[GreenKeys] Model 15 timing

[Don Robert House]

At 11:56 AM -0500 2/12/2003, david freeman wrote:
>While noodling through some problems on a new Model 15, I ran across 
>an odd gear set in one of my three units. As I was working out the 
>reductions on paper I cannot make sense of the basic timing, saying 
>nothing about this odd machine. Can some one help me. I=92ve assumed 
>45.45 baud, 7.5 bits/letter, and 6.06 letters/word. That gives me 
>22msec per bit which I seem to remember is correct, 60WPM and 363.6 
>operations/minute. Operations per minute is referred to in some of 
>my Teletype manuals, and 364 is a figure shown for 60WPM machines. 
>My question is, I have a 1800 RPM motor, and a reduction to the main 
>shaft of 7teeth/30teeth equals 420 RPM. Shouldn=92t this be 363.6 RPM? 
>Does the machine use more than one revolution of the main shaft per 
>letter, and if so how?
>OK at any rate, as I was swapping typing units, I found one of my 
>machines has a different set of gears driving the keyboard. Two have 
>21 teeth driving 24 teeth, the odd ball has 24 teeth driving 26 
>teeth. The cams tripping the electrical contacts look identical, but 
>a small difference would be hard to detect I imagine. So assuming 
>the main shaft RPM (420) from above is correct the keyboard drum 
>would turn at 367.5 RPM for the =93standard=94 units, and 387.7 RPM for 
>my oddball. 367.5 is pretty close to my 364 OPM ideal. What is the 
>387.7 unit? I=92ve had it on the air and had good reports with it. 
>Just a mystery I=92d like to know the answer to.
>
>Dave, WW8S

Dave,

You could have a set of gears for a model 20 which is 6 level instead 
of 5.  If you record the Teletype part numbers stamped into the 
gears, and send them to me, I can look them up for you.

Don
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Don Robert House
North American Data Communications Museum
URL: http://www.nadcomm.org
Computer Museum of America
URL: http://www.computer-museum.org