E Z Peaces wrote:
Curt Welch wrote:
Brian Lawson wrote:
On Mon, 30 Jun 2008 20:17:24 -0400, E Z Peaces
wrote:

Brian Lawson wrote:
On Mon, 30 Jun 2008 09:29:33 -0400, E Z Peaces
wrote:

Smaug Ichorfang wrote:
The more I look at 1338, I wonder if it is indeed aa
metal-foil
electroscope. Typically these have very thin pieces of metal
foil suspended from a central conductor. The center piece in
this looks way too thick to be an electroscope. Does the
center piece move; can it pivot from side to side? Are the
two
terminals on the sides adjustable? Is it possible this is a
tilt switch of some sort?

How about a line frequency monitor from a time when automated
equipment to keep a generator on frequency was not reliable.

SNIP

Naw. Prior to the 40's, flyball governors were used to do that.

A flyball governor can keep a motor running at a nearly constant
speed, but synchronous clocks, invented in 1916, require precise
speed control If the generator is 1% slow (59.4 Hz), clocks will
lose about 15 minutes a day.

Doesn't that point to the need for a tuning fork to monitor the
governor? A meter could provide the necessary information, but a
man might notice the absence of a hum before he would happen to
look at the meter.

The way to regulate it accurately is to drive a clock with the
current and compare the time of the clock to an accurate time
source
(like the sun).

For the clock problem, the short term frequency is not as important
as the long term average frequency. So when the clock is running
behind, you just speed up the system a bit until it catches up.
The
fact that the frequency is only accurate to 5% is not important if
you can keep the long term average accurate which is easy enough to
do just by driving a synchronous clock from the power.

I was once told that the above is what power companies actually did
(at some point in history). Don't have a clue if it's true
however.

Here's Henry Warren's patent showing the state of the art in the
early
1920s: 1502494.

The device would count up the difference in rotations between a
pendulum clock mechanism and a synchronous electric clock motor. I
think it registered in seconds. The patent shows the generator
engine throttled by a flywheel governor in parallel with a manual
valve. The governor was intended to keep the speed nearly constant,
and the attendant would make adjustments with the manual valve.

Here's a Warren patent showing the state of the art in 1916:
1283431.

He says a large power station normally kept the frequency between 59
and 61 cycles, and a larger deviation shouldn't last more than 20
seconds.

I think it would take an audio signal(in a quiet office in a brick
station) to ensure such a quick response. For example, the price of
my neighbor's favorite stock scrolls across the screen every few
minutes, but he misses it almost every time because he's not paying
attention during the few seconds it's visible. If the sound
stopped,
that would catch his attention immediately.

The attendant would need an indicator to adjust the valve when the
clock device showed the generator had lost or gained time. He
couldn't just open the valve a quarter of a turn, for example,
because the engine's response would depend on the load on the
generator. Perhaps tuning by ear, listening to the hum of a
mechanical resonator, was more reliable than a visual frequency
indicator.

How about just using a mechanical governor?

--
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--John
to email, dial "usenet" and validate
(was jclarke at eye bee em dot net)