An electric clock winder uses a motor to supply the rotation otherwise provided by a winding key. This page illustrates a gearmotor driving a square arbor through a spring-loaded friction clutch. The calculator compares a chosen torque threshold with a reference torque and an entered winding demand.
Electric Winding Device Interactive Calculator
Compare a chosen clutch torque with a reference and winding demand. Watch the separate input and output members turn together or slip while retaining the original torque calculator.
Equation Used
- Ideal constant torque demand.
- Friction clutch transmits up to the chosen threshold.
- Output held when demand exceeds threshold.
- Illustrative rotation speed; clock train omitted.
Reference torque and percentage are user-selected comparisons, not verified safety or adjustment settings.
Follow the shafts through the clutch
The blue input shaft ends at the input flange. A friction lining contacts the gold output plate, which connects to the winding arbor. A compression spring supplies axial preload. The bearing and mounting foot stay fixed while the shafts rotate.
The two end views show the motion that is difficult to see in the longitudinal section. When demand is below the chosen threshold, input and output markers turn together. When demand exceeds it, the input continues turning against a held output and the faces slip. A slipping friction clutch still transmits torque; it is not the same as complete disengagement.
The clock train and its holding click are beyond the square arbor and are omitted. No mainspring turns or run time are inferred from this torque comparison. The diagram is a generic arrangement, not a drawing of the cited patent or a particular commercial product.
A comparison for motorized winding
The useful question here is whether an entered torque demand lies above or below a selected clutch threshold. Both original controls remain, and the added demand control lets the animation demonstrate those two operating conditions.
Clock winders can use other arrangements, including spring clutches and mechanisms which switch or stop the motor. The cited clock patent describes a distinct motor-driven winding system whose clutch permits relative motion after its winding limit. It is a historical example, not evidence for a universal torque setting.
Torque comparison
For reference torque T and selected percentage L, the chosen clutch threshold is Tc=T·L/100. The numerical difference is T−Tc, and the remaining reference fraction is 100−L percent.
The illustration compares demand Td with Tc. Its ideal transmitted torque is the smaller of Td and Tc. Below the threshold the prescribed shafts move together; above it the output is held while the input slips. At equality the real transition depends on clutch behavior, which is not modeled.
These inputs do not establish a safe torque, a physical preload setting, motor speed, frictional heating or spring energy. Display speed is chosen for readability. Changing demand affects the scene and its transmitted-torque readout, while the four original threshold-comparison results remain independent of demand.
Default comparison
A 400 mN·m reference and a selected 60% threshold give Tc=240 mN·m. The difference is 160 mN·m, or 40% of the reference. With 180 mN·m demand, the illustrated shafts are coupled and transmit that demand.
Raising demand to 300 mN·m changes the illustration to slip. The ideal transmitted torque remains 240 mN·m while the motor-side member turns relative to the held output. This does not establish that the real clutch can tolerate continuous slipping.
What the comparison leaves open
The reference torque is entered, not verified. A selected percentage cannot establish that a mainspring, gear train or arbor is protected. The earlier universal percentage settings, wear-life predictions, alleged field-return experience and named installation anecdotes have been removed.
Real friction clutches have specified torque, speed and thermal limits. The preload spring shown here explains the contact force, but its compression is not a calculated adjustment instruction. Motor shutoff, clock holding arrangements and the actual winding mechanism require their own evaluation.
Electric winding questions
Does the percentage specify a recommended clutch setting?
No. It is a user-selected comparison fraction.
Why does the input keep turning when the output stops?
The illustration shows a held load above the ideal friction-clutch threshold. The faces slip while still transmitting that threshold torque.
Why do the original four results not change with demand?
They describe the chosen threshold relative to the reference. Demand changes the operating comparison and transmitted-torque readout in the animation.
Does the animation predict winding time?
No. Motor speed, gearing and spring torque versus turns are not entered.
References
- US2933882A: Motor clock provided with a spring automatically wound — a historical motor winding and clutch arrangement.
- Mayr: ROBA slip hub — frictionally connected torque limiting and limits on slipping operation; not a product selection for this example.
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