Jeamar Winches Product Catalog

Mechanical Engineering Formulae

Power and Torque Imperial Standards

Horsepower (HP)
Common unit of mechanical power, one HP is the rate of work required to raise 33,000 pounds one foot in one minute.

HP		F x x 2R x RPM
	=	-----------------------
		33000 x12
or
		F x R x RPM
HP	=	-----------------------
		63025
or
		torque x RPM
HP	=	-----------------------
		63025

One Imperial Horsepower Equals
33,000 foot pounds per minute.
36 inch pounds torque at 1750 RPM.
.746 Kilowatts.
1.014 Metric Horsepower. (PS)
42.4 BTU per Minute.

Torque (T)
Torque is a twisting force. Torque causes rotation of a shaft, or it will set up a twist in a stationary shaft. It is generally expressed in foot pounds or in inch pounds. Torque is measured by the load or pull and by the distance of the pull from the center of a shaft.

Calculation Examples
A cable wrapped around a 6" dia. drum must lift 2500 pounds weight. The drum rotates at 30 RPM.

To calculate HP:

To calculate T:

Metric (SI) Standards

Power (P)
The basic unit power measrement in the metric (SI) system is the Watt.
1000 Watts = 1 Kilowatt (KW)

Constant g = acceleration of free fall 9.81 m/s²
V = velocity in metrics/sec.

V		d • RPM
	=	-----------------------
		60

Torque (M)
Torque is a twisting force. Torque causes rotation of a shaft, or it will set up a twist in a stationary shaft. It is generally expressed in Newton-Meters.

SI Symbols
M = Torque
N = Newton
m = Meter
P = Power in Kilowatts
Kgfm = Kilogram force meter
N - m = Torque Newton-Meters
• = Multiplication

Calculation Examples
A cable wrapped around a .5 meter dia. drum must lift 5000 kilograms weight. The drum rotates 50 RPM.

To calculate P:
Power in Kilowatts

		W • g • V
P	=	--------------
		1000
			.5 • 50
			-----------
		5000 • 9.81 •	60
P	=	-----------------------------
		1000
P	=	64.2 kilowatts

To calculate M:
Torque in Newton-Meters