Why does increased flow make a water wheel change direction

This model, at the Smithsonian Institution, was donated by the University of Illinois physics department in 1974. The wheels are six inches in diameter, and the model is painted green with gold striping.

This undershot water-wheel model was offered for sale at an Ebay auction in October 2000. It is 10 inches high and 14 inches wide. It came from a university collection in the Prague region, and was probably made in Czechoslovakia. Water wheels of this form were not found in catalogues of American makers.

A very similar model is described in the 1929 catalogue of the Chicago Apparatus Company: "Water Motor Outfit, Complete: A reliable motor, fully guaranteed, intended for grinding and polishing. Becomes a most efficient bottle and flask washer by simply attaching a wire handle brush to the end of the spindle. From a laboratory standpoint the design is such that efficiency tests can be made to good advantage. Develops one-eighth horsepower with eight pounds [per square inch] of water pressure. Outfit includes four-inch motor, four-inch beveled face emery wheel; felt buffing wheel and cake of polish for brass, copper and silver; wood pulley grooved for 1/32-inch round belt; and coupling for threaded faucet. Entire outfit is securely backed in near Corrugated box. Weight about six points . $6.25"

The six-inch model produced one-quarter horsepower.


The raised lettering on this large water wheel in the Greenslade Collection read "Divin Water Motor Co./1905/Utica, NY USA"

The Prony Brake consisted of a band of leather passing over a smooth pulley at the back of the apparatus, with the ends of the band supported by spring balances hung from a crossbar on the vertical rod. It was used to obtain the power output of the motor as a function of the input water pressure.

The apparatus is at the University of Vermont,