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Plaster of Paris

Unread postPosted: Wed May 21, 2008 3:50 pm
Author: Deko
I've been wanting to make a copper piston cannon and am not sure what I should use for the piston. All that I have at my house that I think I can use is Plaster of Paris.

Will this work as a piston, or should I just go and buy something else that would work better?

Unread postPosted: Wed May 21, 2008 3:56 pm
Author: jrrdw
Plaster of paris will not work. Hot glue works well so does wooden dowel rod.

Unread postPosted: Wed May 21, 2008 6:44 pm
Author: OuchProgramme
PLaster of paris?
Are you nuts? LOL.
It'll smash itself into dust on the first shot

Unread postPosted: Wed May 21, 2008 7:08 pm
Author: Eddbot
OuchProgramme wrote:PLaster of paris?
Are you nuts? LOL.
It'll smash itself into dust on the first shot


not if you've got a good bumper, but i do think it's a little too dense and would cut down efficiency

Unread postPosted: Wed May 21, 2008 11:10 pm
Author: Deko
Ok thanks guys I didn't think it would work very well but just wanted to make sure before I went and wasted my money on something else lol

Unread postPosted: Wed May 21, 2008 11:15 pm
Author: MrCrowley
Eddbot wrote:
OuchProgramme wrote:PLaster of paris?
Are you nuts? LOL.
It'll smash itself into dust on the first shot


not if you've got a good bumper, but i do think it's a little too dense and would cut down efficiency

What's density got to do with it aside from weight? Regardless unless you have a very heavy piston, I doubt weight will make much difference.

It's too brittle IMO, even with a bumper.

Unread postPosted: Wed May 21, 2008 11:41 pm
Author: FordGtMan
Yep too brittle and it would be hard for it to get smooth enough i would think cause i dont think that will slide well with pvc.

Unread postPosted: Thu May 22, 2008 12:10 am
Author: OuchProgramme
FordGtMan wrote:Yep too brittle and it would be hard for it to get smooth enough i would think cause i dont think that will slide well with pvc.


Yeah it grinds itself out like sandstone.

If you can make a efficient piston out of plaster of paris i will be AMAZED

Unread postPosted: Thu May 22, 2008 1:04 am
Author: ammosmoke
Plaster of Paris has the consistency and feel of sidewalk chalk when dry. I don't think you want to use that. :lol:

Unread postPosted: Thu May 22, 2008 1:38 am
Author: BigGrib
I think it would slide fairly well with it's cured consistency but i agree way too brittle, unless of course you added something else to the mix (ie kaolin or portland cement) and then bake the damn thing in an oven. heck try some different things and let us know how it works. I'd be interested to see the results.

Unread postPosted: Thu May 22, 2008 10:26 am
Author: jimmy101
If you want to explore other materials you might try casting the piston from Bondo. Make the casting in a piece of the chamber pipe.

To keep mass down (good for both reducing the opening time and reducing the force the bumper has to absorb) you could use the largest PVC cap that fits in the chamber pipe and the Bondo to bring it up to the correct diameter. Again, using a piece of the chamber pipe as a mold.

Unread postPosted: Thu May 22, 2008 10:57 am
Author: sniper hero
jrrdw wrote:Plaster of paris will not work. Hot glue works well so does wooden dowel rod.


I tried making a piston from hot glue
is hard
I couldn't get the glue out when it was hardened (yes I used anti stick spray)
but I didn't bother after all because I already could see the surface wasn't exactly straight