What is a Dynamometer?

Dynamometer or dyno is a device that measure force, power or speed. Dynamometer is for measurement of brake power. To measure brake power, engine torque and speed have to be calculate. So you can figure out how much power you need or how much you have to hand. But dynamometers come in all shapes and sizes. Let’s take a look at how they work and types of Dynamometer.

Types of Dynamometer

Dynamometer can also be used to find out torque and power required to operate driven machine such as pump. In that case, dynamometer is used for motoring or driving. For example, power produced by an engine, motor or other rotating prime mover can be calculated by measuring torque and rotational speed (RPM).

Dynamometer can be broadly classified into two types. They are Absorption Dynamometer and Transmission Dynamometer. Following are two types of dynamometers, used for measuring brake power of an engine. Check Brake System Types, Functions, and Types of Brakes in automobile

Absorption Dynamometer: In the Absorption dynamometers, entire energy produced by engine is absorbed by friction resistances of brake and is transformed into heat, in process of measurement. In this type, work done is converted into heat by friction while measured. They can be used for measurement of powers only.

Transmission Dynamometer

In Transmission dynamometer, energy or power produced by engine is passing on through dynamometer to some other machines where power developed. This energy is not wasted in friction but is used for doing work. These are also called torque meters.

Classification of Absorption Dynamometer

There are two types of absorption dynamometers. Such as Prony brake dynamometer and Rope brake dynamometer. Below are following two types of absorption dynamometers. Also you want to know about Difference between Diesel and Petrol Engine

Prony Brake Dynamometer

It is simplest form of Absorption type dynamometers for measuring power output. It is to try to stop engine using brake on flywheel and measures weight which an arm attached to brake will support to rotate with flywheel. It consists of two wooden blocks placed around pulley fixed to shaft of an engine whose power is need to be measured.

However it works on principle of converting power into heat by dry friction. Spring is provided between nut and upper block to adjust pressure on pulley to control its speed. This spring bolts are provided to increase friction by tightening wooden block. And upper block has long lever attached to it and carried weight W at its outer end. This weight is place at other end of lever which balances brake when unloaded. And brake power is given by formula.

Brake Power (bp) = 2π NT

Where T= Weight x distance (i)

Rope Brake Dynamometer

Rope brake is another form which is commonly used for measuring brake power of an engine. It consists of more ropes wound around flywheel or rim of pulley fixed to output shaft of an engine. Upper end of ropes is connected to spring balance while other side to loading device. In operation of Brake, engine is made to run at constant speed. Due to Rope, frictional torque must be equal to torque being transmitted by Engine.

Therefore power is absorbed in friction between rope and drum. So drum in rope brake need cooling. Rope brake dynamometers are cheap and can be built quickly but brake power cannot be measured because change in temperature with change in friction coefficient of rope.

Brake Power = π DN (W-S)

Where D is diameter of brake drum, W is weight of load and S is spring balance reading.

Transmission dynamometers

Transmission dynamometers are also called torque meters. In transmission dynamometers, energy are measured before it is use to drive machine. In other words, work is not absorbed while being measured.  Followings types of transmission dynamometers are as follows-

Epicyclic-train dynamometer

In this types of dynamometer, it consists of epicyclic gear train which is placed between prime mover and this machine is used to measure power transmitted. Spur gear is key to engine shaft and it rotates in anticlockwise direction. Apart from this, annular gear is also keyed to driving shaft and rotates in clockwise direction.

However, power is fit together with both spur to annular gears and pinion revolves freely on a lever. In order to keep it in position, weight is placed at smaller end of lever. This efforts use by spur gear on pinion and reaction of annular gear on pinion are equal.

Belt Transmission Dynamometer

In this dynamometer, pulleys are connected to continuous belt passing round the two loose pulleys,which are increase on lever. This lever carries dead weight at one end and balancing weright is attached at other end.

Torsion Dynamometer

Torsion dynamometer is used to measure large power developed by turbine or marine engines. And large number of torsion dynamometers is used to measure angle of twist.