How to Shorten a Clock Pendulum
A pendulum clock requires periodic maintenance to ensure that it runs smoothly and keeps the correct time. One task involved in maintenance is inspecting and resetting the pendulum. Age, room temperature and time can cause a pendulum to lengthen and cause the clock to run slowly. Even the most minuscule change to the pendulum can cause incorrect timekeeping, so it is important to know how to shorten, or calibrate, the pendulum. Does this Spark an idea?
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Things You'll Need
- Clock or watch with a second hand (a computer clock works well)
- Calculator (optional)
Instructions
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Instructions
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1
Find the adjustable weight, or screw mechanism, near the pendulum arm. On most clocks, it looks like a decorative screw on the pendulum, or bob. Depending on the type of clock, the location of this mechanism is either directly below the pendulum or on the pendulum arm. Newer clocks have a door that opens from the front but if the clock is very old, you may need to gain access from the back.
The mechanisms on some clocks, such as French mantel clocks or grandfather clocks, use a small key in the face of the clock in place of the screw. The keyhole is usually at the 12 or 1 o'clock position and usually displays the initials "f" and "s" on either side of the keyhole. -
2
Stop the pendulum and hold it gently so that it cannot turn as you rotate the screw or key.
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3
Shorten the pendulum by turning the screw mechanism to the right, one-half turn. For keyhole clocks, turn the key in the direction of "f." Small adjustments have a big effect so make sure to keep the one-half turn rule. For example, one complete turn will speed the time on a clock by one-half minute every 24 hours.
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4
Wind the clock fully, restart and check it against your computer clock or watch. If it is obviously running too fast, repeat the process. Otherwise, wait to two or three days and recheck it.
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Tips & Warnings
For math experts, a mathematical equation to calculate the correct length of the pendulum is T = 2 *pi * sqrt (L/g).
Handle a pendulum clock with care. Internal clock mechanisms are delicate and can bend or break easily.
Do not expect a pendulum clock to keep perfect time. A deviance of one to two minutes per week is normal.
