SpudFiles

Hey all.
I built my first combustion cannon a while ago and over time and with several problems it turned out to be quite good. It's reached the stage where where its just as easy/fun to build a new one rather than make futher improvements.
I'm fairly constrained by materials in NZ am stuck with what I think you guys call 4" pipe (~11cm) for the chamber and 2" pipe (~6.5cm) for the barrel.
Could someone please explain the C:B ratio thing to me and suggest appropriate lengths?
Also, just outta curiousity, are different electrodes for BBQ igniters any better? Eg: copper screws rather than steel or something.
Any ideas on what else I can with a simple(ish) combustion to make it more interesting?
Thanks!

Try a chamber fan,they are said to increase power by upto 60% and they are cheap if you ask and bargain to a computer guy about a old one they are dirt cheap and the C:B ratio is the ratio of the barrel to chamber so if you have a volume of 1.5L chamber the best size barrel to use has a volume of 1L.And the easyerst way to measure the volume is with water and measuring jugs.

You are correct about the chamber fans rna, but you also have to realize that the optimal c:b ratio depends on what fuel you are using. The optimal ratio for propane is .6-.8:1. I think though, that 1.5:1 may be a good general rule for aerosols. But I'm not sure on that.

A chamber to barrel ratio is a simple thing really...

If the volume of your Chamber is 5 L (About 63.5 cm long peice of 4" Pipe)
You divide 5 L by 1.5 you get 3.3333, so your barrel should be 3.333 L in volume if your chamber is 5 L in volume...

To get a barrel to be 3.3333 L in volume made out of 2" pipe it needs to be about 164.5 cm long.