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[update](new vid)Piston material.

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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Unread postAuthor: Hubb » Sun Mar 09, 2008 8:04 pm

Try to find you some neoprene. Inner tube rubber will work, but it is very flimsy and will probably have to be layered. It is also more likely to get sucked out of the barrel.

The neoprene may be able to be picked up at Home Depot. Get a sheet and cut it to shape.
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Unread postAuthor: Counterstriker » Sun Mar 09, 2008 8:09 pm

Thanks you guys have been a real help! But I have saved the stupidest question for last..I see these diagrams drawn by people, Are the just using MS paint? (No not the 3d ones..)
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Unread postAuthor: Hubb » Sun Mar 09, 2008 8:13 pm

A lot of them are.
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Unread postAuthor: Counterstriker » Sun Mar 09, 2008 8:30 pm

Ok! I have my idea, Does it look like it would work?
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Unread postAuthor: STHORNE » Sun Mar 09, 2008 8:48 pm

an o-ring would be best
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Unread postAuthor: Counterstriker » Sun Mar 09, 2008 8:51 pm

sthorne wrote:an o-ring would be best


Oh yah! I almost forgot!
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Unread postAuthor: STHORNE » Sun Mar 09, 2008 8:52 pm

lol, its ok....questions are meant to be asked, otherwise, everybody would half-ass everything they do
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Unread postAuthor: Hubb » Sun Mar 09, 2008 9:13 pm

Assuming this is not drawn to scale, it will work. But it looks like your pilot volume would be massive, having the pilot valve coming out of a tee like that. I would suggest using a brass or galv tee (schrader threads are 1/8" npt) and hook the blowgun up to that.
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Unread postAuthor: Counterstriker » Mon Mar 10, 2008 3:23 pm

hubb017 wrote:Assuming this is not drawn to scale, it will work. But it looks like your pilot volume would be massive, having the pilot valve coming out of a tee like that. I would suggest using a brass or galv tee (schrader threads are 1/8" npt) and hook the blowgun up to that.


Yah, I think I will add the shrader on the blowgun, But as far as what you said.. you lost me. Can you link me to what it looks like?
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Unread postAuthor: brother361 » Tue Mar 11, 2008 1:39 pm

or basically coppper is for small ammo at high pressure
pvc big ammo for lower pressure
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Unread postAuthor: Counterstriker » Tue Mar 11, 2008 2:57 pm

Thanks Guys, I will keep you updated with picture, I am gonna guess around hmm.. 34-40 bucks.. But its cool.. Do the sell like.. copper pipe around.. 8mm - 10mm?
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Unread postAuthor: Hubb » Wed Mar 12, 2008 5:07 pm

The barrel / piston was slid back. A small tee was used and connected the schrader and blowgun.
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Unread postAuthor: Counterstriker » Wed Mar 12, 2008 5:29 pm

Nice , did you just edit the already done picture? Cause it looks pretty much the same. What it the thing around the pipe at the end of the piston? What pieces would need to connect the blowgun to the tee. Sorry for all the questions , I don't want to spend 2 hours at home depot figuring everything out.. (I did that the first time I made a cannon) :lol:
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Unread postAuthor: Hubb » Wed Mar 12, 2008 5:54 pm

Sorry for not clarifying (and, yes, I simply edited the original pic).

First, the piece around the piston is something I did not erase from the original pic. It is whatever you intended it to be.

As far as connecting it together, tap a 1/8" npt hole in the end of the cap and put a pipe nipple (short piece of pipe threaded on both ends) through the hole. Secure the tee to that, then the schrader and blowgun.
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Unread postAuthor: DYI » Wed Mar 12, 2008 6:02 pm

I'm glad I read the rest of the thread, because I was about to start ranting about how poor a piston material copper would be...

Your design looks fine. If you live in the U.S., you can get some wonderful piston materials from McMaster-Carr. You can buy 1/4" butyl rubber sheet that would make an excellent sealing face, and polycarbonate bar stock is one of the better piston materials. It has high impact resistance, and the clear variety allows you to see any developing defects.

I'm almost sure that you don't want to take the time to order materials online, so the neoprene sealing face/wooden piston setup should work quite well, especially at such low pressures.
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