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PCP design (start)

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PCP design (start)

Unread postAuthor: maverik94 » Mon May 18, 2009 9:34 pm

Ok, as I am finishing up my current project, i'm looking to build a pcp pistol next. Here is the design for the chamber and valve setup. Do you think it will work? Any ideas? Also, I will post pictures of the trigger mech and barrel etc later, I already have them drawn on paper, but I still have to draw them on my computer. Thanks!
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Unread postAuthor: Gippeto » Mon May 18, 2009 9:58 pm

No major problems.

A couple things you might wish to change though;

You will likely realize some benefit by moving the valve face in, closer to the branch of the tee. This will reduce dead space, and improve flow.

The valve stem o-ring WILL depart with the first shot. I promise you. Use a flat washer, and retain it in position.

Or secure the flat washer to the steel washer, and leave the valve stem without a "mounted" seal.

Radius the bend in the tee, this will improve flow and power.
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Unread postAuthor: maverik94 » Tue May 19, 2009 4:20 pm

ok, thanks for the feedback, I will make those changes!
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Give me a lever long enough, and a fulcrum on which to place it and I shall move the world.
–Archimedes
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–Carl Denham

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Unread postAuthor: jackssmirkingrevenge » Tue May 19, 2009 4:39 pm

What pressure will you be using? Don't forget that commercial PCPs get their power and multi-shot capacity from using either CO<sub>2</sub> at 850 or so psi or HPA at around 3000 psi.
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Unread postAuthor: POLAND_SPUD » Tue May 19, 2009 4:54 pm

all in all, I think you should buy an airgun... that's gonna be easier and you won't be disappointed with the results...

it's not a big problem to build a homemade high power gun but it's quite difficult to build something really small
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Unread postAuthor: mark.f » Tue May 19, 2009 5:56 pm

Have you taken a look at a few of the commercial designs for CO<sub>2</sub> or HPA hammer valves? Crosman has been using this basic design for decades...

You could also take a look at the Girandoni air rifles here, which are PCP by design, and 200 years old to boot. If you'll look towards the bottom of the page, a bicycle shop owner built a version of a PCP air rifle during WWII. Pretty damn neat.
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Attachments
crosmanpoppet.gif
Little confusing, but this is the valve for a multi-pump pneumatic. The other valves are usually nearly identical, but I could be wrong.
crosmanpoppet.gif (3.96 KiB) Viewed 2671 times
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Unread postAuthor: maverik94 » Tue May 19, 2009 9:31 pm

well, I am planning on using 300-400 psi on this. However, I will be happy if I get 10 somewhat powerfull shots out of it. Do you think that's possible?
@POLAND_SPUD well yeah, I could buy an airgun, but I wouldn't have the feeling of satisfaction I would if I built one myself. I would like to give this a try, and if it ends up sucking, so be it, I'll have learned. Thanks for the feedback yall, anyone else?
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Unread postAuthor: jackssmirkingrevenge » Wed May 20, 2009 1:55 am

Don't forget that a blowgun is a ready made hammer valve that just needs a hammer, and stuff like a toy cap gun or an automatic staplercan be adapted as ready made hammers.

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Unread postAuthor: maverik94 » Wed May 20, 2009 3:36 pm

yeah i know, but I would prefer to make something completely homemade. Thanks. Anyone else?
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Unread postAuthor: CpTn_lAw » Wed May 20, 2009 4:22 pm

Why not invent something new yourself?
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Unread postAuthor: Brian the brain » Wed May 20, 2009 4:45 pm

Using epoxy will likely give you problems.
You can build a hammer valve like that from small brass fittings without those problems.

Like said before, the oring won;t work.Use a flat rubber washer and superglue it in place.

You will have to go small caliber on this one, just because of the countering force behind the hammer valve at 400 psi.
This means you;ll have to use a small diameter valve, wich limits your barrel size.

I'm very confident it will work based on my previous builds.
You will have to weigh power over number of shots, and you are limited in caliber by using a hammer valve.But a 6 mm 6 shooter is very cool if you do it right!

Homemade all the way baby!!
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Oh my friggin god stop being so awesome, that thing is pure kick ass. Most innovative and creative pneumatic that the files have ever come by!

Can't ask for a better compliment!!
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Unread postAuthor: jackssmirkingrevenge » Thu May 21, 2009 12:39 am

maverik94 wrote:I would prefer to make something completely homemade.


Why not cast your own chamber then :roll: :wink:

I think there's enough effort involved putting pre-existing components not designed for the purpose you're going to use them for together to give enough merit as a homemade project, plus it gives you a much more realistic chance of actually completing your project.
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Unread postAuthor: maverik94 » Thu May 21, 2009 2:32 pm

yeah, I'm thinking 5/16" barrel, ok, would using steel and rubber washers instead of epoxy for the back wall of the valve and epoxy for the size reduction work?
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–Archimedes
Defeat is always momentary.
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Unread postAuthor: jackssmirkingrevenge » Thu May 21, 2009 3:00 pm

Epoxy based construction is only as good as your ability to apply it to the design at hand, that's up to you to figure out ;)
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Unread postAuthor: maverik94 » Thu May 21, 2009 8:37 pm

i have ideas....hehe. I will upload the pics for the rest of the construction soon. As for the construction, I plan to start as soon as the school year is over (next week)
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Give me a lever long enough, and a fulcrum on which to place it and I shall move the world.
–Archimedes
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–Carl Denham

Current Project: None, I'm in Spudremission.
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