Disc Clutch Torque Capacity Calculator (Uniform Wear and Uniform Pressure)
The torque a plate clutch or disc brake can transmit from its friction coefficient, clamping force and lining diameters, for a worn-in and a new lining, with the power and pressures involved.
Results
What this tool does
A new clutch lining presses evenly (uniform pressure) and carries the higher torque, T = μFn(D³ − d³) ÷ 3(D² − d²); after running in, the lining wears faster where it slides faster, and the pressure peaks at the inner edge (uniform wear), giving the lower and safer T = μFn(D + d) ÷ 4. Design with the worn-in figure. Dry friction linings are often around μ = 0.3 and oil-wetted ones around 0.1, but the datasheet value, with a safety margin for glazing and heat, is the one to use. Every pair of surfaces in contact counts: a single-plate clutch has two.
Formula
uniform wear: T = μ F n (D + d) ÷ 4 · uniform pressure: T = μ F n (D³ − d³) ÷ (3 (D² − d²)) · peak pressure = 2F ÷ (π d (D − d))
Variables
| Symbol | Meaning | Unit |
|---|---|---|
mu | Friction coefficient of the lining (μ) | — |
fa | Axial clamping force | N |
d2 | Outer diameter of the friction surface | mm |
d1 | Inner diameter of the friction surface | mm |
nn | Number of friction surfaces | — |
rp | Speed | rpm |
TW | Torque capacity (worn-in, uniform wear) | N·m |
TP | Torque capacity (new, uniform pressure) | N·m |
PW | Power it can carry at that speed (worn-in) | kW |
PA | Average pressure on the lining | MPa |
PX | Peak pressure (worn-in, at the inner edge) | MPa |
Worked example
- Friction coefficient of the lining (μ)0.3
- Axial clamping force2000 N
- Outer diameter of the friction surface200 mm
- Inner diameter of the friction surface120 mm
- Number of friction surfaces2
- Speed1500 rpm
- Torque capacity (worn-in, uniform wear)96.0 N·m
- Torque capacity (new, uniform pressure)98.0 N·m
- Power it can carry at that speed (worn-in)15.08 kW
- Average pressure on the lining0.099 MPa
- Peak pressure (worn-in, at the inner edge)0.133 MPa
Limitations
- Coverage and consumption figures vary between products. Take the values from the manufacturer's datasheet for the product you are actually using.
- The result is an estimate based only on the values you type. Real situations often include factors this calculator does not know about.