What makes a good two inch piston?

[iisthemuffin]

Im making a coaxial cannon. The barrel is 1 inch and the chamber is 2 inches. ive got the cannon all put together and ive been toying with pistons.

I started with an endcap and wrapped it in tap and then put a rubber washer on the front. It sealed fine but it wasnt big enough around and it wouldnt seal right way because air was getting around it. It would shoot things but most of the air would come out of my 1/2 inch ball valve because the piston was too small. So i said okay ill just put more tape around the piston and problem solved. When i did that, i could not get the piston to go in past the adapter on the back

So my question is, can i get around the fact that it wont go in and still have it be large enough. Maybe a new piston all together.

Any ideas are appreciated.

[i-will]

all i did was find a small bottle or object that fit just right then cut it as needed, then u put a rubber seal where needed. then u got ur piston. it worked for me.

if u think the piston should work but its not moving too easily u might need to lubricate it. i had the same problem. lube was the solution.

[noname]

A lot of the larger orange pill bottles fit really well in 2" PVC. I've used those before, filled with foam with a rubber circle bolted onto the front.

[MrCrowley]

http://www.instructables.com/id/Golfbal ... That-Shoo/

[Demon]

i already maked an 2 inch piston with an encap.

all you need is to put electrical tape very, very slowly and put engine lubrificator around it, its maded for pistons.

i was able to pilot it with an 1/4 inch ball valve

[Pilgrimman]

I like 2" washers on threaded rod. Easily adjustable!

[jrrdw]

2 1/4" hole saw through a 2" X 4" oak board, then sand untill fitted.

[psycix]

I used TWO endcaps, joined together with a piece of pipe. Bolted on a sealing face, DONE

[brogdenlaxmiddie]

I used a tomato sauce can

[frocksie]

My best success came with 2" PVC stock, although it can only be bought in 4' lengths I believe, and it is rather expensive...

[iisthemuffin]

Thank you everybody for your great ideas!

Im going to try a few out today and see if i cang et some good success.

[psycix]

My best success came with 2" PVC stock, although it can only be bought in 4' lengths I believe, and it is rather expensive...

You mean a massive rod? Unless you machine it so its hollowed out, it would be way too heavy to be a quick acting piston.

[mark.f]

Nonsense. Both me and Velocity have used 1-7/8" PVC rod for pistons before, with very good performance.

[john bunsenburner]

I guess you could use a metal pipe with two enc caps filled with foam, this is strong, light and there is no problem with preasure

[iisthemuffin]

Thank you john but ive already finished this cannon. I ended up using the end cap and putting a medicine bottle inside the back.