Prony Brake Measuring Steam Engine Horsepower - Mt Hope Show

Uncut video of a historic Prony Brake measuring the horsepower of 2 different sizes of Baker Uniflow steam traction engines.

This Prony Brake was built by A. D. Baker Company for use in testing engines prior to shipment. It is built around a standard Baker flywheel, a platform scale, and various pieces of iron and wood. It was donated to National Threshers Association of Wauseon, Ohio by A. D. Baker himself, who was one of the founders of N. T. A.

The lever arm and platform scale give a precise measurement of torque in foot-pounds, and the tachometer provides RPM, to allow computing true horsepower. The balance scale is inherently accurate, and extensive work has been done to calibrate the tach. The brake is lubricated with animal fat, and water cooled.

It is typical for engines like these to significantly exceed their rated horsepower, that is the honest way things used to be. The 21-75 was recently completely rebuilt, and the piston rings are probably not fully seated yet. The owner has observed that each time the engine is operated, power increases, and it runs smoother.

The 43.7 HP on the board was posted by the 1 year old "nominal" 6 HP Advance.

The 23-90 finished at 110.7, but had more to give.

Mount Hope Steam Show
Mount Hope, Ohio
August 1, 2015

#506
150801d Prony Mt Hope