Airgun for developing countries
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Airgun for developing countries
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Topic: Airgun for developing countries (Read 7943 times))
Gippeto
Sharp Shooter
Posts: 864
Re: Airgun for developing countries
«
Reply #60 on:
March 09, 2017, 12:41:36 AM »
Have found the program to be fairly accurate providing it's fed accurate information and the predicted velocities are below 900fps...above 900fps it's just not accurate at all.
1" npt and smaller fittings are available to you? Can you get hydraulic fittings? They're usually machined inside as opposed to the cast varieties.
Checked a 1" coupling I had on hand, it's just over 2" in length, some quick and rough calculation shows it having roughly .9 cuin once assembled.
Al
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Alberta, Canada
nikp
Shooter
Posts: 30
yes
Real Name: Nick Potter
Re: Airgun for developing countries
«
Reply #61 on:
March 10, 2017, 07:10:17 AM »
Couldn't help myself.
Chamber is made from 30 mm steel. Spool also steel but drilled out to lighten. No Oring as yet. Feed to reservoir and from pump both NPT compression fitting elbows. Barrel in place is only for test purposes. Hopefully I get to test it tomorrow
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Nakhon Sawan, Thailand
rsterne
Member 2000+fps Club
Bob and Lloyd
GTA Senior Contributor
Posts: 26958
GTA Forums Person of the Year 2017
Real Name: Bob
Re: Airgun for developing countries
«
Reply #62 on:
March 10, 2017, 02:41:05 PM »
It looks like there is a lot of volume to the right of the spool.... That air must be dumped to shift the spool and create the shot.... The larger the volume, the slower the air will dump out through the blowgun nozzle when you pull the "trigger".... The slow dump of air won't slide the spool very quickly, and opening it slower will reduce the velocity of the shot.... Also, the small inlet below the spool won't help either....
It should fire, just not perform well, IMO....
Bob
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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).
nikp
Shooter
Posts: 30
yes
Real Name: Nick Potter
Re: Airgun for developing countries
«
Reply #63 on:
March 10, 2017, 11:20:14 PM »
You're right. Working on the fix.
Gippeto, the semi circle hole you drill into the oring groove - it's obviously only as deep as the groove but does it matter where on the circumference it is? Your spool would rotate placing the hole opposite to the reservoir outlet I assume. I'm guessing it's irrelevant where it is as the air is moving around the spool and into the reservoir. Probably over thinking this
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Nakhon Sawan, Thailand
Gippeto
Sharp Shooter
Posts: 864
Re: Airgun for developing countries
«
Reply #64 on:
March 10, 2017, 11:46:29 PM »
You got 'er..any where around the circumference is fine.
If you drill out the spool, that volume becomes part of the pilot volume. What some folks have done is fill it with something light but bulky and then cap it with epoxy...JB Weld/Araldite.
Pilot volume can be a killer, and it can be hard to get rid of while maintaining a .2" (~5mm) diameter passage you need for air to vent off.
Other thing some folks have trouble with is the fit of the spool to its bore...needs to be a very good fit...almost snug. The use of the o-ring will take care of that.
Your final build should not make use of that plastic tubing to feed the valve...it will hurt performance.
Al
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Alberta, Canada
nikp
Shooter
Posts: 30
yes
Real Name: Nick Potter
Re: Airgun for developing countries
«
Reply #65 on:
March 11, 2017, 10:46:13 PM »
Al,
Did you ever do any work on fitting your hand pump to an airgun? I'm looking at modifying your design to make it an integral part.
The lever action and the fulcrum affects are of interest.
Nick
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Nakhon Sawan, Thailand
Gippeto
Sharp Shooter
Posts: 864
Re: Airgun for developing countries
«
Reply #66 on:
March 12, 2017, 03:21:07 AM »
No, I never tried to fit in on. Quite a few folks around that have built pumpers based on the Crosman rifles...maybe one of them could chime in with some dimensions as a starting point on the geometry??
Al
Logged
Alberta, Canada
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GTA
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All Springer/NP/PCP Air Gun Discussion General
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(Moderators:
Rocker1
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Wayne52
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Airgun for developing countries