I enjoyed the history of the Gaspar de Prony brake and Doug Wise’s demonstration machine (Farm Collector, January 2008, page 22). I made a dynamometer to test 3 hp engines for my small engines class. To measure torque, I used an auto rear brake assembly, a master cylinder and a 500-pound spring scale. To measure speed, a small engine tachometer was used. The brake was stronger than the engine, so the shoes had to be greased often.
From the test data, students graphed the torque and horsepower curves. Since horsepower has many faces, we discussed engine design for specific purposes from racing motorcycles to industrial diesels. Handy also was a tractor dynamometer and a John Deere H tractor. Gaspar is the name; De (of) Prony is the place where Gaspar resided.
–Robert Ramsay
Longmont, CO
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