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Homemade Polystyrene for piston

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Homemade Polystyrene for piston

Unread postAuthor: euskalspud » Sun Apr 19, 2009 12:32 pm

Hi

Well, I was planning a mini pneumatic coaxial gun, but I didnt know which material use for the piston. Some weeks ago I made a Polystyrene catridge, and its very strong and light.

I wanted to know if it would be used for a mini pneumatic coaxial gun piston, piloted by a schrader valve, something like jackssmirkingrevenge´s (http://i164.photobucket.com/albums/u28/ ... 512443.jpg).
It would go with some neoprene or rubber in the sealing face.

Please sorry my bad english, I´m spanish :)
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Here´s the catridge. It fits great in 3/4" pipe

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Unread postAuthor: dudeman508 » Sun Apr 19, 2009 12:53 pm

I think you should shorten it a little
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Unread postAuthor: euskalspud » Sun Apr 19, 2009 1:01 pm

The plastic in the photo isnt the piston, is the ammo for my pneumatic rifle. I want to know if this material can be used in a piston.

Or are you telling me to cut the CATRIDGE? I´m new on piston spudguns.
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Unread postAuthor: Gaderelguitarist » Sun Apr 19, 2009 1:19 pm

It should work for a piston, provided you machine/cast it correctly and give it a decent bumper.

I'm not sure how impact resistant polystyrene is.

What pressures where you planning to run the co-axial at?
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Unread postAuthor: euskalspud » Sun Apr 19, 2009 1:23 pm

I´m going to use it at 90-120psi, but I´m going to make the chamber and the barrel longer than the gun shown in the photo.

EDIT: Sorry but could you explain me what the bumper is? Or post a link where it is explained.
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Unread postAuthor: ramses » Sun Apr 19, 2009 1:45 pm

a bumper is a piece of squishy material that keeps the piston from slamming into whatever is behind it. stuff like nerf footballs, pool noodles, etc. have been used. a good test is to put the bumper on a piece of wood and hit it with a hammer. It shouldn't be too loud, and the bumper should spring back up quickly.
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Unread postAuthor: boom_o_matic_2.0 » Sun Apr 19, 2009 1:47 pm

how did you make that? I just made a rifle with a 3/4" barrel
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Unread postAuthor: euskalspud » Sun Apr 19, 2009 1:54 pm

Oh, Ok. Thanks! So, It may be something like a sponge or a spring.

Edit: I´m going to make a tutorial soon to make it.
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Unread postAuthor: boom_o_matic_2.0 » Sun Apr 19, 2009 2:18 pm

ok sweet. thanks.
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Unread postAuthor: euskalspud » Sun Apr 19, 2009 3:33 pm

how did you make that? I just made a rifle with a 3/4" barrel


http://www.spudfiles.com/forums/viewtop ... tml#240569

Then, that material can be used as a piston at those pressures?
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Unread postAuthor: jackssmirkingrevenge » Sun Apr 19, 2009 3:40 pm

By polystyrene you mean expanded foam used for packing?
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Unread postAuthor: euskalspud » Sun Apr 19, 2009 3:53 pm

No, I take polystyrene (expanded) and pour it in big quantities in a container with some acetone. The plastic "melts" and gets "compressed". So that big quantity of expanded polystyrene became into a much smaller mass, and when it gets dry, it is very very strong. Similar as polycarbonate (which is stronger than methacrylate).

I´m going to shoot it with my rifle at high pressure against a rock. Then i will see if it is strong or not. im going to record it.
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Unread postAuthor: jackssmirkingrevenge » Sun Apr 19, 2009 4:10 pm

Sounds good :) personally I think epoxy resin is more convenient but this is definitely a cheap and practical way of casting, I would think it would make good material for a piston as long as there was some rubber added as a sealing face.
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Unread postAuthor: dudeman508 » Sun Apr 19, 2009 10:02 pm

euskalspud wrote:The plastic in the photo isnt the piston, is the ammo for my pneumatic rifle. I want to know if this material can be used in a piston.

Or are you telling me to cut the CATRIDGE? I´m new on piston spudguns.



Never mind sorry. :lol: :lol:
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Unread postAuthor: jackssmirkingrevenge » Mon Apr 20, 2009 12:34 am

From the locked how-to thread:

jrrdw wrote:I can see trouble happing a mile away with this. If another moderator or PCGUY want's to unlock this for more discussion so be it. Also I will PM PCGUY and ask if this should be open or not.

Welcome to Spudfiles euskalspud, lets try and stick to building spud guns


While I understand your concerns (presumably involving the potential of such a mixture to be used in a napalm-like manner), in this case it was presented as a useful construction method and therefore I don't think the topic should have been locked. After all we use many techniques here that can be used for other more dangerous/illegal purposes but still discuss freely.
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Last edited by jackssmirkingrevenge on Mon Apr 20, 2009 7:39 am, edited 2 times in total.
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