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Gathering info

Post questions and info about combustion (flammable vapor) powered cannons here. This includes discussion about fuels, ratios, ignition systems, safety, and anything else relevant.
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Gathering info

Unread postAuthor: joe blogs » Sun May 17, 2009 5:57 am

Where some people mount their fans in cannons is puzzling. Doesnt having the fan between the sparks and the barrel subject it to lots of escaping pressure?

do you count the volume of the complete fan assembly (fan and vent tube) or just the wall thickness of the vent tube and the fan in your ratio calculations? because i was thinking that the inside of the vent tube would also provide some pressure on ignition.

Jager told me it was important that i run the vent tube to the bottom of the chamber, how far off the end of the chamber (the dead zone) is acceptable for combustion cannons?, i was thinking of running the vent tube from the top to 1 inch off the bottom with vent holes for the last 6 inches.
The fan blowing (all examples include a fan mounted on a vent tube) would introduce air into the bottom of the chamber and pushing the vapour out on the outside, the fan sucking would remove the vapour from the bottom through the vent pipe and introduce oxygen from around the chamber. Which is preferable?

Is the spark strip placement important?

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Unread postAuthor: psycix » Sun May 17, 2009 6:47 am

Yes, if you place your fan near the barrel opening, it will be subjected to a big rush of air, possibly breaking it.

Ratio calculations? Do you mean "does the vent tube add up to the chamber volume?" If it is filled with fuel mixture that is ignited, then it adds up to the chamber volume.

Ehhm what is all this thing with vent tubes? Just open up your chamber at the back using a screw cap, or even better, ball valve and let the fan flow the air in through that and out through the barrel (or reverse).

Spark strip placement is important. The sparks should be divided equally in the chamber. 1 spark should be at 1/2, 2 sparks should be at 1/4 and 3/4, 3 sparks at 1/6, 3/6 and 5/6 and so on.
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