Spark Gap:

The gap for my coil is a 'static gap', so called because the electrodes in it do not move, thus differentiating it from the more exotic varities of rotating electrode gaps. It is build from a 6 inch diameter piece of tubing (polyethylene) with 3.5 inch long sections of 28mm copper pipe bolted to it. Different total gap spacings are obtained by connecting the wires to different pipes.

The mounting holes I drilled were not quite spaced properly so some of the tubes had to be deformed, reducing their width, to achieve the correct spacing. Each gap was set to between 10 and 20 mil (thou) using a feeler gauge. Mounting hardware was all 6mm brass, with a little extra machining on the inner nuts, to allow for the curve of the pipe.

 

Blower:

After the first coil run, it became clear that some sort of cooling would be needed if I wanted runs of more than 30 seconds at a time, before letting the gap cool down for 5 minutes!

I aquired the motor from a broken (it had been dropped from a height) vacuum cleaner and fitted it into a home made wooden box. I cut up some packing foam rubber to form a fat tube and glued it to the base, around an inlet hole. The cleaner motor was then glued on top of it, aligning the inlet hole with the foam tube. The foam acted as an anti-vibration support for the motor and an inlet guide. This was OK except for the fact that the foam was not airtight. This was cured by coating the inside surface of the tube with silicon sealant.

The lid has holes located where the air flow is needed, and I located a plastic tube in the center to further help direct the flow.