THE TURRET CLOCK KEEPER'S HANDBOOK - Horology - The Index

To make the clock gain, raise the pendulum bob.
Turn the nut underneath the pendulum clockwise as viewed from underneath.
or
Turn the nut on top of the pendulum clockwise as viewed from the top.
To make the clock lose, lower the pendulum bob.
Turn the nut underneath the pendulum anti-clockwise as viewed from underneath.
or
Turn the nut on top of the pendulum anti-clockwise as viewed from the top.
Expect a change in time keeping of around half a minute a day to a few minutes for one turn
of the regulating nut.
If the nut is underneath the pendulum first stop the pendulum. Do this carefully as some
pendulums are very heavy (1 Cwt or more). Once the pendulum has stopped make the adjustment
holding the bob so that you do not twist the whole pendulum and damage the suspension spring (the
thin steel strip from which the pendulum hangs). On very heavy bobs it is worthwhile wedging a
wooden block under the bob whilst making an adjustment; this stops the bob moving and saves
your hand in the unlikely event of the suspension spring giving way. If the pendulum has not been
adjusted for years the nut may have rusted and need releasing. A penetrating oil or dismantling
fluid often helps to release seized up parts.
Adjuster
weights
Rate Adjuster on a
Compensation Pendulum
circa 1875
Some clocks, usually late 19th century clocks which have
compensation pendulums, use small weights for fine regulation.
These work by effectively raising the centre of gravity of the
pendulum. Regulation weights are often in the form of large
washers and slip on to one or two vertical rods close to the top of
the pendulum. Sometimes people put a number of odd items on
the top of a pendulum bob to help bring it to time.
To make the clock gain add regulation weights.
To make the clock lose remove regulation weights.
Expect a change in time keeping of a second or so a day
for removing or adding one washer-type weight.
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