horse power (machine)

A horse power (also rendered horse-power) is a now largely-obsolete machine for using draft horses to power other machinery. It is a type of animal engine somewhat more sophisticated than a horse mill. A common design for the horse power was a large treadmill on which one or more horses walked. The surface of the treadmill was made of wooden slats linked like a chain. Rotary motion from the treadmill was first passed to a planetary gear system, and then to a shaft or pulley that could be coupled to another machine.
See more at Wikipedia.org...