This revision uses a documented radial-pin single-revolution clutch topology and limits calculations to declared pin/hole clearance and ideal revolution time.
Radial-Pin Clutch Geometry Explorer
Choose pin diameter, engagement-hole diameter and driver speed. The worksheet reports geometric clearance and ideal one-revolution time without predicting strength, impact or safe operation.
Equation Used
- Pin and hole diameters are declared nominal values.
- Positive C_d is diametral clearance; negative C_d is nominal interference.
- The ideal revolution time assumes constant driver speed.
- The displayed cam and pin sequence is schematic and phase-prescribed.
- Torque, shear, bearing stress, impact, acceleration, wear, tolerances, lubrication and guarding are excluded.
Removes an arbitrary fit-risk score and limits the worksheet to exact nominal clearance and ideal timing identities.
A radial pin couples the hub and output cap
US patent 4,466,520 describes a continuously driven inner hub surrounded by an output cap. A radial pin passes through the cap and can enter a periodically aligned hub opening, coupling the two rotary members. Camming surfaces then extract the pin to complete a single output cycle.
The animation shows this documented topology schematically. It does not predict contact forces, impact or stopping behavior.
Documented single-revolution rotary coupling
The patent identifies sheet feeding and toner dispensing in copier/duplicator equipment as example uses for one output revolution from a rotating input. Earlier US patent 1,131,671 documents the same general cycle logic: release a stop, engage spring-biased clutch members, then use a cam and pin to separate them after one revolution.
This page is an explanatory geometry worksheet, not a machine-control or safeguarding guide.
Declared clearance and ideal cycle time
Hole diameter minus pin diameter is nominal diametral clearance. Half that value is nominal radial clearance. At constant N rpm, one ideal revolution takes 60/N seconds.
These identities do not calculate pin shear, bearing pressure, torque capacity, engagement impact or stopping distance.
A declared geometry example
For a 12.00 mm pin and 12.05 mm hole, diametral clearance is 0.05 mm and radial clearance is 0.025 mm. At 120 rpm, one ideal revolution takes 0.500 seconds.
Those values do not establish a suitable manufactured fit or safe clutch design.
Geometry is not clutch capacity
The former page converted clearance to an arbitrary fit-risk percentage. That score had no sourced threshold model and is removed. Its unsupported torque, material, tolerance, maintenance, repair and application claims are also removed.
A real design needs actual material properties, tolerance stack-up, load spectrum, pin engagement depth, contact geometry, impact dynamics, actuation timing and guarding analysis.
Radial-pin clutch worksheet questions
Does positive clearance mean the clutch is safe?
No. It only means the declared hole diameter exceeds the declared pin diameter.
Does 60/N include acceleration or stopping?
No. It is ideal constant-speed revolution time.
Is the displayed pin motion dynamically solved?
No. It is a prescribed illustration of the patent's engage/cam-out sequence.
Radial-pin clutch references
- US patent 4,466,520: radial pin, surrounding cap, driven hub, aligned openings and single-revolution cam-out sequence.
- US patent 1,131,671: spring engagement, stop pin and automatic cam separation after one revolution.
- US patent 2,787,355: positive single-revolution clutch with a driven member held against rotation when disengaged.
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