A friction pin clutch combines pin engagement with a friction band. In Hiscox’s figure 1313, the band can slip as the pins engage, cushioning the transfer of motion between two aligned shafts. Either shaft can provide the drive. The animation shows the pins engaged and illustrates where relative slip can occur.
Friction Pin Clutch Interactive Calculator
Set total normal contact force at the band, friction coefficient, effective drum radius and torque demand. The drawing is a simplified end view with a separate band-contact detail. Rotation is illustrative; no shaft-speed input is required.
Equation Used
N_total is the sum of normal contact-force magnitudes around the band, not an axial engagement force or a spring setting. The effective drum radius r is in meters in the equation. A uniform coefficient and one contact radius are assumed. The model does not calculate band tension, engagement impact, slip speed or heat. A dash for capacity/demand means zero torque demand.
Pins engage; the band cushions the drive
The historical arrangement couples two shafts on the same axis. Engagement pins transfer motion to a friction band around the mating member. The band provides a frictional connection rather than a completely rigid one. Hiscox explains that its slip reduces the shock when the pins engage.
The end-view animation separates the three roles by color: blue arms and pins provide the input, the gold band receives their motion, and the green drum represents the output. The two visible pins are drawn already engaged with band lugs. The view is a simplified explanation of the torque path, not a dimensioned reproduction of the original hardware.
When demand is at or below the calculated limit, all three members turn together. Above it, the pins and band continue together while the drum turns more slowly. This slower drum speed is chosen only to make the sliding visible. It is not calculated from inertia or load. The enlarged contact detail shows the same difference in tangential movement.
Changing radius changes the dimension used by the calculator; the drawing stays at a readable schematic size. Total normal force and coefficient change the friction limit. The illustration does not animate axial pin insertion, establish an engagement sequence or model the historical band-tightening linkage.
Connecting a drive without a rigid engagement shock
The purpose of this arrangement is to combine a pin connection with a yielding friction interface. A rigid pin coupling can transmit an abrupt change in motion; the additional band allows relative sliding during that transfer.
The drawing explains that principle. It does not establish the clutch’s suitability for a particular press, conveyor or motor, and a friction band alone does not guarantee reliable overload protection. A practical coupling must be evaluated for its load, speed, engagement energy and duty.
An idealized band-contact torque limit
At a small contact patch, a normal force magnitude dN gives an ideal friction-force limit μ dN. If all patches share the same coefficient and drum radius r, their limiting torques add to T_limit = μ r ∫dN = μ N_total r. Here N_total is a scalar sum of normal forces; it is not the vector resultant around the drum.
The calculator also displays F_t = μ N_total. For positive torque demand T, capacity/demand is T_limit/T. Excess demand is 100 × max(0, T − T_limit)/T_limit. A ratio above one means demand is below this ideal threshold; it is not a certified safety factor. With zero demand the ratio is undefined and displays a dash.
For a flexible band, tight-side and slack-side tensions, wrap angle and friction determine its loading. The familiar band relation T_tight/T_slack = e^(μθ) applies at impending slip under its own assumptions. Shaft torque is (T_tight − T_slack)r. Those tensions and wrap angle are not inputs here, so this tool cannot convert a screw adjustment or spring preload into N_total.
Example: a 50 mm effective drum radius
With N_total = 2,500 N, μ = 0.15 and r = 50 mm = 0.050 m, the tangential force limit is 375 N and torque limit is 18.75 N·m. For a 15 N·m demand, capacity/demand is 1.25 and excess demand is zero.
Changing demand to 25 N·m leaves the friction limit unchanged. Capacity/demand becomes 0.75, and demand exceeds the limit by 33.3%. Halving μ to 0.075 would halve the theoretical limit if the same normal contact load were maintained; the control permits increments of 0.01.
The controls span ideal torque limits from 0.09 to 300 N·m. These are arithmetic bounds, not ratings for the illustrated coupling. The calculator does not specify pin dimensions, band thickness, tightening torque or a spring.
What determines actual engagement behavior
Relative sliding converts mechanical energy into heat. During slip, frictional power is transmitted torque multiplied by the difference in angular speeds. Estimating temperature also requires slip duration, material properties and heat removal. None is determined by the torque threshold alone.
Actual friction changes with surface condition, lubrication, wear and temperature. Static and sliding coefficients may differ. Pin loading and impact depend on geometry, clearances and the speeds before engagement. These effects need the particular clutch’s design information; the animation supplies no universal service interval, slip-speed rating or adjustment procedure.
Frequently asked questions
Where does this clutch slip?
At the friction band and its mating drum. The pins engage the band mechanically, and the band can move relative to the drum when its friction limit is reached.
Can either shaft drive?
Hiscox describes either shaft as a possible driving shaft. The animation chooses the pin carrier as its input to make the torque path easy to follow.
Is total normal force the spring preload?
No. It is the sum of normal contact forces at the band. Determining it from an adjustment or spring requires the actual tightening geometry and band loading.
Is the entered radius the pin radius?
No. It is the effective radius where the band acts on the drum. The engagement pins lie outside that surface in the simplified end view.
Does an overloaded output always keep turning?
No. Its actual speed depends on the load and dynamics and can fall to zero. The animation uses a slower nonzero speed only to illustrate relative slip.
Why does the capacity ratio show a dash at zero demand?
Capacity divided by zero demand is not a finite ratio. Torque capacity and tangential force are still calculated.
Can the result certify overload protection?
No. It is an ideal contact-force calculation. Engagement impact, friction variation, heat and component strength are not evaluated.
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