SpudFiles

Just a thought i had in reading this topic- if you did go through with further development of this gun, the only thing i was thinking about was building materials... dealing with combusting hydrogen is no joke so you would probably want something pretty solid, either thick schedule pvc or metal, but if you use metal for your chamber/valve/barrel remember not to use something that will eventually corrode because combusted hydrogen turns back into water vapor i think, right? That's what i've heard anyways. If it's true, and you do use metal, go with stainless steel or something. I know you said that even a pringles can will hold up to hydrogen but if you decide to scale up the size of the gun and make it more serious then that's what i'm suggesting.

I think you would be fine with plain old mild steel. Paint the outside and the small amount of water vapour would either pour out or evaporate

tips
get a better hydrogen generator
build a better chamber
and btw the ideal H2-oxygen mixture is 2/1(wich is produced by a electrolysis cell)
and for H2/air the mixture 0.418/1
that's 41.8%hydrogen

i myself am currently working on a hydrogen-powered mini encased in a glue gun, using a aluminium chamber
for H2 generation i use a hydrogen cell from a estes hydrogen rocket(€40)
it is powered by a 10 amp battery charger
drawing 5 amps it produces 2ml/s

hope this helps

Well if you'd like to push the envelop use 2:1 hydrogen to oxygen; using pure oxygen. You might get a tab bit of water as a result, but when a spark is applied it goes "boom".

Yea, thanks for the information. It was powerful enough at 10:1, I might lose my cannon at 2:1