Best RSG ever?

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Mr Gregory Peters by way of Terry Fritz <twftesla-at-qwest-dot-net>" <s371034-at-student.uq.edu.au>

Last night, I was thinking about my airblast/RSG arrangement, and came 
up with an idea that may or may not be original, but which I think has 
great potential. Firstly, let's discuss the role of an RSG in a Tesla 
coil. I'm no expert on this subject, and I'm no electrical engineer. 
But I have read lots of books and have had practical experience. Think 
of the following as me "thinking out loud". I may be barking up the 
wrong tree here. 

Now, in low power systems, an RSG with no static gaps is fine. It will 
quench the spark quite well by itself. The role of the RSG is to 
control the "switching"  rate of the primary capacitor. This has two 
aspects. Firstly the breaks per second, which we all can appreciate the 
importance of, and secondly the dwell time, or time that the electrodes 
are within a close enough proximity to allow arcing to occur. It is 
well known that, up to a point, the smaller the dwell time the better. 
A problem that arises in high power coils is that the switching 
efficiency of a sole rotary gap decreases. The arcs tend to "follow 
`round", or continue to occur for a short distance after the rotating 
electrode has passed the stationary electrode. This effectively 
increases the dwell time and lets primary voltages drop significantly. 
This effect is similar to an air blast static gap running without the 
air blast - the arc just won't go out, the caps don't charge well, and 
the coil output is reduced as the gap is over powered. 

Traditionally, to combat this, the clearance in the rotary gap is set 
as small as possible. A static gap is placed in series. In this 
arrangement, the static gap (air blast or similar) takes care of the 
quenching, and the rotary is used purely as a device to control the 
BPS. The result is better performance and longer RSG electrode life.

Now, last night I thought "why not combine the two gap types in the one 
unit?" My idea is to pass, say, 150 psi of air through the CENTRE of 
the stationary RSG electrodes. This has several advantages. Firstly, 
follow `round is reduced and quenching is improved. So coil performance 
is better. Secondly the rotary and stationary electrodes won't get as 
hot. So maybe we can forget about using tungsten electrodes, and use 
cheaper disc materials that don't need high temperature abilities.

One way I have thought of doing this is to make the stationary 
electrodes from copper pipe. You could hammer the end of the pipe until 
it is almost flat. If you align the flat pipe perpendicular to the 
rotating electrodes, the width will be less than 1/4", so the dwell 
time will still be quite small. You would then blow air through this 
pipe. The air would spread out, like a garden hose nozzle. It would 
quench the arc and would also cool the stationary and rotating 
electrodes and also the RSG rotor in the immediate vicinity of the 
rotating electrodes. This would help prevent melting of the rotor and 
would increase the life of the electrodes. What do you think?


Cheers,


Greg Peters
Department of Earth Sciences,
University of Queensland, Australia
Phone: 0402 841 677
http://www.geocities-dot-com/gregjpeters