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On Sun, 04 Jan 2009 14:54:47 -0700,  wrote:

> But there is much more to precision time keeping than pendulum
> compensation.
> For example, variations in the driving force that keeps the pendulum
> going will result in changes in the length of its arc, as will changes
> over time in the oil that lubricates the escapement. Variations in
> atmospheric pressure and air density also set limits to what is
> achievable. Richard J Matthys' book "Accurate Clock Pendulums" will tell
> you more than most people will wish to know about the subject.

I have been reading this book for the past few days.  I see my attempt to
vary the suspension point of the weight, for temperature compensation, was
crude compared to the shims and tubes of Invar and brass the author tried
and recorded.

For example, I had not realised there was such a long delay between the
rod reaching its new length (say to an arbitrary 99 percent), and the
greater mass of the brass weight coming to the new equilibrium temperature
by the same percentage.  This leads to a step in accumulated time error,
even if the temperature compensation is perfect at both temperatures.
 From what I read in his book, an Invar tube inside the lower half of the
weight, and a brass tube of the proper length below the weight (both over
the Invar rod) would seem to produce the smallest step.  Does this seem
reasonable to you?

I was also very surprised by the difference in pendulum rate caused by the
tightening of the suspension nuts.  Milling a spring and suspension block
 from a solid billet resulted in one of the least sensitive arrangements.

I was also intrigued by the "zero friction" crossed spring suspension,
although it seems sensitive to the total weight of the pendulum system,
 from the way I read that page or two.

The surface layer effect of the air inside the case causing a change in
rate was conceptually expected, as was the effect of barometric pressure,
but I had no idea on the numbers.

Thank you for the recommendation, I'm having fun

--
Richard . . .

Using Opera 9.2.4 after the "Dog" died

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