SpudFiles

ok i built my first cannon...and damn this thing is awsome...piezo ignition..propane metered at 35 psi through a 3 inch pipe with a 3/4 id..
21x3 in combustion chamber..48 x1 1/2 in barrel..iv'e only fired this thing about 20 times and i'm wondering how crazy i can get with this..i work at a chemical plant so i have unlimited axcess to schedule 80 pipe and fittings...and one more question how are you guys mounting these computer fans in the combustion chamber...don't explosions and heat usually screw them up pretty good..thanks .... REV.

the fun sounds really good, get some pics of the gun and some damage pics.

Welcome to spudfiles

Right now, your launcher has a 1.56:1 chamber:barrel ratio
You could increase velocity about 13% (energy by about 27%) by lengthening the barrel to 8' - but that's somewhat impractical.

You or you could run MAPP gas, which should increase velocity by about 10%.

Other than that, a fan would drastically increase performance - you'd be expecting a velocity increase on the order of a 30%.

Yes most fans will get torched over time but some take long to get damaged enough to effect opperations.
Now on to the cannon please please post pictures of the gun and what it has done to some targets.
As they say "A picture is worth a thousand words."

considering you can get shc. 80 i would make a hybrid, i would but i live in a small town and its hard to get anything