Horsepower is a term we have all heard at some point in our lives. Whether it was uttered while admiring pricey sports cars or considering your next tractor, horsepower is an important thing to have, and understand, when it comes to the operation of equipment. With so much attention being focused on horsepower, it can be easy to get sucked in and lose track of what horsepower, and the addition of it, means in terms of the performance of the machinery in your life.
The term 'horsepower' was coined by man named James Watt. If the name sounds familiar but you cannot quite put your finger on from where you recognize it, take a look at the light fixtures in your home. Contained in them are light bulbs, which are rated in watts. Light bulb wattage aside, this man was an inventor and engineer and had a hand in the evolution of steam engines. Horsepower came about as a means for him to convey the power of those steam engines on a level his peers could understand which was, at that time, comparing them to the power of one horse.
Horsepower, much as it sounds, was a way of measuring the amount of power that was able to be put out by working animals of the equine variety-horses, ponies, and mules. Watt's initial calculations amounted to the claim that one equine was capable of 33,000 foot-pounds of work in one minute of time. This ultimately goes on to be translated to mean that one horse generating one horsepower can move something weighing 1,000 pounds at a distance of 33 feet in one minute of time.
By measuring horsepower, what we are actually doing is measuring the exertion of force combined with a distance traveled in a certain time frame. All of this combined results in a number that equates to horsepower. In this equation, the force itself is known as torque.
To further complicate things, horsepower feeds upon itself. It takes horsepower to create and maintain horsepower. This depends on the components of the machine in question and how they are working at any given time. Horsepower, as luck would have it, is never as simple as black and white. It all starts with something known as Indicated Horsepower. This is the bare bones amount of horsepower an engine can generate. This is not, however, the actual measurement of an engine's useful power. As horsepower is transferred through the moving components of an engine, energy is lost to friction, leaving you with Brake Horsepower. What this amounts to is taking the Indicated Horsepower and lessening it by the amount of friction it will incur.
After considering the loss of power upon the introduction of friction as well as figuring the amount of power an engine requires to operate itself prior to calculating its potential output, you have Effective Horsepower. This is the number relative to the work an engine can do after feeding the needs required to operate itself first. A variation will be present in the numbers between Indicated and Actual Horsepower due to compensating for other operational factors.
Essentially it all boils down to an engine having a lot of horsepower but also requiring some of that horsepower to do the job of running itself. Much as the horse would require some of its own energy to maintain function, doing things such as eating, breathing, and digesting food, so does the mechanical engine require a power source. It just so happens that the energy is applied in different ways; for an engine it may be friction whereas for the horse it equates to calories, since the horse loses calories as he works and requires more calories to work again. What it all comes down to is that you have to feed the beast, be it equine or machine, as both take energy to generate the output that is horsepower.
True horsepower at work: