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#1
01-01-2010, 06:54 PM
 Sapo Guest Join Date: Dec 2006 Location: Puerto Rico Posts: 6,786
How many horses in a horse? (HP in a mammal)

If I wanted to picture a horse capable of delivering one HP over a work day, what kind of horse am I looking at? A thoroughbred, a draft horse, a glue factory reject, a non-existent superhorse?

The wiki entry states that the current measure might be more than an actual horse can deliver for any useful length of time.

What would be the actual power rating of the common types of modern horses? Wiki also mentions a peak performance of almost 15 HP from a horse but doesn't go into much detail as to what kind of horse, doing what and for how long?

What's the power output of a racing horse during a race distance (which varies, I know)?

In short, tie the mechanical unit to actual animal performance in any way you can.
#2
01-01-2010, 07:12 PM
 GIGObuster Charter Member Join Date: Jul 2001 Location: Arizona Posts: 27,921
Not sure about the power comparison of the horse types, but here is information mentioning the type of horse used to figure out the original HP, the Draft Horse:

http://www.daigwy.co.uk/torque.htm#history
Quote:
 James Watt set to work devising a way of measuring the amount of Work that his engines could do. The obvious benchmark was the horse, or more specifically the Draft Horse that was the ‘industry standard’ of the time. Using a hoist, he conducted experiments to determine how quickly a Draft Horse could raise a heavy load. He observed that a load of 550 Pounds (nearly ¼ of a ton) could be raised at a rate of 1 foot per second. That’s 550 foot-pounds per second of work done. Multiply by 60 and that is 33,000 foot-pounds per minute of work or 1 Horsepower (1 HP). So - Horsepower is a measure of the engines rate of work i.e. how much work in a given time. The higher the horsepower the more work it can do or the faster it can do it. Simple really.
#3
01-01-2010, 07:19 PM
 Covered_In_Bees! Guest Join Date: Apr 2009 Posts: 4,566
#4
01-03-2010, 12:51 PM
 Sapo Guest Join Date: Dec 2006 Location: Puerto Rico Posts: 6,786
There you go. I knew this had to be covered ground. Will read and come back with further questions if.

Thanks.
#5
01-03-2010, 01:33 PM
 Una Persson Straight Dope Science Advisory Board Join Date: Mar 2000 Posts: 15,989
Nobody ever remembers...
Quote:
 How did we end up with the “horse” in horsepower? The term was coined by James Watt (1736-1819), the British inventor best known for his improved steam engines, who used the term to relate steam engine performance to that of horses. At the time horses were the primary energy source for applications ranging from pumping water from mines and turning grinding mill wheels to pulling carts and loads. Although sources differ on exactly how Watt arrived at the number, it’s generally thought that in 1782, he noted how quickly a brewery horse could turn a mill wheel of a certain radius, estimated the amount of force the horse needed to exert to turn the wheel, did the math, and came up with a value of 32,400 ft-lbf/min, later rounded to 33,000 ft-lbf/min. Comparing the power output of a steam engine to an equivalent number of horses was an easy way for prospective engine purchasers to compare power ratings, so the term stuck. What type of horse was a brewery horse? In England at the time a work horse most likely would have been one of the three British "heavy breeds" – the Suffolk punch, the shire horse, and the Clydesdale. The Clydesdale is said to have originated in the latter 1700s, perhaps too late to be a common work horse at the time Watt was doing his horsepower calculations. So it seems likely the horse in question was either a Suffolk punch or a shire horse.

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