Just a question.....

[Delta Wingnut]

I have noticed in several pictures that some cannons have computer case fans in them. What is the purpose of this?

[joannaardway]

Short Version:
They act as a mixer for the combustible gases and the air. The better mixed the fuel, the higher the performance of the cannon.

Long Version:
They homogenise the mixture, allowing a much faster and cleaner burn, producing a higher pressure and increasing efficency. Additionally, they produce in chamber turbulence, which increases flame speed, and therefore, a peak pressure is reached much earlier, the power of the cannon.

They have a three-fold set of advantages:

They increase power
They make fuelling easier
And they increase reliability.

[mega_swordman]

Since we're on the topic, what is preventing the fan from getting burned or destroyed in the explosion?

[willarddaniels]

yeah, what joannaardway said.

what is preventing the fan from getting burned or destroyed in the explosion?

The combustion is a very short blast with no prolonged high temeratures. Since the fan is within the blast, it is not obliterated. Besides, it isn't exactly a huge shockwave that destroys everything around it.

[mega_swordman]

I see, thank you very much.

[Recruit]

Albeit a large number of fans will eventually melt or crack breaking them but if done right they will last a long time.

[lukemc]

also chamber fans rid the barrel OF SMOKE quickly improving reload time

[crazyfreak0075]

Their worth installing because their so cheap and help your mixture alot.

[Delta Wingnut]

Thanks.I just built a spud gun w/ my Uncle, and we test fired it a fewrounds. we'll post pics and maybe video soon.

[Pete Zaria]

Chamber fans, in addition to everything joannaardway said, also help to vent the exhaust gases from the previous shot out of the chamber.

The reason the fan doesn't melt or get f#$%%d quickly is because the temperature spike in the chamber is very momentary - just a fraction of a second, which isn't really enough to get the fan up to a high enough temperature that it would start melting.

My old propane gun saw 500+ shots, on one fan. The housing of the fan developed a crack or two, and one or two of the blades got chipped (don't ask me how...), but it didn't die before I ripped the gun apart for parts.

Peace,
Pete Zaria.

[joannaardway]

Ah. Completely forgot the venting - that's not the true benefit of them though IMO.