Formulas for Calculating Load Torque

2026/05/07

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Torque (T) when an external force is applied to a rotating body




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D: Drum diameter [m]
F: External force [N]

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Torque (T) due to friction and external forces on the lead screw: T

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P: Lead of the lead screw [m]
M: Mass of the load [kg]
g: Acceleration due to gravity [m/s²]
μ: Coefficient of friction of
the lead screw F: External force [N]

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(Typically, μ: approximately 0.05 to 0.2)






Torque (T) due to friction and external forces in a rack-and-pinion system: T

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D: Pinion diameter [m]
M: Load mass [kg]
g: Acceleration due to gravity [m/s²]
μ: Friction coefficient of the
rack-and-pinion F: External force [N]

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(Typically, μ: approximately 0.08 to 0.1)






Torque caused by friction and external forces on a conveyor belt: T

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D: Roller diameter [m]
M: Load mass [kg]
g: Acceleration due to gravity [m/s²]
μ: Coefficient of friction of
the conveyor F: External force [N]

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(Typically, μ: approximately 0.05 to 0.1)






Torque (motor shaft equivalent): To

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Z1: Number of teeth on the motor-side gear
Z2: Number of teeth on the load-side gear
R: Reduction ratio (Z2/Z1)
η: Transmission efficiency (%) / 100
T: Load-side torque [N·m]

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*Please note that the values of the coefficient of friction (μ) vary depending on factors such as the machine’s machining accuracy and lubrication conditions; therefore, please exercise caution when calculating the load torque.

*The transmission efficiency (η) between the motor and the load varies depending on the type of connection, but generally follows the values below: Spur gears: 0.85 Chains: 0.9 V-belts: 0.9



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