From: dm561 at
torfree.net
------------Original Messages:
Date: Thu, 22 Nov 2007 12:17:31 -0800 (PST)
From: Fred Cisin
Subject: Re: FD400 drive troubleshooting
Many/most drives have 50Hz/60Hz zebra discs on the
flywheel, for using a
flickering fluorescent light.
Which just happens to be the ratio of 300RPM vs 360RPM, so that on a 300RPM
strobe disk w/a 60Hz light the 60Hz bars = 300RPM and the 50Hz bars = 360RPM.
FWIW,
Hi
I think you have the ratio backward. The 60 Hz disk for 360 RPM
can be used for the 50 Hz 300 RPM.
Dwight
----------Reply:
Well, unless you're just saying that a 60Hz 360RPM strobe disk (if you had one)
would also sync at 300RPM under a 50Hz light, I don't see what's backward.
Hi
That is what I said. The disk with 20 bands would work for both
a 360 RPM and 60Hz light or a 300 RPM and 50 Hz light.
Tony mentioned that one could increase the number of bands for the
problem of the 50Hz with a 360 RPM drive. It makes sense.
A strobe disk with 50 bands would work for this problem.
One could multiply the number of bands by any integer and it
would still work. Multiplying 16.667 times 3 gives a nice integer
value of 50.
Tony mentioned that most 8 inch drives were speed controlled by
the mains and as long as the belt was in good shape, using a strobe
wasn't much needed.
Yaers back, a friend and I were able to aquire drives that were
setup for 50Hz 220V. We wanted to use these with a put together
Series II Intel machine. We're 60Hz 115V here. We put a strobe disk
on the flywheel and took a flat file to the motor pully. About 20 mintes
of grinding brought the drive to the right speed.
The voltage was solved by a buck transformer created from some
universal transformers we got from some surplus supplies.
Dwight
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