Enter your clutch's Outer Diameter, Inner Diameter, Friction Coefficient, Maximum Pressure, and Number of Friction Surfaces into this Clutch Torque Capacity Calculator to find your Maximum Torque Capacity, along with the Effective Radius and Total Normal Force — so you know exactly how much torque your clutch can handle before it slips.
Maximum Torque Capacity
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Torque Capacity (ft⋅lb)
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Effective Radius
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Total Normal Force
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Clutch torque capacity is the maximum torque that a clutch can transmit without slipping. It depends on the friction coefficient, applied pressure, disc dimensions, and number of friction surfaces.
Friction coefficients vary by material: organic materials (0.25-0.35), sintered metals (0.35-0.45), and carbon-carbon composites (0.35-0.50). Consult manufacturer specifications for exact values.
Each friction surface contributes to the total torque capacity. A multi-plate clutch with more surfaces can transmit more torque for the same size and pressure compared to a single-plate clutch.
If the applied torque exceeds the clutch capacity, the clutch will slip, causing heat generation, wear, and potential damage. Always ensure adequate safety margin in clutch design.
Higher pressure increases the normal force and thus the torque capacity, but excessive pressure can cause premature wear, heat buildup, and material degradation. Optimal pressure balances performance and longevity.
The effective radius is the mean radius where the friction force acts. It's calculated as 2/3 × (R³ - r³)/(R² - r²) where R is outer radius and r is inner radius.
To convert Newton-meters to foot-pounds, multiply by 0.7376. To convert foot-pounds to Newton-meters, multiply by 1.356. The calculator provides results in both units for convenience.
Typically use a safety factor of 1.5 to 2.5 for clutch applications. Critical applications may require higher factors. Consider operating conditions, duty cycle, and consequences of failure when selecting the safety factor.