New 4 inch piston valved cannon

[spudthug]

Hello all, i plan on making a new launcher for fun at the 4th of july. I want it to shoot potatoes and caulk tubes/nerf footballs. I am going to have a 4 inch chamber and a 4 inch piston valve. The piston is going to be a 3 inch end cap. I am planning on pilotting it with a 3/4 sprinkler valve. It is going to be a 2 inch port with interchangeable barrels (2" and 1.5"). I will work out come diagrams right now but i have some questions first.

1. Can i use a 3 inch endcap with a barrel sealing tee valve?

2. is a 3/4 modded sprinkler valve good enough to pilot it fast?

3. what is the best method of attaching neoprene to an endcap piston?

4. what is the best method of creating the sealing face (on the port not the piston)

If you could i would like to see some pics of inside 4inch tee piston valves. And 3 inch endcap pistons. Thanks to everyone who is going to help me!! <spudthug>

[iPaintball]

1. Yes.
2. Yes as long as the piston has a good seal against the sides of the tee, but
1" sprinkler or even a 3/4" QEV would increase performance.
3. Probably the best way would be to drill a hole in the piston and bolt it on with a washer through the other side.
4. Just make sure the port pipe has a smoothe, square edge.

[Fnord]

1. I Think a 3" cap just requires a little sanding, but it should fit.

2. Judging by the results from my 2" piston, I would go with a 1" valve.

3. I think superglue actually disolves neoprene. It's what I used, but I'm not sure how well it bonds to pvc. Just experiment.

4. If you want an added sealing face on the barrel, I would try putting a thin layer of gasket sealer or caulking on the end. Whatever sticks.

Thats all the advice I can give (I only have 1 working piston valve atm, lol ).

[spudthug]

ok thanks for the help! whats the best method to get it through to the other side of the bushing. jsut bore a bushing out and put a peice of 2" pipe through it and epoxy it there?

how far should it be in?

here are my plans tell me if they are good



oh and what can i use for a bumper? will half a tennis ball work for this?

[rednecktatertosser]

I think that would be the best method of atteching the barrel. and i believe that the barrel should end halfway into the tee.

[mopherman]

instead of putting the sealing face on the piston, i would put a rubber coupler on the inside end of the barrel. schammaman did that and it seems to work

[spudthug]

ok guys im going to get my parts at ace right now and i found a bumper.. how thick does the neoprene have to be on the piston? does anyone know how much 10' of 1.5 and 2" sch 40 will run me?

ill try that. waht are they called?

[mopherman]

I dont know what they are called but they sell em right next to the pipes at home cheapo. just ask the dude (doh!) about adjustable couplers.

[iPaintball]

they are normally called flexible couplers

[spudthug]

well ace was closed...damn.. so my dad suggested we go to the local diy store..i didnt think they would have anything. they didnt..i did get my psi guage, quick connects, and i saw the couplers but i didnt want one. and then...(rising action) i went to the register and saw a guy with a 10 foot peice of 3/4 cpvc. i thought there had to be more pipe (thought i might be able to get my barrels 1.5 and 2). i asked where he had gotten it and he pointed. i went back and looked and saw a whole bunch of dwv pipe and sdr 21 pipe...and then!!! 1.5 sdr 21 (golfball barrel) !!!!!!in 10 foot lengths for $6.00 each!!!! u bet ur ass i bought it. although i wasnt able to get my potato or rocket barrel, i know have 3 interchangeable barrels!!!

golfball!!
potato!!
caulk/footballs!!!

[noname]

I'm not sure if a 3/4" sprinkler would be able to pilot it, but just so you know, if it couldn't, neither could a 1" valve. They are EXACTLY the same, except for the threads. The flow is choked by the 360* of turns and by the small diaphragm seat diameter (which is the same for both sizes).

[spudthug]

what about schmanmans? and frankredes? they were both pilotted by sprinklers..

[Velocity]

3/4" QEV's work great for piloting any size piston valve... though, once you get above a valve in a 4" tee, you might want to step it up...

I have never seen frankrede's large piston valve... could you provide a link?

[VH_man]

seeing as a 3/4 inch sprinkler can launch a marble 350 feet, i think it should pilot a valve just fine. just for kicks, i hooked one up to my 1/2 inch porting coaxial (2 inch chamber) and WOWOWOWOW was it powerful......... kinda broke the barrel. should have used barrel supports.........

[iPaintball]

What was the name of the diy store?