Physics Photo of the Week

September 24, 2010

Horsepower Treadmill
Farms of the 19th century needed much power to run mechanical equipment - saws, churns, hay packing grinders, threshing in addition to work in the fields.  Horses were plentiful and versatile; gasoline engines and tractors hadn't yet been developed, and steam engines were too expensive for small family farms.  This is a treadmill powered by a horse walking in the "box" on an inclined conveyor.  This unit powered a reciprocating crosscut saw used to saw cordwood for heating fuel and is part of the extensive collection of antique farm equipment by Fred Webster of Coventry, Vermont.

At right is another treadmill with owner and collector Fred Webster.  The well-worn  wooden treads on the conveyor that the horse walks on are clearly visible.  I was lucky to have a tour led by Fred of his exensive collection of antique farm equipment.  About six of us visiting people got into a horsepower treadmill and were able to power it - an interesting experience.

Fred Webster's mission in collecting these antiques is to document the technological progress of farming equipment. Horse "sweeps" soon replaced treadmills as more practical and more efficient.  A sweep consists of a long rod attached to a gear box.  A horse (or team) is hitched to the sweep rod and walks in a circle driving the gear box that drives a
shaft to power stationary machinery such as a threshing machine, hay press, or lift equipment.  In the photo at left, the drive shaft can barely be seen - it resembles a pipe in the upper center of the photograph pointing away from the gears.

Animal powered machinery has been used for centuries.  In the development of steam power in the 18th century, the horse became the "standard" unit of power.  With similar devices as these machines, James Watt was able to measure that a typical horse could hoist a 100 lb load a distance of 330 feet in one minute (33,000 ft-lbs/minute = 746 Watts).  See PPOW on horsepower for September 18, 2009

Physics Photo of the Week is published weekly during the academic year on Fridays by the Warren Wilson College Physics Department.  These photos feature an interesting phenomena in the world around us.  Students, faculty, and others are invited to submit digital (or film) photographs for publication and explanation.  Atmospheric phenomena are especially welcome.  Please send any photos to

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