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A drum motor, also referred to as a motorized pulley, is a highly efficient motor drive which has been encased with a metal shell. They are typically seen in conveyor belts of all kinds, including airport X-ray machines, supermarket checkout terminals, and food processing conveyor belts. In all of these instances, multiple drum motors are installed beneath the surface of the belts, helping to pull the belts along. These motors work by transferring the torque from the engine through the gearbox and into the drum shell. This causes the device to turn, producing the desired motion.
Completely enclosed by its metal shell, a drum motor can operate in a wide variety of conditions. Dust usually cannot penetrate a drum motor, nor can chemicals or high pressure water streams, making them adaptable to a large scale of potentially hazardous conditions. They can function in temperatures ranging from -40°F (-40°C) to over 122°F (50°C), making them suitable for a large number of different climates. Additionally, they can be installed either horizontally or vertically without compromising their functionally, further increasing their usefulness.
The outer drum shell of a drum motor is typically constructed from either steel, aluminum, or stainless steel. Additionally, the casing itself is typically crowned in order to produce smooth tracking of the central belt in the gear. This means that the casing is notched slightly, like a crown sitting on its side, providing a more consistent operation of the device.
During operation of any mechanical or electrical device, some of the power generated will be lost to friction and other cannibalistic forces as the original signal makes its way through the drive train. This loss of power is quite natural, occurring in all types of engines. Drum motors use helical or planetary gears — gear structures which provide little loss through friction — allowing them to operate at around 95% efficiency in many cases. Only about 5% of the motor's output fails to actually power the device connected to the motor.