Ned Simmons wrote:

On Thu, 20 Oct 2011 18:07:52 -0500, Jon Elson
wrote:


I presume anything close to that size is going to be a screw
compressor... But I could be indicating my lack of knowledge with that
guess too.
Well, I did see some gigantic Ingersoll one-lung compressors in a
factory here on a tour. I was amazed they were from 1952. Gigantic
horizontal cylinder about 8 - 10" diameter and probably a stroke
of a foot.


It may have been driven by a low speed synchronous motor that was
supplying power factor correction in addition to driving the
compressor.

Yes, that is EXACTLY the machine! I didn't mention those details
as they have nothing to do with the air supply, but that was the
setup. On the way was a phase angle meter that looked like it came out of
Edison's own lab. I never found what the phase meter controlled, but
it would have to be a variable voltage rectifier, probably with
big Tungar bulbs in it.

Jon