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→History of the term "horsepower"
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== History of the term "horsepower" == | == History of the term "horsepower" == | ||
The term "horsepower" was invented by | The term "horsepower" was invented by James Watt to help market his improved [[steam engine]]. He had previously agreed to take royalties of one third of the savings in coal from the older Newcomen steam engines[http://www.pballew.net/arithm17.html]. This royalty scheme did not work with customers who did not have existing steam engines but used horses instead. Watt determined that a horse could turn a mill wheel 144 times in an hour (or 2.4 times a minute). The wheel was 12 feet in radius, thus in a minute the horse travelled 2.4 × 2π × 12 feet. Watt judged that the horse could pull with a [[force]] of 180 pounds (just assuming that the measurements of mass were equivalent to measurements of force in pounds-force, which were not well-defined units at the time). So: | ||
:<math> power = \frac{work}{time} = \frac{force \times distance}{time} = \frac{(180 \mbox{ lbf})(2.4 \times 2 \pi \times 12 \mbox{ ft})}{1\ \mbox{min}}=32,572 \frac{\mbox{ft} \cdot \mbox{lbf}}{\mbox{min}}</math> | :<math> power = \frac{work}{time} = \frac{force \times distance}{time} = \frac{(180 \mbox{ lbf})(2.4 \times 2 \pi \times 12 \mbox{ ft})}{1\ \mbox{min}}=32,572 \frac{\mbox{ft} \cdot \mbox{lbf}}{\mbox{min}}</math> | ||
This was rounded to an even 33,000 ft·lbf/min[http://sections.asme.org/Philadelphia/sept02.htm]. | This was rounded to an even 33,000 ft·lbf/min[http://sections.asme.org/Philadelphia/sept02.htm]. | ||