Early Dynamometers (from Muscle to Steam Power)
Spring balances, based on Hooke’s law, have been used for weighing since the early 18th century. At the end of the century, naturalists such as Buffon felt the need to quantify the muscular force of men (humans) and animals. The first practical, portable “dynamometer” was designed in 1798 by Regnier, in Paris, using for the first time an oval, closed spring and displaying the indication of the maximum force, tension (“loins”) or compression (“hand”). It was promptly used by ethnologists to test the strength of “savages”. A smaller improved model (Mathieu/Collin dynamometer) is still manufactured today and sold to medical and para-medical practitioners. Used for measuring the rolling resistance of horse-driven wagons, the Regnier device is an example of a transmission dynamometer. Since the early 19th century, the development of agricultural and industrial machinery resulted in the need to measure not only the force between the motor and the load, but also the work done and the delivered power. The name “dynamometer” came to be applied not only to force-measuring devices, but also to work-measuring ones (actually, they should have been called “ergometers”). Inventors and mechanics competed to combine heavy force-measuring machinery with newly invented delicate, precise graphic-recording apparatus and/or integrators and planimeters. Focusing on transmission dynamometers, I will examine a few examples of either linear-motion ones or rotary-motion ones, as well as on the totalizing/integrating devices connected to them.