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Rotary Refresher
Quoting Glenn <gcerny-at-megspo.megsinet-dot-net>:
> Indoor activities have begun to resume as the cooler weather
> has moved in. My rotary now spins in its bearings with 12
> thoriated tungsten points via the Carter 10,000 rpm belt drive
> (a pic or two will appear in the near future). My burning
> question is how many vacume gaps should I run with this setup
> to start? How can you tell if there are enough vacume gaps or
> too many and is max spark off the torroid still the proper
> way to tune, or are there signs to watch for in the way the
> primary circuit acts other than the obvious kick back? Can
> I expect "rough spots" in the way the circuits act as I vary
> rotary speed?
Start out initially without any static gaps at all, and set your
rotary to the closest safe gap distance. This will get the coil
up and running with a minimum of stress and problems. This is
where you run the gap up and down and looks for thoses speeds
which produce the smoothest operation and the best spark. You
should not hit "rough spots", you will find the min and max speed
ranges on the rotary with the system.
After a few minutes of cumulative run times open your gap spacing
on the rotary up. This will increase the effective tank circuit
peak voltage, decrease your quench time a bit, and get you more
familiar with the "feel". As you go through these steps do not be
surprised if you have to make a number of coupling adjustments.
After a few more minutes of run time, close down the gap distance
on the rotary back to the minimum safe distance. Then place the
vacuum gap in series with the rotary. Now when you have problems
like over-coupling, erratic performance, flashovers, etc., you
can be pretty sure that everthing is related too, and can be
solved by, adjusting the vacuum gaps. With the vacuum gaps in
series the peak powers are going to climb pretty steeply, which
is why I suggest doing a series of runs with the rotary alone to
work out unrelated kinks. Most of the problems with flashovers
and erratic performance can be traced to simply having too much
total gap distance, so be prepared to reduce the number or amount
of spacing between gaps until smooth and reliable performance is
obtained.
Once you have have everything all settled out, and they system
has accumulated about 10 minutes of firing time with the vacuum
gaps, take the vacuum gaps off-line and examine them carefully
for arc/heat damage that would cause the performance to drop off.
Richard Quick
... If all else fails... Throw another megavolt across it!
___ Blue Wave/QWK v2.12