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Front Spark

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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Front Spark

Unread postAuthor: MisterSteve124 » Sat Dec 02, 2006 4:17 pm

Ok well I'm done my propane metered combustion except I need to hook up the bbq igniter. I was thinking I should just put the screws on the front where there is the pipe and reducer since already have a hole for the elbow and the fan on the rear fitting. Will putting the spark gap on the front decrease performane? Keep in mind I have a high powered fan in the back that will get the propane up to the front and my chamber is only 10 inches long. So do you think it will decrease it at all? I could probably put it in the rear if it would be bad to put it in the front.
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Unread postAuthor: cannon freak » Sat Dec 02, 2006 6:45 pm

For such a small chamber I don't think it would decrease preformance much, if you want simply run wires to the back of the chamber through the hole in the front to two screws in a thin peice of wood epoxyed to the side, works great.



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Unread postAuthor: rna_duelers » Sat Dec 02, 2006 7:41 pm

The spark should be towards the back of the chamber,and after the chamber fan.Were the fuel is ignited does effect the performance because which was the flame front travels is important.With the ignitor towards the front the flame front is traveling towards the back fo the chamber but if it at the back the flame front travels towards the barrel.Which by common sence would seem to be better for performance.
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Unread postAuthor: boilingleadbath » Sun Dec 03, 2006 3:43 pm

I suspect that the ideal spark placement has more to do with combustion dynamics (front ignition doesn't move the mixture that has yet to be burned; thus that mixture doesn't develop turbulence; thus it burns slower) than "common sence" - but either way, RNA has it right: towards the rear.
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Unread postAuthor: SpudBlaster15 » Sun Dec 03, 2006 4:22 pm

Use two spark gaps, each one about 1/4 of the way in from each end. By doing so, the fuel will burn in a shorter period of time than it would if a single gap were situated in either the front or rear.
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