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Re: [TCML] rotary gap disk



Hi Phillip,

One thing I didn't point out is that dwell time affects are psu and cap dependent. Same problems can happen in large discs also. But more likely in smaller disc sizes given the typical psu and cap sizes used. I have no clue what psu, cap size, or disc size you used, so my comments are more of a condition that is possible. Worst case is a small psu current, small disc, and relatively large cap. I'm not sure if you were in this territory, but thought I would throw it out there as food for thought (though you may already realize this aspect).

Bart


bartb wrote:
What can happen in a small rotary is that the electrode mechanical dwell time can become excessive, up to the point of the cap charging and discharging a time or two during the mechanical dwell. This can cause a problem with steady firing voltages and so it tends toward a chaotic voltage at each break. Actually, in this situation, it helps to have a bit larger gap to prevent these occurrences. But as the disc is larger in diameter, the dwell time reduces linearly. A 10" rotational diameter would have 1/2 the dwell time as a 5" rotational diameter. As the diameter of the disc is increased, it doesn't take long before a tight gap is ideal (as tight as is mechanically sound). It's simply another cool aspect to larger rotational diameters. Of course, the stresses on the disc increase with larger diameters, and another good reason to use G10 or G11 as an insulated disc (at least for hobby coils).

Regards,
Bart
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