Re: rotary gap electrodes

>From: Chip Atkinson <chip-at-poodle.pupman-dot-com>
>To: Tesla List <tesla-at-poodle.pupman-dot-com>
>Subject: rotary gap electrodes

>My questions are: How much cooling of the stationary electrodes do I 
>need to do?  Will putting the W (tungsten) rod into a piece of 5/8" brass 
>rod 2" long be enough to prevent the rod assembly from getting so hot 
>that it melts the plexiglass?  I have also considered some sort of 
>non-thermoplastic insulator to surround the brass.  Another option is a 
>1" rod of Al with the W rod in it.  The Al could have cooling fins turned 
>on it too if necessary.  I don't figure ohmic heating will be much of a 
>factor, but the arc will be hot and so heat the electrodes.
I'm using 1/4" plexiglass to hold my stationary electrodes.
(sacrificial, in case of collision) They are 1/4" stainless steel
bolts, my rotaries are also stainless.

If I power my system with my rotary gap stationary (~20A -at- 220V ->
4.4kVA), it takes 30 seconds or so to soften the plexiglass enough to
indent the 1/2" washers into the plexiglass.

If my rotary is running, I've never even gotten them warm to the
touch. This has even been true during my pig/ballast/gap testing that
I did last month when I ran the system for several minutes at a time
to scope the (HV) output voltage.

There are NO heat sinks or forced air cooling on this rotary. The only
air flow is that generated by the moving points. It is enough to even
cool the 4 stationary electrodes.