David Bond Clock Repairs
Transport:
The pendulum bob (weight) must be removed before moving the clock. It is designed for easy removal and unhooks from the pendulum leader. On removal of the bob, the pendulum leader may oscillate and should not be restrained and must not be held against its movement limit. This may damage the escapement and will certainly affect subsequent running.
Once the pendulum bob is removed, the clock may be transported in any orientation, but it is preferable to keep it upright.
It is preferable to attach the bob with the clock in its final position. If this is not possible, place the clock on a piece of paper (to avoid the feet marking the surface), attach the bob and then gently rotate the clock into position with the pendulum at rest and keeping the base level. Then withdraw the paper.
When re-attaching the bob, it is essential that it is fully seated on the hook. A gentle push down on the bob should ensure this. Care should be taken to ensure the rating nut is not moved as this will affect the timekeeping.
Location:
The clock must not be placed on a surface that can move, for example an unattached bookcase on flexing floorboards. A wall shelf or similar is by far the best option.
The surface should be level and flat. It is important to get side-to-side levelling as accurate as possible – use a spirit level. Front to back levelling is less critical but make it as level as reasonably possible. Consider using paper shims to level the clock.
There must be no detectable wobble - this will take energy away from the pendulum and may ultimately stop the clock. Any wobble will certainly affect timekeeping.
Avoid locations subject to extremes of temperature or prolonged periods of direct sunlight.
Winding:
The clock should not be allowed to move during winding, care must be taken as quite a high force is necessary to wind fully.
There are two spring barrels which have to be wound; the left one powers the strike operation right one powers the timekeeping part of the movement.
The barrels should be wound once per week. Although they can be wound more frequently, once per week will give the best timekeeping consistency. Most clocks will actually run for ten days or more before stopping.
Try not to let the clock run down, but if it does, before doing anything, the strike should be fully wound . Then allow the chime strike to complete before advancing the minute hand to the correct time. Stop if you feel any restriction other than the normal hands setting friction.
Rather than letting the clock run down, consider stopping the pendulum if you will be unable to wind the clock for more than a week.
If it is anticipated that it will not be possible to keep it wound, the left barrel should be fully wound and the right allowed to run down first. Alternatively, stop the clock.
It is impossible to overwind the spring barrels – when winding, the key will come to a very obvious stop.
Starting the clock:
The clock may be started by gently nudging the pendulum bob. It is essential to only use enough movement to start it ticking and not to move the pendulum to its limit.
Another method is to gently slide the clock to one side (keeping it level - don't lift) sufficient to set the pendulum swinging. Once you hear a tick, it should be self sustaining.
Setting the time:
Use only the minute hand for adjusting the time.
Never move the minute hand backwards by more than 5 minutes, and do not move it backwards at all within 5 minutes either side of the hour or half-hour.
Move the minute hand slowly to allow the strike mechanism to work.
When adjusting the time, the strike train (left winding square) should be fully wound.
When advancing the hand through the hour or half-hour, allow the strike to complete each time.
For the Autumn time change (clocks go back), stop the pendulum for more than the hour so that you can then advance the minute hand to the correct time. Remember to let the strike complete on each hour and half-hour.
Regulating the time:
The clock is a self-contained mechanical system and is therefore subject to external influences. Temperature, barometric pressure, vibrations, location (latitude and height) can all affect the timekeeping.
If the clock has just been repaired, it will have been regulated over several weeks such that it will keep reasonably good time aggregated over the week-long winding period. Within the week, there may be variations. Typically, a spring driven clock will gain for the first part of the week and lose for the last two or three days.
If it is felt that the clock is subject to a permanent change such that there is a consistent change in rate, the gain or loss can be reduced by adjusting the rating nut on the pendulum rod. Looking down from the top of the clock, turning the nut anti-clockwise will cause the clock to run faster (turning the nut in this direction has the effect of shortening the pendulum). It is very sensitive and only tiny individual adjustments should be attempted – no more than 1/16th of a turn. As a very rough guide, 1/16th turn will change the rate by about 10 seconds per day.
After making an adjustment, the clock should be left for another winding cycle before making a further adjustment. It is essential not to “chase the rate” as the clock will take a day or more to settle to the new adjustment.
For more specific regulation, if the clock has been serviced by me, there will be a copy of the "Train Count" and this will include a figure indicating the number of degrees to turn the rating nut for a given correction in terms of seconds per day (S/D). For example, assume the figure is 233 S/D. Also, say the clock loses a total of 40 seconds over the week. First calculate the daily error, which in this case is 40/7=5.7 S/D. Then divide that figure by the provided correction value (233) and multiply it by 360. That will then be the number of degrees to turn the rating nut. So, 5.7/233 x 360 = 9degrees (a very small amount).
On some clocks not all the instructions are strictly necessary, but if you follow them, you are guaranteed not to hurt your clock.
Two-Train pendulum Mantel Clocks