Dynamometer

A dynamometer, or dyno, is a force measuring device. Different scientists invented different dynamometers. George Graham and John Desagulier invented the Graham-Desaguliers Dynamometer in 1719. It measures the moment of force, torque or power generated by a motor or engine or other prime movers that rotates. It also measures a machine’s power and torque, such as a pump, using driving or motoring dynamometers. Passive or absorptive dynamometers are constructed to drive, and those that can both drive and absorb are called active or universal dynamometers. 

What is a dynamometer?

A dynamometer consists of the following parts:

1. An absorption unit measures torque and speed of rotations. The absorption unit contains a type of rotor. The rotor is attached to the engine, and it rotates at a specific speed needed. A breaking torque is also developed; it can be hydraulic, frictional, electromagnetic, or according to the absorption unit’s type.

2. The dyno housing is the outer cover of the machine, the rotor is present inside the dyno house, and the weighing scale and a torque arm are connected to it.

3. The torque arm is present outside the dyno housing and is basically a break to stop the turns or rotation. 

4. The weighing scale is attached to the torque arm, used to measure the force applied by the dyno housing trying to spin.

5. A load cell transducer is sometimes used to generate a proportionate electrical signal to torque.

The working of a dynamometer

In the engine dynamometer, resistance to the engine is caused by flowing water proportionally to the required applied load. Each absorption section has a controlled water flow aimed at the centre of the rotor through the inlet manifold. Centrifugal force then propels the water to the outer body of the dynamometer. The water is forced into the pockets present on the plates of the stationary stator, where it moves slowly when going outwards. The dynamometer absorbs the power generated by the engine due to this constant going inward and outward flow of the water. Through this energy transfer of the engine, the water gets heated and released.

Types of dynamometers

Dynamometers are divided into two types:

1. Power absorption dynamometer

This dynamometer absorbs and measures the power given out by the engine. The absorbed energy is released as heat in some way. Examples are Prony brake dynamometers, rope brake dynamometers, Eddy current dynamometers, hydraulic dynamometers, etc.

• The hydraulic dynamometer works under fluid friction rather than dry friction. It consists of an inlet and outlet for water, rotors, and an impeller attached to the outer shaft. The flow of fluid in a continuous manner carries the heat dissipated in this dynamometer.

2. Power transmission dynamometer

It is also called a torque metre. In this type, power is transmitted to the load attached to the engine once it is indicated on a scale. Examples are Torsional dynamometer, Epicyclic train dynamometer, etc.

• The epicyclic train dynamometer contains an epicyclic train of gears. These gears are annular gear, spur gear, and pinion. The spur gear is attached to the engine shaft and rotates anticlockwise, and the annular gear is attached to the driving shaft and moves clockwise.

The uses of a dynamometer

A dynamometer determines the power and torque of machines under test, electric motors, power engines, motors with brakes, etc.

The encoder input is used to measure revolutions per minute, and the load cell input is used to measure torque, generally in conjunction with a lever arm (RPM).

Calibration of engine management controllers, extensive examinations into combustion behaviour, and tribology are examples of development efforts.

The data acquisition system is an integral part of a dynamometer. 

In the medical sector, hand-held dynamometers test the grip and strength of the hand of a patient suffering from hand trauma and any dysfunction.

The force dynamometers are used to check the strength and grip of the legs, arms of athletes, workers, and patients, kinesiology, ergonomics, etc.

Conclusion

Dynamometers are machines of different shapes, sizes, and functions. They are sophisticated and high-technology instruments. Dynamometers are used in the mechanical sector to measure the power of engines. They are used to determine the torque of motors and in the medical industry too. They are divided into two categories: power absorption and power transmission. The hydraulic dynamometer is widely used.