Craig:

Fascinating little posting . . . some great nuggets here!! We always here about power reserve, but your focus on efficiency is interesting.

One question: You say "manual winding - 3 to 4 twists on the crown" . . . Isn't there a huge difference, statistically, between 3 turns and 4 turns? Might be interesting to do a survey among our readers:

• Take your favorite watch, which is entirely wound down.
• Turn the crown exactly four turns.
• How long will it run?

: I have finally have taken the time to determine the efficiency of
: the auto winding mechanism in the Buren cal 11 thru 15 movement.
: I want to start with a comparison of manually winding the
: movement compared to how many rotations the micro rotor needs to
: do the same. This is an initial report. I decided to do this
: because I could not find this information anywhere and there has
: been a fair amount of discussion on the subject.
: Manual winding - 3 to 4 twist on the crown (depending on the person
: winding = around 360 degrees on the mainspring barrel arbor) is
: equal to:
: Auto winding - 180 or so full revolutions on the micro rotor.
: This should run the movement for 6 to 8 hours (from completely
: wound down) without the second hand engaged. If the second hand
: is running, subtract around 1 hour.
: This example is intended to show the efficiency (or inefficiency)
: of the auto winding mechanism in this movement. If anyone else
: has done this test, I would like to hear from you. More later.