SpudFiles

I recently built a spud/tennis ball cannon out of steel pipe and a propane tank, and after a few failedattempts to fire it with propane, I vented my combustion chamber put an Oz of 87 octane in it, and with the hole open I lit it. Kablewy like a rocket. Worked twice in a row like this. The next day same amt of gas, same process, nothing, any ideas why or what to do?

With little information given, I'd venture a guess the mixture is to rich. Try half a ounce only after venting the chamber very well.

Welcome to Spudfiles! :bom:

I tried posting a picture, apparently my files are to large. on top of my combustion chamber (20 lb lp tank) I have a half inch hole where I dump my fuel and ignite the vapor. Infront of the tank is a 6ft steel tube 1/4" wall 3"od. On that tube I have rtwo 1/8" holes that had a bbq igniter that didn't work the barrel is pointing up at an 30 degree angle.

Post a picture of the gun and we'll be able to give you more reliable advice.

To begin with, try starting fluid instead of gasoline. It vaporizes easily from an aerosol can, and tends to leave less soot behind.
I've had limited luck with gasoline sprayed from a windex bottle, try a squirt for every gallon of chamber volume.

jrrdw wrote:With little information given, I'd venture a guess the mixture is to rich. Try half a ounce only after venting the chamber very well.

Welcome to Spudfiles! :bom:

I think your advice is so precious for us and i will surely follow your instructions.

an Oz of 87 octane

The best question is how exactly are you adding that ounce. As Fnord suggested, some kind of atomizing spray bottle is your best bet.