On Mon, 15 Oct 2012 09:21:25 -0700, "William Sommerwerck"
wrote:

What you say makes sense -- but the drive circuit will always compensate
for losses, regardless of design philosophy.

Therefore, it makes sense to have the pendulum swing a tiny bit slow,
and have the drive circuit force it to the correct frequency. This would
also make trimming the frequency a simple matter.

To me the way that makes the most sense is to completely uncouple the
two functions. The accuracy of the cheapest quartz movement is far
better than you can get with the most precise pendulum. The most
efficient pendulum is one that oscillates at it's native frequency.

ALL pendulums oscillate at their native frequency. They can't help but.

Only true if you add the qualifier 'if there are no additional
forces'. A great deal of effort is required to ensure this is true.
Did you ever wonder why the best Grandfather clocks use weights to
provide power?

In a happier time my wife decided we needed a real pendulum clock on
the mantle of our new (to us) home. She picked up one (made in Korea)
that required monthly winding. With a little care I could adjust it
so it was correct at the begining of the month and again at the end of
the month. The force provided by the spring changed depending on how
tight it was, this changed the force on the escapement, which changed
to force applied to the pendulum. The clock would gain time at the
beginning of the month and lose it toward the end of the month.

Look attractive? Yes. Sound good? Definitely. Keep good time - no
way.

PlainBill

Googeling electronic pendulum drive circuit yields a great deal of
information, including some designs that simply provide a boost to a
pendulum at its native frequency.

You're missing the point. The pendulum presumably drives the clock gears. If
all you care about is "efficiency", switch to an all-electronic clock with
an LCD.

If you're going to power the pendulum electronically, it makes sense to have
a system that keeps the pendulum running at the "right" frequency. The
system I described allows the pendulum frequency to be tweaked without
mechanical adjustments.