what-does-horsepower-actually-mean
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05-27-2018, 12:04 PM
#5
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Power is energy per unit time, whether measured in horsepower, watts, foot-pounds per second, newton-meters per second, or some other units.
An engine converts the fuel's chemical energy into mechanical energy and this mechanical energy is used to increase the kinetic energy of the vehicle, which is equal of one-half the vehicle's mass times velocity squared.
So the more power you apply, the faster the vehicle gains kinetic energy.
James Watt in the late eighteenth century did time and motion studies of horses that drove capstans to power pumps that removed water from English coal mines, usually two or four, and determined that an average horse used in this application produced power equal to 550 foot-pounds per second.
Thus the definition of one horsepower.
Duke
An engine converts the fuel's chemical energy into mechanical energy and this mechanical energy is used to increase the kinetic energy of the vehicle, which is equal of one-half the vehicle's mass times velocity squared.
So the more power you apply, the faster the vehicle gains kinetic energy.
James Watt in the late eighteenth century did time and motion studies of horses that drove capstans to power pumps that removed water from English coal mines, usually two or four, and determined that an average horse used in this application produced power equal to 550 foot-pounds per second.
Thus the definition of one horsepower.
Duke
Last edited by SWCDuke; 05-27-2018 at 12:35 PM.
05-27-2018, 03:33 PM
#6
I'm sure this is not complete but what comes to my mind for a defination of one horsepower is "time over work consumed".
I have no idea where I read this, it's got something to do with what Duke referred to in his post about the horse.
I have no idea where I read this, it's got something to do with what Duke referred to in his post about the horse.
05-27-2018, 11:01 PM
#7
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No, it's work per unit time, and work is force times distance. (Work and energy are the same thing.)
Engine torque is a force applied in a circle, say of one foot radius, so the distance covered for the complete revolution is 2pi(1) = 6.2832 feet.
Say the force is 300 pounds and the engine speed is 6000 revs/min, which means one revolution takes .01 seconds.
So we have a 300 pound force exerted at one foot from the axis of rotation over 6.2832 feet in .01 second.
Power = 300(6.3832)/.01 =188495 foot-pounds per second.
Divide by 550 and the answer rounded to three digits is 342 horsepower.
Since we usually use minutes rather than seconds for the period, which is the inverse of revolutions, the formula boils down to:
Horsepower = torque in lb-ft times RPM/5252.
550 ft-lb per second = 33000 ft-lb per minute, and 33000/6.2832 = 5252.
Duke
Engine torque is a force applied in a circle, say of one foot radius, so the distance covered for the complete revolution is 2pi(1) = 6.2832 feet.
Say the force is 300 pounds and the engine speed is 6000 revs/min, which means one revolution takes .01 seconds.
So we have a 300 pound force exerted at one foot from the axis of rotation over 6.2832 feet in .01 second.
Power = 300(6.3832)/.01 =188495 foot-pounds per second.
Divide by 550 and the answer rounded to three digits is 342 horsepower.
Since we usually use minutes rather than seconds for the period, which is the inverse of revolutions, the formula boils down to:
Horsepower = torque in lb-ft times RPM/5252.
550 ft-lb per second = 33000 ft-lb per minute, and 33000/6.2832 = 5252.
Duke
Last edited by SWCDuke; 05-28-2018 at 10:49 AM.
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05-28-2018, 12:22 PM
#8
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