check valve effect in a piston valve using a rubber cap

[iknowmy3tables]

so I recently I've been experimenting with a secretstrike nerf gun and I learned a good bit about it's design, you can find some diagrams here

anyways one of the features is that it uses a piston valve, and for a piston it uses a sort of rubber cap in a way that creates a check valve effect that allows air from the pilot to enter the chamber, but prevents air from the chamber from entering the pilot.

so I think this could be applied to a homemade piston valve, you could make a piston out of a rubber end cap like one of these

they're lighter and softer then a wood or pvc piston so you'd hardly need a bumper.

What do you guys think?

[deathbyDWV]

I don't see why it wouldn't work except for the piston being too soft and bending on the way back... So it'd need to be lubricated some...

[Hubb]

I think it's worth a shot. The only negative I can see right off hand would be the friction of the piston to the pilot pipe.

[MRR]

The only problem I see is that friction increases dramatically with higher pressure. The valve could become slow or doesn't even fire at all.


edit: hubb beat me at that one

[Gun Freak]

I might try this on my new piston valve. Seems logical...

[iknowmy3tables]

here's an thought, could the static friction perhaps delay the opening of the valve so the pilot pressure would be lower before the valve opened?

[Gun Freak]

here's an thought,

The word "thought" begins with a T, which is not a vowel, therefore you would not use "an", but instead "a". Just messin with you.

could the static friction perhaps delay the opening of the valve so the pilot pressure would be lower before the valve opened?

Resulting in a quicker opening time? I don't think it would be much of a difference, but it sounds like it might work.

[Hubb]

I would think that with the increase in friction, the piston will begin to move when the pilot is exhausted, but it will move really slow. I don't think it would work like you think it would.

I think if we could get past the friction issue, that this would be a very nice piston valve. It would have a light weight, low profile, fast opening times,...all the things that a good quality piston valve should have.

With that said, maybe if we could place a ring of pipe inside the walls of the piston to cut the friction. This would still give it the check valve quality, but also be able to be lubed up, which should eliminate a whole lot of friction.

Really, though, the only way to see if this works or not is to try it. I've been wanting to make another piston valve so I might give this one a go when I get a little bit more scratch (probably next Friday).

[c11man]

i see the center of the cap bending into the barrel but it shouldnt matter because its all one peice

[iknowmy3tables]

i believe it's worth a shot cause if it doesn't work well then you can just replace it with a piston made from a pvc end cap

[clemsonguy1125]

It may work but under enough pressure the center would balloon out and possibly "pop" but at say 80 psi it should be fine

[Gun Freak]

It may work but under enough pressure the center would balloon out and possibly "pop" but at say 80 psi it should be fine

You can probably reinforce it with some washers inside of the cap or something. I think with some practice this idea could be the new piston valve technology

[clemsonguy1125]

I agree but maybe a coat of epoxy would work better

[c11man]

i think washers would be better

[clemsonguy1125]

well washers would need to be bolted on which would add more weight than just dumping in some epoxy