mini coaxial

[hi]

this is my mini coaxial. It has a 1'' chamber that is about 11 inches long. The barrel is 1/2 inch pvc and it about 8 -9 inches long. The piston is a dowel and has a piece of rubber bolted on the front. The fill valve/ exhaust valve is a 1/4'' ball valve with a quick release for a compressor. I need to make a new piston because sometimes this one seal and sometimes it doesn't. when it does it is fun to shoot marbles and AA batteries.



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[jackssmirkingrevenge]

Why is the brass pipe at the pilot end so long? That's extra pilot volume which you could reduce and make it more efficient.

[noname]

Mini? Bah, that thing is enormous!
I'll show you mini....just give me a week or two.

[hi]

Thats what someone on spudtech said. it not a brass pipe, its a 3'' copper nipple.

Noname- good luck on making a working piston gun smaller than mine.

[jackssmirkingrevenge]

Mini? Bah, that thing is enormous!
I'll show you mini....just give me a week or two.

Now that's a mini-coaxial ;p

[noname]

It won't be a piston gun, I prefer diaphragms over pistons. I was actually planning on making identical guns, but one of them was to be a mini diaphragm gun, and the other is going to be a strafer. Both of them will be a 3/4" coupler with plug, a short piece of 3/4" PVC, a female coupler, and a threaded plug.

[Hawkeye]

Are a Piston and a Diaphragm really worth differentiating if they are both barrel sealers?

[hi]

yes they are worth differentiating because they are totally different.

they work on the same idea. A piston is a piston shape and a diaphragm is a piece of rubber that seals against the barrel. they are in the same spot, but they are different.

To explain a little better, a diaphragm is a piece of rubber that sits between a union and seals against the barrel, if that helps.

a sprinkler valve uses a diaphragm valve just so you know what it is.

[jackssmirkingrevenge]

I think he knows what it is, but was trying to point out that on such a small scale, performance between diaphragm and piston valves won't be that different.

[A-98]

jacks, is it me or is that epoxy? if it is, you extremely gifted with the stuff, cause it seems that all your ingenious little things are made out of the stuff.

besides, give me government funding and acces to caltech machine shop an i'll show you mini!

nice gun hi, i think i saw it on spudtech.

[jackssmirkingrevenge]

jacks, is it me or is that epoxy? if it is, you extremely gifted with the stuff, cause it seems that all your ingenious little things are made out of the stuff.

Yes it is, extremely versatile material - can be frustrating to work with but it does offer a lot of possibilities that standard fittings don't. It's not cheap, 9 lbs of the stuff cost me around $100 but I bought it 3 years ago and still have half the containers left so the cost per project is minimal.

[noname]

Diaphragms aren't always in a union, hi. I've made three diaphragm coaxials, and I've never even though of doing that.
Hawkeye, the difference is: diaphragms are extremely compact, and don't need travel space, but one of this size will still perform the same.

[subterranean]

wow "hi" im building something very similar and was just about to post it, but im having the same problem. Im using 1/4" brakeline(i cut the flaring off of the piston sealing end) in a 1/2"pvc chamber. I have made 4 different pistons all better but not with a good barrel seal.
1- rolled duct tape with bike tube rubber disk to seal it.
2- hot glue piston
3- rolled duct tape with a concave head filled with silicon.
4- dowl with electric tape to seal it(worked OK) but for a mini NO way.

Each design had a slight leak on the sides to fill the chamber.
Is there any good way to make a mini piston or should i call it quits!?

[hi]

Dont give up, its just that really small ones are hard to make work. The hot glue piston should work if it fits in the chamber well. do they have a rubber disk on them. if the disk is thin them put two on. Use a double thick inner tubes from a bike, thats what i used. Just make sure that it fits well in the chamber.

A really good way to make a piston fit well is wrap painters tape around it and put a little gun oil on it. Why painters tape? because it low friction and it works.

[subterranean]

Are you allowing a slight leak around the piston and the chamber to fill the rest of the chamber or do you have a different method?