You all might have heard of the word “Horsepower” when describing the power of the car. But what actually is this term all about? Let’s see here. “Horsepower” is the unit of the power. In order to improve the marketing of the improved steam engine, James Watt introduced this term in 1782. James Watt (1736-1819) was a Scottish scientist who revolutionized the steam engine. Industrial Revolution in England was started after this.
The history of the term “horsepower” goes like this:
In ancient times, horses were used to turn the mill wheels. James watt observed this and noted that in one hour and by one horse, a wheel of 12 ft radius could be turned 144 times. And it would mean that the horse traveled 2.4 × 2π × 12 feet in one minute. He further calculated that with 180 lbs force horse could pull easily.
Thus, this unit was derived from the horsepower; later this historical value was converted to the SI unit for the power i.e. Watt (W). even though the unit horsepower was replaced by the watt still, this term is being used in the automotive industry as a legacy term in order to measure the power which an internal-combustion engine can generate while working.
Measuring the Value:
The power of the engine can be measured from the several points in the transmission channel (i.e. from the generation of the wheel to the application on the ground surface).
Indicated Horsepower (ihp):
During the 19th century, horsepower was widely used for the steam engines. This term “Indicated Horsepower (ihp)” is applied to such engines in which with the use of gases within the cylinders the energy is generated by expanding those gases. The pressure that develops within is thus used to calculate the horsepower. The “Engine Indicator Device measures this horsepower.”
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Brake Horsepower (bhp):
The power of the engine at the flywheel is a net rating given by the “American Society of Automotive Engineers” (SAE). It is more accurate than the gross rating; however, it does not measure the power at the drive wheels.
Measuring the horsepower of an engine without the loss of power due to water-pump, generator, gearbox or by other auxiliaries are known as “Brake Horsepower.”
It should be noted here that the horsepower which is being delivered to the driving wheels is much less than the actual power being generated at the end of the engine. Hence in order to get the official rating, the engine with another system has to be tested over and over again.
Shaft Horsepower (shp):
The power that is being delivered to the propelling shafts of a ship or an aeroplane is related to the “Shaft Horsepower.” Hence this term has not to be used for the other automobile as such.
Effective Horsepower (ehp) also called Wheel Horsepower(whp):
When the horsepower is effective enough to be converted into the useful work it is known as the “Effective Horsepower.” For example, the forward motion, which is generated by the power of the engine in a vehicle is an example of useful work.
In automobiles, “Wheel Horsepower” is the adequate horsepower. Dynamo-meters is the unit in which the wheel horsepower of the wheels of automobiles is measured. And when the conversion factor has been applied on the engine, the “Brake or net horsepower” of the engine is calculated. However, due to the loss through the train-driven, about 5-15% of the “Brake Horsepower” rating would be higher than the “Wheel Horsepower.”
That’s it from our side, drop your thoughts in the comments section below. Stay tuned to PakWheels.com to get more information regarding the automotive industry.
