Thinking about this some more, I wanted to verify what was actually supplied with the PW units. Looks like we all were off a little.
I made the mistake of using a 25 tooth worm wheel, like those used in the 41 switchers, for my calculations.
Ted S was the closest using 8.33:1 overall.
Before I opened my original GP7's gear train to count teeth, I did what I had asked Dan to do, count the armature revolutions to 1 wheel turn. Something wasn't right, they never fully aligned with the original marks (all gear lash was removed). Not at my calculated 9:1, and 8.33:1 should have aligned at 25 turns of the armature.
Here's what I found:
PW GP7 gearing
3 start worm
23 T worm wheel
25 T pinion
17 T idlers
27 T wheel gears
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Original:
23 T worm wheel / 3 start worm = 7.6667:1 worm ratio
27 T wheel / 25 T pinion = 1.08:1
7.6667 x 1.08 = 8.28:1 total ratio
New (Dan's):
27 T wheel / 10 T pinion = 2.7:1
7.6667 x 2.7 = 20.7:1 total ratio
Other:
9 T pinion = 23:1 total ratio
11 T pinion = 18.8:1 total ratio
Dave