Daft question, any idea of the ID and wall thickness of the CO2 cylinder.

Bonfire night is coming up and a mate has a explosives display license. He's going to apply for a something or other pass so we can make lots of noise and stuff (upto fire an AK47 with blanks and set of army flash bangs - hes also part of a vietnam re-enactment group).

Under health and safety he won't let me make a butane mortar out of 1.5mm wall steel. He knows its safe but he's legally responsible therefore has to take reasonable precautions. His suggestion was a welding cylinder, i just happen to have a couple spare Before i hack i wanted to know what i'm letting myself in for.

Not an answer..... but I did see an episode of "How it's made" on Discovery, the other night that showed high pressure gas cylinders being made.

Cold formed in a press from a disc of alloy steel, then drawn to length and finally placed in a lathe and the open end heated up and rolled inward till it closed off, further heat ttreatment then drilled and tapped.

I'd guess that at 320 bar working pressure (for an oxygen cylinder) that the wall thickness was more then 1.5mm, I'd guess at nearer 5mm.

In theory you could work it out from the weight of an empty one - and a few assumptions

we guessed at 5mm.

Think i might end up cutting two tanks up - one to make the expansion chamber, one to make the barrel. Using a little trickery it could then be classed as a gas powered catepult - and becomes a lot more legal

Mike,

Its probably a good idea to let us know when you will be testing said device, so that:

a) we can make sure we are very far away at the time

b) phone for legal assistance when somebody happens to tell the home secretary that some guy testing a morter in the west midlands, and oh I think he looked a bit foreign

Sounds fun though

we'll have a display license - heck, Jon might even be dressed in full Vietnam gear ...... now that would make it interested, he's even got a willey's jeep in his garage