400 day clocks with a three or four-ball pendulum have a regulating disc near the top of the pendulum. On Kundo and Schatz clocks, turning the regulating disc clockwise slows down the clock; and turning it counterclockwise speeds up the clock. Some brands of 400 day clock regulate in the opposite direction. The clock usually has labels to tell you which way to turn the disc.
The photos below show typical regulating discs.
An effective way to regulate a 400 day clock is to grasp the pendulum when as comes to a stop at the end of a rotation, hold it in place, turn the regulating disc, then release the pendulum. This a good procedure as long as you are CAREFUL NOT TO YANK DOWN ON THE PENDULUM, AS THE SUSPENSION SPRING IS THIN AND COULD BREAK.
- When the pendulum comes to a stop at the end of a rotation, grasp the pendulum in one hand and hold it stationary. Lift it up slightly to take the pressure off the suspension spring;
- With your other hand turn the regulating disc a small amount (Clockwise for slower, Counterclockwise for faster);
- Release the pendulum, and the clock will start going again.
This procedure is good because it doesn’t disturb the rotation of the pendulum very much, reducing the timekeeping variations caused by the changing the amount of swing of the pendulum. And it doesn’t disturb the pendulum as much as taking it off would.
Video showing the procedure:
For clocks that have a pendulum lock, (such as the Schatz “London Coach” many Kundo clocks), you can lock the pendulum and then turn the regulating disc.
- When the pendulum comes to a stop at the end of a rotation, use the locking lever to lock the pendulum in place;
- Turn the regulating disc a small amount (Clockwise for slower, Counterclockwise for faster);
- Gently unlock the pendulum. The clock should start.
- (If the clock doesn’t start, gently rotate the pendulum 1/2 turn and release it.
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