SpudFiles

ok so heres my piston gun so far

it is my first and i know its not very good

anyway the blowgun is to small to vent it so i was thinking since i need the blowgun for my overall desgin could i vent my larger piston with a smaller one and use the blow gun to vent the small one?

heres a diagram of the set up plz if it can be refined to work better plz help


plz can anybody help me

-U2

You can use a piston valve to trigger another. I've drawn up designs which use smaller qev's to dump the pilot of a larger qev.

I think you have the ports the wrong way round there.

The branch of the small tee should be connected to the pilot port of the first.

How is the blowgun too small to vent? You can use a schrader to vent the pilot of a gun that size.
You should just attach it directly rather than adding a huge pilot volume with the hose.

I have to kinda agree with Hawkeye, you can shorten the hose a little at a time untill it fires your cannon. If you get to no hose and it still don't fire, the pilot volume is to big to be vented with a blow gun by its self. Then i sagest a modded sprinkler valve, but i dought if you will need that on this cannon. By the way, you don't give yourself enough credit, it's a good looking cannon to me!

yeah, it looks good dude, give yourself a break. But ya, you might want to reduce the volume of air that needs to exhausted from the pilot side. The blowgun should be able to actuate the large piston but a piston actuating another piston would be real neat.

try modding your blowgun. im not sure if it works on pistol ones though

thats a old picture iv changed it so there is only a 4cm bit of hose now and it still wont vent

What size is that tee? I made a 1" piston valve triggered by a 1/2" piston valve triggered by a blowgun. It really sucked b/c of the complexity and b/c I had some leaky joints, so I just cut it up. But my current gun has a 1.25" tee piston vented by a blowgun and it works admirably. I'd suggest taking the piston out and trying to make it a little more of an airtight fit with the cylinder it slides in. What's your piston made out of?

BTW, very nice looking gun for a first try. You'll have fun with that when you get it working.

thax solo im trying to add a oring to my piston now witch is made out of 3/4 poly pipe with neoprine glued on one side

Honestly, blowguns do exactly that: they blow. They are really only good for actuating QEV's, for they have a tiny amount of pilot volume. If you put on an o-ring or two, it probably would work, but if I were you, I would just add a 1/4" QEV to the back of the piston valve and attach the blowgun to that; would work a lot better. Or you could just attach a 1/4" ball valve.

Also: in your diagram, I would make the secondary piston valve much smaller than the primary. If it is just a tiny bit smaller, then I doubt the blowgun would be able to exhaust it anyways.

And yeah, this is a very nice looking cannon. Very clean. I am sure it will be fun to use once you get all the bugs worked out.

You might want to question your piston workmanship if you can't get a blowgun to work the piston. I don't even mod them and they work great.

Hawkeye wrote:You might want to question your piston workmanship if you can't get a blowgun to work the piston. I don't even mod them and they work great.

What size piston valve do you build that allows a blowgun to work properly as a pilot valve? And what type of blowgun do you use?

and experament u2, is that a slipxslip elbow?!

I use copper pipe of 3/4-1 inch to house the piston.
I realize you need more flow when you are building large diameter pistons but most of the complaints seem to come from guys trying to build smaller guns.
I just use a regular blowgun that comes with a compressor.

i added a oring last night and cut down the pistons size to about 200mm now it works perfectly thank you for all your help and special thanks to killa and chaos