Endless Cord-winding Device for Clocks: How It Works, Diagram, Parts and Maintaining Power Explained

Winding without removing the driving load

The main weight hangs from a movable pulley between the winding wheel and the clock’s drive wheel. A second, lighter pulley weight tensions the return part of the endless cord. During running, the winding wheel is held. During winding, it turns to raise the main weight while the drive wheel keeps moving forward.

The expanded front view makes both weight pulleys visible. The cord follows common tangents and wraps around each wheel. Its total length stays fixed as the weights exchange height.

The output torque changes slightly during the demonstration because the inclined support strands change angle. The sequence is prescribed and accelerated; it is not a prediction of clock rate or the duration of a winding operation.

Explore weight, pulley size and net drive torque

The original three controls remain: main mass, return mass as a percentage of the main mass, and drive-wheel pitch diameter. Main mass scales both weights. Return percentage changes the opposing chain-side tension. Diameter scales the complete illustrated geometry and the torque arm.

This is a specific, dimensionally scaled example. The fixed upper centres are about 4.23 drive-wheel diameters apart. The main pulley centre moves from about 2.40 to 3.08 diameters below them, while the return pulley position follows the constant cord length. These proportions are not measurements of a particular clock.

Use strand tension, not the whole suspended weight

The return mass is mc=M p/100. Each lower pulley is supported symmetrically by two strands. If the main-side strands make angle α from vertical, their tension is Tm=Mg/(2 cos α). For the return pulley at angle β, Tc=mcg/(2 cos β).

The live net pull at the drive wheel is Tm−Tc, and its torque is (Tm−Tc)D/2000 N·m when D is entered in millimetres. The return-tension share is 100Tc/Tm percent. This share describes the opposing load; it is not a frictional energy-loss percentage.

For vertical strands only, the torque simplifies to (M−mc)gD/4000. The earlier expression used the complete weight difference directly at the upper wheel and omitted the movable-pulley support factor. The new calculation also includes the strand angles actually shown.

Compare the default weights

At M=4 kg and p=5%, the return mass is 0.20 kg. The two weights exert approximately 39.23 N and 1.96 N. Those forces are shared by the pairs of strands supporting the lower pulleys.

At a 60 mm drive-wheel diameter, the vertical-strand comparison would produce approximately 0.559 N·m. The live result differs because the displayed strands are inclined. Move through the cycle to see their changing direction and the corresponding live torque.

Doubling the main mass while holding its return percentage fixed doubles both strand tensions and the net torque. Doubling the wheel diameter scales this example’s geometry and doubles its torque without changing the direction cosines.

Scope of the calculation

The force balance is quasi-static. Cord and pulley masses, bearing friction, groove traction limits, winding acceleration and escapement demand are omitted. The calculation does not approve a winding force, predict pendulum amplitude or guarantee that a given clock will run.

The displayed wheel and suspended-weight dimensions are an illustrative layout. The entered diameter sets its scale; it does not reconstruct an existing clock from one measurement. For a different routing, the support angles and effective radii must be measured separately.

Unsupported service intervals, universal counterweight settings and historical claims from the earlier article have been removed.

Endless-cord winding questions

Why is the whole main weight not the force on one strand?

Two strands support its movable pulley. Their vertical force components add to the weight.

Why does torque change during the animation?

The support strands change inclination as the pulley weights change height.

Is the return-tension percentage a mechanical efficiency?

No. It compares the opposing return-side tension with the main-side tension.

Does the main weight remain connected during winding?

Yes. The winding wheel changes the cord position while the drive wheel remains loaded.