I'm not absolutely certain, Hal, but I think high Q has to do with the
spectral purity of the source, but not necessarily with its long term
stability, which depends on other design factors. I can only say about the
damping that I dimly remember it in connection with the Shortt clocks but
cannot remember where.
This track caused me to go into my stacks (I really thought I was free of
the pendulum compulsion, but apparently 'taint so). There are two books i'd
recommend:
Mathys, Robert J, "Accurate Clock Pendulums",Oxford University Press, NY,
2004, ISBN0 19 852971 6 (Hbk) ; this is a real bible about vertical pendula.
Amazon lists this one, both used and new
And for a personal, very entertaining, refreshing, and thorough examination
of pendulum clock building,
Woodward, Philip, "My own Right Time : An Exploration of Clockwork Design",
Oxford University Press, NY, 1995, ISBN 0 19 856522 4 I really enjoyed this
book! Amazon has this one both used and new.
If you get these used, you'll spend about $170, but you will avoid endless
hours of fooling around. OTH if the fooling around amuses, then. . .
BTW, Invar has a really low tempcoefficient, but tends to random shifts in
its structure, yielding to abrupt length changes. Can't have everything, I
suppose...
Best to all,
Don Latham
----- Original Message -----
From: "Hal Murray" <[email protected]>
To: "Discussion of precise time and frequency measurement"
<[email protected]>
Sent: Monday, January 11, 2010 8:04 PM
Subject: Re: [time-nuts] Non electrical time-nuttery
[email protected] said:
Also, according to some info I read on pendulum clocks, vacuum does
not work because some viscous drag is needed to damp the free
pendulum;
Why do I need damping?
I thought the general idea on oscillators was to get the highest Q (lowest
damping) that was reasonable. But now that I think about it, I'm not sure
why.
--
These are my opinions, not necessarily my employer's. I hate spam.
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