Charlie, your guess is confirmed, see:
http://catalog.teledynereynolds.com/Asset/1431.html#:~:text=At%20sea%20level%2C%20about%2030%2C000,will%20arc%20across%20the%20electrodes.

Wonder if a capacitor across the brushes would reduce the spark?  Works for point ignition systems.
Regards,
Jim

Logic: Method used to arrive at the wrong conclusion, with confidence.  Murphy


On Monday, October 9, 2023 at 12:41:48 PM CDT, CL in NC via Milsurplus <[email protected]> wrote:


The fellow based in Atlanta that refurbishes WW II aircraft electric turrets, known as "The Turret Guy", has to also rebuild the amplidynes that make the power to run them.  We were talking brushes and I asked him where he was buying his.  But, he said that the amplidynes and dynamotors that run at ground level, last almost indefinitely compared to those that actually ran at 20-30,000 feet in their heyday.  Guessing the lower air pressure at altitude promotes more arcing and burns them up quicker.  He mentioned he had one turret he uses for demos he put brushes in many years ago and they still look almost brand new, after countless shows and demonstrations.

Charlie, W4MEC in NC
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