Why not use like a lawn tractor battery and just use a car charger. This is really only practical if you already have a car battery charger though....

You may have it hooked up wrong. If not you might need a faster way you pilot it, but a blowgun should be plenty to open the valve.

Yes. You need to figure out how much pressure to put in the pipe before releasing it into the chamber. Thats how i made all of mine, I've never used a regulator. Just a torch head with a hose clamped on, a set of ball valves and a piece of pipe between them with a pressure gauge on it.

Just take a rubber balloon and take the air out of it. Edit- ... never mind. haha just kidding, but keep us posted if you make it, i've never heard of that concept before. i think the problem would be having a truly air tight balloon/frame. Maybe having a vacuum constantly suck air out would be a so...

Just got to get the fuel mixture right. A lot of people think more is better, and that certainly isn't true in the case of spud guns.

I have the same valve. If you take it apart you will find a small white plastic piece on the diaphragm. I have no clue why it is there, but you need to remove it. Its small, white, and has holes in it. Just pull it out. After you remover it, it should work.

I think we need to think about this a little more. Higher pressure and a more efficient valve is a must, but there may be a point where a longer barrel simply doesn't yield more velocity. I know that in real firearms, shotguns in particular, after about 12-15'' of barrel length the muzzle velocity r...

Yup. I've never made it, but apparently it doesn't take much of it to make it bullet proof. Its very very strong and doesn't melt as fast as regular ice.

Well the operating pressure of a 30.06 semi-auto rifle is about 53,000 psi if i remember correctly. People here manage to get an auto working with about 100-200 psi. If you were much more specific about what exactly you are trying to work out we could probably help a little more.

You fooled me! That is a pretty good looking pen gun.

A simple phone call would get you an answer.

You might try just a little bit of grease. I have only worked with valves without a valve guide, but to me it sounds like a bit of bearing/lithium grease work work well.

Check out hobby shops. They usually have small brass and aluminum tubes. You can also use steel brake line. Just get it at any auto parts store. There are different sizes of break line, i think they make 1/4'', which is what you would want.

If you were making one a spring loaded ball bearing would probably work ok.

Just run an electrical cable over the local hospital, they have back up generators... haha totally kidding.