Rotating Shafts and Torques

Torsional moments acting on rotating shafts

A torsional moment or torque acting on a rotating shaft can be expressed as

T = Php 33000 12 / (2 π w)

   = 63057 Php / n                            (1)


T = torque - or moment (lb in)

Php = horsepower (hp)

n = revolution per minute (rpm)

  • 1 hp (English horse power) = 745.7 W
  • 1 lb in = 0.113 Nm

Example - Car Engine Torque vs. Power and RPM

Car acceleration

A car combustion engine deliveres 100 hp at 5000 rpm to the shaft. The torque in the shaft can be calculated as

T = 63057 (100 hp) / (5000 rpm) 

   = 12611 lb in 

   = 143 Nm  

Torque vs. Power and Revolutions Calculator

Power (hp)

Revolution speed (rpm)

Related Topics

  • Mechanics - Forces, acceleration, displacement, vectors, motion, momentum, energy of objects and more

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