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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 James Watt to help market his improved | 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]. | ||