Thanks, Tom! That all makes sense! Come to think of it, the Briggs &
Stratton engine on my 5500 watt generator maintains its speed well. I don't
know what sort of feedback it uses, but it's effective! If I make a big load
change, like bringing on a water heater, I can hear a "pitch" change but the
speed remains constant. In the old days I've seen trucks and tractors used
to run saws for cutting timber. I guess that sort of give awa y how old I
am and what a "hillbilly" I am! :-)
Take care down there!
73,
Charlie, K4OTV
-----Original Message-----
From: Topband [mailto:topband-bounces@contesting.com] On Behalf Of Tom W8JI
Sent: Wednesday, February 12, 2014 8:29 PM
To: Charlie Cunningham; 'topband List'
Subject: Re: Topband: Yikes! Heavy snow, freezing fog and 23 degrees F in
Raleigh, NC
> Gee, that should work great, Tom! How is the shaft rotatoion speed
> controlled to maintain 60 Hz?
>
Tractors are like almost any other thing that has an engine and a manual
throttle control, including lawn mowers. They have engine speed feedback
that works like "mechanical ALC". It isn't like car or something that has
an open loop system with a human stuck there pushing a pedal to regulate
power with varying loads. If it didn't have that feedback system, a person
would have to constantly adjust the throttle when mowing or plowing. I guess
you could think of it like a cruise control, except unlike cruise it is the
primary throttle and has wide dynamic range. Lawnmowers regulate the
carburetor throttle plate with a connection to a flapper plate. Air from a
finned wheel hits that plate. The plate works against a spring, and the
throttle just changes spring tension. The tractors around here are a little
more sophisticated, but same basic concept. They stay put pretty good.
Within a Hz or so at the most.
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