At one time I found my 0.25 inch Tungsten electrodes were overheating badly, with rapid ablation of the fixed electrodes. This meant constant re-gapping was needed: often even after just 5 mins of run-time.
I was very fortunate in kindly being given some 0.375 inch Copper / Tungsten rod imported from America. I found it is very easily machined, and the alloy has good thermal and conductive properties, so I thought, it would be fairly resistant to ablation as well. Obviously the fact it is a larger diameter than my previous pure Tungsten ones would help matters as well.
At the same time I took the opportunity to also increase the heat sinking of the electrode holders as well. This was achieved by using solid one inch diameter copper rod for the holders, replacing the 0.675" Cu rod I had been using (since replaced with 1.5 inch diameter). I realised however that the dwell angle would then be increased because of the electrode's larger diameters, and this then made me consider the whole the matter of dwell on a RSG, and how it affects things.
What is the dwell angle some people ask? And how critical is it?
On a RSG (Rotary Spark Gap), be it an ARSG or a SRSG type, the dwell angle is the period that one electrode is actually passing over another. So technically it starts the moment the edge of one electrode passes 'over' the other, and finishes when no part of any one electrode is over another.
The fixed electrodes are shown offset
to enhance the effect.
I had mentioned earlier about the suggestion that the ablation rate of 0.375 inch Copper / Tungsten rod would be slower than pure Tungsten. We sadly it actually ablates the same - if not a bit quicker.
In its favour though is the fact that cutting and machining replacements is much, much easier.