Dynamometers are devices used to measure force, power, and torque. There are two main types: absorption dynamometers, which absorb all the power produced and convert it to heat, and transmission dynamometers, which transmit power without absorbing it to allow measurement. Absorption dynamometers include Prony brakes and rope brakes, while transmission dynamometers include belt drives, epicyclic trains, and torsion dynamometers. Prony brakes consist of wooden blocks that frictionally absorb power from a pulley attached to the shaft being measured, while rope brakes use friction between ropes and a drum.

1. Dynamometers
Kashif Riaz
Muhammad Hamza
Hamood Ur Rahman
Basit Nazir

2. Contents
• Introduction
• History
•Types of Dynamometers
• Absorption dynamometers
•Transmission dynamometers

3. Introduction
• A device used for measuring force,
power and torque
 Engineering associated dynamometers
 The dynamometers that are used to measure
power or torque of a machine are termed as
engineering associated dynamometers
 E-g load rating of engine or calibration of engine
controls
 Medical associated dynometers
 The dynamometers that are used to measure
power or toque of a human are termed as
medically associated dynamometers
 E-g hand-held dynamometers are used for
routine screening of grip and hand strength

4. History
• The Graham-Desaguliers Dynamometer was
invented by George Graham in 1719
• Gaspard de Prony invented the de Prony brake
dynamometer in 1821
• The first commercial dynamometers were
produced in 1881 by Heenan & Froude which is
a hydraulic dynomameterer
• The eddy current dynamometer was invented by
Martin and Anthony Winther around 1931,

5. Types of Dynamometer
• Absorption Dynamometer:
 Prony Brake Dynamometer
 Rope Brake Dynamometer
• Transmission Dynamometer:
 Epicyclic train dynamometer
 Belt Transmission Dynamometer
 Torsion Dynamometer

6. Absorption
Dynamometer
• In these types of dynamometers, the
entire power produced by the prime
mover is absorbed by the frictional
resistance of the brake and is
transformed into heat, during the
process of measurement
• Examples:
 Prony brake dynamometer.
 Rope brake dynamometer

7. Prony Brake Dynamometer
• It works on the principle of converting power into heat by
dry friction.
• In this method of measuring horsepower is to attempt to
stop the engine by means of a brake on the flywheel and
measure the weight which an arm attached to the brake
will support, as it tries to rotate with the flywheel.

8. Prony
Dynamometer
• It consists of two wooden blocks placed
around a pulley fixed to the shaft of
the prime mover, whose power is to be
measured. The blocks are clamped by
means of two bolts and nuts. A helical
spring is provided between the nut and
the upper block to adjust the pressure
on the pulley to control its speed.
• The upper block has a long lever
attached to it and carries a weight W
at its other end. A counter weight is
placed at the other end of the lever
that balances the brake when
unloaded. Two stops are provided to
limit the motion of the lever.

9. Prony
Dynamometer
• When the brake is to be input in
operation, the long end of the lever is
loaded with suitable weight W and the
nuts are tightened until the prime
mover shaft runs at a constant speed
and the lever is horizontal position.
Under these conditions, the moment
due to weight W must balance the
moment of the frictional resistance
between blocks and pulley.

10. Rope Brake
Dynamometer
• It consists of a number of turns of rope
wound around the rotating drum
attached to the output shaft. One side
of rope is connected to a spring balance
and the other to a loading device.
• The power is absorbed in friction
between the rope and the drum. The
drum therefore require cooling.
• Rope brake is cheap and easily
constructed.
• It is not very accurate because of
changes in the friction coefficient of
the rope with temperature.

11. Rope Brake
Dynamometer
• The upper end of the ropes is attached
to a spring balance while the lower end
is kept in position by applying a dead
weight. In order to prevent the
slipping of the ropes over the flywheel,
wooden blocks are placed at intervals
around the circumference of the
flywheel. . During operation of the
brake, the prime mover is made to run
at constant speed.

12. Transmission Dynamometer
 Dynamometer in which power is
measured without being absorbed or
used up during transmission
 Reverse of Absorption Dynamometer
 The energy or power produced by the
engine is transmitted through the
dynamometer to some other machines
where the power developed is suitably
measured.

13. It Consists of
i. Driving pulley, rigidly fixed to the
shaft of the prime mover
ii. Driven pulley, mounted on another
shaft, to which the power from
pulley is transmitted
iii. Belt, passing through the two loose
pulleys which are mounted on the
lever
iv. Dead weight, at one end and a
balancing weight, at the other end
Transmission Dynamometer Types
Belt Transmission Dynamometer

14.  For large power measurements i.e.
power developed by a turbine
 By measuring angle of twist we can
calculate torsion
Transmission Dynamometer Types
Torsion Dynamometer