[time-nuts] Non electrical time-nuttery

Don Latham djl at montana.com
Tue Jan 12 08:41:18 UTC 2010


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" <hmurray at megapathdsl.net>
To: "Discussion of precise time and frequency measurement" 
<time-nuts at febo.com>
Sent: Monday, January 11, 2010 8:04 PM
Subject: Re: [time-nuts] Non electrical time-nuttery


>
> djl at montana.com 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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