On 1/15/2013 7:33 PM, Chris Tromley wrote:
I remember a post years ago (maybe from Lee?) about speed controls on
trolley cars that were quite smooth and sophisticated. I think it was a
drum-style multiple position switch with all sorts of clever enhancements
to transition from stage to stage, ensure you couldn't engage two stations,
etc.
Could have been me, or Bob Rice. He was also familiar with these trolley
car controllers.
Some were simple and crude (slow, medium, fast). Others were more
sophisticated, when the routes had more hills and traffic, and thus
required more speed control finesse.
Basically they were big rotary switches. Between the main
slow-medium-fast contacts, there were extra contacts that switched in
resistors to smooth the transitions between speeds, and to provide a
path for inductive currents to flow during the transitions.
I have to wonder if you couldn't make a really slick mechanical
controller. With enough stages it would be almost as smooth,
more efficient, and a lot cheaper.
You can look at the controllers for the 1920's Detroit Electrics to get
an idea what this might look like. They had 7 or more steps, and indeed
acceleration was pretty smooth. There were no resistors except when
starting from a dead stop.
But I don't know about "cheaper", unless you used surplus contactors,
and built it yourself.
--
First they ignore you; then they mock you; then they fight you; then you
win. -- Mahatma Gandhi
--
Lee A. Hart, http://www.sunrise-ev.com/LeesEVs.htm
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