Piston Help

[Sergeant Dotson]

I'm not typically the type to ask for help, but well, I need some. I just made the main construction of my first piston cannon about a week ago now. Since then, I've been tinkering around with materials but have never found something that works.

Specs:
-Chamber is made of black metal
-Chamber is 1'
-Barrel is 1/8"

Any help would be appreciated, and as always, thanks for the help.

-Sarge

[jrrdw]

Do you want to know what to make the piston out of? What have you used so far? A list of what you tryed will elimanate repeats.

[Sergeant Dotson]

Well, I've tried rubber cork, wood, types of plastic caps. And yes, I do need help with what materials I need to use.

[jrrdw]

Did you lube the piston? Maby the blow gun isn't piloting the chamber fast enough, try unscrewing it fast and see if it fires then. You mite be able to hold you thumb over the hole and test it that way.

[Sergeant Dotson]

I've tried all of that, I just need some kind of material that would work.

[jrrdw]

Bondo <-----is a maby
Epoxy<-----talk to JSR
Wood<------thats what I use
PVC caps glued together<-----pretty much a standered build

Are you possitive air is getting past the piston into the chamber? What exactly happens when you try to fire it?

[MrCrowley]

Are you palnning on having the piston travel inside the galv chamber? Good lukc getting it to work, not only do you have to make a groove for the pipe seam, but you can never get a good fit with the galv.

The piston will hardly actuate at all because of the gap between the galv and piston. If your piston is a good fit, it wont move. You really need to sleeve the galv chamber with PVC or copper.

For a 1" chamber, 3/4" PVC with a groove cut for the seam works perfectly. That's how I made mine. I used a wooden dowel, which was easy to make o-ring grooves in with just a dremel.

http://www.spudfiles.com/forums/crowley ... 13459.html

[Sergeant Dotson]

Well, all I know is that it is supposed to be a barrel sealing piston. And yes, i'm sure it's leaking. When I even fill this with air, it just leaks out the barrel.

[jrrdw]

I wasn't even considering that the cylinder wasn't smooth. Yes what MrCrowley says, the piston and cylinder have to be matched. You have a few bugs to work out. You can sand down the inside of the chamber/cylinder and make a bigger piston for a nice fit. Try to get all the air leaks stopped, that helps.

[Sergeant Dotson]

I think that the sanding is unnescesary. I'm sure I can make one to fit it. I just need something to make it with. I guess I'll research some more.

[MrCrowley]

Just do what I told you to do, sleeve the metal chamber with PVC or copper, then find wooden doweling at your hardware store that fits. If it's a bit off, a small amount of sanding will only take a few minutes.

Sanding is sometimes necessary.

You wanted help, and that's what I gave you. It is a good option.

It is very hard to get a piston working in a galv chamber, it's too rough, has a seam and the front is slightly tapered inwards which will leave a gap around the piston inside the chamber.

[Sergeant Dotson]

Well, I'm in the process of making one of wood and using felt around it to make it fit. On the end is a rubber washer and on the outside of the barrel, I put rubber tubing that will even further help it seal against the barrel. And, MrCrowley, there is actually not a seam on the inside of my pipe and there is also not a lip on the inside. Not trying to put you on the spot, but just stating what is there.

BTW,
How snug should the piston fit in the chamber?

[jrrdw]

"BTW,
How snug should the piston fit in the chamber? "

If you made equilization holes make it have a slight drag. If you don't have the holes it should fit loose enough to let air go in but not allow the piston to tilt.

[Sergeant Dotson]

Which do you think would be easier, equilization holes, or loose fitting?

[jrrdw]

Power and relieabilty wise I like equlization holes.