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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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[update](new vid)Piston material.

Unread postAuthor: Counterstriker » Sun Mar 09, 2008 6:18 pm

I think its about time I make a piston gun. I understand how a coaxial piston works but not the other ones. I kind of understand but can someone help me out. I have researched and found some good info but no all I have been on the wiki and that taught me alot but still some help.


-What material works best for the piston?
- Is copper or PVC better?


I plan on using Copper.
Like I said I have the basic idea of the piston blocking the barrel etc...

Thanks again!
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Last edited by Counterstriker on Sat Mar 22, 2008 6:12 pm, edited 1 time in total.
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Unread postAuthor: mopherman » Sun Mar 09, 2008 6:27 pm

A tee valve piston is just a coaxial piston with a branch coming off the chamber. You can make a piston out of anything air tight. I would recommend epoxy casting. Use the material to suite your needs. If you cant surpass 150psi, use pvc.
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Unread postAuthor: Hubb » Sun Mar 09, 2008 6:27 pm

The best way to explain a piston valve is in this thread.

As far as the materials to use, PVC tends to be brittle and may require a bumper to keep it from shattering. A bumper may also be wise if you use a copper piston, as it may break your launcher. Others have used hot glue and epoxy as piston building materials. I used a wooden dowel.
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Unread postAuthor: STHORNE » Sun Mar 09, 2008 6:37 pm

If you are planning on staying towards low pressures (0-125 psi) i suggest you stick with nsf-pw pvc. It's easier to work with than copper and less costly (in most cases). But for the higher pressures, i suggest copper.
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Unread postAuthor: Counterstriker » Sun Mar 09, 2008 6:41 pm

hubb017 wrote:The best way to explain a piston valve is in this thread.

As far as the materials to use, PVC tends to be brittle and may require a bumper to keep it from shattering. A bumper may also be wise if you use a copper piston, as it may break your launcher. Others have used hot glue and epoxy as piston building materials. I used a wooden dowel.


That helps alot! I didn't mean the piston, I meant if the gun in general should be pvc or copper. I think I'll go with copper. Hmm... May I ask what you used for piston material?
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Unread postAuthor: STHORNE » Sun Mar 09, 2008 6:48 pm

Counterstriker wrote:May I ask what you used for piston material?


Depends on the size of the T you plan to use. Give me a size and i can tell you some convenient objects you can use for a piston, although, i suggest just a plain epoxy piston, because it takes the exact shape and remains air tight (expands a little in the curring process).
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Unread postAuthor: Hubb » Sun Mar 09, 2008 6:50 pm

I tend to build smaller launchers. My piston was a 1 in dowel with a neoprene face bolted on the front. It has a spring in the rear, because I fill from the chamber. The spring also acts as a bumper. The dowel was wrapped in electrical tape (the black kind; it tends to be smoother than the rest) to make for a good fit.

If you plan on building a copper launcher, I would suggest either a copper or epoxy piston, depending on the size. PVC tends to be too large for a small (bb or marble shooting) copper launcher. JSR has a post somewhere about casting epoxy pistons.
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Unread postAuthor: Counterstriker » Sun Mar 09, 2008 6:53 pm

sthorne wrote:
Counterstriker wrote:May I ask what you used for piston material?


Depends on the size of the T you plan to use. Give me a size and i can tell you some convenient objects you can use for a piston, although, i suggest just a plain epoxy piston, because it takes the exact shape and remains air tight (expands a little in the curring process).


I am gonna guess I will use 3/4". I think I will just make a mini coaxial. But when you say make it out of epoxy do you mean epoxy putty? I have Plumbing epoxy putty will that work. Put still whats a good size for that?
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Unread postAuthor: Hubb » Sun Mar 09, 2008 7:06 pm

Here is the link to the above mentioned thread:

http://www.spudfiles.com/forums/making-epoxy-pistons-t8919.html
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Unread postAuthor: STHORNE » Sun Mar 09, 2008 7:09 pm

no, i mean the 2 part epoxy, aka "5 minute epoxy". when it dries, it keeps a nice rubbery texture and is semi soft. the putty you talk about dries hard and would serve no purpose as a piston unless you were to add an o-ring.
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Unread postAuthor: Counterstriker » Sun Mar 09, 2008 7:16 pm

Do you think they sell that kind of Marine epoxy at Home Depot?
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Unread postAuthor: STHORNE » Sun Mar 09, 2008 7:17 pm

yeah, thats where i buy mine. either home depot or fleet farm.
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Unread postAuthor: Counterstriker » Sun Mar 09, 2008 7:23 pm

In the tutorial you linked me he tells about using a screw and washer. Should the washer be smaller then the barrel its up against, so it like.. fits in? I would guess so.
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Unread postAuthor: STHORNE » Sun Mar 09, 2008 7:28 pm

yeah, smaller would be better
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Unread postAuthor: Counterstriker » Sun Mar 09, 2008 7:59 pm

Ok sounds good. What should I use for the piece of rubber? Bike inner tube?
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