This document is a presentation report on dynamometers submitted by Anand Kumar. It provides an introduction to dynamometers, explaining that they are devices used to measure force, torque, or power. It then describes the different principles of operation for constant force and constant speed dynamometers. The document proceeds to describe the components and measurement techniques of dynamometers. It outlines different types of dynamometers including absorption and transmission dynamometers. It also provides a brief history of dynamometer development.

1. PRESENTATION REPORT ON
Dynamometers
Submitted By:
Anand Kumar (ME/13/710)
Department of Mechanical Engineering
SHRI BALWANT INSTITUTE OF TECHNOLOGY
Approved by AICTE, Min of HRD, Govt of India & DTE, Govt of Haryana
Affiliated to DCR University of Science and Technology, Murthal, Sonepat
Meerut Road (Pallri), Near DPS, Sonepat-131001, Haryana

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Abstract
My report focuses on the topic Dynamometers and its operations. In the following report I
have studied about the basics of Dynamometers, their operations and their uses. As well as the
report covers the inside view of the Dynamometers and its operations.

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CERTIFICATE
This is certify that the seminar Topic entitled as Dynamometers and submitted by ANAND
KUMAR having Roll No ME/13/710, embodies the bonafide work done by him under my
supervision.
Signature of Supervisor:
Place:
Date:

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Table of Contents
1 INTRODUCTION ......................................................................................................................................................... 5
2 PRINCIPLE OF OPERATION.................................................................................................................................... 6
2.1 CONSTANT FORCE ....................................................................................................................................................6
2.2 CONSTANT SPEED.....................................................................................................................................................6
3 DYNAMOMETER DESCRIPTION ........................................................................................................................... 8
4 TYPES OF DYNAMOMETERS.................................................................................................................................. 9
4.1 ABSORPTIONDYNAMOMETERS................................................................................................................................9
4.1.1 Prony Brake Dynamometer ...........................................................................................................................9
4.1.2 Rope Brake Dynamometer.......................................................................................................................... 10
4.2 TRANSMISSION DYNAMOMETERS.......................................................................................................................... 10
4.2.1 Belt Transmission Dynamometer.............................................................................................................. 10
4.2.2 Torsion Dynamometer................................................................................................................................. 11
5 TYPES OF DYNAMOMETER SYSTEMS ..............................................................................................................12
6 HISTORY .....................................................................................................................................................................13
7 REFERENCES..............................................................................................................................................................14

5. DYNAMOMETERS
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1 INTRODUCTION
A dynamometer is a device for measuring force, torque, or power. For example, the power
produced by an engine, motor or other rotating prime mover can be calculated by
simultaneously measuring torque and rotational speed (RPM). A dynamometer can also be
used to determine the torque and power required to operate a driven machine such as a pump.
In that case, motoring or driving dynamometer is used. A dynamometer that is designed to be
driven is called an absorption or passive dynamometer. A dynamometer that can either drive
or absorb is called a universal or active dynamometer.
In an engine dynamometer, water flow, proportional to the desired applied load, creates
resistance to the engine. A controlled water flow through the inlet manifold is directed at the
center of the rotor in each absorption section. This water is then expelled to the outer
dynamometer body by centrifugal force. As it is directed outward, the water is accelerated
into pockets on the stationary stator plates where it is decelerated. The continual acceleration
and deceleration causes the dynamometer to absorb the power produced by the engine.
Through this transfer of energy the water is heated and discharged.
Dynamometer is a device to measure the output (brake power) of a prime mover. The power
is measured by applying the fictional torque by means of a brake. By knowing the fictional
torque, the power of the engine can be calculated.

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2 PRINCIPLEOFOPERATION
An absorbing dynamometer acts as a load that is driven by the prime mover that is under test
(e.g. Pelton wheel). The dynamometer must be able to operate at any speed and load to any
level of torque that the test requires. Absorbing dynamometers are not to be confused with
"inertia" dynamometers, which calculate power solely by measuring power required to
accelerate a known mass drive roller and provide no variable load to the prime mover. An
absorption dynamometer is usually equipped with some means of measuring the operating
torque and speed.
The Power Absorption Unit of a dynamometer absorbs the power developed by the prime
mover. This power absorbed by the dynamometer is then converted into heat, which
generally dissipates into the ambient air or transfers to cooling water that dissipates into the
air. Regenerative dynamometers, in which the prime mover drives a DC motor as a generator
to create load, make excess DC power and potentially - using a DC/AC inverter - can feed
AC power back into the commercial electrical power grid. Absorption dynamometers can be
equipped with two types of control systems to provide different main test types.
2.1 Constant Force
The dynamometer has a "braking" torque regulator the Power Absorption Unit (PAU) is
configured to provide a set braking force torque load, while the prime mover is configured to
operate at whatever throttle opening, fuel delivery rate, or any other variable it is desired to
test. The prime mover is then allowed to accelerate the engine through the desired speed or
RPM range. Constant Force test routines require the PAU to be set slightly torque deficient as
referenced to prime mover output to allow some rate of acceleration. Power is calculated
based on rotational speed x torque x constant. The constant varies depending on the units
used.
2.2 Constant Speed
If the dynamometer has a speed regulator (human or computer), the PAU provides a variable
amount of braking force (torque) that is necessary to cause the prime mover to operate at the
desired single test speed or RPM. The PAU braking load applied to the prime mover can be
manually controlled or determined by a computer. Most systems employ eddy current, oil
hydraulic, or DC motor produced loads because of their linear and quick load change
abilities. Power is calculated based on rotational speed x torque x constant, with the constant
varying with the output unit desired and the input units used.

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A motoring dynamometer acts as a motor that drives the equipment under test. It must be able
to drive the equipment at any speed and develop any level of torque that the test requires. In
common usage, AC or DC motors are used to drive the equipment or "load" device.
In most dynamometers power (P) is not measured directly, but must be calculated from
torque (τ) and angular velocity (ω) values or force (F) and linear velocity (v):
or
Where.
P is the power in watts
τ is the torque in Newton meters
ω is the angular velocity in radians per second
F is the force in Newton
v is the linear velocity in meters per second
Division by a conversion constant may be required, depending on the units of measure used.
For imperial units,
Where,
Php is the power in horsepower
τlb·ft is the torque in pound-feet
ωRPM is the rotational velocity in revolutions per minute
For metric units,
Where,
PkW is the power in kilowatts
τN·m is the torque in Newton meters

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3 DYNAMOMETERDESCRIPTION
A dynamometer consists of an absorption (or absorber/driver) unit, and usually includes a
means for measuring torque and rotational speed. An absorption unit consists of some type of
rotor in housing. The rotor is coupled to the engine or other equipment under test and is free
to rotate at whatever speed is required for the test. Some means is provided to develop a
braking torque between the rotor and housing of the dynamometer. The means for developing
torque can be frictional, hydraulic, electromagnetic, or otherwise, according to the type of
absorption/driver unit.
One means for measuring torque is to mount the dynamometer housing so that it is free to
turn except as restrained by a torque arm. The housing can be made free to rotate by using
trunnions connected to each end of the housing to support it in pedestal-mounted trunnion
bearings. The torque arm is connected to the dyno housing and a weighing scale is positioned
so that it measures the force exerted by the dyno housing in attempting to rotate. The torque
is the force indicated by the scales multiplied by the length of the torque arm measured from
the center of the dynamometer. A load cell transducer can be substituted for the scales in
order to provide an electrical signal that is proportional to torque.
Another means to measure torque is to connect the engine to the dynamometer through a
torque sensing coupling or torque transducer. A torque transducer provides an electrical
signal that is proportional to the torque.
With electrical absorption units, it is possible to determine torque by measuring the current
drawn (or generated) by the absorber/driver. This is generally a less accurate method and not
much practiced in modern times, but it may be adequate for some purposes.
When torque and speed signals are available, test data can be transmitted to a data acquisition
system rather than being recorded manually. Speed and torque signals can also be recorded
by a chart recorder or plotter.

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4 TYPESOFDYNAMOMETERS
In addition to classification as Absorption, Motoring, or Universal, as described above,
dynamometers can also be classified in other ways. A dyno that is coupled directly to an
engine is known as an engine dyno. A dyno that can measure torque and power delivered by
the power train of a vehicle directly from the drive wheel or wheels (without removing the
engine from the frame of the vehicle), is known as a chassis dyno. Dynamometers can also be
classified by the type of absorption unit or absorber/driver that they use. Some units that are
capable of absorption only can be combined with a motor to construct an absorber/driver or
"universal" dynamometer.
4.1 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. The absorption type of dynamometers can be classified as:
4.1.1 PronyBrakeDynamometer
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 lever attached to it and carries a
weight W at its other end. A counter weight is placed at the other end of lever that balances
the brake when unloaded. Two stops are provided to limit the motion of the lever. When the
brake is to be put 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 the weight W must balance
the moment of the frictional resistance between blocks and pulley.
Fig 1: Prony brake Dynamometer

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4.1.2 RopeBrakeDynamometer
It consists of one or more ropes wound around the flywheel or rim of the pulley, fixed to the
shaft of the prime mover. 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. The frictional torque due to the ropes must be equal to the torque being transmitted by
the prime mover.
Fig 2: Rope brake Dynamometer
4.2 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:
4.2.1 BeltTransmissionDynamometer
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. 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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Fig 3: Belt transmission Dynamometer
4.2.2 TorsionDynamometer
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.
Fig 4: Torsion Dynamometer

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5 TYPESOFDYNAMOMETERSYSTEMS
A 'brake' dynamometer applies variable load on the Prime Mover (PM) and measures the
PM's ability to move or hold the RPM as related to the "braking force" applied. It is usually
connected to a computer that records applied braking torque and calculates engine power
output based on information from a "load cell" or "strain gauge" and a speed sensor.
An 'inertia' dynamometer provides a fixed inertial mass load, calculates the power required to
accelerate that fixed and known mass, and uses a computer to record RPM and acceleration
rate to calculate torque. The engine is generally tested from somewhat above idle to its
maximum RPM and the output is measured and plotted on a graph.
A 'motoring' dynamometer provides the features of a brake dyne system, but in addition, can
"power" (usually with an AC or DC motor) the Prime Mover (PM) and allow testing of very
small power outputs (for example, duplicating speeds and loads that are experienced when
operating a vehicle traveling downhill or during on/off throttle operations).

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6 HISTORY
The Graham-Desaguliers Dynamometer was invented by George Graham and mentioned in
the writings of John Desagulier in 1719. Desaguliers modified the first dynamometers, and so
the instrument became known as the Graham-Desaguliers dynamometer. The Regnier
dynamometer was invented and made public in 1798 by Edme Régnier, a French rifle maker
and engineer. A patent was issued (dated June 1817) to Siebe and Marriot of Fleet Street,
London for an improved weighing machine. Gaspard de Prony invented the de Prony brake in
1821. Macneill's road indicator was invented by John Macneill in the late 1820s, further
developing Marriot's patented weighing machine. Froude Hofmann, of Worcester, UK,
manufactures engine and vehicle dynamometers. They credit William Froude with the
invention of the hydraulic dynamometer in 1877, and say that the first commercial
dynamometers were produced in 1881 by their predecessor company, Heenan & Froude. In
1928, the German company "Carl Schenck Eisengießerei & Waagenfabrik" built the first
vehicle dynamometers for brake tests that have the basic design of modern vehicle test
stands.
The eddy current dynamometer was invented by Martin and Anthony Winther around 1931,
but at that time, DC Motor/generator dynamometers had been in use for many years. A
company founded by the Winthers brothers, Dynamatic Corporation, manufactured
dynamometers in Kenosha, Wisconsin until 2002. Dynamatic was part of Eaton Corporation
from 1946 to 1995. In 2002, Dyne Systems of Jackson, Wisconsin acquired the Dynamatic
dynamometer product line. Starting in 1938, Heenan & Froude manufactured eddy current
dynamometers for many years under license from Dynamatic and Eaton.

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7 REFERENCES
 Winther, J. B. (1975). Dynamometer Handbook of Basic Theory and Applications.
Cleveland, Ohio: Eaton Corporation
 http://www.dynomitedynamometer.com/dyno-dynamometer-article.htm
 http://www.explainthatstuff.com/how-dynamometers-work.html
 http://www.setra.com/blog/test-and-measurement-dynamometer