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piston help

Post questions and info about pneumatic (compressed gas) powered cannons here. This includes discussion about valves, pipe types, compressors, alternate gas setups, and anything else relevant.
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piston help

Unread postAuthor: roughboy » Wed Jun 27, 2007 6:30 pm

Can someone help, my piston cracked, it was a pill bottle with bolt, nut, and a rubber washer, so can someone tell me what to use as a piston? The piston has to fit inside my 2'' chamber because my cannon is a barrel sealer DUH!
Thanks!!!!!!!!! :wink:
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Unread postAuthor: hi » Wed Jun 27, 2007 6:33 pm

i could have told you it would have cracked....

you can use a 1.25' end cap wrapped in tape.

you can also mold one out of hot glue.
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Unread postAuthor: Redcoat » Wed Jun 27, 2007 6:48 pm

well if you're incredibly desperate you can make an excessively large spitball.I did that and it worked when i made my first piston valve.
but if you want something good get a rubber and push it down over the top of the cylinder which houses the piston until it cuts out and you should have a perfect fit rubber piston.Worked for me as well.
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Unread postAuthor: roughboy » Wed Jun 27, 2007 6:56 pm

OK, thanks guys i'll try one of the methods.also it'll help more if anyone has a link on this site with pics. or also other sites other than this site. Thank yous!
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Unread postAuthor: roughboy » Wed Jun 27, 2007 6:59 pm

OK, thanks guys i'll try one of the methods.also it'll help more if anyone has a link on this site with pics. or also other sites other than this site. Thank yous!
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Unread postAuthor: Redcoat » Wed Jun 27, 2007 7:18 pm

ah you posted he same thing twice.(well thats my captain obvious for the day :D )

Good Luck.

Happy SPuddin
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Unread postAuthor: Arborman » Wed Jun 27, 2007 7:32 pm

Nube question of the day, i know epoxy and hot glue pistons will work, but i dont have that.

I do have a butload of bondo (spelling?)

will that work?
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Unread postAuthor: Redcoat » Wed Jun 27, 2007 7:37 pm

It would probably work im guessing as long as it doesn't stick at all.I dont know anything about bondo but im pretty sure if it isnt sticky (creating friction) once its dried and its airtight and if it's strong enough you got yourself a piston.You be the judge if it matches the criteria.
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Unread postAuthor: jackssmirkingrevenge » Wed Jun 27, 2007 11:07 pm

Arborman wrote:Nube question of the day, i know epoxy and hot glue pistons will work, but i dont have that.

I do have a butload of bondo (spelling?)

will that work?


It probably would work, you could use the same technique as for epoxy pistons.

Roughboy, did you include some sort of bumper to stop your piston slamming into the rear of your launcher on firing?
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Unread postAuthor: roughboy » Wed Jun 27, 2007 11:34 pm

The bumper is half of a tennis ball I think the pill bottle cracked coz it was thin and the bumper maybe too hard for it to handle I Don't Know, Maybe.
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Unread postAuthor: jackssmirkingrevenge » Wed Jun 27, 2007 11:39 pm

try another pill-bottle but this time fill it with bondo?
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Unread postAuthor: Modderxtrordanare » Wed Jun 27, 2007 11:52 pm

jackssmirkingrevenge wrote:try another pill-bottle but this time fill it with bondo?


Or epoxy? :wink:

Even filling it with spray foam would help absorb some of the impact and keep it from cracking. It'd be lighter too.
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Unread postAuthor: Gepard » Thu Jun 28, 2007 8:32 am

I wouldn't make a piston out of Bondo. It's made of polyester resin mixed with talc so it can be very brittle. It isn't impact resist at all and after a coupel of fires if that it'll break up. If you do choose to go that way cover it in something like a layer of fibreglass otherwise prepare to replace them over and over....

Michael
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Unread postAuthor: goose_man » Thu Jun 28, 2007 6:13 pm

Being as this thread is called "piston help" I have a question:

Firstly, I am using a 1.25" endcap with two O-rings around it. It can travel about 3/8" backwards. I want to pilot it with the smallest possible valve (hopefully a blowgun). To do this I assume that need to reduce pilot volume. Will filling the back of the endcap with epoxy be helpful? Or would the added piston weight overpower the benefit of the reduced pilot volume?
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