Dynamometer
A dynamometer, often referred to as a "dyno," is a device designed to measure force, torque, or power. There are two main types: active (or universal) dynamometers, which can either drive or absorb power, and passive (or absorption) dynamometers, which are driven by external machines like motors or pumps. Historically, the dynamometer was developed in the late eighteenth century by Edme Régnier to assist naturalists in measuring human strength across various ages and health levels. His innovative design has since evolved into various forms, including hydraulic and eddy current dynamometers, to serve a broad range of applications.
Modern dynamometers are utilized in diverse fields, from mechanical engineering to athletic training, measuring everything from engine performance to grip strength. While advanced models exist that can provide precise measurements, simpler versions, such as spring dynamometers, continue to be used for straightforward force measurements. Additionally, dynamometers play a crucial role in ensuring machinery operates efficiently and effectively, helping select the appropriate engine size for specific tasks. Overall, the versatility and historical significance of dynamometers highlight their importance in both scientific research and practical applications today.
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Dynamometer
A dynamometer is a device used for measuring force, torque, or power. The two general types of dynamometer, also called a dyno, are the universal, or active, dynamometer and the absorption, or passive, dynamometer. Passive dynamometers are designed to be driven by a machine such as a motor or pump; they absorb the power that the engine produces. Active dynamometers can be universal devices, used to either drive or absorb. Many kinds of dynamometers have been developed for many uses, including the Prony brake, hydraulic, and eddy current dynamometers.
These devices were first developed during the late eighteenth century to aid naturalists in their research. The versatility of the first dynamometer, a spring balance, eventually led to its refinement and use in many other fields as well.
A speedometer on a vehicle is a common example of a dynamometer.
Background
Edme Régnier invented and built the dynamometer during the eighteenth century. He undertook this effort at the request of naturalists who wanted a way to measure one human's strength against another's. They hoped to compare humans of different ages and degrees of health as part of their research. Although some naturalists were already using devices to gain this information, the devices were cumbersome and not transportable, and were not versatile enough to test the strength of more than one finger or hand. Régnier was tasked with developing a device that could variably test strength of a single finger, hand, limb, or the whole body.
He built his device through trial and error, and by the late 1790s was able to assess the strength of any human, from an infant to an older adult. Régnier's device went well beyond his initial goal, however. It could measure the strength of horses as well as measure the resistance of a loaded carriage on various slopes. Other potential applications included measuring the recoil of firearms and the force of the projected items and testing motors' strength, but in Régnier's time, these uses were not explored.
Régnier's original dynamometer is about twelve inches long. It consists of an elliptical spring and an engraved double scale, which is a fan shape. Testing involved efforts to either pull the elbows of the ellipse apart (tension) or squeeze the ellipse together (compression). It could be mounted on an iron stand with hooks for use. In a test of a human's back strength—a tension measurement—the subject would stand on the iron stand's base and pull on a wooden handle attached to the dynamometer with an iron hook. To measure the strength of a horse, the dynamometer would be hooked to a sturdy post and an iron hook would link it to the horse's harness. The first scientific study using measurements taken using Régnier's device was conducted between 1800 and 1804 and published soon after.
A number of other people developed dynamometers similar to Régnier's device over the next century. The need to measure force developed new purposes as industrial machinery was designed and became more common during the nineteenth century. In addition to measuring force and load, researchers were interested in knowing how much power was delivered and the effects of the power. New devices were designed for these applications.
Measurement instruments used in twenty-first-century applications generally are more complicated. They use a rotating shaft to transmit the force that is to be measured.
Overview
Power is the product of angular speed and torque, which is turning force. Dynamometers that measure mechanical power are in fact measuring torque.
Régnier's dynamometer is a spring balance. It is an example of the simplest type of dynamometer used in modern times, a spring dynamometer. A two-part mounting is connected by a spring. One end is anchored in place, while the force to be measured is linked to the other end. The displacement of the mounting parts is measured using the device's scale. A spring dynamometer is calibrated in units of force, for example newtons, while a spring balance is calibrated in units of weight. Spring dynamometers are useful in measuring simple pulling force, but are of no use in measuring machine power or force.
Absorption dynamometers can measure torque, power, or speed of an engine or motor. They provide resistance to the turning of a shaft, producing the torque that is being measured. The resistance may be mechanical or fluid friction or electromagnetic induction. A Prony brake, for example, has brake blocks that press against the wheel, creating mechanical friction. Power-measuring dynamometers use a motor or other mover to produce torque. A torque meter or shaft measures the torque.
Electromagnetism can be used as an absorption dynamometer. A motor's driving axle can be connected to a generator's axle; as the motor drives the generator axle, it creates an electric current. The power of the motor can be measured by measuring the current. A vehicle's speedometer also is an example of a dynamometer that uses electromagnetism. A cable connects a spinning metal disc with the tires and a magnet inside a metal cup. The magnet rotates, creating currents that make the cup rotate, which moves the speedometer needle.
An electric motor is an example of a universal dynamometer. It can run on electricity and drive another machine. It can also be run by using another machine to drive its axle, which will reverse the motor's action, generating a measurable electric current.
Dynamometers are used for many purposes. They can help determine if an engine or motor is capable of powering machinery, such as industrial machines in factories. The reverse is also true—dynamometers can ensure that the right size engine or motor is chosen to meet the demands of equipment. They can also be used in quality control to ensure an engine is operating at peak performance.
Although many dynamometers are quite sophisticated and may provide precise measurements, devices similar to Régnier's remain in use. For example, athletes may use handgrip dynamometers to measure their strength. These may use simple linear scales, such as a gauge with a needle, or digital readouts. Even something as basic as a handgrip dynamometer may incorporate hydraulic or electronic components.
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