Re: RSG

To: "'Tesla List'" <tesla-at-poodle.pupman-dot-com>
Subject: Re: RSG
From: Tesla List <tesla-at-stic-dot-net>
Date: Tue, 25 Nov 1997 21:01:36 -0600
Approved: tesla-at-stic-dot-net

From: 	Jim Lux[SMTP:jimlux-at-earthlink-dot-net]
Sent: 	Tuesday, November 25, 1997 10:17 AM
To: 	Tesla List
Subject: 	Re: RSG

> This is similar to the route I'm going to try with mine.
> 
> The only thing I'd worry about is having current pulses going through
> the bearings. I was thinking about a wide copper or alunimum flap 
> running against the shaft or face of the disk, perhaps with a bit
> of conductive paste to help prevent welding during the high current
> pulses.
> 

In commercially manufactured rotary spark gaps (popular for radar
magnetrons in days gone by), a common strategy was the "sparking sector"
which was a electrode that was a few mils away from the rotating conductive
disk. The idea was that it is big enough that mechanical precision wouldn't
be an issue if the bearing runout caused the disk to move around. The short
gap between the sparking sector and the rim caused minimal voltage drop.

I would be concerned about running the current through a ball bearing. A
spot of oil could cause a short arc when it broke down, pitting the race or
ball. Why not use regular old bronze sleeve bearings? They aren't all that
bad friction wise and shouldn't have any conductivity problems.

On the other hand, I have run regular old 220VAC through a ball bearing at
20 Amps and had no end of problems with arcing and pitting. It doesn't take
much crud in the bearing to ruin it, particularly at high speeds.