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Author Topic: .25 cal Disco Pumper Carbine  (Read 36844 times))

Online rsterne

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.25 cal Disco Pumper Carbine
« on: October 12, 2012, 08:43:54 PM »
I started work on the internal parts for my .25 cal Disco Pumper today.... It will use the MRod barrel and Disco breech I mated up the other day, plus an extended Disco valve with a check valve built in just ahead of the gauge port.... The valve extension will include a gauge mount for a 1500 psi gauge.... Here is the piston and the front mounting block to fit a Benjamin 392 linkage into the Disco....



There will be a barrel band mounted on the stub of the front block which projects 3/8" ahead of the shortened Disco tube.... The barrel band will be 1/8" behind the muzzle of the MRod barrel....



The next step is to cut the Disco tube to length, and machine an 8" slot in the bottom for the linkage.... and drill the hole for the front pivot pin....

Bob
  • Coalmont, BC, Canada
Dominion Marksman Silver Shield - 5890 x 6000 in 1976, and downhill ever since!
Airsenal:
1750 CO2 Carbine, .177 Uber-Pumper, .22 Uber-Carbine, .25 Discovery, 2260 PCP 8-shot Carbine, 2260 HPA (37 FPE), 2560 HPA (52 FPE), XS-60c HPA in .30 cal (90 FPE), .22 cal QB79 HPA, Disco Doubles in .22, .25 & .30 cal, "Hayabusa" Custom PCP Project (Mk.I is .22 & .25 cal regulated; Mk.II is .224, .257, 7mm, .308 & .357; Mk.III is .410 shotgun and .458 cal), .257 "Monocoque" Benchrest PCP, .172/6mm Regulated PCP and .224/.257 Unregulated, Three regulated BRods in .25 cal (70 FPE), .30 cal (100 FPE) & .35 cal (145 FPE), .257 Condor (180 FPE).

Offline bradyman1

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Re: .25 cal Disco Pumper Carbine
« Reply #1 on: October 12, 2012, 08:57:33 PM »
Nice little project. What is your projected fpe and # of pumps per shot? Are you expecting to get multiple shots per pumping session?
Myself, my wife, 11 year old and 7 year old sons. A whole family of hunters!!

Online rsterne

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Re: .25 cal Disco Pumper Carbine
« Reply #2 on: October 12, 2012, 10:05:50 PM »
I'm hoping to get in the 30 FPE range.... I was hoping to do that in about 10 pumps, but I have been told that is unrealistic, it will take more like 14-15.... In addition, I was originally going to use a 24" barrel, but settled on an MRod 20" for this protptype.... Because of this I have adopted the attitude of "que sera sera".... what will be, will be....

I will have the option of adding a 20 cc auxiliary reservoir to the ~5 cc Disco valve so that I can experiment with retained air for either multiple shots, or just a few pumps to top up the pressure.... like a poor man's FX Independence....

Bob
  • Coalmont, BC, Canada
Dominion Marksman Silver Shield - 5890 x 6000 in 1976, and downhill ever since!
Airsenal:
1750 CO2 Carbine, .177 Uber-Pumper, .22 Uber-Carbine, .25 Discovery, 2260 PCP 8-shot Carbine, 2260 HPA (37 FPE), 2560 HPA (52 FPE), XS-60c HPA in .30 cal (90 FPE), .22 cal QB79 HPA, Disco Doubles in .22, .25 & .30 cal, "Hayabusa" Custom PCP Project (Mk.I is .22 & .25 cal regulated; Mk.II is .224, .257, 7mm, .308 & .357; Mk.III is .410 shotgun and .458 cal), .257 "Monocoque" Benchrest PCP, .172/6mm Regulated PCP and .224/.257 Unregulated, Three regulated BRods in .25 cal (70 FPE), .30 cal (100 FPE) & .35 cal (145 FPE), .257 Condor (180 FPE).

Offline bradyman1

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Re: .25 cal Disco Pumper Carbine
« Reply #3 on: October 12, 2012, 10:19:13 PM »
Sounds like an exciting project. I am exited to follow your progress. The auxiliary reservoir sounds quite promising.
Myself, my wife, 11 year old and 7 year old sons. A whole family of hunters!!

ten.ring

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Re: .25 cal Disco Pumper Carbine
« Reply #4 on: October 12, 2012, 10:59:58 PM »
this is GREAT your on the same line as my idea. i have a love for pumpers, it will be late june before i get back to my shop. by then you'll be shooting this disco pumper. i have allready learned alot from your uber-pumper guns. THANK YOU FOR SHARING! 

you are not just some guy with a dream, you also have an understanding of engineering and machine work.

not a common combination.

i just ordered a turbocad software package. lucky thing i got lots of time on my hands it's been a few years since i used a cad-cam system. by june i should have my pumper modeled and detailed.  and with what i am learning from you it will be 10x further along on my 1st gun than i could have imagined. r&d is my favorite thing in life.

one more thing,  i have an idea for a varriable displacement resevoir. that will increase the pressure for the BACK-UP shot. to keep the feet/sec up. it's a simple idea. a diespring and a piston in the breach w/a very small dia orifice to slow down the replacement air. i plan on a one inch dia full shroud so i will have some room under the barrel in the breach. i have not done any calc's yet but i think it could work.

mark   
« Last Edit: October 12, 2012, 11:25:26 PM by ten.ring »

Online rsterne

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Re: .25 cal Disco Pumper Carbine
« Reply #5 on: October 12, 2012, 11:44:45 PM »
Variable displacement reservoirs have been used before in retained air pumpers.... The problem I foresee is that you end up needing two reservoirs, joined as you say, by a small orifice.... In order to get good power, the reservoir feeding the valve has to be a good size, and the air has to be able to get into the valve faster than it can get out.... It becomes the same problem as a regulated PCP, where ideally you need a plenum of about 1 cc per FPE feeding the valve.... If you could figure out the mechanism, and find a place to put it, using a gas ram style die spring could possibly provide a more constant pressure than a coil spring.... Just a thought....

Bob
  • Coalmont, BC, Canada
Dominion Marksman Silver Shield - 5890 x 6000 in 1976, and downhill ever since!
Airsenal:
1750 CO2 Carbine, .177 Uber-Pumper, .22 Uber-Carbine, .25 Discovery, 2260 PCP 8-shot Carbine, 2260 HPA (37 FPE), 2560 HPA (52 FPE), XS-60c HPA in .30 cal (90 FPE), .22 cal QB79 HPA, Disco Doubles in .22, .25 & .30 cal, "Hayabusa" Custom PCP Project (Mk.I is .22 & .25 cal regulated; Mk.II is .224, .257, 7mm, .308 & .357; Mk.III is .410 shotgun and .458 cal), .257 "Monocoque" Benchrest PCP, .172/6mm Regulated PCP and .224/.257 Unregulated, Three regulated BRods in .25 cal (70 FPE), .30 cal (100 FPE) & .35 cal (145 FPE), .257 Condor (180 FPE).

Offline 1377x

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Re: .25 cal Disco Pumper Carbine
« Reply #6 on: October 13, 2012, 03:46:21 AM »
wow! shooting for 30fpe in ten pumps.i must be more of a beast to pump that the benji's
still 30fpe in 15 pumps is something not to be overlooked
keep up the good work its great seeing the guns you turn out
many have inspired my builds.
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Offline Powder burner

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Re: .25 cal Disco Pumper Carbine
« Reply #7 on: October 13, 2012, 10:49:34 AM »
  anyone ever tried this with two tubes, one for the mechanism and one as a reservoir?  just curious.
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Offline Dead nuts dog

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Re: .25 cal Disco Pumper Carbine
« Reply #8 on: October 13, 2012, 11:04:15 AM »
Very very very cool. Can't wait to see it finished
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Online rsterne

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Re: .25 cal Disco Pumper Carbine
« Reply #9 on: October 13, 2012, 05:03:15 PM »
Quote
anyone ever tried this with two tubes, one for the mechanism and one as a reservoir?
I "think" that is how the FX Independence works but not sure.... If I was going to go that route, I would likely put the pump underneath on a Disco, like Lloyd does with his Disco Double.... The choice of pump would depend on what pressure you wanted to run.... I understand the Benji maxes out at about 1400-1500 psi (so a Disco based pump - 3/4"ID - would be similar).... but if you used a 5/8" ID pump (like on a 13XX/2100/1400) and got the linkage stiff enough, 2000 psi should be possible without going to a multi-stage design.... The problem is that the more power you ask the gun to produce, the more air it needs.... and the more air you have to add per shot.... which means more pumping.... My Benji pump linkage in a Disco tube will deliver about 53 cc per stroke (3.2 CI) but if you shrink the tube down to 5/8" ID and keep the same 7.5" stroke, that drops to only 37 cc (2.3 CI).... Divide your expected power output in FPE by the CI per stroke, and you will get a feel for the number of strokes of the pump.... Then add more to allow for pumping losses.... subtract a bit if you can get the efficiency over 1.0 FPE/CI....

Bob
  • Coalmont, BC, Canada
Dominion Marksman Silver Shield - 5890 x 6000 in 1976, and downhill ever since!
Airsenal:
1750 CO2 Carbine, .177 Uber-Pumper, .22 Uber-Carbine, .25 Discovery, 2260 PCP 8-shot Carbine, 2260 HPA (37 FPE), 2560 HPA (52 FPE), XS-60c HPA in .30 cal (90 FPE), .22 cal QB79 HPA, Disco Doubles in .22, .25 & .30 cal, "Hayabusa" Custom PCP Project (Mk.I is .22 & .25 cal regulated; Mk.II is .224, .257, 7mm, .308 & .357; Mk.III is .410 shotgun and .458 cal), .257 "Monocoque" Benchrest PCP, .172/6mm Regulated PCP and .224/.257 Unregulated, Three regulated BRods in .25 cal (70 FPE), .30 cal (100 FPE) & .35 cal (145 FPE), .257 Condor (180 FPE).

EBSW0820-e

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Re: .25 cal Disco Pumper Carbine
« Reply #10 on: October 13, 2012, 06:36:36 PM »
wow! shooting for 30fpe in ten pumps.i must be more of a beast to pump that the benji's

If that's the reason that pump-pneumatics are held back, then I say design a mechanical assistance for the pump. A crank mechanism? I don't know. I'm not an engineer, but I do know it's not impossible

ten.ring

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Re: .25 cal Disco Pumper Carbine
« Reply #11 on: October 13, 2012, 08:22:09 PM »
yup!  i was hoping you knew what i was talking about, and you do.

  a single quick follow up is very humane, i use my pumpers for hunting and i can't count the number of times i needed one before i could pump-up again. that's the number one goal for my build, a large enough reservoir is the simple way. and if it is not too long (taking up pumper volume) that would be the only way to go. even if a second shot required one pump to keep the f.p.s. equal, that would be a big improvement. and a gauge is nessary. to keep track of your pumping with an over sized reservior.

mark   
« Last Edit: October 13, 2012, 08:24:57 PM by ten.ring »

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Re: .25 cal Disco Pumper Carbine
« Reply #12 on: October 16, 2012, 08:49:58 PM »
I machined the Disco tube today.... cut it to length and squared the end and then machined the slot for the pump linkage....



The tube is 1/2" behind the front of the MRod barrel, and the 3/8" barrel band will fit over the stub of the aluminum front plug.... leaving the front of the barrel band 1/8" behind the muzzle.... The pivot pin is 5/8" behind the front of the tube, and the slot is 8.2" long.... The stroke is 7.6" and the piston is 6.7" from the link pin to the compression face.... That leaves the compression face 0.3" ahead of the front of the gauge hole, which leaves room for the O-ring to seal the valve....

The next step will be to make the extended front end for the valve incorporating the gauge mount and check valve.... Incidently, the front of the Disco stock comes to just behind where the spring sticks through the lever (the bump in the photo).... It will be cut just in front of the gauge, with the forestock becoming the pump handle.... Should work perfectly....

Bob
  • Coalmont, BC, Canada
Dominion Marksman Silver Shield - 5890 x 6000 in 1976, and downhill ever since!
Airsenal:
1750 CO2 Carbine, .177 Uber-Pumper, .22 Uber-Carbine, .25 Discovery, 2260 PCP 8-shot Carbine, 2260 HPA (37 FPE), 2560 HPA (52 FPE), XS-60c HPA in .30 cal (90 FPE), .22 cal QB79 HPA, Disco Doubles in .22, .25 & .30 cal, "Hayabusa" Custom PCP Project (Mk.I is .22 & .25 cal regulated; Mk.II is .224, .257, 7mm, .308 & .357; Mk.III is .410 shotgun and .458 cal), .257 "Monocoque" Benchrest PCP, .172/6mm Regulated PCP and .224/.257 Unregulated, Three regulated BRods in .25 cal (70 FPE), .30 cal (100 FPE) & .35 cal (145 FPE), .257 Condor (180 FPE).

ten.ring

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Re: .25 cal Disco Pumper Carbine
« Reply #13 on: October 17, 2012, 10:29:07 PM »
way to go bob

mark

Offline bradyman1

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Re: .25 cal Disco Pumper Carbine
« Reply #14 on: October 17, 2012, 10:43:55 PM »
Looking good.
Myself, my wife, 11 year old and 7 year old sons. A whole family of hunters!!

Offline 1377x

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Re: .25 cal Disco Pumper Carbine
« Reply #15 on: October 17, 2012, 10:59:59 PM »
now your getting somehere!!
cant wait to see this finished
short list
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2) survive!!
3)go to bed!!!

Online rsterne

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Re: .25 cal Disco Pumper Carbine
« Reply #16 on: October 17, 2012, 11:47:59 PM »
I got the valve front end done today.... Here are the parts....



The extended front end incorporates a shortened check valve from a male Foster fitting.... It is held closed by a 1" long 0.020" wire spring sitting against a washer located on a shoulder inside the valve front.... I opened up the last coil of the spring to 5/16" so that it can't get past the washer.... Behind the washer is a QB hammer spring, and the location of the shoulder for the washer was chosen to provide the same force holding the valve poppet closed as on a stock Disco valve.... This was achieved by drilling progressively deeper, assembling the valve, and pushing the stem against the stem of a stock valve until they opened at the same time....

The rear (spring) chamber of the valve front is drilled to 3/8" and the front portion to 5/16".... and then a 1/8" NPT hole intersects the front part for a gauge mount.... For initial tests, I will be using a simple male to female 1/8" NPT extension to mount the 1500 psi gauge, which is located in the stock position for a Disco.... At the moment the rear portion of the valve is dead stock....The total volume as built, including the gauge mount, is ~5.5 cc.... That gives me a bore/valve volume ratio of 3:1 with the MRod barrel.... I plan on boring out the rear portion of the valve to unshroud the poppet and increase the volume by nearly 1 cc.... and to drill the throat to 1/4", thin the stem, and increase the port diameter and angle it for improved flow.... but I think I'll try it with the stock valve initially.... Then comes the fun part....



I have made a gauge mount that connects a 16 gr. thread CO2 cartridge to the valve.... It has an internal volume of just over 20cc, and is rated at 250 bar MSWP, >500 bar burst.... It installs into the mount with  3/8"-24 threads which will be either glued or soldered to seal them.... The cartridge just clears the main tube, and will live in a hollow in the stock just in front of the gauge.... It will be invisible when the pump arm is closed.... With the cartridge installed, the total valve volume will be ~27cc, and the gun would, of course, be tuned to retain air and operate like a PCP with an onboard pump to top up the pressure between shots....

I'm pretty excited to see all the parts coming together for this project.... It won't be too long before I can install the parts in the tube and try out the pump.... I still have other parts to make before the gun can be fired, however....

Bob
  • Coalmont, BC, Canada
Dominion Marksman Silver Shield - 5890 x 6000 in 1976, and downhill ever since!
Airsenal:
1750 CO2 Carbine, .177 Uber-Pumper, .22 Uber-Carbine, .25 Discovery, 2260 PCP 8-shot Carbine, 2260 HPA (37 FPE), 2560 HPA (52 FPE), XS-60c HPA in .30 cal (90 FPE), .22 cal QB79 HPA, Disco Doubles in .22, .25 & .30 cal, "Hayabusa" Custom PCP Project (Mk.I is .22 & .25 cal regulated; Mk.II is .224, .257, 7mm, .308 & .357; Mk.III is .410 shotgun and .458 cal), .257 "Monocoque" Benchrest PCP, .172/6mm Regulated PCP and .224/.257 Unregulated, Three regulated BRods in .25 cal (70 FPE), .30 cal (100 FPE) & .35 cal (145 FPE), .257 Condor (180 FPE).

ten.ring

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Re: .25 cal Disco Pumper Carbine
« Reply #17 on: October 18, 2012, 09:47:17 PM »
houston we have lift-off

mark

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Re: .25 cal Disco Pumper Carbine
« Reply #18 on: October 18, 2012, 09:47:38 PM »
I assembled the pump today, using a stock Disco rear valve half.... and a conventional gauge mount.... Valve volume is ~ 5.5 cc and the swept volume is ~ 54 cc.... The following pressures were achieved:

5 pumps - 600 psi
10 pumps - 1100 psi
15 pumps - 1500 psi

After sitting for an hour, the pressure is still 1450 psi, which I would imagine is the effect of cooling.... I can't comment on the pumping effort as I had no stock on the gun, and it's not exactly easy to pump sitting upside down across my knees and pushing on the 1/4" wide metal pump linkage.... I would say the effort is significant but do-able.... and ergonomically shouldn't be a problem once the stock is fitted.... 

I'm quite pleased with these results.... I have to make the barrel band and the transfer port and a bolt, so initial testing isn't too far away.... I'm not expecting too much with the stock valve and porting, but need those results as a baseline.... I also have to modify the stock before any serious testing can be done.... 

Bob
  • Coalmont, BC, Canada
Dominion Marksman Silver Shield - 5890 x 6000 in 1976, and downhill ever since!
Airsenal:
1750 CO2 Carbine, .177 Uber-Pumper, .22 Uber-Carbine, .25 Discovery, 2260 PCP 8-shot Carbine, 2260 HPA (37 FPE), 2560 HPA (52 FPE), XS-60c HPA in .30 cal (90 FPE), .22 cal QB79 HPA, Disco Doubles in .22, .25 & .30 cal, "Hayabusa" Custom PCP Project (Mk.I is .22 & .25 cal regulated; Mk.II is .224, .257, 7mm, .308 & .357; Mk.III is .410 shotgun and .458 cal), .257 "Monocoque" Benchrest PCP, .172/6mm Regulated PCP and .224/.257 Unregulated, Three regulated BRods in .25 cal (70 FPE), .30 cal (100 FPE) & .35 cal (145 FPE), .257 Condor (180 FPE).

Online rsterne

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Re: .25 cal Disco Pumper Carbine
« Reply #19 on: October 20, 2012, 12:02:58 AM »
Well I couldn't wait any longer.... I made a new bolt and transfer port and threw the gun together for a few shots.... no stock, harder than heck on the hand to pump and all.... First a string with the Disco hammer spring set just off coil bind.... varying the pump numbers and recording the pressure and velocity.... I used 25.4 gr. JSB Kings....



The gun started retaining air at over 10 pumps (1100 psi).... It delivered 490 fps (14 FPE) on 6 pumps (700 psi) and 590 fps (20 FPE) on 10 pumps (1100 psi) and peaked out at 667 fps (25 FPE) at 15 pumps (1500 psi).... To run the gun as a pump and dump, without changing to a heavier hammer spring, the most I can get is ~590 fps with 10 pumps to refill to 1100 psi....

I then started playing with the RVA (power adjuster), to find out how that affected the velocity and the pressure remaining after each shot.... It turns out that I can back the adjuster out about 3 turns and only lose 10 fps but the pressure drop for the shot is about 150 psi less, which means a big gain in efficiency....



At 7 turns out, I can get two shots at 590 fps (20 FPE), and still have ~350 psi remaining.... It takes 12 pumps to refill after the two shots.... or about 5-6 pumps after the first shot.... Compare that with the pump and dump, same power but 10 (easier) pumps to refill.... At 3 turns out, I get one shot at 656 fps and 7-8 pumps to refill to 1500.... with having a gauge, it is a simple matter to know when to stop pumping....

Now remember that these are preliminary results, using a stock Disco rear valve half, stock barrel port, and matching transfer port (all 0.150").... The next step is to bore out the valve and port everything out to 3/16".... While I'm at it, I have to get the stock done, this thing is killing my hand pushing on the 1/4" wide pump lever....

Bob
  • Coalmont, BC, Canada
Dominion Marksman Silver Shield - 5890 x 6000 in 1976, and downhill ever since!
Airsenal:
1750 CO2 Carbine, .177 Uber-Pumper, .22 Uber-Carbine, .25 Discovery, 2260 PCP 8-shot Carbine, 2260 HPA (37 FPE), 2560 HPA (52 FPE), XS-60c HPA in .30 cal (90 FPE), .22 cal QB79 HPA, Disco Doubles in .22, .25 & .30 cal, "Hayabusa" Custom PCP Project (Mk.I is .22 & .25 cal regulated; Mk.II is .224, .257, 7mm, .308 & .357; Mk.III is .410 shotgun and .458 cal), .257 "Monocoque" Benchrest PCP, .172/6mm Regulated PCP and .224/.257 Unregulated, Three regulated BRods in .25 cal (70 FPE), .30 cal (100 FPE) & .35 cal (145 FPE), .257 Condor (180 FPE).