I'm well aware of the danger in putting a 45 year old hot arm of questionable origin into a vintage setup.
But only a madman like me with nothing to lose would gamble on this combination:
-ugly arm with big wire and bubbles in the epoxy
-old magnets in a 45 year old can
-huge airgap (works well on modern 16D setups)
-teeny vintage 16D brushes (gifted by Brian McPherson years ago - Thanks Brian )
-no pre-radius of brushes, and only back yard methods of magnet and EB hardware alignment
The good news is, can and mags were recently zapped and arm refurbished by Hershman.
It was a tap dance making the steel pinion extend far enough to reach the teeth of a Parma 29T crown
The arm spacing (magnet placement) was more critical than usual.
Buttoned it up, fed it 2 V and it didn't start - I had to hand-spin it. She immediately sucked 2, then 3, then 3.5 A. Temp was hot. Stop. Not good
I thought, brushes too small for the big .200 comm. Bad arm. Airgap too big. Mags too weak for this arm. Short circuit. Bad arm. Bad brushes. Spring tension too light.
First thing to suspect in a new motor that runs bad is: brushes.
Removed brushes to check break in progress and wear patterns.
Negative brush: wear looks good, needs a little more break in.
Positive brush: trailing edge not mating with the comm.
Tweaked the positive spring, then 3 V again. Started up nice, but still draws high Amps. 3, 2.8, 2.5, indicative of a new break in, since I had changed an alignment. Amps steadily decreased to about 1.8. She wasn't as hot as the first run. Hmmm, maybe this is a simple brush break in issue, and there is hope after all ?
Cool off, re-oil, 3 V again. Started right up, draws 1.8 A. After a couple minutes, down to 1.4 A.
Sounds and feels great, nice cool temp. It's a missile
Probably going to be way more power than I need for a 45 year old slot car