by Facia Nearside
We brag about it, we compare it, our cars all have it, and usually we are looking for more of it. What? Horsepower. But what does it really mean? Horse power has been around for a very long time, but not until it was no longer provided by horses did it become the subject of discussion.

Thomas Newcomen invented the ?rst practical steam engine, and by 1750 early adopters were using them all over Britain. In 1781 James Watt, a Scottish mechanical engineer, was tasked to repair a Newcomen engine and immediately recognized its’ inef?ciency. He made improvements which doubled that ef?ciency, allowing it to use only half as much coal. But how to quantify this improvement to inform potential buyers was a dilemma.

Initially Watt took royalties on the coal saved by his engines compared to the Newcomen engines. But this system did not work for potential customers who were still using horses for power. When one of Watt’s customers ordered an engine that could do the work of his strongest horse, Watt recognized the solution. He determined a horse could turn a 12-foot mill wheel 144 times an hour pulling with a force of 180 pounds. Using those ?gures he calculated the amount of work being done, and in 1783 this ?gure was standardized as 33,000 foot-pound’s/minute, equal to one horsepower. One hundred years later, in 1882, the British Association for the Advancement of Science honored James Watt by adopting the “watt” as the name of the unit for measuring power.

Today there are many standards and types of horsepower, but the most common is that of mechanical horsepower which is de?ned as 745.7 watts. But no matter how you rate it or try to quantify it, the horse is still out of a job.

Reprinted from British Boots & Bonnets Chronicle — November 2018 issue.