SpudFiles

I haven't seen this done yet but maybe i've just missed something. It's just a theory, but would the shrader valve have enough flow to act as a pilot in such a relatively small coaxial pengun setup like this? what do you guys think? I think if I can work out the pilot volume to be super small without hindering exhaust flow to the barrel then it would work quite well. Remember too that it's just a pen gun, its purpose is not to be a powerhouse. Ultimately i'm trying to figure out a super simple design that uses only one valve for filling and piloting a piston for a coaxial pen gun. I want it as compact as possible. Which has better flow- a presta or shrader valve? With this setup i could use either one. *Notice* in the drawing i showed the shrader valve coming out of the housing as if it were unscrewed but in the real design i wouldn't do this, it is just for illustration purposes.

This has been discussed before here.

Oh sorry i didn't see that post, thanks for pointing me there though starman. So maybe this isn't a new idea, but again i am wondering if a shrader valve will have sufficient flow. I understand what iisthemuffin's pen gun was having trouble with, but i haven't seen what his piston looked like or just how tight to the chamber wall it was. Also we don't know what his pilot volume was or how much resistance his spring had which are all factors that could have rendered the shrader valve acting as a pilot way less effective. But assuming i would make an ideally shaped piston with a fairly tight but still 'leakable' face against the chamber wall for equalization, with a relatively small pilot volume and a relatively low pressure spring, i'm thinking i'd be in business. 8)

I've used schraders to pilot pistons as big as 1", it shouldn't be an issue as long as a) your piston is a tight enough fit that less air leaks around it than can flow through the schrader and b) you limit your piston travel to less than the diameter of your barrel.

Coincidentally, I'm currently making a (slightly more elaborate but still ghetto and with epoxy galore) trigger mechanism for my latest schrader piloted coaxial - this project - should have it ready in a few days, watch this space

Hey man, have you considered using a burst valve to an air compressor and then just pulling the ring as a trigger? That gets a heck of a lot more flow than the shrader at least.

Wow if that's a pengun the barrel must fire bucky balls.

Your trigger will not work, and even if it did, it is way to small considering the scale of the gun. The trigger would need a pin to push in the little thing inside the shrader, and your trigger is just rotating, not pulling it in.