Cad drawing project (PCP airgun)

[Necrosis]

I am looking for some help!

Mainly in valve choise.
And how to trigger this stuff.

This thread is also a container of stuff I am going to model.

I got my dad to agree to machine the needed stuff if I could draw a working model.

So off to solidworks I go!

(Sorry for the chaotic nature of this post, I am sure that it will get better)

[benstern]

uh pneumatics usually don't have enough power to make use of rifling.

[Brian the brain]

excuse me?!?!?

he did overdo the number of turns on it though....

[origin unknown]

You are very lucky that your dad can machine things for you. If I were you, I would design something like a 40mm rifled PCP cannon with a CO2 fill system and a piston valve.

[DYI]

My only comment so far would be that the rifling is really overdone.

This looks like it could be a really interesting project. If you have the capabilities to machine complex parts, I would suggest a piston valve. If not, and you plan on using high pressures (as I hope you do), you could just use a pneumatically actuated or spring loaded ball valve. And don't use CO2, it's just a waste of power, unless you already have a CO2 fill setup.

[benstern]

I ment that pneumatic can't use rifling on metal of plastic ammo that fits tightly.

[Necrosis]

The rifling is indeed overdone, The power source will be compressed air, as we can get that for free, in 12 litre 200 bar packages*.

And yes the rifling is a bit overdone, But it's just a matter of typing let's say, 5 in stead of 20 in the box that says number of turns.

*that does not mean I will actually use those 200 bars, I will probably end up at a maximum of 50 bars using a reducer valve.

[DYI]

Even 50 bar is a respectable pressure, and air will certainly be more impressive than CO2 for that pressure. Just make sure that there isn't anything particularly flammable in the chamber or valve and you should be fine.

In my opinion, if you have the ability to, you might as well use the 200 bar. I've wanted to see a real high pressure cannon here for a while.

[jackssmirkingrevenge]

Most PCPs use a hammer valve like this antique Girandoni:



Modern designs haven't changed much, though they tend to use helical springs to hammer the valve. This flash demo or a pump-up pneumatic might also be helpfil

[Necrosis]

Just a quick question, doesn't CO2 turn liquid at 50 bars? or was that some other gas..

[jackssmirkingrevenge]

closer to 5 bar actually.

[Necrosis]

That's what I meant.

[williamfeldmann]

Yeah, I wish I could machine parts.

If you really have access to the machines and skilled labor, a piston valve would be one of the first things I'd make. Sure a piston is a piston but with the lathe you can make one hell of a nice fitting and performing piston.

I couldn't find any mention of what size you are making the barrel. What is the ammo of choice? The choice of ammo might make the decision on rifling easier (wadded marbles could user higher turn rate than say a spud or tennis balls.

[jackssmirkingrevenge]

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I couldn't find any mention of what size you are making the barrel. What is the ammo of choice?

For a small calibre there's a variety of black powder calibres (0.44 etc.) that would be ideal as ammunition would be easy to find and velocity from a long air rifle would be analogous in terms of velocity to a shorter BP pistol for which twist rate data is already available.

[Necrosis]

The caliber and ammo are still to be decided.
It's probably going to be a lead projectile, though.