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Post by cizzl03 on Jul 12, 2005 14:03:59 GMT -5
OK, i just finished my new spud gun. It has a chamber fan, stun gun ignition, pass through barrel, all that good stuff. But I can't get it to fire. I tried all kinds of different amounts of propane, so I'm sure it's not a fuel problem. I have the stun gun leading to three spark plugs. I know the plugs are working, but they make small sparks. Could the small sparks be the reason I'm not getting combustion? Do you guys think i need to ditch the plugs and just go for some standard electrodes? Or is there something I'm missing?  |
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Post by cizzl03 on Jul 12, 2005 14:14:07 GMT -5
I have one more question. Does a bigger stun gun (higher voltage) mean bigger sparks? Is the difference pretty significant?
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Post by darthtator on Jul 12, 2005 14:42:19 GMT -5
A bigger stun gun doesn't mean a bigger spark it means the spark is stronger. How many volts is yours? I have never tried spark plugs so I can't really say anything there. You might try gapping the spark plugs to make the spark jump further. That may help. When I built my first combustion gun, it took me nearly an hour to find the perfect mixture. I use butane(the bottle type to refill lighters) in mine. You might try a different fuel and really experiment in how much you put in. by the way what are your specs on your gun? chamber and barrel size?
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Post by sgort87 on Jul 13, 2005 1:45:20 GMT -5
More voltage means the spark is able to travel farther. It doesn't make it any stronger. Also try using screws that nearly touch instead of the spark plug design, the screws allow the spark to be in near the middle of the chamber allowing it to reach more of the propane. Also how are you measuring the amount of propane going in? And are your spark plugs wired in series or parallel?
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Post by turbosuper on Jul 14, 2005 15:45:03 GMT -5
Generally even the smallest spark is enough to ignite a good fuel mixture. Is your fuel injection system metered? If it is try rechecking your calculations.
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Post by sgort87 on Jul 14, 2005 17:18:28 GMT -5
Yeah, try a gauge, before I put a gauge on, I would always put too much gas in and thought it was a small ammount.
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Post by cizzl03 on Jul 21, 2005 14:49:11 GMT -5
I switched to some machine screws instead and it works great. Thanks for your help.
And, by the way, I do have a propane meter with the gun. So I knew I had the right fuel mixture.
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Post by ghippleh on Jul 23, 2005 18:59:41 GMT -5
coming from an electrical engineering major, the 'strength of the spark' is directly proportional to how far it can travel. It is a one dimensional concept. any way, my geuss is that you have too many spark plugs. the weak spark is probably overwhelmed by the propane. try using just one with a stronger spark. The spark must be able to overcome the liquid in the air before it can actually ignite the propane. hope this helps.
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