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Ideas for piston

Post questions and info about pneumatic (compressed gas) powered cannons here. This includes discussion about valves, pipe types, compressors, alternate gas setups, and anything else relevant.
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Ideas for piston

Unread postAuthor: jmeyer1022 » Wed Mar 04, 2009 4:44 pm

My frustration is growing. I've built at least 5+ pistons ranging from wood to 1 1/4 coupler to pill bottles. So far the pill bottle was the best so far but lacked in strength. All of them work just not to the extent I want. I've seen epoxy pistons and hot glue, but from what I've read both catch. I'm tempted to try a bolt style piston I believe it's called a "toolie", not positive.
So please throw your suggestions at me. Thanks.
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Unread postAuthor: SpudsMcGee » Wed Mar 04, 2009 4:51 pm

How about a potato piston.... Its seems like it would work, you would just have to swap them out every once in awhile. And I don't think anyone has tried it, so you could be a pioneer.

Or you could buy one from any of our two good sponsors, but it sounds like to me you really want to build your piston valve, so its only a suggestion.
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Unread postAuthor: thedeathofall » Wed Mar 04, 2009 4:51 pm

Size? Shape? What were the problems with the others? we need a little more info please.
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Unread postAuthor: jmeyer1022 » Wed Mar 04, 2009 4:56 pm

Wow, sorry about that typed that in frustration. 2" piston valve Prefer a cylinder. The problems ranged various from to big of equalization, to much drag, and just structurally weak. Spuds my valve is built and it shoots just not to the performance I'd like.
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Re: Ideas for piston

Unread postAuthor: SpudsMcGee » Wed Mar 04, 2009 4:56 pm

Potatoes come in all shapes and sizes, thank you for further supporting my idea. And he said that they all worked, they just didn't work as strongly as he wanted. Here is the quote.
jmeyer1022 wrote: So far the pill bottle was the best so far but lacked in strength. All of them work just not to the extent I want.


Edit: Opps, you beat me to it. Oh, and the potato idea was a joke.... But I still think it would be fun to try.
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Unread postAuthor: thedeathofall » Wed Mar 04, 2009 5:12 pm

Hmm.. well you could try PVC rod. McMaster sells it. You can do all kinds of things with it. (drill it out, machine it, etc..)

If you do make a piston out of a bolt, make sure the washers not only fit into the housing, but also on the bolt itself. (If the center holes are even slightly too big, they wont align properly and it will drive you crazy :wink: ) Also, you might want to consider plastic washers because those types of pistons can be REALLY heavy.
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Unread postAuthor: mark.f » Wed Mar 04, 2009 10:35 pm

Usually 1-1/4" fittings work fine. I don't know what you're doing but some more details would be helpful.
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Unread postAuthor: jmeyer1022 » Wed Mar 04, 2009 10:39 pm

markfh11q wrote:Usually 1-1/4" fittings work fine. I don't know what you're doing but some more details would be helpful.



1 1/4 coupling with a 2" washer on each side with rubber+ a smaller washer on the sealing side a bolt running through then a nut to hold it all together. It fits rather loose inside the 2" pipe, sure it actuates but only at very high PSI. I'm not sure if the Lowes I go to has weird 1 1/4 pieces but I've tried numerous ones. I've been pondering other ideas, I'm sure something will come along
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Unread postAuthor: mark.f » Wed Mar 04, 2009 10:44 pm

If it fits loose, wrap it in duct tape until it fits with some friction and then lubricate. Me and Velocity's first piston valves just used some PVC rod wrapped in duct tape. It's more effective than you think.

Also, when listing specifications for a piston valve, a more helpful list of values would be:

1.) Configuration. If a tee valve give tee size.
2.) Piston diameter (you already said 2").
3.) Seat diameter (what the piston seals against).
4.) Piston construction (you've already provided that).
5.) Exhaust valve and setup.

For you, I'd recommend the duct tape around the piston and a small Q.E.V. for piloting. Just remember to keep your pilot volume down and it'll work fine.
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Unread postAuthor: jmeyer1022 » Wed Mar 04, 2009 10:50 pm

Will do for future
2" Tee
1 1/4 seating
numerous pistons =)
5.) 1" sprinkler valve
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Unread postAuthor: mark.f » Wed Mar 04, 2009 11:07 pm

Well, it sounds like all you need to do is tighten up the piston in the 2" pipe (duct tape or electrical tape, like I said) and lubricate the piston and it should be working good.
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Unread postAuthor: jmeyer1022 » Wed Mar 04, 2009 11:09 pm

Will do tomorrow, I'm exhausted, thanks for the help if anyone else has suggestion shoot them at me I'll look tomorrow.
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Unread postAuthor: pharmboy » Wed Mar 04, 2009 11:22 pm

Actually, I'm using the 1 1/4" pipe/fitting piston in my cannon. Gassed it up tonight and it worked pretty good, definitely fast dumping.

http://www.spudfiles.com/forums/viewtop ... tml#233824
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Unread postAuthor: jeepkahn » Thu Mar 05, 2009 5:20 pm

Are you going coax or chamber...

here's a pic of my 2" piston... but it's for a coax only...
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Attachments
coax piston.jpg
notice the doorknob stop on the bottom to cushion the blowback impact...
inside of piston.jpg

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Unread postAuthor: Hubb » Thu Mar 05, 2009 6:52 pm

I did a search for you (boy, am I feeling generous tonight). These links may help you.

http://www.spudfiles.com/forums/how-to-easy-o-ring-grooves-without-a-lathe-t17348.html
http://www.spudfiles.com/forums/making-a-2-piston-without-o-rings-or-sheet-pvc-t9527.html
http://www.spudfiles.com/forums/slayer-valve-plans-t9427.html
http://www.spudfiles.com/forums/easy-o-ring-grooves-t2478.html

Please note that that is just a quick search of the how-to database. I'm sure there are plenty more in the Pneumatics Cannon Discussion and the Wiki. I'll let you try those, though.
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