be a cool side benefit of this solenoid and rotating breech.
You have to submit an order via email, and wait for them to respond with a PO. It took roughly a week and a half to get a response from them with a PO. It took several calls during that time as a reminder.
When I ordered my barrels from LW, I was assured that they would ship the same day that they received the funds, since they were in stock.
They do not take credit cards, so you must send a cashiers check or money order. I paid extra to send my funds quickly. I waited a week, then called to check on the shipping. They said that they had not yet shipped, but were going out that day. I waited another week, and made another phone call. They, then, told me that they didn't think they had shipped, but there was no real way they could be sure. They told me to send them an email with the PO again, and they would get back to me. They were not very nice, and they seemed to want me to feel bad for them because they were so busy. I never received a response, but the barrels showed up a week and a half later. When I order from them again, I will factor in 6 weeks for delivery....at least.
Things happen to people that disrupt their normal expected functioning. Some folks are frank about circumstances and apologetic when things fall short on their end......others try to make the customer feel bad when they don't do what they said they were going to do. My dealing with LW has been of the latter category. Whether it's true or not......I feel that if I had not followed up with them repeatedly......I may not have any barrels today. If they told me they were real busy and it would take 6 weeks.......and it did.......nobody would be upset.
That said, I'm pleased with the barrels. I really don't know what other options are available, either.
Mike
The impression I got was that if I ordered anything BUT the in stock items they would me made overseas and shipped here, and then I would get tracking info on the shipment.
Bill
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It has been a while, but the disposable flash cameras I had ran 80-160 uF/330V caps. If you've got room I bet you can tune hammer energy with the cap size. Boost the voltage and you'll be able to run smaller caps...and I can't help wondering what metalized mylar in the 150 V range would do for you...
cheers,
Douglas
Some sort of voltage regulation for the charge would have to be put into place. When I was initially messing with the camera circuits, the voltage was all over the place......which is why I abandoned it for the boost converter. The boost converter maintains an exact output over a very broad range of input voltages.
I don't know anything about metalized mylar caps. What is their claim to fame?
Bill.....I would prefer to have the barrels shipped from overseas with tracking than deal with the US distributor.
Mike
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Mike,
I came in late on this project but have read thru all the posts. Very impressive, and darn fast too. Type A personality? LOL. Honestly, first class all the way.
I'd like to bother you for so more information if I can, please. Do you have a PN and source for the boost convertor and solenoid that you are using? That will be a nice reference starting point to put in my hat for later, should the need to strike, strike. Also, and this is second hand information, but I have heard that over voltaging a solenoid might eventually start to magnetize the armature. I don't know if that is fact, or if it is even a concern in your case. That armature looked pretty stout.
And lastly, for now anyway ;D , a possibility of any detail photos of the swing breech?
Thanks for sharing this great project!
Lloyd
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Hi Lloyd,
This is the solenoid......http://www.onlinecomponents.com/guardian-electric-tp8x16i12d.html?p=11480738 (http://www.onlinecomponents.com/guardian-electric-tp8x16i12d.html?p=11480738)
I purchased the return spring kit from the same place, but am unable to find the number for that at the moment.
The boost convertor is an ebay item.....http://www.ebay.com/itm/LM2577-3-34V-to-4-60V-DC-Step-up-Convert-Power-Supply-Boost-Charge-Module-5-12V-/390642391009?pt=LH_DefaultDomain_0&hash=item5af419d7e1 (http://www.ebay.com/itm/LM2577-3-34V-to-4-60V-DC-Step-up-Convert-Power-Supply-Boost-Charge-Module-5-12V-/390642391009?pt=LH_DefaultDomain_0&hash=item5af419d7e1)
I also bought another boost converter that was capable of 97v output, but it never showed up. The 60v model seems adequate for my gun's power level, though.
There is a place on the web called solenoid city, and they have a much larger array of solenoids in this basic size (and many others). The solenoid that I used measured 9ohms, and using the same components with a solenoid of 4.5ohms would result in twice the power. If the one I bought proved to be inadequate, I was going to do just that. Because of the 3-5 millisecond duty cycle, I don't think the voltage rating really means much. I have been unable to detect any heat buildup whatsoever after thousands of repetitive cycles.
I don't know anything about magnetizing armatures, as this is my first foray into capacitive discharged operation.
What exactly would you like to see about the breech? It may be easier to see the cad drawings that I used to make the parts.....otherwise, there is not much to see on the outside.
Mike
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Mike,
Thanks, just what I needed. Always good to find new sources for components.
So if I have this right, the convertor is just to supply the higher charging voltage for the caps, the pot on the board controls the regulated output voltage, the resistor on the input to the caps controls the charge rate, and the resistance in the solenoid coil controls the discharge rate. No need for a diode to protect the convertor from the solenoid, or is that built in?
Regarding the swing breech, does that swing out between the transfer port and the barrel? Just trying to visualize the layout and the sealing technique used used at the breech.
Thanks,
Lloyd
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Ya.....that's pretty much it. The discharge rate and power is more of a combination of voltage, capacitance, and resistance in the solenoid.
I do have a diode to protect the booster......it's a separate part from the boost converter. Its nothing special......just some 1000v diode I had here.
I first bought some scr's to keep the current out of the switch, but have not actually found a reason to use them, yet.
Just a small microswitch.
This link is to a calculator that can be played with to get a feel for the relationships of the above variables. http://hyperphysics.phy-astr.gsu.edu/hbase/electric/capdis.html (http://hyperphysics.phy-astr.gsu.edu/hbase/electric/capdis.html)
The swing breech is the transfer port on my gun.......and the Mac1 USFT. It was the motivation for my rendition. If you look at my valve, you will see 2 Orings. There is a crossdrilled .100" hole in the valve body between the orings......which lines up with the transfer port in the part that I have been calling the swing breech. I didn't know what else to call it. I guess it may be more of a rotating transfer port. The rotating transfer port then has an oring that seals to the back of the barrel when turned into place. There is about .001" clearance between the cylindrical valve body and rotating transfer port (RTP from now on). The valve body bottoms into the plenum, creating a .500" space for the thickness of the RTP and a pair of Delrin washers. It rotates as if was on very snug, but smooth, bearings.....due to the shock absorber like friction from the orings that it rides on.
I originally though I would have the cylindrical valve body turn with the RTP, but it seemed overly complicated since that would require the valve body to dynamically bear the air pressure load.
I have no idea how the USFT works......I just saw some pictures, and made it work for me. It's the simplest way I could come up with.
Bob noted that I have roughly the volume of a hogged out .22 Marauder between the bottom of the valve and the pellet. Surely more efficiency could be had if that was smaller, but there isn't any practical way that I can readily see to make it appreciably smaller with the design as it is.
It seems reasonably efficient as it is.
My original goal was to get at least 50 consistent shots once regulated, but it appears as if I'll get at least double that.
Mike
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These may be more helpful.
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I don't know for sure, I'm just guessing from the few pictures I've seen, the USFT breech seems to have an angled hinge which allows the breech swing arm to move back as it swings to the side. Your system appears to be much easier to construct. Great stuff!
Tom
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Michael,
The pictures and your explanation make the functionality pretty clear. I see that you have used a fairly thick cross section o-ring which I guess aids in the smooth closing operation you describe. Getting the correct compression on an o-ring for a special application can be a little tricky sometimes. Looks like you got it figured out. Nice!
Lloyd
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Haven't had much to say lately.....I've been doing a lot of shooting, though. ;D
Still have the muzzle weight, and some other pieces to finish......and then some anodizing.
The butt stock is stolen from my "modified" Avanti753. I finished the knee rest, but don't have it painted, either.
Pics are of the intended look, and the gun in it's current condition. I got the base coat on, and decided to put it back together and shoot for a while. I'll have to wet sand, recoat, then do the charcoal......then clear.
Shooting from a vise at 40 yards yields a maximum 5 shot group of size of .335" c to c. Smallest are just about a pellet width. I shot 25 groups on individual index cards. I think it can still improve some.
I'm gonna polish the bore and retry some more vise groups. My typical 20 shot groups shooting from 30 yards off a front bag are about .280" or so with the occasional flyer messing things up.
I'm moving forward......but not nearly as fast now that I'm having fun shooting the thing.
I found out that the valve stem was galling the aluminum valve body. It eventually stuck open and dumped the whole reservoir in one shot.
I took it apart, reamed, then polished it good with the stem. The efficiency went way up, along with the power. It's now doing a steady 1.45FPE/CI at 19.6FPE with JSB Exact Heavies around 925fps.
The JSB Exact 8.44's were grouping the best, but I ran out of them, so I have been using the heavies. I think it will probably be shooting the 8.44's a bit hot, now. I will probably drop the capacitance and try to get them in the 930 range......when the order shows up. ;D
Mike
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Sweet.. and a big congrats on job well done...
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Very nicely done!
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Thanks, guys......it feels like a mighty weight has been lifted from me. I'm sleeping good, again.....lol.
Mike
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I think I've been reading this thread about a dozen times.... I now know what my winter project will be.... 8)
I've ordered the bits and parts from DX, Ebay and a 12V 12 Ohm solenoid from a Danish dealer...http://www.conrad.de/ce/de/product/502261/Zylindermagnet-Intertec-ITS-LZ-2560-D-12VDC-12-VDC-Befestigung-Schraubgewinde-Ausfuehrung-drueckend-Anfangs-Endkraft-07 (http://www.conrad.de/ce/de/product/502261/Zylindermagnet-Intertec-ITS-LZ-2560-D-12VDC-12-VDC-Befestigung-Schraubgewinde-Ausfuehrung-drueckend-Anfangs-Endkraft-07)
Thank you Michaelthomas ;)
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Yep.....no problem.
It will keep you entertained for the cold season. ;D
If I can be of any help, just let me know.
Mike
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Awesome project Michael, I might have to try this someday after seeing your 30yd FT scores..
Simply an amazing design, well done!!!
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Beautiful work! I'm very familiar with how much work is involved when you custom build every part of gun, then add some electronics to boot, A trying task to say the least.
I'm curious why CD and not direct drive? A simple regulated boost topology could give you the power you need with out the discharce curves, temp and tolerance issues associated with HV caps. You could also control the current in the winding via PWM. Just thoughts :).
Tom
Stop speaking GREEK !!!
Lol ... had too
Thy are not speaking Greek they are speaking "geek" . Former USN ETR Telecom central office switchman and now HVACR manager
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Awesome project Michael, I might have to try this someday after seeing your 30yd FT scores..
Simply an amazing design, well done!!!
Thanks Joel,
Over time, I think I will post the drawings, schematics, and material list so others can have a go at the build if they feel like it. I worked from a basic drawing, but some things changed on the fly and I have not gone back to revise them yet. On an individual part level, there is nothing complicated. I suppose it's a bit unconventional, but certainly not complicated. The main part is just a bunch of tubes and threads......all doable on a regular lathe and mill.
I have also given a little bit of thought of maybe offering some of the more difficult parts for sale if there was any interest. I don't know.
The electronic part is ridiculously simple..... and so far it has proven itself to be very, very consistent.
I need to finish up mine, first. ;D
Mike
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I need to finish up mine, first. ;D
More appropriate words never spoken :P
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Beautiful work! I'm very familiar with how much work is involved when you custom build every part of gun, then add some electronics to boot, A trying task to say the least.
I'm curious why CD and not direct drive? A simple regulated boost topology could give you the power you need with out the discharce curves, temp and tolerance issues associated with HV caps. You could also control the current in the winding via PWM. Just thoughts :).
Tom
Stop speaking GREEK !!!
Lol ... had too
Ναι, μπορο να σας βοηθησο ? (yes,i can help you ?)
Very nice job.
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Hi Lloyd
You talked about Solenoid city and their more powerful solenoids.
I was contemplating building a solenoid striker for a Benjamin Discovery.
I dont know yet the particulars about the hammer spring force on the mechanical version yet, or the strike cycle in ms. (research here I come)
But any help would be appreciated. I was looking at this: s-20-100hp1
Which is 1" dia, might be to big. but they come in .25 increments, so I am sure there is one who nicely would fit inside the Disco tube.
Love your write up, very informative.
T
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I'm not Lloyd, but I assumed that you were addressing me. He probably has a lot of info on this sort of thing too, though. ;D
Yes.....solenoid city seemed to have solenoids with much lower resistances available. (Compared to the 9ohms of the one I used.)
I suppose you would have to find the largest physical size that would fit into your space......then just keep increasing the voltage (or possibly capacitance) until it does what you need. Lowering resistance is pretty much the same as increasing voltage.
Increasing voltage will shorten lock times, whereas increasing capacitance probably won't.
I don't know exactly what the lock time on my rifle is. For all practical purposes, it seems instantaneous. Mathematically, it was somewhere around 2-5ms for the solenoid plunger to do it's work.....but in reality, I don't know.
I can say that when shooting my rifle......it sure doesn't seem slow.
Mike
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Lowering resistance is pretty much the same as increasing voltage.
Slight correction. The power in the winding goes up by the ^2 of the voltage. If you double the voltage there is 4 time the power in the solenoid.
Edit:
I had this wrong although the statement is correct as typed but confusing. Thanks to Mike for calling me on it.
The power (Watts) does go up by the ^2 of the voltage but the motive force is linear. As you raise the voltage the efficiency goes down the inv^2 of the voltage. This is why these things are designed to operate at specific voltage. For the ultra low duty cycle of this application there is a lot of voltage leeway.
Tom
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Thanks guys!
Making the hammer action solenoid powered rather than spring/mechanical seems to me to be an interesting option for tuning the power.
T
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Yes, Mike has done a fantastic job demonstrating this. The technology is very compelling, especially in the sub 20fpe range where the components and power remains small and easy to manage.
Tom
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That said, I'm pleased with the barrels. I really don't know what other options are available, either.
Mike
Mike,
Nice work. I love to see a project like this come together.
For pellet use there is not many options. Lothar Walter, BSA, FX, and Crosman IIRC. I considered using LW once. After the trials to just receive the PO I decided to use a company that is based in this century.
I have had a lot of luck using Green Mountain. http://gmriflebarrel.com/barrelblanksround (http://gmriflebarrel.com/barrelblanksround)
Of course I tend to shoot larger lead and cast my own bullets.
TJ barrel liners is another option. I have not tried any but may in the future.
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How many amps/volts for the diode that you used and also the watts of the resistor?
Thanks Michael!
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I used a 10a 1KV diode, and a 1/2w 1k resistor.
Mike
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Rescue35.....thanks for the GreenMountain link. Hadn't heard of those, before. How do they compare for accuracy to the LW?
Mike
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Rescue35.....thanks for the GreenMountain link. Hadn't heard of those, before. How do they compare for accuracy to the LW?
Mike
I've never used a LW. I have used .25, .30, 9mm, .45 and all where excellent. Green Mountain supplies Crosman with the .25 barrels for the Marauder.
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Rescue35.....thanks for the GreenMountain link. Hadn't heard of those, before. How do they compare for accuracy to the LW?
Mike
I'm not Rescue35, but know folks who swear by the Green Mountain barrels. As mentioned, Crosman uses them in the 25 Marauder - which has a reputation for a tack driver. They also supply muzzle loading and other barrels, all of which have a good rep. A good barrel deserves good fitting and crowning. A poorly fitted and crowned Lothar Walther will shoot worse than a run of the mill Crosman that is set up properly. Good quality components with good quality work = good quality shooting.
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Moved to: http://www.gatewaytoairguns.org/GTA/index.php?topic=53284.0 (http://www.gatewaytoairguns.org/GTA/index.php?topic=53284.0)
Sorry for hijacking..
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Couldn't help...... needed to share... 8)
Woow, haven't worked much in Solidworks before... It's amazing what you can make... to make it look goooood.. ;)
The gun will be made as a semi auto.
Right now I'm working on how to lock the probe when firing. One solution is to have an arm locking it, but I'm worried about problems and wear..
The power to make the probe go back comes from a piston inside the shroud.
The simple solution is having the probe so heavy and the returnspring so strong that the probe stays in place during the shot. Heavy spring won't do it alone, then the shroudpiston can't give enough force to cycle the probe.
Anyone know how to calculate that?
Data:
2200 psi (max-regulateded)
.25 kaliber
Maximum energy 890fps / 48 grains >> 84FPE
Barrellength 600mm
Don't think I'll get that high, but just to play it safe
If you can get your hands on an ar-15 bolt/carrier it contains a simple way to convert linear motion to rotary motion and thus lock a bolt with a lug or a cross pin, then unlock it when you pull the assembly to the rear.
Hmm maybe AR-180 picture shows the feature better.
(https://encrypted-tbn2.gstatic.com/images?q=tbn:ANd9GcRI79kJGbss_OsyIxPoD4bXJs1SuaCCiGDvn_ombYqlRqETTDVv)
Bill
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Very nice design work! The force is significant at 83 lbs. It's simply the bolt face area * the peak operating pressure, SW will give the area easily or use pi*r^2. Keep us posted.
Rotating bolts are easier designed than executed, they are great if you can create the geometry and finishes needed to operate smoothly. Other options are over center and falling block mechanisms. Also consider a pneumatic pin type lock that can be operated by the same source as your bolt, orifice and piston size can be used as timing control.
Tom
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Moved to: http://www.gatewaytoairguns.org/GTA/index.php?topic=53284.0 (http://www.gatewaytoairguns.org/GTA/index.php?topic=53284.0)
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Hi Bent......drawings look nice.
You should probably open your own build thread..... so this one doesn't pile up with a bunch of posts that are unrelated to this particular build.
Mike
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Oops, didn't even notice where it was posted. Perfect for a new thread in the R&D gate. Tom
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Mike, I Just about have all the bits together but the hammer return spring I have is .049" wire diameter and from looking at the one in your picture I am guessing it is about .020" wire diameter? I am looking at Mcmasters but not finding one with the right dimensions. I might have to modify one if I can not find a source.
Any suggestions?
Thanks Joel
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You needn't look too far......lol. Mine is a spring from a pen.
Mike
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The poppet return spring looks like a pen spring, However I was talking about the solenoid hammer return spring in your first pic on the far right? Hmmm Maybe I need a different pen?
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Hmmm....yes, you did say hammer spring didn't you?
Sorry.....I don't have the number, but it is a solenoid return spring kit from the same place I listed for the solenoid. Guardian brand.
If I remember correctly, I had to get the number of the return spring kit from the guardian site......then use it on the other sites search bar.
Mike
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Thank you Sir! :D
I think this is it. http://www.onlinecomponents.com/guardian-electric-a49036746011.html?p=11480492 (http://www.onlinecomponents.com/guardian-electric-a49036746011.html?p=11480492)
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No Problem. :D
Mike
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;D ;D ;D Mike just wanted to say really great job on your project, also want to add that now I understand your statements on the tack driver thread just a tad better. In a past life I was a Navy ET after the Navy ended up working for a company called ISC Telephonics here on Long Island N.Y. and had the good fortune of working in the engineering lab with a great engineer doing R&D, repeatability was the watchword and if there was no consistent repeatable results under diverse conditions it did not mean squat. Again amazing rifle if I ever get into PCP Something that High Tec and that high a cool factor would be on my wish list ;D ;D ;D 8) 8) 8)
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Thanks Don.....that's nice of you to say.
I should point out that I am certainly aware that I seem to have a knack for wording things in ways that can be misunderstood. I don't fathom the "other" way while I'm typing.......but I becomes apparent to me after it's too late. I can't count the number of posts that I have made where the point I was attempting to make has gone badly awry......and trying to explain myself further only seemed to make the matter worse. I suppose that is partly due (or wholly) to my sarcastic style of humor.
I seldom, if ever, run into this trouble in person. The cold truth is that once a person finds something I have said to be inflammatory......from that point on, anything I say is viewed in the worst possible light since the internet doesn't convey body language, tone, and other very important clues about the speakers intended angle. My wife suggested that I learn to use the smileys to help with things......and I've been giving it a go. :D
Since this is my thread.....I feel like I can ramble a bit without drawing criticism for a hijack. ;D
I don't posses the ability to feel brand loyalties or their ilk. I think this comes across as disturbing or abnormal, too. I believe that everything can be objectively assessed for quality and ranked accordingly. If brand loyalty or emotional attachment is present, the ability to objectively view something is compromised.....if not completely destroyed.
I seriously believe that the first step towards improvement for anything is the full acceptance that the current state of things is not good enough......no matter how much is invested. Brand loyalties, knowingly skewed results, and emotional attachments are impediments to this realization......in my narrow mind, anyway. ;)
I apologize (to everyone) for sometimes using abrasive, sardonic, and blunt dialog to convey my points.
I'm working on it. ;D
Mike
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I tried to fix some spelling errors and ended up quoting my own post with nothing additional to say. ;D
Oops.
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I tried to fix some spelling errors and ended up quoting my own post with nothing additional to say. ;D
Oops.
Still totally impressed with your FT project ;D
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Well....thanks again. It's been (and still is) a great learning experience for me.
Joelw.....I see you added to your post with the return spring parts link.....thanks.
Mike
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...................
I should point out that I am certainly aware that I seem to have a knack for wording things in ways that can be misunderstood. .............
..........
I apologize (to everyone) for sometimes using abrasive, sardonic, and blunt dialog to convey my points.
I'm working on it. ;D
Mike
Certainly no problem Mike. Your wife's :-* suggestion of the smilies was a good one :D . I know from personal experience how hard it is to take words back once they are out of my mouth :-X .
Going back to the previous page and the brief discussion of barrel sources, I have to say that I agree with all the comments. I have used some of the LW barrels.. nice quality, heavy barrels, but if its not in stock, plan on a long wait. The barrels from TJs are really liners.. some of them are kinda thin-walled, but I find them perfect for airguns. And Mike Sayers (TJs) is a dream to work with. He always gets the order correct and out the door pronto. I haven't personally used any GM barrels but have only heard good things about them. And of course, as was said by AmBraCol, it is easy to turn a good barrel into a piece of junk by improperly preparing it. Personal experience on that one, too :-[ .
Another good source is http://www.gunpartscorp.com/ (http://www.gunpartscorp.com/)
They have all sorts of stuff but I do find their search engine very difficult to navigate and ferret out what you are looking for. Maybe its just me. I have bought barrel blanks and barrels, and other stuff from them. Prices vary and some things are dirt cheap. Many of the barrels are too short (in my opinion) for airguns, but the site is worthy of a good search if you are fabricating airguns or firearms.
Sorry for wandering from your original topic ;) , but it seemed relevant.
Lloyd-ss
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I got my board tonight and put all the bits together like your picture shows. Powered it up, adjusted the voltage to 60.1v, flipped the switch and WHACK.. This solenoid setup is pretty powerful. ;D
Can't wait to stuff it in this Mrod and try it.. Thanks Mike!!!
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LLoyd.....thanks for the links and barrel info.
I've had good luck on the LW barrels so far......but my first one is about a half inch shorter than it was supposed to be. ;D
Joel......I'm glad it's working for you. Keep us posted on the progress.
Mike
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I set up a pinball type setup that would shoot a small 55 gram cylinder with the spring and hammer. I allowed it .5" to accelerate and compressed the spring almost fully. It would shoot the cylinder 38 inches from a height of 33 inches.
Mike
One more question please Mike. Your last sentence confuses me a bit here. Were you launching straight up or at a 45 degree angle or out off of a 33 inch high shelf?? Just trying to compare the power of mine to the power of yours. I can smack a much lighter marble 32- 48" straight up depending on the caps used but I still need to compare that to my hammer and spring in some kind of pinball setup that I have not figured out yet. ;)
Thanks Joel.
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Hi Joel.
My test setup was a level table 33 inches off the floor.
http://hyperphysics.phy-astr.gsu.edu/hbase/traj.html (http://hyperphysics.phy-astr.gsu.edu/hbase/traj.html)
This was the calculator that I used. Horizontal launch was the one that was most pertinent.
Hope that helps.
I finally fine tuned mine today for 885-890 with the Exact Heavies. I couldn't get where I wanted to be with capacitance changes, so I had to drop the voltage to 57 for my particular application. One turn seemed to equate to a 2 volt change on my boost converter.
Mike
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The actual ftlbs are not really important, I guess. You just have to be able to duplicate the distance that your regular hammer spring will "shoot" something.
Remember that I have intentionally made my valve very small so opening force required would be less. I don't know how that plays into your setup.
What caliber are you working on?
Mike
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That clears it up completely. Thank you. ;) I looked at the horizontal launch calculator but that is about as far as I can go with that as it is smarter than me.. Hahahha
This will be in a regulated .22 setup with 13.43gr jsbs aiming for 20fpe. Still waiting on my barrel from Jim... :'( but I did stick the solenoid to the gun and it definitely opened the valve with 1500psi many times. It's very loud like that so that makes me think it might actually be close.
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Are you making it for field target or heavy varmint bench rest?
Mine was really loud, too.
If it's not enough you can always get a higher voltage boost converter. I had ordered a 97v from the same place as the other one......but it got lost in the mail and I just never ordered another.
You could steal a barrel off a junk rifle to see how it goes in the meantime. I guarantee that if you spend a fair amount of time on a substitute barrel for testing.....the one you are waiting for will show up moments after you complete it. ;D
Mike
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It will be for field target use mostly as that looks like a lot of fun to try. Might need lighter pellets? Still waiting on the solenoid return spring and that will slow it down and change the testing results but I am having fun with this! Very cool project... Thanks again for all of your help..
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Number 2 is nearing completion. ;D
This one got a walnut stock with an oil finish. All of the aluminum is brushed instead of polished. The barrel block, muzzle weight, scope rail, and tube caps will be anodized flat black, and the rest of the aluminum will be anodized clear.
I like the look of this one so much that I made another walnut stock to replace my first painted one. I have a third gun for a friend that will be Wenge.....but will be similar to this one, otherwise.
I should have this one totally completed by next Friday if the anodizer comes through. ;D
I'll get some more pics, then.
Mike
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Mike ... this has been a VERY fun thread, Nice work !!
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Mike,
Aren't you the guy who needs only on air gun?
Beautiful Walnut stock. Where did you get the blank?
Great and speedy work as usual :)
Tom
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Thanks, guys!
I sorted through a whole bunk of 8/4 walnut to find one 8" wide x 10' board.....lol. I know the guys at Intermountain Wood over here very well.... so as long as I stack things back the way I found them, they will let me dig all day.
I am, indeed, the guy that only needs one gun......for myself. ;D
I have an ulterior motive for designing and building this field target rifle. I am trying to get a field target club off the ground over here. The first gun I built has been on perpetual loan to anybody that even shows a bit of interest in FT. ;) I hope to have a few more loaners by next spring.....and maybe a dozen other folks that get on board with their own rifles. The biggest impediment that I have seen to people that would like to compete is the cost of a competitive rifle. I have been able to start a few guys into a rifle by supplying some of the machined parts (or the machines) and letting them contribute their own labor with whatever they can. I really enjoy teaching people to use CNC machines......whether wood, metal, or otherwise, so it's a win win for me.
Mike
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Here's a fall picture of the finished rifle..... ;D.
It was a beautiful shooting day here......sunny, mid 60's, and 1-4 mph winds. Very nice.
Mike
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That is awesome!!!!!
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Beautiful job, Mike.... and unique as well.... Congratulations!!!!
Bob
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looking good Mike
(http://www.gatewaytoairguns.org/GTA/index.php?action=dlattach;topic=50414.0;attach=71038;image)
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;D definitely serious hardware and pretty to boot and anyone who knows me knows I'm a sucker for serious and pretty in the same package
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Thanks a lot guys!
Mike
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Superb job. Would like to see a video of it shooting.
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Beautiful.
Gorgeous.
My jaw hit the floor!
That is an amazing work of art you have there, Mike. 8)
Thanks for sharing!
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Thanks, again. ;D
Mike
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Yes, very nice work! Kudos!
T
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Sweet job Mike, what oil finish did you use?
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What great stuff!!!!! Well done sir :)
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Mike, I know nothing about FT shooting or FT guns. But I can tell you that your gun is gorgeous! Absolutely stunning. I've always loved the modular look of FT guns and yours is a beautiful blend of shiny silver and rich brown of the stock. Well done sir!
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Thanks a lot.
I really like the look of this one, too. It beats the pants off of the red one. I much prefer the brushed aluminum look over the polished, too. The anodizer said I might see a slight yellow tinge on the clear anodized parts, but there isn't.
I used the Minwax Antique Oil Finish. I had never used it before, and was a bit skeptical of it......but I am now convinced that it's an excellent finish for a gun stock. It has such a wonderful smooth feel compared to a film finish. My wife gets a kick out of me, because every time I walk by the gun I have to feel the stock and make some comment to her about it. She'll laugh and say, "Ya, I know.....it's really smooth" before I get a chance to say it myself. ;D
She's a trooper.....she finds my obsessive nature to be somewhat endearing. ;D
Mike
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Thanks a lot.
I really like the look of this one, too. It beats the pants off of the red one. I much prefer the brushed aluminum look over the polished, too. The anodizer said I might see a slight yellow tinge on the clear anodized parts, but there isn't.
I used the Minwax Antique Oil Finish. I had never used it before, and was a bit skeptical of it......but I am now convinced that it's an excellent finish for a gun stock. It has such a wonderful smooth feel compared to a film finish. My wife gets a kick out of me, because every time I walk by the gun I have to feel the stock and make some comment to her about it. She'll laugh and say, "Ya, I know.....it's really smooth" before I get a chance to say it myself. ;D
She's a trooper.....she finds my obsessive nature to be somewhat endearing. ;D
Mike
;D ;D Lucky man when my wife gets tired of my obsessing she rolls her eyes and just shakes her head or when I repeat myself she'll tell me with a smile "heard that already" ;) :D
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Here's a fall picture of the finished rifle..... ;D.
It was a beautiful shooting day here......sunny, mid 60's, and 1-4 mph winds. Very nice.
Mike
That pic makes me homesick. It's all green down here - sure miss the fall colors up in Montrose (and the rest of the Rockies). Thanks for sharing your build with us. I hope you get the FT group off the ground. Where are you shooting? Years ago I put a lot of lead down range at the Montrose Rod and Gun club out on HW50 east of town, but that was with powderburners. Also put some time in at the San Juan range south of town. They were (are?) mostly CAS oriented but had a rifle range across the road from them. Anyway, hope you get the FT group going there.
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With 4 giant Maple trees in my small yard, I'm kinda wishing for the green again......lol. I like the colors, but could do without the leaf pickup. Snowed here last night......supposed to be back near 60 through the weekend. Kinda funny.
We will likely end up shooting on private property. One of my friends has a lot of land off Jade rd......they farm and raise cattle. Lots of interesting places to shoot there.
Do you come back through here ever?
Mike
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With 4 giant Maple trees in my small yard, I'm kinda wishing for the green again......lol. I like the colors, but could do without the leaf pickup. Snowed here last night......supposed to be back near 60 through the weekend. Kinda funny.
We will likely end up shooting on private property. One of my friends has a lot of land off Jade rd......they farm and raise cattle. Lots of interesting places to shoot there.
Do you come back through here ever?
Mike
My mom was born and raised out in Shavano valley and there's still uncles and cousins in the area, plus MCC is one of our supporting congregations so we get back up there every couple years or so. It's one of my favorite areas in the US of A, just wish we'd time to spend there more often.
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MCC is a stones throw from my house on York. If get over this way.....make your presence known.
Mike
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MCC is a stones throw from my house on York. If get over this way.....make your presence known.
Mike
Sure thing. It'd be good to see your project in person. :) And the person who did the project, of course! ;D
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I finished up my regulator over the weekend, and was able to fool with it quite a bit since then.
The regulator has a moveable seat, and it was a bit of a task to get it at the pressure that I wanted. I made a small test rig, but all I had for a gauge was a poor quality little Ninja jobber. It was graduated in 500 psi increments, and wasn't really accurate at all. I eventually was able to just do testing in the rifle using an air tube that was 1/4 the size of the normal one. After a lot of trial and error, I got the reg set to what I believe is about 1950 psi.
I wanted to try out the regulator installed in the coupling between my air tube and valve block, since it could be easily vented to atmosphere through the coupling. This gave me a plenum volume of about 12cc. Based on Bob's calculations, that wouldn't be enough to maintain the energy that the gun was tuned to prior to the regulator (18.4FPE). I figured I could try it out in this location, and if I wasn't happy......I could move it more outboard and drill a hole in the reservoir.
Long story short......I stayed with my same solenoid voltage and shot some strings with a lower power output than normal
I charged to 3000psi and shot down to 1850. I used the gauge on my Hill pump for the start and end pressures.
220 cc adjusted reservoir volume.
I got 85 shots at an average of 831 fps. 16FPE average. 1.28 FPE/ci
Extreme spread was 15fps with a standard deviation of 3.
I'm happy with that spread, and I believe I can get another 15 shots or so if I charge to 3200.
I'm gonna shoot the gun for a while at this speed and see what I think of it.
Mike
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Well......I didn't really do any shooting with the lower power. I made a new coupler that moved the regulator outboard by 8cc to get a plenum volume of 20cc. Obviously.......this cut down the reservoir volume to 212cc.
I got a good quality large diameter gauge that displayed 50 psi increments......but 25, even 10 could be read since the gauge was so big. I checked the regulator setpoint and it was actually 2050psi. The new regulated air gauge matched the Hill pump gauge exactly.....so that was good.
It seems that my reg takes about 30-45 seconds to settle. I guess that's not a big deal since that's about what it takes (at least) in a competition. I would like it to recover quicker, though. Not sure what would help it, though.
Any Ideas? I'm using single stacked Bellevilles....but I'm guessing they are pretty close to their limit arranged that way.
Charged to 3000
Shot down to 1850
High 864
Low 853
ES 11
SD 2
Shots 75
17.1 FPE Average
1.25 FPE/CI efficiency
Seems pretty good.....I like the SD of 2. ;D there were about 4 wild shots in there that kinda hurt the string. I was hoping to be under 1%. I just shot pellets out of the tin, so I suppose that could have accounted for some of the variance.
Mike
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It seems that my reg takes about 30-45 seconds to settle. I guess that's not a big deal since that's about what it takes (at least) in a competition. I would like it to recover quicker, though. Not sure what would help it, though.
Any Ideas? I'm using single stacked Bellevilles....but I'm guessing they are pretty close to their limit arranged that way.
Charged to 3000
Shot down to 1850
High 864
Low 853
ES 11
SD 2
Shots 75
17.1 FPE Average
1.25 FPE/CI efficiency
Seems pretty good.....I like the SD of 2. ;D there were about 4 wild shots in there that kinda hurt the string. I was hoping to be under 1%. I just shot pellets out of the tin, so I suppose that could have accounted for some of the variance.
Mike
If you use a harder material for the seat, it allows more flow... I made one for my scubatank, first try was using a hard type of nylon... it was creeping slow the last 20 bar from 180 to 200 bar... changed to a Delrin seat instead...
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Hi Bent,
I am using white delrin as the seat. I removed everything last night and closely inspected the seat. I could see a very, very slight inconsistency in the marking from the spool. I took an extra spool and made a makeshift arbor for it so I could spin it against the seat with some polishing compound. I did this until the seat marking looked good all the way around.
I also removed any silicone grease from the belleville stack. The current stack is very near flat when pressured up, and I figured that the grease was creating more "stiction" at that point.
I put everything back together and reset the setpoint, and now it charges pretty quickly (5 seconds or so) to within about 25psi of the ultimate setpoint......then takes another 30 seconds or so to creep that last 25psi. This seems like it will be very good for the application. Shooting at 3000 psi gives shots of 358-361, and shooting just above the setpoint gives me 356-359. I'm sure there will be some variables from pellets, but it looks like it's gonna be good for FT or bench to me.
I believe I can improve it further on the next one by using a smaller low side piston to get the bellevilles much closer into their working range.
If I set the reg at 1200 or so.......its rock solid, and takes way more movement of the seat to produce pressure differences. At 2050 psi, a .001" change in length will up the pressure by 50 lbs or so. I believe that operating the stack where it is more linear will improve things.
I'm using a single stack()()()()() of 10 bellevilles. I tried double stacking(())(())((, and the performance was total junk. It would creep 200-300psi. :o
I didn't do a full string because it's just a pain in the neck to fire off that many wasted shots. I'll do some target testing pretty soon.
Thanks for the input.
Mike
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Sounds like you need thicker Bellevilles in a single stack.... You could also try polshing the edges of them with 600 grit paper or finer....
Bob
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Well......I didn't really do any shooting with the lower power. I made a new coupler that moved the regulator outboard by 8cc to get a plenum volume of 20cc. Obviously.......this cut down the reservoir volume to 212cc.
I got a good quality large diameter gauge that displayed 50 psi increments......but 25, even 10 could be read since the gauge was so big. I checked the regulator setpoint and it was actually 2050psi. The new regulated air gauge matched the Hill pump gauge exactly.....so that was good.
It seems that my reg takes about 30-45 seconds to settle. I guess that's not a big deal since that's about what it takes (at least) in a competition. I would like it to recover quicker, though. Not sure what would help it, though.
Any Ideas? I'm using single stacked Bellevilles....but I'm guessing they are pretty close to their limit arranged that way.
Charged to 3000
Shot down to 1850
High 864
Low 853
ES 11
SD 2
Shots 75
17.1 FPE Average
1.25 FPE/CI efficiency
Seems pretty good.....I like the SD of 2. ;D there were about 4 wild shots in there that kinda hurt the string. I was hoping to be under 1%. I just shot pellets out of the tin, so I suppose that could have accounted for some of the variance.
Mike
Fooling with QUITE A FEW PCP regulators, production and prototypes .... find the type seat and sealing diameter play a huge part in recovery speed and quickness is stabilizing.
Also found out was WHAT type Seats work and which ones don't :P
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Getting regulators to work the way you want them to can certainly be exasperating. I am glad some of you guys have the patience to follow it through.
Lloyd-ss
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Also found out was WHAT type Seats work and which ones don't
How about sharing, that's what Forums are for, IMO....
Bob
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Without a photo gallery of what Not too do .. photos, drawing and such on what works, getting into a dissertation on all these fine points would be a very in depth thread all by it's self.
If OP wishes to share his regulator pictures, would be more than willing to engage in a conversation on whats felt right or wrong with the design as it is now, then suggest what may be a course in taking correcting the slow stabilizing, pressure drift or creep.
Scott
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Sounds like a great thread, I'd look forward to seeing what you have learned....
Bob
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Here are my drawings.
After shooting a few hundred shots today, the setpoint climbed just enough to need a bit more hammer. This happened a few days ago when I was out shooting some doves. Maybe it was the cold....or maybe everything finally took a set. I don't know. It seemed to stay there......until i took it apart again. I was in the shade, today, and it was about 47 degrees. It worked great for about three hours, then the setpoint climbed.
Anyway......my initial plan is to reduce the spool diameter on the low pressure side to .370" ish. That's going to be one Oring size give or take. This will put the stack I have in the working load (or at least a whole lot closer)......rather than near flat at 2050psi. That will also create less differential so creep over the 1000psi working pressure should be reduced.
The thing seems to perform great (quick reacting) at 1200psi......and I'm attributing that to the bellevilles being in the working range. I could be wrong, of course.
These are the thickest bellevilles I could find in this size. I will try sanding the edges that contact each other. The washers ID's are about .012" larger than the spool shank. The ID's were larger than listed.
Anyway......that's what I have. I'm open to suggestions.
Mike
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I'll post in JPG, too.....so it should show up without downloading.
Mike
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I looked at your diagram, and I notice that the O-ring grooves are very wide and have a lot of compression on the O-rings (I assume they are "0" series, eg 010, with a 0.070" cross section).... A Ninja regulator has very narrow grooves, only about 0.002" side clearance, and minimal compression, again only about 0.002".... I assume this is done to reduce friction also play in the groove....
FWIW, I never use the "proper" specs on O-ring grooves, I always make mine deep and narrow.... Crosman seem to agree with me (actually, I copied them)....
Bob
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What i would like to see is PATH HP air takes getting to the seat ?
Diameter of HP end of spool and if seats sealing edge is at that diameter or less than ?
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If I understand it correctly, the HP air enters through the ports above and below the seat into the chamber surrounding the seat and then travels into the conical end on the spool, up through the spool to pressurize the large end.... When that pressure overcomes the Bellevilles, the conical end on the spool seals on the (Delrin) seat.... so yes I would say that the seat diameter is basically the OD of the small end of the spool, ie the diameter of the open end of the cone.... I'm thinking that design may make the diameter of the seat irrelevant, but I'm not positive about that.... The pressure differential across the seat is at 90* to the motion of the spool, is it not?.... However, the tank pressure, which varies of course, is pushing on the smaller O-ring all the time, which would require varying amounts of pressure on the output side to close I would think....
Bob
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The best for moving parts are wiper rings. O-rings have a tendency to get stuck when they aren't used/moved. You just have to change the high pressure side of the groove so you can mount them.
http://www.m-seals.dk/da/shop/hydraulik/skraberinge (http://www.m-seals.dk/da/shop/hydraulik/skraberinge)
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Bob, you are correct on the flow path.
I see what you are saying about the Oring grooves. I just pulled the specs right from the Parker book for dynamic Orings. On the next round I will make them as you suggested. I'll probably pick up some 90 durometer urethanes for the spool as well.
After my gun sat in the 65 degree heat of the house.....it functions exactly as it did before I went to shoot outside yesterday. I think that, maybe, the boost converter is sensitive to cold. It was supposed to be 47 degrees where I was at, but in the shadows......there was still lots of snow. I'll have to set it outside and measure the voltage after it has cooled down.
My logic when designing this was to keep the small end of the spools' area as small as possible to keep the HP influence, due to fluctuation, to a minimum.
Ant thoughts about my idea of making the low side piston diameter smaller to put the stack in a more favorable (linear) condition?
Bent......I don't think I can get wipers small enough for my needs, here. The spool oring is a 004.
Mike
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I think you are right about that.... smallest I could find is 3mm/7mm but I've seen them smaller in some of the machines we made in my former job (Shambanrings they were called, but I think that was just the name of the maker).... but they must have been custommade....
It is possible to make yourself in PTFE...
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In playing with various seat types and air path routes ....
Found those seats which take HP air in at end of the spool / adjustment cap routing air once passing under the open seat threw a side hole in small end of spool under the seat that upon closing has the ENTIRE spool under the lower regulated LP pressure are the more stable.
Those seats and designs that allow HP to access small end of spool from the side and when seat is open travel up and threw seat at the top of spool always have influence to a small degree on the spools bevel stack because the HP present bears against the o-ring. * as HP side pressure changes ever so slight is the pressure felt on the bevel stack from pressure exerted on small end of the spool.
Next is seat size & material used ???
Larger the diameter, less the contact pressure exerted over its area ( Tho with this greater area comes a far greater chance for it to leak from contact pressure inconsistency if not VERY square and true. Smaller the seat diameter easier it is to seal quickly and accurately.
Because the bevel washers move so little when the seat opens and closes, ANY yield in the seat surfaces and you have changed travel distance spool travels and there for it's set point.
Delrin is far to soft finding PEEK hands down the best material as the seat base.
Also find in seat designs that isolate the HP air once shut do best with very small diameter seats under high contact pressure are very fast to settle, recover very fast and generally very stable shot to shot.
Hope this helps ya some more ...
Scott
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One more little snippet ....
Once you have the HP flow into seat area being shut off upon closing, No longer do you need to worry about HP influences on the small end of spool. Now you have MANY more options to seat design.
Regulators set up in this way go about sealing in these noted ways ...
Audrius / Ninja and some others bring air to the seat via a small diameter soda straw tube whose end rests on a seal material placed on the end of the spool.
Huub uses a floating disk that is sandwiched between the spools end & a raised seat on the end cap.
generally found the I.D. of hole feeding seat between .050" and @ .070" with the seat diameter being .100" or less.
** Likely reason we see such small diameter seats is because greater the area seat has, greater the HP side air bears against it attempting to open it. A small seat only getting contact of .050" - .070" with HP in storage, less this overall influence regulator feels dealing with changes in storage pressure. Less valves sealing surface feels in tank pressure changes more accurately it will continue to seal off by what LP side is exerting against it.
All these successful regulators have spool drilled from LP end NOT going all the way to the LP end, but stopping a short way from the end being intersected by a cross drilled hole.
Scott
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I suspected that PEEK might be a better surface, and ordered a 1/2" round from McMaster yesterday. Good to now that it will likely be a better seat material, and that I didn't waste my money. Stuff is kinda pricey.
I see the reasoning behind a side entry hole being better than a straight through like mine......on paper. When mine is sealed....the HP air is bearing on is the small Oring channel of the spool. This equates to about 20 pounds of difference in the HP influence on the spool. That would seem to suggest that the pressure should vary by 100psi or so on the low side......but I have not been able to witness that with a gauge and a test rig over the pressure spectrum that my gun sees on the HP side (2100-3000). I see about 50-60.
My gun seems to deal with the 50-60 psi variance well enough that the shot strings are pretty tight over the spread.
I suppose putting the small spool oring on the ID of the body, instead of the OD of the spool would accomplish the same thing.....actually it would be better, since the HP air would not be acting on anything when the valve was closed. That was my original intention, but I didn't want to buy an expensive little ID groover that could do it.
I really just want to fix the sluggish top up rate for now. If I could knock it down to under 15 seconds.....I'd be plenty happy.
I'll see what the PEEK seat and the change in the spool diameter will do......and I guess I'll go from there.
Thanks for sharing your findings.
Mike
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Actually.....what I said about the HP side pressing on the oring channel wasn't right. It presses on the front and back of the channel equally, so they cancel each other out.....so its just the difference in diameter between the spool and the body that presses on the ring itself. If this isn't correct......someone please say something. I see it as air pressure being applied to all surfaces.
That works out to around 1lb or so. So overall maybe 5 psi difference in the LP side due to the oring alone.
It must be just the HP pressure requiring more force to keep the valve closed at the seat juncture that makes the fluctuation.....and that would seem to be equal no matter what the design....provided the seat diameter isn't huge.
I guess a more prudent question would be......what sort of fluctuation between 2000 and 3000 psi is noticed with the Ninja, or those other brands of regulator?
Mike
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Michael,
What I find odd is the TIME it takes your regulator to stop creeping and settle in.
Places to look would be o-ring compression amount ( Groove depth too little ) causing excessive drag on spool within body.
A seat that is actually closing at a lower pressure, is leaking until sufficient LP side pressure is built up having seat yield enough to finally seal.
* Here a Harder seat will make matters worse if there is a mismatch of seat contacting squarely / evenly around it's circumference.
Would also suspect the HP bearing down on the small end of spool o-ring has it further being expanded outward adding to the drag preventing accurate and speedy settling in at pressure set point ???
My Audrius and both my Huub regulators recharge and settle within seconds of the shot being taken. This just an FYI ;)
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In any design (such as yours) that has the small O-ring on the spool exposed to the HP air all the time, even after the seat is closed, you are going to experience a variance in output pressure with tank pressure.... It wouldn't matter if the O-ring itself is static or moving, it's the pressure on the area of the stem that causes the changing force.... If the HP inlet is closed off once the regulator seat closes, then the only force on the spool that changes is in proportion to the diameter of the sealing surface of the seat.... As Motorhead states, in a Ninja reg, the inlet hole is very small (I think under 1/16"), so that change in force is likewise very small.... However, it is still noticable, I find about 50 psi difference between a full tank and one that is just above setpoint....
Bob
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I'm going to make another body and turn the big end down tomorrow. At least that will tell me if an improvement can be had from the belleville's working in their proper range.
Thanks for the suggestions.
Mike
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;D Michael this thread has opened my eyes to just how tec savvy you need to be once fully immersed in playing with toy guns can become. Now I need to go back to school and take some mechanical engineering classes next year when I retire
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Don......just get yourself a small lathe and mill with the money you would use to take classes. ;D Then get on Practical Machinist and read everything you can......ask a lot of questions, and make a lot of parts. You'll be learning hands on.....and a lot faster than by going to school. ;D
When I was fooling around with my reg a few days ago, I went outside and did a bunch of shooting at 56 yards. I wanted to see the practical operation of the gun with the regulator in it. I didn't have a bench where I was at, so I laid out a mat and some blankets in the snow and shot from the sitting FT (off the knee) position, and the prone position rested on a front bag.
The wind was varying from 0-3mph, and was not changing direction very much. I didn't have any sorted pellets, so I just shot them out of the tin (JSB Exact Heavies).
Nothing really all that consistent from the sitting position......lots of strays here and there. One notable sitting group is #24......with a core group of 4 at .255" c ot c, then some serious fliers. Definitely need a lot more practice sitting.
I had a wind flag at the target......and when I was paying attention to it and timing my shots with repeatable conditions I got my best groups. Big surprise, there. I could see the mirage coming off the top of the target box, to back up the flag. I have been studying the wind for the last few months using a wind meter and observable signals such as specific movement of leaves, etc. and mirage. I test myself by looking around at anything I can use to get an idea of wind speed, then going and actually taking a wind reading with the meter to see how I did. It's been kinda fun.....and a very good learning experience.
Anyway.....there are some decent prone groups spread around.....but one that really stood out. The fourth group down in the sighter column is a keeper at .150" c to c for 5 shots. Wind was about as calm as could be outdoors for those 5 shots......and it took me a good 5 minutes to get the shots off waiting for the exact conditions.
Pretty fun stuff.
Mike
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56 yards amazingly tight group it can be suprising when it all comes together ;D ;D
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I made a new reg body and turned down the spool. It really didn't make much difference.
I then decided to machine the seat to a concave form. That made a dramatic difference. Now it settles in 10-15 seconds. I'm OK with that, but I'm gonna make another seat when I get the PEEK in. Maybe that will improve the recovery time further?
I'm getting really nice spreads now......whether I pull the trigger at 15 second or 15 hour intervals. ;D
Mike
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Very good ..... nibbling away and sorting it all out !!!
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Although I'm getting great strings with very small deviations......it seems that a shot after an overnight sitting is on the higher pressure side of the bell curve, and a shot taken quickly (although they produce nearly identical FPS readings) is on the downhill side of the bell curve. The latter is certainly consuming more air.
The curve without a reg on my gun is very narrow.....maybe 10 shots within 1%. This would seem to indicate some creep after a long sit.
I contacted Huub, and he may have a reg that I can easily fit into my coupling.
I would like to see how they perform side by side.
I'm definitely not married to the idea of producing my own regulator......just didn't see one that would work in my small space between the valve block and the tube.
If his can maintain better pressure spreads, I may be able to tune for better efficiency.
Mike
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I was still waiting on the regulator that I ordered from Huub, so I decided to work on mine a little more.
Since mine seemed to work very consistently at lower pressures......I thought I would attempt to get my gun to operate in it's peak at a lower pressure. I was wanting to do this anyway since the old peak was around 2050-2100 psi.
I opened up the throat from .140" to .160". I also enlarged the exhaust, transfer port and the barrel port fro .100" to .136".
This effectively lowered the peak from 2050 ish to 1400 psi. I also lowered the capacitance from 600uf to 500 since I was anticipating the solenoid having a much easier time opening the valve at the much lower operating pressure.
I shot a few strings without the reg to verify the bell curve and help me decide where to set the reg. I was peaking at about 905fps at 1450 or so.
I set the reg to 1550 and gave it a go.
I got 21 shots on my mini test cylinder that is 43.5cc. Filled to 3000psi........ Hi of 883.... low of 876....average of 879....extreme spread of 7....and a standard deviation of 2. I shot down to 1450psi. 17.8 FPE average and an efficiency of 1.3 FPE/CI. I think I can back the hammer out a little more, too. This is the first time I have seen my CE chronograph with 5 duplicate shots in a row. ;D
My normal reservoir is 220cc, so it's 5.15 times bigger. I haven't run a full string with the normal reservoir, but mathematically speaking......I should get 105 shots at this power level and spread.
I was told by Huub that a plenum volume of 8cc for my gun would give the tightest spreads. I lowered mine from 20cc to 12cc and that is where I tested it. I may try a spacer inside the plenum to reduce it even further and see what happens.
I'm pretty happy with this, though. The reg tops up very quickly at the lower pressure......you can even hear it. Takes maybe a second or so.
It seems to hold pressure without the creep at 1550.
I have not changed out the seat material, yet.
Mike
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Good deal .... Having a stable regulator is so important in a competition air rifle.
Could not be happier with the Huub in my .177 Custom M-rod ..... deadly stable and accurate for 80+ shots at 19+ # energy.
Hope you get your Huub soon and install it ASAP .... smile time ;D ;D ;D
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I'm definitely looking forward to trying it. Hopefully sometime next week, although there probably will be a lag in shipping due to the holiday.
Mike
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Good deal .... Having a stable regulator is so important in a competition air rifle.
Could not be happier with the Huub in my .177 Custom M-rod ..... deadly stable and accurate for 80+ shots at 19+ # energy.
Hope you get your Huub soon and install it ASAP .... smile time ;D ;D ;D
Huub regulator for Mrod??
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Good deal .... Having a stable regulator is so important in a competition air rifle.
Could not be happier with the Huub in my .177 Custom M-rod ..... deadly stable and accurate for 80+ shots at 19+ # energy.
Hope you get your Huub soon and install it ASAP .... smile time ;D ;D ;D
Huub regulator for Mrod??
Indeed ;D
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Did a little more messing with the setup today......mostly just fine tuning the hammer (solenoid) for better efficiency. I love this baby tank.
Lost a few FPS......about 4, but gained a lot in efficiency.
Reg is still at 1550psi......JSB Exact Heavies......10.4 average.
3000psi high
1450psi low
Hi 878
L0869
Ave 875
ES 9
SD 2
17.7 FPE average
Efficiency of 1.45 FPE/CI
23 shots on the 43cc (42.8 actual) tank
With the standard tank of 220cc.......maybe get 120 shots in 1 - 1.2% spread.
This scenario was an average of 3 sessions.......which were almost identical.
I may try enlarging the porting again and see if I can lower the reg even more and still maintain power. I'm pretty sure I can.
If I shoot down to 1000psi......I'm still getting about 830 fps in the current form.
Mike
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As you enlarge the porting, you are creating wasted volume between the valve seat and the pellet.... That decreases the pressure available to drive the pellet down the barrel.... In addition, as you know, the bigger the ports the "peakier" the velocity curve.... It's just like using a hot cam in an engine, more peak power but over a narrower range.... If you go too big on the ports, you will start to get a drop in efficiency from the wasted volume.... You may start to get a larger ES because even slight pressure variations between shots will move you away from the "sweet spot".... Then, as you reduce the setpoint, you will lose efficiency just from the lower operating pressure.... What you will do is get a wider pressure range to use from the tank, which may increase your shot count....
Before you make ANY more changes, I strongly suggest you draw a curve of velocity vs. hammer strike.... If you are operating on the "knee" of the curve, and if you are happy with the FPE level you have.... DON'T change the operating pressure.... Finding that perfect balance between pressure and hammer strike is the most important thing once you get to the FPE level you want....
For reference, my .177 cal 2260 PCP setup for FT got the following results with the same pellets, over a total of 105 shots, 1500 psi setpoint, 13 CI Ninja tank:
3000 psi high
1100 psi low
Hi 933
Lo 915
Ave 924
ES 18
19.5 FPE average
Efficiency of 1.20 FPE/CI
The maximum velocity occurred at 1300 psi, the ES and efficiency if I stayed above the 1500 psi setpoint was significantly better, but I did lose some shot count....
Bob
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OK.....I'll make a graph and see what I come up with.
I'm happy with the power level......going much higher has proven to be slightly less accurate for me. Going lower has been equally accurate, but I suppose it is more susceptible to the wind. I have wondered if my 6000ft elevation has played into that since the speed of sound is slower here.
Mike
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Good deal .... Having a stable regulator is so important in a competition air rifle.
Could not be happier with the Huub in my .177 Custom M-rod ..... deadly stable and accurate for 80+ shots at 19+ # energy.
Hope you get your Huub soon and install it ASAP .... smile time ;D ;D ;D
Huub regulator for Mrod??
Indeed ;D
;D Once I'm comfortable with the stock version and squeeze as much performance them I will begin the Modding process. Right now saving for the rest of my PCP support equipment . Going the Nitrogen route as it is readily available and I have a steel 80 cu ft tank already from doing HVAC repairs, Just need to upgrade the tank regulator to a a PCP rated rig and a Guppy tank for play dates ;D ;D
PS: Once I am a little more familiar with the mechanicals of the rifle it will be easier to feel comfortable tearing into it
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Most of the FT guys I know find the JSB Heavies good to the high 800's (890ish) but usually don't push them over 900 for the best accuracy.... I guess it would depend on the barrel and twsit rate.... You're not far off that now anyway, and the efficiency will drop if you push the FPE higher....
Bob
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Bob, I figured out the chart......for the most part. Copying and pasting was giving me trouble.
Anyway......I started each voltage change at 3000psi and shot til I exceeded 1-1.25% extreme spread. The last column at 57 volts, however, would not hold 1% right from the start. I'm not too worried about that since I won't be using that setting anyway.
The reg is still at 1550psi and everything else was untouched.
If I stick with the 4th column (58.5volts).......I should net 145 shots on the full sized reservoir at 17.3FPE and 1% extreme spread. This is about the point where the gun starts to quiet down a lot, too.
It's pretty interesting......I'm glad I made a chart, now. Thanks, Bob.
There really does not seem to be too dramatic of a drop in velocity over the range of adjustments.
Mike
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I forgot it doesn't show pdf's without downloading.
Here is a scanned jpg.
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Most of the FT guys I know find the JSB Heavies good to the high 800's (890ish) but usually don't push them over 900 for the best accuracy.... I guess it would depend on the barrel and twsit rate.... You're not far off that now anyway, and the efficiency will drop if you push the FPE higher....
Bob
That is similar to something I read that quoted .8 mach. I have shot a bunch of 250's on the international 25m benchrest target at anywhere from 830-885, but none over 900fps with those pellets.
Mike
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I put the standard size tube back on and tried a full string at 58.5 volts.
For grins I charged to 3200psi
I shot down to 1300psi. The reg was at 1550psi.
I got 135 shots average fps 873.
Efficiency was 1.35 FPE/CI.
It seems to behave a bit differently with the bigger tube. Looks like I can lower the voltage more.
The high was 878, and the low was 866. Around 1.4% spread.
I had to put the data on two strings, so the first string had a standard deviation of 2......and so did the second one, but together they may have been different. I don't know, and don't feel like calculating. ;D
Mike
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Looks like you have a short plateau at 59.5 and 60 volts, I would expect that to continue.... Anywhere from 58-59 volts looks good, I'd use 59 if the spread is tight and the accuracy good....
Bob
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The 58.5 with the large tube seemed to act like the 60v with the small tube. The gun was definitely loud compared to what I was getting with the same voltage and the small tube.
Is there any sense to be made from that?
I really don't need more shots than I'm getting right now......so I need to see if the accuracy is still there.
I'm expecting the Huub regulator to perform a little better than mine......although a few small changes on mine should improve it a fair amount.
He said I should be able to hold less than 1% over the entire string at this power level. I need to get out and shoot once that is in.
Sometimes the first shot on mine is weird after a fill......sometimes it's not.
I am experimenting with harmonic tuning. A fellow named Tony Purdy has some calculations that have been performing very well for some bench rest (air rifle) guys. I ordered a reamer that I need to finish the barrel tuner slide.......always waiting on something.
If anyone is interested in reading about it there is some stuff on benchrest central.
Mike
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Michael,
The loudness almost always indicates higher residual pressure in the barrel as the pellet leaves the muzzle. But why? Maybe the larger tube flows the air a little more freely? If the tube is larger on the regulated side, I can see that happening. Louder also usually indicates lower efficiency because of the excess air.
I have to say that the consistency and shot count you are getting is pretty incredible!
Lloyd
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I can't understand why your reservoir size is making a difference unless it is the Plenum volume you are changing.... OR unless the larger tube flows the air better INTO the regulator, but even that would be a stretch to explain why.... Mystery, that!....
However, I do have a suggestion.... Redo your chart using the larger tube.... You only need to shoot a few shots at each voltage, not a complete string, to plot velocity vs. voltage, and that is all you care about.... finding the "knee" on the curve....
Bob
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Thank guys.
That's a good idea, Bob.
Mike
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I got the regulator from Huub today. He recommended that I set it no lower than 1600psi....I guess it doesn't work as well. You can rearrange the springs to go lower....but there is a little gap in the pressures between the two settings.
Anyway..... I set it at 1600 and tried it with a 12cc plenum. He recommended 8cc.....but I would need to make a spacer for 8cc. Tried it out, and it was all over the place......something like 28fps spread on 25 shots or so.
I made an aluminum tube (spacer) to fit in my 12cc plenum......so I could make it 8cc. Tried again, and this was way better. It shot about 10fps slower....but held 6fps on 25 shots with my little tube on the gun.
I left it like that and put the normal tube back on and shot 60 shots from 3000 to 2150. I got 1.33 FPE/CI with an average of 874 fps and 17.6FPE. It held 10fps ES, and had a SD of 2. Used 14psi of air per shot. Should be able to get another 53 shots if I shoot down to 1400.
I may try a different spacer to choke the plenum down a little more tomorrow.
This regulator likes a big change in pressure to reset, if you want a tight spread.......which is what Huub said.
I'm happy with it. It settles to its peak faster than mine.
Mike
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Ahhhhhhhh.... so it requires a small plenum to get a large pressure change during the shot to reset consistently.... Got it!.... That would mean his design is better suited to low to medium power applications.... The only way to get high power with a small plenum is to greatly increase the setpoint so that the AVERAGE pressure during the shot is what is needed to provide the FPE you want.... unless the regulator design is so fast-operating that it can top up the pressure DURING the shot, which I have never seen....
Bob
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Some fine tuning and you will get there I'm sure.
Just ordered another Huub for my AT44 this morning. Really like his regulators ;D
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I have been doing 25m indoor benchrest shooting over here for winter, since FT practice outdoors is done.
I de-tuned my rifle to 12FPE, and am very happy with the way it shoots indoors. I set the reg at 1150, and am shooting 8.44 JSB's at 788 or so.
I got about 280 shots today on one charge (3000-1050)......so that's pretty cool.
Late week I shot 2 25m targets with the gun at 18FPE, and got a 250 8x, and a 250 9x with JSB Exact Heavies.
Today, I shot 8 targets, and the best was a 250 12x, and the lowest was a 248 15x.......all on one charge.
The gun seems to like a slightly larger head pellet in the 8.44's.......but not much.
It seems to be a little easier to shoot at 12FPE. I like it.
If there is anybody close that wants to come shoot in a really nice, well lit, 70degree, 55 yard indoor building.......let me know. I would enjoy the company. Selittle came out last week for a few hours.
Mike
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;D ;D Congratulations Michael it looks like you are getting your getting the new rifle dialed in
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Thanks, Don.
I still haven't fooled with the barrel tuner......but maybe by next weekend. I need to make a good adjustable front rest, too. It's getting old shooting off two bags on the bench.
Mike
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A while back I said that I would post some drawings of the rifle.
I am currently making 8 more of these, so I will post the drawings of the pieces as I go. If you have a lathe, and a mill......you should be able to make these parts without too much trouble.
I milled the first Maple stock on my CNC mill.......but had a friend mill the last few Walnut ones on his CNC Router. He said he would mill them for anyone for $150.00 plus the wood cost. That's not too bad, really.
All in all, a person should be able to duplicate this rifle for around $500.00 or so in material.
If you can follow along piece by piece.....it shouldn't take too long, either.
The first two parts are the reservoir end cap and the tube coupler. The regulator will slide inside the coupler. I have built my own (reg), and have used a Huub. If you wish to use the Huub......he can turn the body of his reg to fit .800" ID and supply the proper Orings. Material is 6061 aluminum. 1.5" 6061 bar should cost about $6.00 per foot.
I order the foster fittings from Mac1.
I will probably be selling a few of these to help pay for my FT donor rifles and the other stuff I need to get FT matches going here in Montrose next summer. If you may be interested in a rifle.....please PM me.
Mike
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Didn't get any further on the gun parts, but I got some more time to shoot 25m benchrest practice after Christmas. Gun is tuned for the LV class (12 FPE).
Shot 4 targets with JSB 8.44's......sorted for a roll arc 2.9-3.1 on my glass plate. These are the favorites of the gun, for sure.
This thing is consistently shooting 249 and up with an average of 12-13 X.
The 10 ring on these practice targets is .080"......which is the international 25m target size, but the 8 and 9 rings are actually smaller than the international by a fair amount to be able to fit 25 scored shots and 5 sighters on a 8 1/2 x 11 paper. Doesn't seem to matter, though. :D
All targets are scored with a .224 plug.
I still have not had time to make an adjustable front rest.......so everything is still off a cheapo front and rear bag. I can't wait to see how it will do off a proper rest. ;D
Mike
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;D If you show up at any match that I was thinking of shooting in I hope they have an old fart division. otherwise I'll just give you my money and place friendly wagers on the outcome probably win a bigger purse that way ;) :D
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Not to worry Don......I'll just loan you a rifle. ;D
Mike
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Michaelthomas,
Just found this thread. Very nice work man. Looks like it has the accuracy as well. Well done. Peace
Pete
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Thanks, Pete.
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Well, I have read this thread 3 times and like some Disney rides, I pick up something new each time. The down side is now I have even more questions.
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Well, I have read this thread 3 times and like some Disney rides, I pick up something new each time. The down side is now I have even more questions.
Well.......you have my number. ;D
Anytime.
Mike
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Hi
Fantastic thread !
Thank you for sharing
I am currently reading on a pad and trying to see if there is a circuit diagram for the project
I have been looking at a similar project but looking at controlling with a microprocessor
Possibly even blue tooth and controlling from a phone - my brother is a developer for android so maybe we will end up this route
In the meantime just looking to get something going
Thanks again
Simon
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Mike,
You really should start another thread, "My Benchrest Project" and outline how your rifle has evolved since this thread ended.
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And maybe we can see it and get in a shot or two at the USARB National Championships coming up in Pheonix? Will you be going? I've never shot in a sanctioned event before and there should be quite a few custom airgun there, yours sure would fit in.
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I haven't given much thought to attending......I'm sure it would be fun. I'll have to research it a bit. It would be nice to take some other rifles for a test ride, too.
I have never shot outdoors with flags, yet. Would probably be an eye opener. :o
Mike
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Both you and I first timers show up at a national championship with home built airguns. That is a big leap but I'm going to give it a try. Hope you do also, I dont want to be the only newbie in town.
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Ha Ha......I know. I've never even seen or touched another PCP in person before.....seriously. Seen lots of pictures, though. ;D Like I've been living under a rock.....with internet access. :o
I wasn't educated enough about airguns to know that my design wouldn't work. lol
Mike
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Ha Ha......I know. I've never even seen or touched another PCP in person before.....seriously. Seen lots of pictures, though. ;D Like I've been living under a rock.....with internet access. :o
I wasn't educated enough about airguns to know that my design wouldn't work. lol
Mike
Very impressed I didn't know this was your first AG build and PCP to boot
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Michael, a fabulous project with fantastic results.
As a hobby machinist I appreciate how much work it takes to make all the parts for a single gun. What's amazing to me is how you find the time to accomplish so much. The electronic trigger is amazingly simple and efficient... well done!
The quality of your work shines in your benchrest scores.
Very inspirational...
Fantastic post,
Boomer
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With knowing the thickness of your air tube I'd think that a 12tpi thread will cut way too deep and not leave enough wall thickness for safety.
Some finer pitch standard 1-3/8 threads are the 20UN, 24UNS, 28UN, The 20, 24 or 28tpi may be more appropriate.
I've got a nice spread sheet with all the thread info of most standards, It makes a good reference. PM me with you email if you are interested. Too big to post.
Tom
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No.....they are not standard threads. You'll have to single point.
If you are going to deviate from what I have shown......I would have the tube hydrotested prior to use......for the reasons that Tom mentioned. I would have it hydrotested, either way......it's cheap insurance.
The tube I tested from my last batch did not yet reach yield at 10,000 psi. I didn't bother to have it tested beyond that. The company that tested it used a 10,000psi max test cell, because they didn't think they would make it to 5000 on an aluminum tube.
Anyway......get it tested before you pressurize it. Costs 50.00$
Mike
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Adding to what Mike said about the need to single point. The ID of common tubes almost never matches the minor diameter of a standard thread. It would be nice but life is not that easy. If you pick a standard thread you will likely have to open up the ID to match the minor diameter of the tread. Then subtract the depth of the tread from your reduced wall thickness to see what you are left with. You will probably be shocked how little will be left. A single point allows you to use the ID of the tube as your minor diameter, leaving the maximum material possible for strength.
Remember, your tube is only as strong as the weakest section.
Tom
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Probably best not to jack Mike's thread so I'll quickly state my thoughts. You may want to look in the R&D gate for tube threading specifics, there is a lot there, or start a new one.
1) Using Barlow's formula for pressure vessels, with your tube, I get a SF of only 2.5 @ 3000psi. Not enough IMO and material fatigue could be an issue.
2) The closest standard internal thread is a 1.313x16. It has a minor of 1.25 which is good and a thread depth of 0.041 which leaves you a wall thickness of 0.084 which is a SF of 3.4 and is adequate to handle the force of the end plug BUT if the threaded sections sees pressure(o-ring location), this reduces your SF to 1.7 at 3000psi
You need to take a hard look at your pressure requirements and material choices.
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http://en.wikipedia.org/wiki/Unified_Thread_Standard (http://en.wikipedia.org/wiki/Unified_Thread_Standard)
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Hi
I am revisiting my project for an electronically triggered rifle - I am looking to modify an existing gun rather than build from scratch as I really don't have the tools for that
Anyway I would be interested in which solenoid you ended up using ? Just may point me in the right direction
Thanks
Simon
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Hi
I am revisiting my project for an electronically triggered rifle - I am looking to modify an existing gun rather than build from scratch as I really don't have the tools for that
Anyway I would be interested in which solenoid you ended up using ? Just may point me in the right direction
Thanks
Simon
Simon,
somewhere, on the first or second page you will find a link to the solenoid he used.
Pat
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I know it's a rather old post but interested in if you are selling parts or guns.
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what an awesome build. are you out there Michael,
or does anyone know how to contact him- i too am interested in talking to him about the rifles he might be selling?!
thanks
wayne
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Gentlemen
his gun has won so many records that he is backlogged almost 6 months
http://www.usairriflebenchrest.com/records/ (http://www.usairriflebenchrest.com/records/)
and very expensive
i have one and it is the most expensive gun i have
here is a pict of Paul Bendix shooting Mikes gun
Paul holds the 750 69X record with this gun :-)
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thanks strever- appreciated. would still love to chat to mike- if hes about.
thanks
wayne
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is mike around?