Machined plastic pistons.

Show us your pneumatic spud gun! Discuss pneumatic (compressed gas) powered potato guns and related accessories. Valve types, actuation, pipe, materials, fittings, compressors, safety, gas choices, and more.
User avatar
Mitchza89
Sergeant
Sergeant
Posts: 1056
Joined: Tue Jan 09, 2007 12:05 am

Fri Jul 17, 2009 7:15 am

Hey guys,

I'm looking to go pro with my cannon building. I'd love to get into machining my own pistons but I have no real idea on what plastic to use. I saw Nylon, HDPE and a few more but I don't know where to look to find the stuff.

What are some recommendations to use?

Thank you,

Mitcho.
Image
User avatar
inonickname
First Sergeant 4
First Sergeant 4
Posts: 2606
Joined: Sun Dec 07, 2008 3:27 am

Fri Jul 17, 2009 7:35 am

If I had to pick one, it would be HDPE. It has excellent characteristics basically all around.

Though, if you wanted to do an ultra-high performance gun teflon would be excellent due to it's ultra low friction.
Attachments
Hell...you could make this piston. I designed it for my soon to be rifle. Teflon or HDPE body, integrated high flow check valve.<br /><br />Valve in open position, spring not pictured
Hell...you could make this piston. I designed it for my soon to be rifle. Teflon or HDPE body, integrated high flow check valve.

Valve in open position, spring not pictured
PimpAssasinG wrote:no im strong but you are a fat gay mother sucker that gets raped by black man for fun
User avatar
Mitchza89
Sergeant
Sergeant
Posts: 1056
Joined: Tue Jan 09, 2007 12:05 am

Fri Jul 17, 2009 7:44 am

That's a great idea. I just have no idea where to get HDPE in Brisbane or how much it is. Tomorrow I may have a fiddle with car body filler. I have heaps of it here. I think it may crack and crumble though... Hmm..
Image
User avatar
inonickname
First Sergeant 4
First Sergeant 4
Posts: 2606
Joined: Sun Dec 07, 2008 3:27 am

Fri Jul 17, 2009 7:50 am

Mitchza89 wrote:That's a great idea. I just have no idea where to get HDPE in Brisbane or how much it is. Tomorrow I may have a fiddle with car body filler. I have heaps of it here. I think it may crack and crumble though... Hmm..
Bondo, as the Americans would call it. If it's the same type, it's extremely strong (usually a kind of fiberglass resin)

Try a plastic supplier, or one that makes signs or similar.
PimpAssasinG wrote:no im strong but you are a fat gay mother sucker that gets raped by black man for fun
User avatar
Mitchza89
Sergeant
Sergeant
Posts: 1056
Joined: Tue Jan 09, 2007 12:05 am

Fri Jul 17, 2009 7:53 am

Yeah the stuff we have in Aus is like a resin. It's a white paste along with a separate red past. It's got talc powder in it so it can be sanded. I wonder if this is what you guys have..
Image
User avatar
MrCrowley
Moderator
Moderator
Posts: 10078
Joined: Fri Jun 23, 2006 10:42 pm
Location: Auckland, New Zealand
Been thanked: 3 times

Fri Jul 17, 2009 8:11 am

My hardtech teacher always has teflon rod laying around, up to 40mm. If I ever needed it, i'd ask him to order me some haha. Just check on Google for some websites I guess, maybe even eBay?
User avatar
Mitchza89
Sergeant
Sergeant
Posts: 1056
Joined: Tue Jan 09, 2007 12:05 am

Fri Jul 17, 2009 8:13 am

Just as I looked just then, I saw some plastic mobs about 20-30 min from me. I'll be sure to have a good look around. Price is just a bit of a problem for me. An epoxy piston (probably Bondo) might be the best bet for now I think.

Cheers for the tips up Crowley.
Image
User avatar
MrCrowley
Moderator
Moderator
Posts: 10078
Joined: Fri Jun 23, 2006 10:42 pm
Location: Auckland, New Zealand
Been thanked: 3 times

Fri Jul 17, 2009 8:22 am

What diameter are you looking for anyway?
For diameters about 40mm and up, check out these:
http://www.spudfiles.com/forums/get-you ... 18661.html

Went to a boat-store today and they have solid plastic rods about 4-6" long, so they're not all necessarily in the hour glass shape.
User avatar
Mitchza89
Sergeant
Sergeant
Posts: 1056
Joined: Tue Jan 09, 2007 12:05 am

Fri Jul 17, 2009 8:30 am

To fit inside a 1'' Brass nipple. I may duck to BCF (boating-camping-fishing) tomorrow. They may have some thick HDPE or nylon cutting boards for pretty cheap. I could just use the drill press to punch out pistons close to the size I need and just turn them down on my drill press. That may be my best option.
Image
User avatar
inonickname
First Sergeant 4
First Sergeant 4
Posts: 2606
Joined: Sun Dec 07, 2008 3:27 am

Fri Jul 17, 2009 8:35 am

I am in aus mitch..so ya 'we' have the same stuff :wink: :roll:
PimpAssasinG wrote:no im strong but you are a fat gay mother sucker that gets raped by black man for fun
User avatar
Mitchza89
Sergeant
Sergeant
Posts: 1056
Joined: Tue Jan 09, 2007 12:05 am

Fri Jul 17, 2009 8:38 am

Ohhhh that really helps. Sorry ino, I had no clue :D. I reckon I may go ahead with the car bog idea. My only problem could be it's viscosity and cure time. It's pretty pasty so it's not going to run easily into a mold. I may have to just scrape it in and pray for the best..
Image
User avatar
velocity3x
Corporal 4
Corporal 4
Posts: 828
Joined: Fri Jun 05, 2009 3:09 pm
Location: Yuma, Arizona
Contact:

Fri Jul 17, 2009 9:40 am

"DuPont Delrin® acetal polyoxymethylene (POM) resins are highly versatile engineering polymers that bridge the gap between metals and ordinary plastics."

I make pistons using Acetal or Delrin. It has a high natural lubricity and is hard enough to be machineable .....extremely strong stuff!
User avatar
inonickname
First Sergeant 4
First Sergeant 4
Posts: 2606
Joined: Sun Dec 07, 2008 3:27 am

Fri Jul 17, 2009 9:44 am

Velocity brings up a good point. Delrin (commonly engineering plastic for prototyping) would make an excellent piston. I have long rods of it. It has good properties, and machines excellently.
PimpAssasinG wrote:no im strong but you are a fat gay mother sucker that gets raped by black man for fun
User avatar
velocity3x
Corporal 4
Corporal 4
Posts: 828
Joined: Fri Jun 05, 2009 3:09 pm
Location: Yuma, Arizona
Contact:

Fri Jul 17, 2009 9:54 am

inonickname wrote: Delrin (commonly engineering plastic for prototyping)
It's hard enough that it makes great bearings too. HDPE can't do that!
User avatar
Moonbogg
Staff Sergeant 3
Staff Sergeant 3
United States of America
Posts: 1731
Joined: Mon Oct 13, 2008 10:20 pm
Location: SoCal
Has thanked: 153 times
Been thanked: 98 times

Fri Jul 17, 2009 10:38 am

UHMW all the way. It comes oil impregnated for self lubrication and is specifically designed for impact resistance and bearing usage.
Post Reply