HPA Booster Finished - and it LEAKS !
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HPA Booster Finished - and it LEAKS !
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Topic: HPA Booster Finished - and it LEAKS ! (Read 4506 times))
rsterne
Member 2000+fps Club
Bob and Lloyd
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Real Name: Bob
HPA Booster Finished - and it LEAKS !
«
on:
November 26, 2015, 08:51:33 PM »
About a year ago I bought, on sale, a Pneumatic Cylinder and control valve with the intention of building an HPA Booster.... Last spring I got the gauge and fittings, and the steel I needed.... and today I machined the piston and cylinder base.... Here they are....
Above is the Pneumatic Cylinder and Control Valve.... It is an 80mm bore x 200mm stroke, and the piston rod is 25mm OD.... The booster will operate on the "pull" stroke.... You can see the piston installed on the end of the piston rod.... The control valve moves left or right to extend or retract the ram, and you can see the QD on the control valve inlet for 130 psi shop air.... That should provide enough force to compress HPA or Helium to about 3800 psi.... The swept volume, which is between the ID of the cylinder and the OD of the piston rod, is about 30cc.... Control is manual for each stroke....
Next is the HP cylinder, made from a piece of 1.50" OD x 0.188" wall CrMoly tubing.... Also shown is the aluminum piston and the steel base for the HP cylinder....
The next photo shows the piston and the base.... You can see the O-ring grooves in both.... The base slides over the end of the HP Cylinder and will be Silver Soldered and bolted in place....
The last photo shows the manifold to handle the HP air.... It has a male Foster on the inlet and a female on the outlet, along with a 5000 psi gauge and a bleed valve.... Attached to the inlet side is a braided hose and connector which will fit a Helium tank.... but the booster could also be hooked to a SCUBA tank which was too low to use for filling a gun.... Under the gauge, facing the table in the photo, is the 1/8" male inlet which will be threaded into a tapped hole in the side of the HP cylinder base....
At this point, I have silver soldered the base to the HP cylinder and I'm waiting for it to cool.... After dinner I plan to drill and tap the HP air inlet through the base and cylinder wall.... I will install some 5/16" setscrews to add strength to the joint between the base and cylinder tomorrow, at which point I should be able to pressure test it....
Bob
«
Last Edit: November 28, 2015, 05:33:59 PM by rsterne
»
Logged
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).
rsterne
Member 2000+fps Club
Bob and Lloyd
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Posts: 26958
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Real Name: Bob
Re: HPA Booster
«
Reply #1 on:
November 26, 2015, 11:13:01 PM »
The silver solder job turned out great.... so I drilled through the base and cylinder and tapped it 1/8" NPT for the manifold.... Here is the HP assembly....
There is a check valve each side of the "T" that is attached to the cylinder so that the flow only goes one direction.... it fills through the male Foster and discharges through the female....
Bob
Logged
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).
Gertrude
"The man who complains about the way the ball bounces is likely to be the one who dropped it."
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Posts: 7465
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Real Name: Ron
Re: HPA Booster
«
Reply #2 on:
November 27, 2015, 03:38:18 AM »
nice work Bob,
and Helium at 3800 psi should make for some interesting shot strings !
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Geoff
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Re: HPA Booster
«
Reply #3 on:
November 27, 2015, 12:34:07 PM »
looks very nice. nice work there
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rsterne
Member 2000+fps Club
Bob and Lloyd
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Re: HPA Booster Finished - and it LEAKS !
«
Reply #4 on:
November 28, 2015, 05:24:44 PM »
I finished assembling the booster today, and everything works great, except for one little detail.... IT LEAKS!
The low pressure side is perfect, as is the HP manifold (both were tested before) and the piston I made seals perfectly.... Unfortuately, the O-ring that seals the base of the HP cylinder to the shaft on the pneumatic cylinder leaks, and quite badly.... I originally used a 70D Buna, and pulled it apart and replaced it with a 90D, but it still leaks like a sieve, and it doesn't make any difference which end of the travel it's at....
Unless somebody has a suggestion for a different kind of seal that will work, I'm out of luck....
.... The shaft is 25mm OD and I cut the O-ring groove to 30.2mm ID x 3.6mm wide, as per the dimensions I have for a dynamic seal.... The O-ring is a 3mm cross-section.... it assembles with decent drag with the 70D O-ring and is hard to assemble with the 90D but slides OK once together.... I used an almost identical fit on the # 119 O-rings (ie compression and width, relative to the 0.103" CS) used on the piston, and it works great!.... There are two on the piston, but I only had room for one at the base because of the short length of 25mm shaft when retracted.... I have centered the O-ring on the protruding portion of the shaft, so that is not the problem.... It is not excessive clearance causing extrusion of the O-ring, because it leaks even at 500 psi, in fact it will leak down to zero.... The cylinder floats on the shaft, so is self centering (it operates on the pull stroke), so concentricity of the cylinder and shaft cannot be the issue either....
Bob
«
Last Edit: November 28, 2015, 05:38:35 PM by rsterne
»
Logged
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).
calixt0
Plinker
Posts: 193
yes
Re: HPA Booster Finished - and it LEAKS !
«
Reply #5 on:
November 28, 2015, 11:04:07 PM »
Wish I could help you but your knowledge is far above mine.. work looks excellently done. Good luck in finding a solution.
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Tuttle Ok
tkerrigan
Expert
Posts: 1176
Real Name: Tom
Re: HPA Booster Finished - and it LEAKS !
«
Reply #6 on:
November 28, 2015, 11:28:33 PM »
Is there room to make a screw in packing gland with a U cup hydrualic or V packing seal set up? Something like these?
http://www.theoringstore.com/index.php?main_page=index&cPath=649_690_484&sort=2a&page=3
Regards, Tom
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Jefferson, OR
rsterne
Member 2000+fps Club
Bob and Lloyd
GTA Senior Contributor
Posts: 26958
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Real Name: Bob
Re: HPA Booster Finished - and it LEAKS !
«
Reply #7 on:
November 28, 2015, 11:56:29 PM »
My problem is that I made the base before silver soldering it to the cylinder.... I can't put the 1.5" OD cylinder through the headstock of the lathe (it's only 3/4" bore).... I have a steady rest, but I can't imagine using that and obtaining the rigidity and accuracy required to remachine the O-ring groove.... although there would be room (barely) for such a seal.... but it would have to pop in place, there is no room for a threaded in gland....
Bob
Logged
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).
MJP
Member 4400+Fpe Club
GTA Senior Contributor
Posts: 2136
I'll make it real. For me.
Real Name: Marko
Re: HPA Booster Finished - and it LEAKS !
«
Reply #8 on:
December 01, 2015, 05:16:54 PM »
That was my main consern about your design, how do you seal the sliding shaft. Try square or x rings they seal much better than o-rings. Square rings could be found in automotive parts as brake caliber seals are square rings or lip type.
Marko
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Finland
Impossible just takes a little bit longer to achieve.
If an engineer is not presented with a suitable problem, they will create their own!
rsterne
Member 2000+fps Club
Bob and Lloyd
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Posts: 26958
GTA Forums Person of the Year 2017
Real Name: Bob
Re: HPA Booster Finished - and it LEAKS !
«
Reply #9 on:
December 01, 2015, 05:43:29 PM »
I don't see why sealing the sliding shaft is any different than sealing the piston?.... In both cases it is a dynamic seal.... Perhaps you could explain that?....
Good idea about the square, or quad (X), rings.... I will see if I can get them in the metric size I need.... 25mm ID x 3mm CS....
Bob
Logged
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).
MJP
Member 4400+Fpe Club
GTA Senior Contributor
Posts: 2136
I'll make it real. For me.
Real Name: Marko
Re: HPA Booster Finished - and it LEAKS !
«
Reply #10 on:
December 02, 2015, 02:34:46 AM »
I'll try, it would be easy to tell you in Finnish but in English I'll try. I don't know why but the o-rings tend to expand outward more easily and that works good on sealing them against cylinder wall, but using them as shaft seals don't work as good, and that's why shafts are usually sealed with lip type seal or square ring. It's got something to do how force is applied to the o-ring when the shaft is gliding, it pushes the ring to the bottom of its groove and expands it outward.
I use L type ptfe seals usually backed up with an O-ring the L takes most of the pressure and ORing is just to hold it tight.
Edit: think of it like how a piston ring works, and using that principle to seal a shaft, it doesn't work. The oring acts little bit similar.
Hope this helps, I'm not that good in explaining things in English.
Marko
«
Last Edit: December 02, 2015, 02:49:03 AM by MJP
»
Logged
Finland
Impossible just takes a little bit longer to achieve.
If an engineer is not presented with a suitable problem, they will create their own!
rsterne
Member 2000+fps Club
Bob and Lloyd
GTA Senior Contributor
Posts: 26958
GTA Forums Person of the Year 2017
Real Name: Bob
Re: HPA Booster Finished - and it LEAKS !
«
Reply #11 on:
December 02, 2015, 01:55:52 PM »
Makes sense, I guess.... I'll have to see what I can find, there is really no possibility for me to change the O-ring groove accurately without making a whole new cylinder....
Bob
Logged
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).
sr1sws
Sharp Shooter
Posts: 533
yes
Real Name: Steve
Re: HPA Booster Finished - and it LEAKS !
«
Reply #12 on:
December 07, 2015, 04:49:50 PM »
Maybe make your own square seals (I'd be surprised if you hadn't already considered this)?
http://www.theoringstore.com/index.php?main_page=index&cPath=117_569
The also carry the Cyanoacrylate in quite a variety of formulations.
Good luck!
Steve
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Tampa, FL
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rsterne
Member 2000+fps Club
Bob and Lloyd
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Posts: 26958
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Real Name: Bob
Re: HPA Booster Finished - and it LEAKS !
«
Reply #13 on:
December 07, 2015, 11:19:15 PM »
Those are US sizes, I need 3mm CS Metric....
Bob
Logged
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).
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HPA Booster Finished - and it LEAKS !