[GreenKeys] Odd Model 15/20 gears

[Jim Haynes]

So I went out to the Baudy House and counted the gear teeth.  Guess if I
had done that earlier I could have figured all this out without having to
ask. 114460 pinion has 10 teeth and 114461 gear has 39 teeth.  With an
1800 rpm motor that gives a receiving shaft speed of 461.5 rpm.  For 360
opm, 45.45 baud, the corresponding number is 420 rpm.  So for a 5 level
machine, taking the ratios of those two numbers gives a baud rate of
50 and a character rate of 404 opm, or 67 wpm.  If the 50 baud signal is
transmitted as 7.5 unit code (European standard) rather than 7.42 then
the speed would be 400 opm or 67 (rounded) wpm.

I can't do the calculations for 6-level code right now, because I don't
know if that is transmitted as 8.00 units, or 8.42, or 8.5, or 9.0, or
something else.

It would be interesting to know why A.P. chose to go from 45.45 to 50
baud, or 60 to 67 wpm.  If they wanted more speed they could have
switched to 75 wpm, a standard speed for the Model 15.