On Thu, 29 Sep 2011 15:07:40 +0100,
lid (Adrian Tuddenham) wrote:

Does anyone happen to know the official speed of a Dictabelt?

Which maker and what model?
They followed the same speeds at record platters.
ips time
15 15 min
7 1/2 30 min
3 3/4 60 min
1 7/8 120 min
However, I'm not sure of the times. There were also versions that
offered 4 channels per tape, which decreased the run time. For
example, the Kennedy tapes were 4 channel mostly at 3 3/4 ips, but
only ran for 15-20 mins.
http://whitehousetapes.net/info/kennedy-tapes-overview#TECHNICAL_NOTES

Mo
http://www.videointerchange.com/audio_history.htm
Scroll down to "Dictabelt 1947".
12" circumference, 15 minutes play time, 3.5" wide.
The problem is I don't know how how many tracks per inch across the
3.5" wide belt. If you have a device, you can measure tracks per inch
or calculate it from the gearing.

It seems
to be around 6 inches per second or 30 belt revolutions per minute, but
there must be a proper specification somewhere.

30 rev/min = 0.5 rev/sec. At 12" per revolution, that's:
0.5 rev/sec * 12 in/rev = 6 in/sec.
Close enough to 7.5 ips.


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