11 replies to this topic

[Carbon]

This project stems from a discussion on Boltsniper's forums about plunger size. Bolt was talking about the relationship between plunger size and plunger acceleration; a larger plunger with a slower acceleration can equal the same power as a smaller plunger with a faster acceleration. It's why the NEAR and the SNAP get similar ranges.

Anyway, just recently I discovered that 1.25" endcaps fit perfectly in 2" PVC. Doing some rough calculations, I discovered that a plunger made out of 2" would have a little over 2.5 times the volume of a normal SNAP. I was guessing that the plunger would be heavier, but most likely not 2.5x heavier...so I should see some performance gains with such a design. As such, here's the Big SNAP...



It's really justa normal SNAP, scaled up. And that it makes this great THOOMP noise when it fires.


I used the compact plunger, and a full 1.25" endcap for a catchface. I used a 2" washer for the gasket supporting surface, and also had to use a washer in front (my finishing washer wasn't large enough, considering the hole in the rubber washer).

Early results look like it gives a performance boost. Using my breech barrel, I shot 90'. Considering that the normal SNAP with compact plunger and breech shoots somewhere in the neighborhood of 80', it's a nice gain. I should be able to pulla little more out of this size as well, because the plunger could stand to lose some weight (possibly a nylon 2" washer, cut down the 1.25" endcap, stuff like that). This might be what gets the SNAP over the century mark...

Edited by Carbon, 30 May 2016 - 04:48 PM.

[Flaming Hilt]

Interesting idea. Nice work putting it to use.

Out of curiosity (if you remember), what #O-ring did'ja use? Thanks.

[GeneralPrimevil]

That's what I was going to do. Too bad I never finished due to my bad luck streak with any designs of homemades other than basic pneumatics...

Very nice. I think I like it. Oh yeah, the barrel seems a bit...off...

ANd uhh, this new one has a grip 11deg more relaxed than previous. You wanted it to better fit your hand? Increased surface area for adhesion? Just came out like that? Curvature of the camera lens?

[Carbon]

Yeah, I was noticing that the barrel was seeming a bit....limp...in that one picture. That;s actually the cowling for the breech, the barrel itself is straight. As far as the handle, that's the angle that my eyeballing decided to put it at tonight. An assembly line worker I'm not.

As far as o-rings....o-rings? Never use 'em. The seal in this monster is a TWO AND A QUARTER INCH RUBBER WASHER. The sucker's a beast.

[Meaker VI]

If your seal is only a rubber washer, do you lose pressure because of the washer folding back? Or do you have another metal washer behind it? I can't imagine you can get the washer to be folded forward (like in airsoft plungers or the syringe), since it would have to be an angled washer.

But the increase in range makes sense, you've increased the volume of air moving by quite a bit. Perhaps you should work to make it pump action and clip-fed. That way it would look less fat at the back and more frightening. After all, much of the power from a gun comes from it's reputation, and much of it's reputation comes from it's looks. These snaps are quite an impressive achievement though, when I get back home in a few weeks we'll see if I get anything built.

[Carbon]

If your seal is only a rubber washer, do you lose pressure because of the washer folding back?

I believe the washer stays folded upward when firing, because it's oversize for the chamber. The washer is 2.25", and my chamber is 2". Of course, I can't say for sure what the washer is doing upon firing, but the seal is good; I can stop the plunger if I seal the barrel with my finger. I actually lose more air from the PVC joints (I can hear them hissing if the barrel is plugged).

EDIT: I see what you mean in your question; the rubber washer doesn't fold back because there's a metal washer behind it, the same ID as the PVC, like you said.

Edited by Carbon, 27 April 2006 - 11:07 AM.

[GeneralPrimevil]

Carbon, you need to make another one, only usign 2" clear Sch40 PVC. The stuffs a bit more expensive, but you can then study what happens to your piston head.

So is this thing holsterable? I'm thinking how big 2" PVC is and, well, I believe not...

[Carbon]

Carbon, you need to make another one, only usign 2" clear Sch40 PVC. The stuffs a bit more expensive, but you can then study what happens to your piston head.

I've never even heard of it. Where can you get it?

As far as a holster....it's not the 2" PVC that causes the problem, it's the the 14" barrel.

[GeneralPrimevil]

McMaster-Carr should sell it. The stuff is pretty neat.

14" barrel...hmm...I see your point

Edit: part 49035K28 is what you could get. $30+shipping for 4' ouch...

Edited by GeneralPrimevil, 27 April 2006 - 08:51 AM.

[Forsaken angel24]

Transparent pvc? That sounds awesome. I might pick some of this stuff up and paint the brass then slide it in the clear pvc. Has anyone seen pictures of this stuff and how transparent it is?

[GeneralPrimevil]

Another source...

The stuff you can, in fact, see into. It is really cool with combustion cannon for spudguns, as the flash can be seen.

A good image is here. That is 4" stuff, by the way.

[CaptainSlug]

Transparent PVC isn't very cost effective. If you want large clear tubes order Polyester.