Big Three road tests

buddyIam wrote:
The 5252 number is not exact. It's just a number that is used in all HP calculations. It was a steam engine salesman's pitch to sell steam engines. :D

Okay, I'll take the bait. You keep throwing that out like mentioning it enough will make it correct.

One horsepower is standardized at 33,000 lb?ft/min. It was base by Mr Watt on what he perceived one individual horse could do. That horse is long dead and beating it won't make it stand up and prove whether he had that much power or not. It's not the only standard we use based on an inexact measurement. The inch was the length of three barleycorns. Our railroad gauge is based on the rear of other long-deceased horses.

As you mentioned power is a function of torque times speed. Since we measure torque in lb-ft we need to get speed in a dimensionless (other than time) unit. To do this we understand that the circumference of any circle is 2xpixradius. A radian is the length of an arc divided by the radius of that arc. This means there are 2xpi radians in a full revolution. So 33,000 lb-ft/min and divide it by 2xpi (6.283) radians/min you get the constant 5252 which is used to convert lb-?ft-rev/min to HP.

Now we all know that a horse can only run so fast and harnessing a bunch of them together won't make them go any faster. But if you want to haul a loaded hay wagon to the top of a hill adding horses helps. :)

(The math is much easier for a linear calculation where force = mass times acceleration. Work is force times distance and power is work divided by time.)