SpudFiles

How close is the piston diameter to the pipe inside diameter?

I've found that if there's only a tiny bit of space and you use only a layer or two of duct tape, it tends to get wrinkled up because moisture from the compressed air can get into the adhesive easier.

I used 1-7/8" PVC rod for my piston, and wrapped it in several layers of duct tape to fit. As for lubrication, I used normal petroleum jelly. Works fine and doesn't eat away the duct tape too bad.

The piston should slide in the aluminum.
The reason the piston shouldn't be wrapped is because if the aluminum slides in the cylinder it would chew the cylinder walls up.

Without duct tape, there's probably less than 1/8" clearance. It only took about one wrap of duct tape to make it tight.

EDIT: So then do you epoxy the aluminum to the inside of the piston carrige?

noob of noobs wrote:Without duct tape, there's probably less than 1/8" clearance. It only took about one wrap of duct tape to make it tight.

EDIT: So then do you epoxy the aluminum to the inside of the piston carrige?

Yes, read the edit to the above post.

That's a good idea. I'll try that as soon as I have time.
Thanks.

noob of noobs wrote:My parents are divorced.

sorry to hear that, apologies if that wasn't funny.

No, it is funny. I was joking by the way.
Also, do you think it would be possible to tape the aluminum or use regular glue instead of epoxy? I'm not very good with epoxy to say the least...

EDIT: They're not divorced, but they don't spend much time together either.

Here are a few tips (some will apply, others won't, I am just listing things that I can think of)

1) Sand the actual piston in order to allow the tape to get a slightly better grip on the piston.
2) Wrap the tape EXTREMELY tightly so it won't fall off.
3) Make sure the piston with the tape is the right thickness; too much, and there will be too much friction and it will get ripped off, along with poor performance; too little, and the air will rush by and the extra space that the piston has to move might also help to rip the tape off.
4) White lithium grease works great for me when I make pistons with duct tape.
5) Make sure your piston seat is smooth.

edit: enough with the lewd KY jokes, this is getting out of hand hehe

Okay, I'm terribly sorry for kicking up an old thread, but I haven't been able to do anything with cannons for a long time due to school.
I tried doing the aluminum can thing, and I still have the problem. Using my mouth, I can blow air into the piston valve through the ball valve pilot, and the piston seals fine. I can also suck air through it, and the piston moves back and forth. But when I charge the valve to 60 psi (much stronger than my mouth) and release the air, nothing happens. I lubed it up with petrolium grease, and it should work fine, but doesn't.
Any help?

noob of noobs wrote:Okay, I'm terribly sorry for kicking up an old thread, but I haven't been able to do anything with cannons for a long time due to school.
I tried doing the aluminum can thing, and I still have the problem. Using my mouth, I can blow air into the piston valve through the ball valve pilot, and the piston seals fine. I can also suck air through it, and the piston moves back and forth. But when I charge the valve to 60 psi (much stronger than my mouth) and release the air, nothing happens. I lubed it up with petrolium grease, and it should work fine, but doesn't.
Any help?

what are using to pilot? try a 1/4 ball valve if you havnt already

I was using a 1/4" blowgun, but now I'm using a 1/2" ball valve.

Can you get a pic up of the entire valve and pilot set up?

Sure, but it'll be a while. The digital camera's in Wisconsin with my dad right now, but he'll be back tonight.

Ah, here we go.
Here's the setup of the valve: http://img264.imageshack.us/my.php?image=img2419kn4.jpg

And here's the piston: http://img172.imageshack.us/my.php?image=img2421dl3.jpg
Thank's for your help.