On 2/7/14 5:46 AM, matty mcqueeney wrote:
The "two bolts on an L-bracket" scheme described by Scott and Carl is a good first start.. BUT..Could anybody help me find a reasonable spark gap, that is simple to make? Thanks Matthew.
Scott's comment about air blowing on it is an essential thing..The problem I find with a "two bolt gap" is that inevitably, it gets hot spots which greatly reduce the gap firing voltage, so adjustment is a pain. A gap that just fires when cold will fire too soon when hot, reducing the voltage on the caps and reducing spark length.
You'll see this as the coil "losing performance" as you run. It will also change sound, because as the firing voltage decreases, you get more sparks/line voltage cycle. And because the charging current/voltage is sinusoidal, you get interesting chaotic behavior. Cool effect in some ways, but makes it really hard to know if you're coil is "in tune".. did the sparks get shorter because I moved the tap too far, or is it because the gap is getting hot.
I'd seriously look for something larger in diameter that has good surface area for cooling. (a couple pieces of pipe, or a pair of pipe couplers, works well)
The other thing that helps is to have a fairly large area with equal gap distance (sort of the opposite of two needles), because then the sparks can jump from anywhere, which reduces the heating at one point.
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