Actually, this is a *useful* project...we use a similar much scaled down design as the signalling device for our regattas...as an aside, I have noticed that most older race officers I have met are hearing impaired...so be careful.

All the fun not withstanding, I want to also make an attempt at communicating two substantial hazards that are not necessarily obvious. First is that just because the gases are rather low density doesn't mean the explosion doesn't have the ability to hurt or destroy; true, the energy density may not be that great, but the power is briefly high enough to present a substantial fluence, enough to transfer destructive amounts of energy faster than anyone's reflexes. Second, when filling any container made of plastic films, especially such as garbage bags, ignition-triggering levels of static electricity are developed. How many times have you opened a plastic garbage bag or grocery sack without static? Probably never. You do not want to have a bag even partially filled near you when it fires.

Ed, your propane and oxygen cannon is similar to a marine seismic source that we used to build and operate back in the 70's. The propane and oxygen sources were fired under water, and the would rattle the ship's hull. They were very impressive to watch from the ship's deck at night. They would light up the water real well.

A man after my own heart.

Dear Ed,
We use to make a similar explosions with an oxygen and acetylene torch. Take a cutting torch setup, light a flame , adjust the gas mixture to a neutral flame and then tap out the flame. Let the gas mixture fill up a small garbage bag, till it is tight with gas pressure. Twist and tie the bag off. Take a long fuse, we us to use an old rag or slow burning rope and tape to side of bag. Light fuse and leave bag on ground…. Run away. The resulting concussion explosion would create a white vapor circle emanating from the vaporized bag, even flattening out the grass it was laid on, some 10-15 feet. Also, standing some 50 plus feet away would take the air out of your lungs. Yes the neighbors hated us, Mrs. London was happy when we all went away to college

Rob