Variable Rotary Spark Gap construction, steel base concern

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Original poster: "Jim Mora" <jmora@xxxxxxxxxxx>

Hi all,

I am in the process of building a variable speed rotary gap. The motor is a
DC Perm magnet type, five by nine inches long. It can only be mounted at the
end plates. I have welded a mounting base out of 1.25" mild steel square
tubing. Here's the rub: there is roughly a 10" closed square under the motor
like an H with one end closed. (The disk is ~3/8" 12" G3).

The stationary electrodes will be mounted on HV standoff's on the open end
of the "H". The motor is bolted to 3" washers extended from the closed loop
(perpendicular). I have not used any ferrous metals in the past. 1. How far
below the primary should this be placed (8kw max .08uf max)? Should I switch
to a non- ferrous solution or shunt the closed loop somehow? Lastly, can
this be placed on earth ground (the ground stakes are 10' away) or is this
inviting RF into the mains? It looked good on graph paper :-)

Thanks for your suggestions,

Jim Mora
Ojai,Ca.