Cardboard is going to get destroyed after one or two shots. Try making some fins out of metal sheet. also if you stick them through both sides (like an equilateral triangle in the middle of the tube rather than two right triangles on the side) it will have a lot more structural integrity.

I really like the stencil job on that, although I would stay away from any airports with that thing. How do other people in your area react to seeing that? Or do you keep it out of sight?

Hot damn! That is just downright gorgeous! I love how clean the setup is. Is it water resistant? It looks like all the electrical workings are contained. I know PCGUY said he was looking for ingenuity, well I think that three way valve is certainly ingenious.

Yes, the valve was DWV, but to be honest, I don't think even Sch40 would have survived. To clarify, it wasn't due to pressure, but the piston impact, that the valve broke. And when it did, the piston was 20 feet behind the cannon :shock:. For the rebuild, the section between the Sch 80 tee and the ...

I use Stick N Seal, it works really well for sticking rubber on pistons. I don't know about gun oil, but white lithium seems to be a proven favorite.

thats a really awesome big ass gun ... but ...but ... its oh no here comes the D word.. or acronym.... DWV oh no I said it but who cares its big and cool

and cool username :D

Yea....really tell me about it. I'm putting together funds to build the Mk. V - Sch 80 4" Tee, two female cleanouts, a ...

Even morer pictures:


http://i152.photobucket.com/albums/s161/deusXmachina_spuds/Full%20cannon%20shots/downthebarrel.jpg

http://i152.photobucket.com/albums/s161/deusXmachina_spuds/Full%20cannon%20shots/IMG_4231.jpg

http://i152.photobucket.com/albums/s161/deusXmachina_spuds/Ammo/IMG_4255.jpg ...

Is there a drastic difference between the tees you get at Home Depot and a Sch 40 one? I'm actually thinking I might go for a Sch 80 4x3x4 tee (the input is 3"), but I think we will still definitely need a lighter piston.

If your piston has o-rings, it shouldn't matter. Once the air starts to leave the pilot, the chamber air will want to move to equalize it, it can't go out the barrel, its only free direction is to the pilot, and since it can't go around it because of the o-rings, it will push the piston back ...

It's a 3" coupler with a drilled out 3" to 1.5" bushing on one side with a grind plate to keep the sealing surface from buckling. And thanks for the tip on SCH 80 plugs, that will definitely help. We might just have to go with a SCH 80 4" Wye, although a) that's a lot of money and b) it might mess ...

Home depot sells vinyl braided hose (the clear kind with webbed look) in the plumbing/faucet section. You can just tap a 1/4 compression fitting into the chamber, and have 1/4 compression/threaded to attach to the gauge. The only other kind of hose I can think of you might be talking about is for ...

You can just tap a 1/4 NPT nipple or street elbow into the chamber, epoxy it, and then screw in the gauge right there. If you want it on a hose, use barb (compression) fittings with hose clamps.

I've kind of run into a dead end with my 3" porting piston cannon because with the current piston, the valve destroys itself on each shot. So we need a much lighter piston. Does anyone have any tips on making lightweight pistons with minimal machining? I'm definitely looking at the two-part bolted ...

The Guillotine

http://i152.photobucket.com/albums/s161/deusXmachina_spuds/Full%20cannon%20shots/guillotinesunset1-1.jpg
Click for full album


Stats:

Chamber: 4" x 10' PVC 1510 cu in
Valve: Mk IV.5 Barrel-sealing 3" piston
Pilot: 1" modded sprinkler valve piloted by electrical 3/4" RainBird ...

My cousin built a replica of the German cannon Big Bertha out of 4" steel pipe and calcium carbide. We had to stop using it when people a quarter mile away reported windows and plates rattling :oops:. But yeah that was bad idea theatre....I like the idea of using pneumatics because a piston valve ...