Think back to your childhood. Did you ride a bike? If you did and rode after dinner, then you may have had a light on your bike. If your bike had a light, then it may have had a dynamo. A dynamo on a bike will come with one slight downside as the pedals are harder to move. The faster the pedals move and the more they turn, the more the lamps on the light will shine. How bright the lights are is a fair offhand measure of how fast you are going and what kind of force you are generating using just your legs.
Now imagine needing to measure the power that a car engine would be able to make. You can’t just ride it and find some inaccurate measurement, so you’ll need a larger dynamo for it. Machines that can measure the speed, force and power of engines are called dynamometer.
What is a dynamometer?
As stated above, this is a device capable of measuring speed, force and power, giving you an idea of the amount of sustained power that you have on hand. However, these machines can come in many different shapes and sizes.
The simplest type is a spring dynamometer; it is a metal spring with two pieces for the mount. You put the anchor to one end and put the other where you wish to measure, reading on the side how much force is generated. It’s very similar to a spring balance, except for calibration: The balance has units of weight, whereas the dynamometer uses Newtons and similar units of force. However, this means it is incapable of measuring a machine’s power or turning force.
Measuring the amount of power
Let’s say you have a gigantic machine that uses various gears, levers, drive belts and corresponding bits — like a car, but perhaps bigger. To measure the size of this motor, you’ll need something called a driving dynamometer. For the most part, it’s standard equipment that runs on its engine and uses tools or monitors to measure your speed, force and power at any given minute.
Imagine having an enormous socket wrench that you can apply 50 pounds of force to the two-foot handle. In this situation, you apply turning force, known as torque, measuring 100 pound-feet, or 50 pounds to the two-foot handle. The same torque could be generated by using a 100-foot handle to apply one pound of force or using a one-foot handle to turn 100 pounds of force.
In a similar vein, attaching an engine with a shaft allows it to add torque to the shaft. The dynamometer monitors and measures this energy. By multiplying torque by rpm/5,252, it’s easy to convert the number to horsepower.
Additional dynamometer tidbits
To get a better idea of what this machine will do for you, consider the following: Think about turning on the engine to a car, shifting it into neutral and then immediately flooring the pedal and attempting to move nowhere. The engine will explode from overuse, and that’s obviously not good. With a dynamometer, you’ll apply loads to a floored engine, measuring what the engine is capable of withstanding at different speeds.
You could hook up the measurement device to an engine, floor it, and then use the machine to apply as much load as needed to keep it at a certain rpm rate. Record what the engine is capable of handling. As you apply each load, knock down the speed to lower rates, about 500 rpm less each time. Record from there.
You can keep up this process all the way down to as little as 500 rpm for best results. Once you have this information, you only convert to horses by multiplying torque by rpm divided by 5,252; the math will work each time.
ICR utilizes dynamometer or for short “dyno” testing to ensure every repair that comes through our facilities will operate as intended. When motors show signs of wear and tear make sure to turn to ICR when in need, and submit a mechanical repair request.