Dynamometers are specialized instruments used to measure an engine's revolutions per minute (RPM) and torque. RPM is a measurement of the number of times the crankshaft revolves inside an engine. The more revolutions a crankshaft makes each minute, the faster and more powerful the engine is.
There are many parts inside a car's engine, including the crankshaft and pistons. The crankshaft is similar to a bicycle's pedals, with the bicyclist's legs being the pistons. The pistons push the crankshaft and cause it to rotate. As a result, the crankshaft causes the drive shaft, which is like the bicycle's chain, to move. This causes the axle and tires to rotate, making the car move.
RPM must be within a specific range in order for a person's automobile to run smoothly and efficiently. Incorrect engine measurements can be a sign of engine troubles. Dynamometers allow the car owner or mechanic to test the RPM to ensure it is where it needs to be.
Charles Babbage, often referred to as the "Father of Computing," created the first dynamometers in the late 19th century. As a mathematician and engineer, he realized the vast margin of error found in many mathematical tables. Therefore, his dream was to create a machine that could do math without error.
Many credit Charles Babbage for coming up with the idea behind computers. Using the same concept, however, he also realized a machine could be created to count the number of times an engine caused a vehicle's tires to turn. Hence, dynamometers were born.
Charles Babbage's original dynamometers developed into two machines. One, called an engine dynamometer, is attached directly to the engine. Engine dynamometers require the engine to be removed from the vehicle before measurements can take place. Therefore, it is not always the most practical option.
Chassis dynamometers are the other type. These dynamometers allow people to read the RPM without removing the engine. The vehicle's tires are placed on the chassis dynamometer's rollers and the vehicle is revved up to a certain speed. Chassis dynamometers give readings of the car's horsepower output as well as how many times the tires have revolved.
Both types of dynamometers absorb power from a running engine and measure the torque required to absorb that power. Once the machine has those readings, it calculates the engine's RPM. Many dynamometers today are hooked up to computers, which can graph the engine's capabilities and output.