First burst disc cannon

[rp181]

This is my first spudgun, originally built as a combustion, but i found it works better as a pneumatic =)

Barrel: 3/4in PVC ~2ft. long
Chamber: 1 1/2 in. x 5.5 in. Tee
It uses about 60 PSI, i can't go higher becaus i just have bike pump.
Shot at 50 PSI, it puts a pen through 1/4 in. plyboard
The burst disc is this yellow plastic i found, thin but really strong.
You can see the plastic in one of the pics.
Pics:







The wires are for the combustion ignition, it uses a 3 spark spark strip.

[BigJon]

Nice cannon for your first, but i would recomend using a larger chamber and get rid of the wires and stuff if your going to keep it a pneumatic.

[elitesniper]

it could be a hybrid since the wires are there :O jk. dont , nice cannon though
but u need a slightly bigger chamber

[rp181]

actually, i filled the whole thing with propane, then pumped to 40 PSI with air. Powerfull =)

[elitesniper]

yeah but its kind of risky since its only sch40

[Hubb]

actually, i filled the whole thing with propane, then pumped to 40 PSI with air. Powerfull =)

And it worked as a hybrid?

[noob of noobs]

Did you ignite the propane?

[rp181]

i did ignite, and it was powerfull. I did remote ignition, with a potato the recoil was semi big. The proportions were all wrong, so i wasn't that afraid. I dont do that much, only when im bored.

[carter]

cool. unsafe but cool. because the smaller chamber it probaly is safe thanks to pascals law but still i think it will eventually blow up

[BigJon]

Yeah you probly could get away with using it as a hybrid like you did for just a few shots but that is really dangerous and sooner or later it will blow up.

[noob of noobs]

I see... I'd stick to a combustion or pneumatic with that thing. I'm a bit supprised that didn't blow up on you. A schedule 40 hybrid isn't an encouraged design, but if you mess up the stoichiometric ratios a lot, then I think it might be safer.
But dude, do yourself a favor and use metal if you're messing with hybrids.

EDIT: But hey, at least you aren't doing a 20x mix using hydrogen in a soda bottle!

[DYI]

PVC hybrids are never particularly safe, especially SCH 40 ones. But that chamber is small, and you have no means of precise metering, so, unless you get really lucky, you'll be fine. But please don't use this thing as a hybrid.

Looks kind of puny, but burst disk valves are the best way of squeezing the most power out of a tiny cannon.

[rp181]

I did 3 shots, and i dont plan to do any more, but i just couldn't resist 8) .

Also i put a plug to seal the end, and a bushing for the other side, so most of the chamber is twice as thick, except the middle.