Art Deco Wall Clock

This clock is shown as an example of what can happen when a clock mainspring breaks.  In this instance a previous ‘quick and easy fix’ made the repair more difficult, and thereby expensive. Regular servicing would have shown up this problem before the damage occurred.

Before Repair

A 1930s Art Deco style striking clock in good condition externally.

The mainspring had broken, the ends can be seen at about the 4 o’clock and 10 o’clock positions.

The barrel after the spring and centre arbor were removed.  The hole in the boss which provides the bearing is out of shape and scored. The lugs which locate the barrel on its wheel are damaged.

The great wheel separated from its barrel.  A previous attempt to repair the worn bearing in its centre by using a punch to squeeze the brass and produce a round hole again has not lasted as the hole is elliptical again.  This is not surprising as this great wheel is only 1.6 mm thick, 4 mm is more usual, and there is considerable force on it when the spring is wound.  The result is that the teeth have worn unevenly, those at the ten o’clock position being much shorter than those at 4 o’clock. When the mainspring broke the shock made the wheel slip against the adjacent pinion until the taller teeth came into contact with it. At this point a leaf on the pinion bent some of the wheel teeth and broke others.  It also bent the leaf of the pinion.

The picture above shows the replacement and original parts.

Movement repair:

If servicing had been done earlier it is probable that most of this work could have been avoided. It included the usual strip down, clean, examine, assemble, lubricate and test procedures and in addition:

 

Repair 1:  The barrel had to be straightened, the lugs reformed and a new boss made and fitted to it.

Repair 2:  I made a new wheel  from brass plate. This involved making a tooth cutter as the teeth were not of the standard flat bottomed type but instead were rounded at the bottom to giver them more strength.  They need this from as the wheel is only 1.6 mm thick. The wheel disc was set up in a dividing head and the teeth cut.  I made annular slots to take the lugs on the barrel.

Repair 3:  I ordered a replacement pinion. Bent pinion leaves can rarely be straightened as the metal is too hard. There are usually cracks running deep into the metal, and this was true in this case, it took little force to crack the leaf out of the pinion. The pinion is of a standard profile and it is more economical for me to order one from a specialist than to do the work myself.

Repair 4:  Rivet the existing intermediate wheel to its pinion.

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