FAQ #193
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BHP Brake Horse Power
What is "Horsepower" or HP?

Lets start at the dawn of time - or at least the beginning of mechanical devices. Any "engine" was obviously going to be compared to the ability of the then main power sources to do labour - horses, men and oxen. As most of the devices were used drive industrial equipment the natural comparison was therefore the 2/1 Favourite at Ascot. So, even the pioneers of the time realised that marketing of the new fangled machin'rey was important so they likened the power of their devices to a certain number of horses.

Moving on from this early start, a famous engineer called Captain Thomas Savoury reasoned that if it took eight to ten horses to operate a mine pump 24 hours a day (two horse working at a time with the next pair taking over when the last two became tired), then a mechanical device that did the same job in the same time had 10 - 12 hp! You can move on through history with this through the likes of James Watt but you are not here for a history lesson!

So what is "brake" Horsepower or BHP

Well simply this is power that has been measured on a brake or normally known now as a Dynamometer. This device provides a load for the engine to "drive" against and then measures the torque produced by the engine, which if it is then multiplied this by crankshaft revolutions per minute and adjusted with the standard figure, it provides a horsepower figure.
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FAQ Posted by Dave-Retired
Info Created: 07 October 2009
Last Updated: 07 October 2009