[time-nuts] jump in pendulum clocks
brooke at pacific.net
Thu Oct 23 16:24:36 UTC 2008
That's interesting. After reading Accurate Clock Pendulums and a number of
other books then researching patents I found:
3036465 Gravity Meter, Robert H. Dicke, May 29, 1962, 73/382R ; 73/514.29
>= 20 cps, Q >1,000,000 optical pick up and electrostatic drive, mostly fused
quartz parts. He also invented the lock-in-amplifier and Dicke radiometer.
It's almost all quartz, but now I see why they are not more popular.
http://www.prc68.com/P/Prod.html Products I make and sell
http://www.prc68.com/Alpha.shtml All my web pages listed based on html name
http://www.prc68.com/I/WebCam2.shtml 24/7 Sky-Weather-Astronomy Web Cam
Carl Dreher wrote:
> This is my first input to the list.
>>From what I've read, the jump in pendulum clocks is due to a spontaneous
> change in the rod length. This has actually been measured, and is
> accredited to crystal lattice slippage of the material. This has been
> found in metal and recently, crystal rod pendulum. It is significant in
> the latter because experimenters went to crystal rods for their
> temperance invariance, only to find the unpredictable spontaneous length
> Carl Dreher
> In : Accurate Clock Pendulums by Robert Matthys (2004) Oxford
> University Press ISBN 0198529716, Pp264
> In Chapter 8 , "The Allen variance and the rms time error", on page 38
> he writes:
> Figure 8.1 shows another characteristic of pendulum clocks - the
> clock will run relatively
> smoothly at one rate , and then after 3 - 6 months it will suddenly
> jump to a new rate
> as shown if Fig 8.1.
> He goes on to say that this is part of a random walk process.
> I hope that is of some help.
> Neville MIchie
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