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No Spark Plug Method

Here is the next evolution in my spudgunning ignitions.  The trouble with traditional electrodes is that they have a tendency to leak.  On a combustion, this isn't really an issue.  A small leak will not hurt performance, and generally cannot be detected.  When making a hybrid spudgun, you have to be sure there are no leaks.  Some have demonstrated doing so with spark plugs.  Spark plugs work well, but in certain situations they are not ideal.  One such situation came about when I was making my copper hybrid.  The walls are too thin to thread directly into, so I opted for a tee fitting to put the spark plug in.  I lacked a tap to make spark plug threads (whatever they are anyways...) so I came up with the next best thing.

 I took a 1/4" brass plug and drilled a small hole in the top.  Next, I fed some television flyback wire through the hole.  Take note that flyback wire has excellent isolative properties.  The wire you use must have a good insulator.  Multimeter replacement wire (found at Radio Shack) should work also.  Next, I filled the gap in the underside of the plug with JBWeld, a high strength epoxy.  The JBWeld will prevent gasses from escaping around the wire.  Make sure the wire is very close to the edge of the fitting, to create a useable spark gap.  

The positive (or negative, makes no difference) lead from you ignition source will attach to the center flyback wire, and the negative (or the other wire... whatever) will attach onto the brass plug.  The no spark plug method can be used with many types of spudgun ignitions, including piezoelectric (BBQ), stungun, or other high voltage methods.

Pic detailing the assembly

Now that its made, you can either tap a 1/4" NPT hole into your chamber (making sure its in a double thick spot), or use the appropriate adapters to go to 1/4" NPT.

BTW, in case you didn't recognize this, its an adaptation of the HIS, hybrid ignition system.


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