Expert: Kenneth Saunders - 9/10/2008

Question
Hi

I have just acquired a reproduction (believe C20) of a C18 French Great Wheel skeleton clock. I have set it in beat by the time-honoured crutch bend method, but am now having trouble setting the minute hand. I have religously set the time by moving the minute hand clockwise only, but it has progressively loosened and now "falls back" when in the "twenty to the hour" position, as I take it that this is the position of maximum resistance to the drivetrain torque.
When it slips the centre drive train seems to move with it. I can't see a clutch as such to adjust, and the hand seems to be firm on the arbour itself. Is there anything I can adjust and if so how should I set about it?

Regards

Tim Gillott
Barnet, North London, UK

Answer
the "hand clutch" system used is loose. The clutching system that allows the gearing to turn the hands but also allows the minute hand to be turned to set the time is loose.

two systems were used often. The minute hands are on a square headed brass shaft that turns around a round steel shaft ending with a hole in it for the tapered pin to hold the hands on.

a) there is a tension washer under the brass shaft assembly that gets more friction by more compression from the round hand washer and the pin that holds the minute hand on - thicker or more little washers on top of the minute hand push the brass assembly down more when the pin is inserted and this tightens the minute hand clutching.

b) the brass tube that ends in the square end for the minute hand is itself crimped in its' middle to grip the steel shaft and provide a constant clutching pressure. Delicately recrimping it with a fine hammer after removal can tighten just enough to restore the friction to the clutching system.


not sure which you have - but if you remove the hand washer and put the pin only in to hold the minute hand on the clock and in turning the minute hand through an hour - it feels as tight as it did with the washer in place (ie works ok from 12 to 6) then you have the system (b). and it is a simple but delicate adjustment best left to a pro.

if it is (a) then simply putting two washers or a thicker one or cupping more the one you have and then reinstalling the tapered pin will restore proper tension to the clutching system in (a)
  
 More modern system uses a spring finger on a gear just inside the rear plate on the back end of the handshaft itself.