Horsepower, TorqueHorsepower, Torque

WORK, Force and DistanceWORK, Force and Distance

Understanding HorsepowerUnderstanding Horsepower

What is HorsepowerWhat is Horsepower

Horsepower is a unit of power Horsepower is a unit of power for measuring the rate at which for measuring the rate at which a device can perform a device can perform mechanical work. Its mechanical work. Its abbreviation is hp or bhp (for abbreviation is hp or bhp (for brake horse power). One brake horse power). One horsepower was defined as the horsepower was defined as the amount of power needed to lift amount of power needed to lift 33,000 pounds one foot in one 33,000 pounds one foot in one minute. minute.

Horsepower was defined by James Horsepower was defined by James Watt (1736-1819), the inventor of the Watt (1736-1819), the inventor of the steam engine, who determined after steam engine, who determined after careful measurements that a horse is careful measurements that a horse is typically capable of a power rate of typically capable of a power rate of 550 foot-pounds per second. 550 foot-pounds per second.

Today the Today the SISI (International System (International System of Units)of Units) unit of power is named for unit of power is named for Watt, and one horsepower is equal Watt, and one horsepower is equal to approximately 745.6999 to approximately 745.6999 wattswatts. .

Work = force x distanceWork = force x distance

Work: the result of applying Work: the result of applying forceforce

Force: is a measurement in Force: is a measurement in poundspounds

Distance: is measured in feetDistance: is measured in feet1.1. Work is defined as a force Work is defined as a force

acting through a distance. acting through a distance. Work is done only when a Work is done only when a force moves an object. force moves an object.

WORK = FORCE x DISTANCEWORK = FORCE x DISTANCE

No work is done by a force No work is done by a force unless the force moves through unless the force moves through a distance. a distance.

force = 20 poundsforce = 20 pounds Distance = 50 feet Distance = 50 feet Work = 1000 ft lbsWork = 1000 ft lbs

Calculating HorsepowerCalculating Horsepower

Magic Formula for calculating Magic Formula for calculating HorsepowerHorsepower

Horsepower = Torque x RPM Horsepower = Torque x RPM Divided by 5,252 Divided by 5,252

5,252 is called a constant 5,252 is called a constant Horsepower: direction of motion Horsepower: direction of motion

is in a straight lineis in a straight line Torque: is related to rotationTorque: is related to rotation RPM: revolutions per minute RPM: revolutions per minute

Horsepower explainedHorsepower explained

OK. Remember Watt? He said that 33,000 foot pounds of OK. Remember Watt? He said that 33,000 foot pounds of work per minute was equivalent to one horsepower. If we work per minute was equivalent to one horsepower. If we divide the 6.2832 foot pounds of work we've done per divide the 6.2832 foot pounds of work we've done per revolution of that weight into 33,000 foot pounds, we revolution of that weight into 33,000 foot pounds, we come up with the fact that one foot pound of torque at come up with the fact that one foot pound of torque at 5252 rpm is equal to 33,000 foot pounds per minute of 5252 rpm is equal to 33,000 foot pounds per minute of work, and is the equivalent of one horsepower. If we only work, and is the equivalent of one horsepower. If we only move that weight at the rate of 2626 rpm, it's the move that weight at the rate of 2626 rpm, it's the equivalent of 1/2 horsepower (16,500 foot pounds per equivalent of 1/2 horsepower (16,500 foot pounds per minute), and so on. Therefore, the following formula minute), and so on. Therefore, the following formula applies for calculating horsepower from a torque applies for calculating horsepower from a torque measurement: measurement:

Torque * RPM Torque * RPM Horsepower = ------------ Horsepower = ------------

5,2525,252

This is not a debatable item. It's the way it's done. This is not a debatable item. It's the way it's done.

What is TorqueWhat is Torque

Torque is one way to measure Torque is one way to measure work.work.

Torque is defined as twisting Torque is defined as twisting forceforce

The work that the engine The work that the engine produces is measured as torque produces is measured as torque at the flywheelat the flywheel

Do Torque and Horsepower Do Torque and Horsepower have anything common?have anything common? Torque is the only thing that a driver feels Torque is the only thing that a driver feels

not horsepower.not horsepower. 300 foot pounds of torque will accelerate 300 foot pounds of torque will accelerate

you just as hard at 2000 rpm as it would if you just as hard at 2000 rpm as it would if you were making that torque at 4000 rpm you were making that torque at 4000 rpm in the same gear, yet, per the formula, the in the same gear, yet, per the formula, the horsepower would be *double* at 4000 horsepower would be *double* at 4000 rpm.rpm.

Therefore, horsepower isn't particularly Therefore, horsepower isn't particularly meaningful from a driver's perspective. meaningful from a driver's perspective.

at 5,252 rpm, the horsepower and torque at 5,252 rpm, the horsepower and torque always come out the same. always come out the same.

Torque formulaTorque formula

Torque = Horsepower * 5252 Torque = Horsepower * 5252

----------------- -----------------

RPM RPM

1.1. If horsepower = 350If horsepower = 350

2.2. And rpm = 6500And rpm = 6500

3.3. Torque = 282.8 ft lbsTorque = 282.8 ft lbs

Putting things in perspectivePutting things in perspective

If we bolted an LT1corvette engine to If we bolted an LT1corvette engine to a water wheel and assuming we a water wheel and assuming we needed 12 rpm for an input to the needed 12 rpm for an input to the mill, we could run the LT1 at 5000 mill, we could run the LT1 at 5000 rpm (where it's making 315 foot rpm (where it's making 315 foot pounds of torque), and gear it down pounds of torque), and gear it down to a 12 rpm output. Result? We'd to a 12 rpm output. Result? We'd have over *131,000* foot pounds of have over *131,000* foot pounds of torque to play with. We could torque to play with. We could probably twist the whole flour mill probably twist the whole flour mill around the input shaft, if we needed around the input shaft, if we needed to :-). to :-).

More Horsepower is not More Horsepower is not always the answer but it helpsalways the answer but it helps TorqueTorque RPMRPM Gearing Gearing Remember , Remember ,

there is no there is no replacement for replacement for displacementdisplacement