Pete Keillor wrote:
On Tue, 08 Dec 2009 22:06:17 -0600, Don Foreman
wrote:


"Karl Townsend" wrote in message
anews.com...
You described the exact issue. Mechanically, I've got it geared down to
raise/lower 12"/minute with a total travel of 60 inches. Gets hard to gear
it much slower. My "plan A" is two stats so you have a dead band, then
play with % run to get response without oscillation. I suppose if you knew
exactly what percent on/off was optimum you could just gear it for 100%
on.
You can't know that because it will change significantly with cloud
cover, sun angle, wind, etc.


It ain't hard, it just ain't cheap. I used a double reduction
Sumitomo cycloid drive of 3400:1 to drive the continuous filter I
invented. Web movement maximum was 60"/hour, min was close to zero.
I'd mark the web, go have a cup of coffee, come back and stick a ruler
on it to make sure it was working.

Pete Keillor


Well, not to be contradictory, but it is both easy and cheep - in software.

Once you have the drive running that can handle the mechanical loads,
controlling the speed is simple stuff.

Richard