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Piston Design

Post about things you have launched or thought about launching. Also post about various materials used for building cannons. No posts about explosive projectiles!
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Piston Design

Unread postAuthor: demilus » Tue Apr 03, 2007 6:55 pm

Hey, it's my first piston. I have some plexiglass rod that I plan to make into my piston. I will drill the holes all around the rod so that the piston will equalize even if it gets turned. If you see anything inherently wrong with my design, please tell me. Thanks![/img]
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Unread postAuthor: noname » Tue Apr 03, 2007 6:57 pm

I'd suggest making two tiny holes, like 1/32." The piston will equalize, but fire better because air will get through the piston, but much slower than if there were multiple larger holes.
Other than that, good luck!
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Unread postAuthor: demilus » Tue Apr 03, 2007 6:59 pm

I was thinking that since they all converge into a smaller central shaft, that it wouldn't inhibit the performance too much. I figured that it would restrict the flow enough.
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Unread postAuthor: hi » Tue Apr 03, 2007 7:46 pm

you dont really need a spring. You do need to have a rubber disk on the front, like a piece of neoprene or a cut a piece from a bike tire inner tube and bolt it on.
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Unread postAuthor: Hawkeye » Tue Apr 03, 2007 9:46 pm

If it's going to seal the barrel and allow air to leak into the chamber the holes would have to be ahead of the second o-ring. No?
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Unread postAuthor: chaos » Tue Apr 03, 2007 10:39 pm

i dont think you need that o ring on the front of it, instead put a rubber disk on the front.
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Unread postAuthor: hi » Tue Apr 03, 2007 10:50 pm

You dont need an O ring at all if it is a good fit. none of my coaxials have O rings and they work fine.
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Unread postAuthor: jackssmirkingrevenge » Tue Apr 03, 2007 10:51 pm

hi wrote:You dont need an O ring at all if it is a good fit. none of my coaxials have O rings and they work fine.


Agreed, I cast my pistons out of epoxy and they fit extremely well so no need for o-rings or equalisaton holes.
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Unread postAuthor: chaos » Tue Apr 03, 2007 10:54 pm

yer but still they sometimes do perform better with o-rings on the back, if he can get the o-rings i think it would be worth it.
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Unread postAuthor: locksmith » Wed Apr 04, 2007 11:29 am

The only problem i would see with using o-rings is the will add friction and slow the piston down.
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Unread postAuthor: demilus » Wed Apr 04, 2007 3:08 pm

Whoops I forgot to label the rubber on the front. It is going to be a barrel sealing piston in a tee fitting. I guess I really don't need the first o-ring. I think I'm gonna leave the second oring though, I think it will improve performance. Thanks for replying guys!
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Unread postAuthor: jrrdw » Wed Apr 04, 2007 3:19 pm

Your equilization holes should go from front to back, or front to side since your useing a tee.
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Unread postAuthor: demilus » Wed Apr 04, 2007 3:23 pm

They do. If my picture is a little unclear, sorry. The black dots are holes going towards the center. They all connect in the center with a shaft going out to the exhaust end (blue line in pic).
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Unread postAuthor: pyromanic13 » Wed Apr 04, 2007 10:30 pm

locksmith wrote:The only problem i would see with using o-rings is the will add friction and slow the piston down.


I think that is the opposite, the air venting gets lower (pressure), faster....
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Unread postAuthor: chaos » Wed Apr 04, 2007 11:28 pm

pyromanic13 wrote:
locksmith wrote:The only problem i would see with using o-rings is the will add friction and slow the piston down.


I think that is the opposite, the air venting gets lower (pressure), faster....


yer i agree with pyromanic13 having a better seal/with lubed o-rings will allow it to open faster.
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