Powerpoint Presentation on Dynamometers

1. Dynamometers
Anand Kumar
ME/13/710
Tuesday, May 23, 2017

2. Dynamometers
Types of Dynamometers
Absorption Dynamometers
Transmission Dynamometers
Contents
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3. Dynamometer
 Dynamometer is a device to measure the output (brake
power) of a prime mover. The power is measured by applying
the frictional torque by means of a brake. By knowing the
frictional torque, the power of the engine can be calculated.
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4. Types of
Dynamometers
 Absorption Dynamometers
I. Prony Brake Dynamometers
II. Rope Brake Dynamometers
 Transmission Dynamometers
I. Belt Transmission Dynamometer
II. Torsion Dynamometer

5. Absorption
Dynamometers
 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 of such dynamometers are
• Prony brake dynamometer.
• Rope brake dynamometer.

6. 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.
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7. Prony Brake
Dynamometer
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 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.

8. Prony Brake
Dynamometer
 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.
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9. Prony Brake
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.
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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.
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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.
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12. Transmission
Dynamometers
 In these dynamometers, the energy is used for doing work.
The power developed by the prime mover is transmitted
through the dynamometers to some other machine where the
power is suitably measured.
 This type of dynamometer can be classified as follows:
• Belt Transmission Dynamometer
• Torsion Dynamometer
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13. Belt
Transmission
Dynamometer
 A belt transmission
dynamometer consists of
driving pulley, rigidly fixed
to the shaft of the prime
mover. There is another
driven pulley mounted on
another shaft, to which the
power from pulley is
transmitted.
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14. Belt
Transmission
Dynamometer
 The pulleys are connected
by means of a continuous
belt passing round the two
loose pulleys, which are
mounted on the lever. The
lever carries a dead weight
at the one end, and a
balancing weight is
attached at the other end.
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15. Torsion
Dynamometer
 A torsion dynamometer is
used to measure large power
developed by a turbine or
marine engines. A large
number of torsion
dynamometers are used to
measure the angle of twist.
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