[GreenKeys] Odd Model 15/20 gears

[Sheldon Daitch]

Jim,

I will hazard a guess or two on why 67 WPM vs 75 WPM.

I seem to recall that there were some spring changes in converting a M15 
and
probably an M20 to 75 WPM, or if not spring changes, some spring adjustments
were required.  If that is the case, a field conversion from 60 to 75 
could not be
performed with only a gear set change.

Second, I also think the maintenance issues went up at 75 WPM and perhaps
the 67 WPM speed was a compromise between how much additional maintenance
would be required to support 75WPM vs the additional material throughput 
of the
system.

My guess is that the AP decided the additional data transported at 75 vs 
67 didn't warrant
the conversion and maintenance costs increase.

Again, an educated guess.

Sheldon


On 5/31/2011 7:43 PM, Jim Haynes wrote:
> 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.
>
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