I would make the "tank" or whatever this is for out of threaded steel fittings. Unless that in impractical....which I don't see why it would be....

10mm is just a hair larger than 3/8" so I'll go for a 3/8" bolt and see how that goes. I went to the hardware today, I could not find any bumpers like the ones you described. Do you see any issue with a very stiff spring, that is about 1" short from touching the piston in the closed position? In the...

Thanks Mr C. I will look at the hardware store latter this evening. The piston needs to be rebuilt, and I wad wondering if anyone knows how much difference piston weight, would make performance wise. I'm thinking about using a 1/2" bolt and hardware, instead of the 1/4" bolt and hardware that keeps ...

The only thing that is preventing me from using higher psi, is lack of a scrabble bumper. The piston has already been built 3 times, after destroying 3 bumpers. 1: 1/2" thick soft rubber 2: spring 3: much much stronger spring. Part of the problem is that the piston only travels about 1". So I need a...

No problem, its goin to be a few days before i get a new longer barrel, and a fitting to feed my friddgy with 60-120 psi on the inlet.

http://www.youtube.com/watch?v=z-87QaU8Tpw

Test fire with a 5 ft barrel (already had it) and a home made rocket with fins.



Also, the kick at 70 psi requires me to lean into the cannon, otherwise it simply will fly backwards.

Define decent pressure. With 1.9" porting, 50psi has already shot a 1.75" Hdpe round through 1/2" pressboard, with no barrel, and the projectile simply set in the threaded barrel port. I will go up in pressure, but very slowly ad this thing is a boss at as little ad 50 psi, and I don't have a barrel...

I am also going to add a 6-10 foot tennis ball barrel, complete with bipod.

Paint is the next thing on the list.

Also, this was a video of that tank with a 1/2'' porting valve at 100 psi.

http://www.youtube.com/watch?v=6Wq4gzX1Rw4

Piston valve is housed in a 2'' T, the porting is 1.9'' (1.85 actually) The valve seat to piston diameter ratio is VERY close to 1/1 The pilot is a 1/4'' QEV, piloted in turn, by a 1/4'' ball valve. The chamber is a old diving tank, aprox 1000 Cubic inches in volume. The cannon weighs over 60lbs, an...

A tribe of canables capture three people, on French, one British, and one American, the men were told that there meat was to be eaten, the bones fed to the dogs, and their skins used for a canoe. The 3 men are each given a last wish, and allowed to speak their last words to the tribe. The Frenchmen ...

Let me play you a sad song on the worlds smallest.... Guitar. Nice.

That qev should be fine at 300 psi. If you want to be safe, don't load any ammo, keep the barrel away from anything important, and fill to 300psi. If you hear any hissing out the barrel, your qev is about to blow.


I have used 1/4" qev of the same style all the way to 600psi.

That qev should be fine at 300 psi. If you want to be safe, don't load any ammo, keep the barrel away from anything important, and fill to 300psi. If you hear any hissing out the barrel, your qev is about to blow.


I have used 1/4" qev of the same style all the way to 600psi.

Gun Freak wrote: I've never heard of the mcmaster diaphragm type QEVs being used at high pressure.

I used mine up to 250 once. it survived, but i can promise yours will. Like i said that was for 1 shot at 250 psi.