[GreenKeys] Teletype motors

[John Nagle]

On 6/16/2013 9:00 AM, greenkeys-request at mailman.qth.net wrote:
> Message: 11 Date: Sun, 16 Jun 2013 10:45:11 -0400 From: Roy Morgan
> <k1lky at earthlink.net> To: Steve <zarco at sonic.net>,
> greenkeys at mailman.qth.net Subject: Re: [GreenKeys] model 15 gear
> identification? Message-ID:
> <8581478A-3A98-48A2-9B2E-60EFAC427A6B at earthlink.net> Content-Type:
> text/plain; charset=iso-8859-1
> 
> 
> On Jun 16, 2013, at 9:26 AM, Steve <zarco at sonic.net> wrote:
> 
>>> Roy, I was able to identify the gear set from your list. They are
>>> for a model 14 running at 75 wpm with a motor speed of 2100 RPM.
...
> 
> I wonder what motors ran at 2100 RPM.  Seems to me that most of them
> are 1800 rpm but I'm not sure.

    Synchronous motors for 60Hz power must run at 3600/N RPM, where
N is the number of poles.  2100 RPM can't be a synchronous 60Hz motor.

    There is at least one ham web site that says 2100 RPM
(http://www.rtty.com/development/teletype/model-14/model14.htm)
but this seems wrong.  All standard Model 14 motors run at 1800 RPM.
I have three working Model 14 tape printers, all with 1800 RPM
motors running at 60WPM (45.45 baud).  Model 15 motors also
run at 1800 RPM and are interchangeable with Model 14 motors
(although the motor pinion and power connector are different).

   There were variations on this.  Teletype motors were
available in DC (governed), 25Hz, 50Hz, and 60Hz.  But
none of those frequencies will give you 2100 RPM.
There's a two-speed governed motor variant.   Teletype Bulletin
1147B lists all the motor options for Model 14/15 machines.
Most motors were made by General Electric, but a few
were made by Oster, and some from the 1920s were made
by Holtzer-Cabot.  I have one machine with a Holtzer-Cabot
motor; it's noisier than the GE motors and has a heavier
frame.

				John Nagle