Association for Machine

bistredingdongMechanics

Oct 31, 2013 (3 years and 11 months ago)

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Dynamics of mechine

5 MARKS

(1)


Association for Machine

Associ
ation for Machines and

India

is the Indian national affiliate of the International
Federation for the Promotion of Mechanism and Machine Science, IFToMM. The main
objective of AMM is to contr
ibute to mechanical design at all levels starting from
academic projects to industrial production, thus enhancing the quality and
the

reliability

of indigenou
s machines. AMM organizes the National Conference on
Machines and Mechanisms (NaCoMM) and the workshop on Industrial Problems on
Machines and Mechanisms (IPRoMM) regularly.

Conferences and Workshops

1. National Conference on Machines and Mechanisms (NaCoMM):

NaCoMM
Conferences lay emphasis on theoretical aspects and experimenta
l studies relating to
machinery. The first NaCoMM Conference, NaCoMM 81 was held at IIT Bombay in
1981. NaCoMM covers a wide range of topics
including

kinematics

and

dynamics

of

machines
,

robotics

and

automation
,

CAD
,

automo
bile engineering
,

rotor
dynamics and

tribology
,

vibr
ation

of

machines
,

condition
monitoring

and

failure analysis
,

man
-
machine

systems and mechatronices, micro
-
mechanisms and

control systems
. The upcoming NaCoMM conference will be held
at

NIT Durgapur
, India on December 17
-
18, 2009.

2

2. Industrial Problems on Machines and Mechanisms (IPRoMM):

IPRoMM
essentially concentrates on industrial problems and practical solutions to

the design of
machines in specific areas. The workshops held so far have covered textile, mechanical
handling agricultural machinery and home appliances. The latest IPRoMM covers
precision instruments and micro

mechanisms. The first IPRoMM , IPRoMM 86, wa
s
held in December 1986 at ATIRA in Ahmedabad.

3. AMM Workshop on Design of Mechanisms for Solving Real Life Problems:

The
workshop aims at giving the participant an opportunity to discuss the design issues for a
host of advanced concepts in rigid and comp
liant mechanisms with the recognized
experts in the field and explore the possibilities of collaborative work. The upcoming
AMM workshop on the design on mechanisms will be held at

IIT
Madras
, India on
October 23
-
25, 2008.

3

Other Activities

4

One prominent activity of AMM is the organizat
ion of the best design project contest for
students. The hosts of a Conference invite students to submit papers based on their
B.E/M.E/B.Tech/M.Tech. projects and present awards to the best design projects. Two
such contests have been conducted so far, one

in Mumbai (NaCoMM 87) and one in
Nagpur (IPRoMM 89).

List of AMM C
alendar Activities

5

1.

NaCoMM 81,

IIT Bombay
, December 1981

2.

6th IFToMM
,

IIT Delhi
, December 1983,

3.

NaCoMM 85, February 1985,

IISc Bangalore

4.

IPRoMM 86, December 1986, ATIRA, Ahme
dabad

5.

IPRoMM 87, December 1987, VJTI, Bombay

6.

IPRoMM 89, January 1989, VRCE, Nagpur

7.

NaCoMM 90, March 1990,

IIT Roorkee

8.

NaCoMM 91, December 1991,

IIT Madras

9.

IPRoMM 92, February 1992, PSG College of Technology, Coimbatore

10.

NaCoMM 93, December 1993,

IIT Kharagpur

11.

IPRoMM 95, February 1995, BMS

College of Engineering, Bangalore

12.

NaCoMM 96, January 1996, CMERI, Durgapur

13.

NaCoMM 97, December 1997,

IIT Kanpur

14.

NaCoMM 99, December 1999,

IIT Bombay

15.

NaCoMM 2001, December 2001,

IIT Kharagpur

16.

IPRoMM 2003, February 2003, VIT, Vellore

17.

NaCoMM 2003, December 2003,

IIT Delhi

18.

DTDM 2004, December 2004,

IIT Madras

19.

NaCoMM 2005, December 2005,

IIT Guwahati

20.

IPRoMM 2005, Feb 2005,

IIT Kharagpur

21.

PCEA IFToMM 2006, Recent Trends in Automation, Priyadarshini College of
Engg & Architecture, Nagpur

22.

Team Tech 2006, Augu
st 2006 Symp Micro & Nano Fabrication

23.

IPRoMM 2007, Jan 2007, Kumaragur College of Tech

24.

iCAMDIA 2007, Int Conf Adv in Machine Design & Ind Auto, College of Engg
Pune

25.

NaCoMM 2007,

IISc Bangalore
.

26.

NaCoMM2009,

NIT Durgapur
.

(2)

Transport and Machine
-
construction

1.

Automobile and automobile industry

2.

Exploitation and service of transport technological machinery
and
equipment

3.

Organization of transportation and management at transport (by all
kinds of vehicle)

4.

Organization and safety of traffic

5.

Technology of machine
-
constructing

6.

Equipment and technology of welding industry

7.

Constructing and manufacturing products fr
om composite material

8.

Machines and technology for increasing wear resistant and
reconstruction of machines and apparatus details

9.

Automation of technological processes and industries (on branches)

10.

Standardization and certification

11.

Metrology and metrological

supply

12.

Mechatronics and robotic

13.

Dynamics and machine durability

14.

Professional education

15.

Technology of printing industry

Institute of Management and Business

1.

Management of organizations

2.

Informational systems and technologies

3.

Journalism

4.

Economics and management of enterprise (in branches)

5.

Business accounting, financial audit and analysis

Technological Faculty

1.

Technology of sewing production

2.

Technology of leather and fur wear

3.

Design of sewing wear

4.

Techno
logy of leather wear

5.

Designing of leather products

6.

Decorative designing of costume

7.

Technology of catering products

8.

Technology of canned products, food concentrates of barmy products
and wine making

9.

Technology of sugary products

10.

Technology of meat and meat
products

11.

Technology of milk and milk products

12.

Technology of bread, macaroni and confectionery

13.

Technology of reprocessing and storage of grain

14.

Machines and apparatus of food production

15.

Food engineering of small industries

16.

Standardization and certification o
f food products

17.

Management (specialization: management and marketing in
restaurant and hotel business)

18.

Chemist
-
researcher, Chemist
-

ecologist

19.

Protection in emergent situation

20.

Engineering protection of environment

Kyrgyz
-
German Technical

1.

Technology, equipment and automation of machine
-
constructing
industries

2.

Technology and management of machine
-
constructing i
ndustry

3.

Transport


telematic logistic

Institute of Mining and Mining Technologies



Me
tallurgy and Geo
-
ecology Department

1.

Metallurgy of ferrous metal

2.

Metallurgy of non
-
ferrous metal

3.

Mineral processing

4.

Geo ecology

5.

Environmental protection and racial use of natural resources

6.

Engineering protection of environment

7.

Applied information science in

ecology



Mining

1.

Blasting operations

2.

Underground workings of mineral deposit

3.

Open mining researches

4.

Mine underground construction

5.

Applied geodesy

6.

Technology and equipment (mining machines and equipment)

7.

Electro technology, electro mechanics, electro technic
s (electro
mechanics of mining industry)



Geological Prospecting Faculty

1.

Geophysical methods of search and prospecting of mineral deposits

2.

Geological survey of groundwater and engineering
-
geological
investigations

3.

Geology of oil and gas

4.

Applied geochemistry
, petrology, mineralogy

5.

Technology and exploration technique of mineral deposits

6.

Applied math and information science

7.

Technology of materials processing

8.

Protection in emergent situations

9.

Nature management



Mining Economy Faculty

1.

Economics (economics of ente
rprise in mineral resource industry)

2.

Business accounting, financial audit and analysis (in mineral resource
industry )

3.

Management of organization (in mineral resource industry)

4.

Information systems and technologies

5.

Automation systems of information processi
ng and management

6.

Mathematical methods in economics

7.

Applied math and information science

(3)

Machine

A

machine

is a

tool

consisting of one or more parts that is constructed to
achieve a particular

goal
. Machines are

powered

devices, usually
mechanically, chemically, thermally or electrically powered, and are
fr
equently

motorized
. Historically, a device required moving parts to classify
as a machine; however, the advent of

electro
nics technology

has led to the
development of devices without moving parts that are considered
machines.
1

The word "machine" is derived from the

Latin

word

machina
,
1

which in turn
derives from the

Doric Greek

μαχανά

(machana),

Ionic
Greek

μηχανή

(mechane) "contrivance, machine, engine"
2

and that
from

μῆχος

(mechos), "means, expedient, re
medy".
3

The meaning of
machine is traced by the Oxford English Dictionary
4

to an independently
functioning structure

and by Merriam
-
Webster Dictionary
5

to something that
has been constructed. This includes human design into the meaning of
machine.

A

simple machine

is a device that simply transforms the direction or
magnitude of a
force
, but a large number of more complex machines exist.
Examples include
vehicles
,

electronic systems
,

molecular
machines
,

computers
,

television

and

radio
.

20 marks

(1)

Electronics

machine

Electronics

is the branch of

physics
,

engineering

and

technology

dealing with

electrical
circuits

that involve

active electrical components

such as

vacuum
tubes
,

transistors
,

diodes
and

integrated circuits
, and associated passive interconnection
technologies. The

nonlinear
behaviour of active components and their ability to control
electron flows makes amplification of weak signals possible and is usually applied
to

information

and

signal processing
. Similarly, the ability of electronic devices to act
as

switches

makes digital information processing possible. Interconnection technologies
such as

circuit boards
, electronics packaging technology, and other varied forms of
communic
ation infrastructure complete circuit functionality and transform the mixed
components into a working

system
.

Electronics is distinct from

electrical

and

electro
-
mechanical

science and technology,
which deals with the generation, distribution, switching, storage and conversion of
elect
rical energy to and from other energy forms
using

wires
,

motors
,

generators
,

batteries
,

switches
,

relays
,
transformers
,

resistors

and
other

passive components
. This distinction started around 1906 with the invention
by

Lee De Forest

of the

triode
, which made electrical

amplification

of weak radio signals
and audio signals possible with a non
-
mechanical device. Until 1950 this field was
called "radio technolo
gy" because its principal application was the design and theory of
radio

transmitters
,

receivers

a
nd

vacuum tubes
.

Today, most electronic devices use

semiconductor

components to perform electron
control
. The study of semiconductor devices and related technology is considered a
branch of

solid state physics
, whereas the design and construction of

electronic
circuits

to solve practical problems come under

electronics engineering
. This a
rticle
focuses on

engineering

aspects of electronics.

Electronic devices and components

Main article:

Electronic component

An electronic component is any physical entity in an electronic system used to

affect the
electrons or their associated fields in a manner consistent with the intended function of
the electronic system. Components are generally intended to be connected together,
usually by being soldered to a

printed circuit board

(PCB), to create an electronic circuit
with a particular function (for example an

amplifier
,

radio receiver
, or

oscillator
).
Components may be packaged singly, or in more complex groups as

integrated circuits
.
Some common electronic components
are

capacitors
,

inductors
,

resistors
,

diodes
,

transistors
, etc. Components are often
categorized as active (e.g. transistors and
thyristors
) or

passive

(e.g. resistors and
capacitors).

Early electronic components

Vacuum tubes

were one of the earliest electronic components. They dominated
electronics until the 1950s. Since that time, solid state devices have all but completely
taken over. Vacuum tubes are still used

in some specialist applications such as

high
power RF amplifiers
,
cathode ray tubes
,

and some

microwave devices
.

(2)

Information processing

Information processing

is the change (processing) of

information

in any manner
detectable by an

observer
. As such, it is a process that
describes

everything that
happens (changes) in the

universe
, from the falling of a rock (a change in position) to
the printing of a text file from a digital computer system. In the latter case,
an

information processor

is changing the

form

of presentation of that text file.
Information processing may more specifically be defined in terms used by

Claude E.
Shannon

as the conversion of

latent information

into

manifest information
citation needed
.
Latent and manifest information is defined through the terms of equivocation (remaining
uncertainty, what value the sender has actually chosen), dissipation (uncertainty of the
sender what the rec
eiver has actually received), and transformation (saved effort of
questioning
-

equivocation minus dissipation)
citation needed
.

In cognitive psychology

Within the field of

c
ognitive psychology
, information processing is an approach to the
goal of understanding human thinking.
citation needed

It arose in the 1940s and 1950s.
citation
needed

The essence of the approach is to see

cognition

as being in
essence

computational

in nature, with

mind

being the

software

and the brain being
the

hardware
. The information processing approach in psychology is closely allied to
the
Computational theory of mind

in philosophy; it is also related, though not identical,
to

cognitivism

in psychology and

functionalism

in philosophy.
citation needed

Two types

Information processing may be

sequential

or

paralle
l
, either of which may
be

centralized

or

decentralized

(
distributed
). The

parallel distributed
processing

approach of the mid
-
1980s became popular under the name

connectionism
.
In the early 1950s,

Friedrich Hayek

was ahead of his time when he posited the idea that
spontaneous order in the brain arises out of

decentralized networks of simple
units
(
ne
urons
). However,

Hayek

is rarely cited in the literature of

connectionism
.

Models and theories

There are several proposed models/theories that describe the way in which we process
information.

Information processing model

The information processing model suggests that information is channeled in different
ways.
citation needed

For example, the sensory register takes in via the five senses: visual,
auditory, tactile, olfactory, and taste. These are all present since

birth and are able to
handle simultaneous processing (e.g., food


taste it, smell it, see it). In general,
learning benefits occur when there is a developed process of pattern recognition. The
sensory register has a large capacity and its behavioral resp
onse is very short (1
-
3
seconds). Within this model, short term memory or working memory has limited
capacity. Its duration is of 5
-
20 seconds before it is out of the subject's mind. This
occurs often with names of people newly introduced to. Images or inf
ormation based on
meaning are stored here as well, but it decays without rehearsal or repetition of such
information. On the other hand, long
-
term memory has a potentially unlimited capacity
and its duration is indefinite. Although sometimes it is difficul
t to access, it encompasses
everything learned until this point in time. One might become forgetful or feel as if the
information is on the

tip of the tongue
.

Cognitive development theory

Another approach to viewing the ways in which information is processed in humans was
su
ggested by

Jean Piaget

in what is called the
Piaget’s Cognitive Development
Theory
.
citation needed

Piaget developed his model based on development and growth. He
identified four different stages between different age brackets characterized by the type
of information and by a distinctive thought process. The four stages are: the
sensori
motor (from birth to 2 years), preoperational (2
-
6 years), concrete operational (6
-
11 years), and formal operational periods (11 years and older). During the sensorimotor
stage, newborns and toddlers rely on their senses for information processing to which

they respond with reflexes. In the preoperational stage, children learn through imitation
and remain unable to take other people’s point of view. The concrete operational stage
is characterized by the developing ability to use logic and to consider multip
le factors to
solve a problem. The last stage is the formal operational, in which preadolescents and
adolescents begin to understand abstract concepts and to develop the ability to create
arguments and counter arguments.

Furthermore, adolescence is charact
erized by a series of changes in the biological,
cognitive, and social realms. In the cognitive area, it is worth noting that the brain’s
prefrontal cortex as well as the limbic system undergoes important changes. The
prefrontal cortex is the part of the b
rain that is active when engaged in complicated
cognitive activities such as planning, generating goals and strategies, intuitive decision
-
making, and

metacognition

(thinking abo
ut thinking). (This is consistent with Piaget’s
last stage of formal operations.
citation needed
) The prefrontal cortex becomes complete
between adolescenc
e and early adulthood. The limbic system is the part of the brain
that modulates reward sensitivity based on changes in the levels of neurotransmitters
(e.g., dopamine) and emotions.

In short, cognitive abilities vary according to our development and stage
s in life. It is at
the adult stage that we are better able to be better planners, process and comprehend
abstract concepts, and evaluate risks and benefits more aptly than an adolescent or
child would be able to.

(3)

Television

For other uses, s
ee

Television (disambiguation)
.

"TV" redirects here. For other uses, see

TV (disambiguation)
.



A
merican family watching TV, 1958

Television

(
TV
) is a

telecommunication

medium

for transmitting an
d receiving moving
images that can be

monochrome

(
black
-
and
-
white
) or colored, with or without
accompa
nying sound. "Television" may also refer specifically to a

television
set
,

television pro
gramming
, or

television transmission
.

The etymology of the word has a mixed Latin and Greek origin, meaning "far sight":
Greek

tele
(
τ

λε
), far, and Latin

visio
, sight (from

video, vis
-

to see, or to view in the first
person).

Commercially available since the late 1920s
, th
e television set has become
commonplace in homes, businesses and institutions, particularly as a vehicle
for

advertising
, a source of entertainment, and

news
. Since the 1970s the availability
of

video cassettes
,

laserdiscs
,

DVDs
and now

Blu
-
ray Discs
, have resulted in the
television set frequently being used for viewing recorded as wel
l as broadcast material.
In recent years

Internet television

has seen the rise of television available via
the

Internet
, e.g.

iPlayer

and

Hulu
.

Although other forms such as

closed
-
circuit television

(CCTV) are in use, the most
common usage of the medium is for

broadcast television
, which w
as modeled on the
existing

radio broadcasting

systems developed in the 1920s, and uses high
-
powered

radio
-
frequency

transmitters to

broadcast

the television signal to individual TV
receivers.

The

broadcast television system

is typically disseminated via

radio

transmissions on
designated channels in the 54

890

MHz

frequency band
.
1

Signals are now often
transmitted with

stereo

or

surround sound

in many countries. Until the 2000s broadcast
TV programs were generally transmitted as an

analog television

signal, but in 2008 the
USA went almost exclusively digital.

A standard

television set

co
mprises multiple internal

electronic circuits
, including those
for

receiving

a
nd decoding broadcast signals. A visual

display device

which lacks
a

tuner

is properly c
alled a

video monitor
, rather than a television. A television system
may use different technical standards such as

digital television

(DTV) and

high
-
definition television

(HDTV). Television systems are also used for surveillance, industrial
p
rocess control, and guiding of weapons, in places where direct observation is difficult
or dangerous.

History

Main article:

History of television

In its early sta
ges of development, television employed a combination of

optical
,
mechanical and

electronic

technologies to capture, t
ransmit and display a visual image.
By the late 1920s, however, those employing only optical and electronic technologies
were being explored. All modern television systems relied on the latter, although the
knowledge gained from the work on electromechanic
al systems was crucial in the
development of fully electronic television.



Braun HF 1

television receiver, Germany, 1958

The first images transmitted electrically were sent by early mechanical

fax

machines,
including the

pantelegraph
, developed in the late nineteenth century. The concept of
electrically powered transmission of television
images in motion was first sketched in
1878 as the

telephonoscope
, shortly after the invention of the telephone. At the time, it
was imagined by early science fiction authors,
that someday that light could be
transmitted over copper wires, as sounds were.

The idea of using

scanning

to transmit images was put to actual practical use in 1881 in
the pante
legraph, through the use of a

pendulum
-
based scanning mechanism. From
this period forward, scanning in one form or another has been used in nearly every
image transmission technology to da
te, including television. This is the concept of
"
rasterization
", the process of converting a visual image into a stream of electrical
pulses.

In 1884

Paul Gottlieb Nipkow
, a 23
-
year
-
old university student in Germany, patented the
first electromechanical television system which employed a

scanning disk
, a spinning
disk with a series of holes spiraling toward the center, for rasterization. The holes were
spaced at equal
angular

intervals such that in a single
rotation the disk would allow light
to pass through each hole and onto a light
-
sensitive

selenium

sensor which produced
the electrical pulses. As an image was focused on the rotating disk,

each hole captured
a horizontal "slice" of the whole image.
citation needed

Nipkow's design would not be practical until advances in

amplifier

tube

technology
became available. The device was only useful for transmitting still "
halftone
" images

represented by equally spaced dots of varying size

over
telegraph

or

telephone
lines
.
citation needed

Later designs would use a rotating mirror
-
drum scanner to capture the
image and a

cathode ray tube

(CRT) as a display device, but moving images were still
not possible, due to the poor sensitivity of the

selenium

sens
ors. In 1907 Russian
scientist

Boris Rosing

became the first inventor to use a CRT in the receiver of an
experimental television system. He used mirror
-
drum scanning to transmit si
mple
geometric shapes to the CRT.
2


Vladimir Zworykin
demonstrates electronic television (1929).

Using a Nipkow disk, Scottish inven
tor

John Logie Baird

succeeded in demonstrating
the transmission of moving silhouette images in

London

in 19
25,
3

and of
moving,

monochromatic

images in 1926. Baird's scanning disk produced an image of 30
lines resolutio
n, just enough to discern a human face, from a double spiral
of

lenses
.
4

This demonstration by Ba
ird is generally agreed to be the world's first true
demonstration of television, albeit a mechanical form of television no longer in use.
Remarkably, in 1927 Baird also invented the world's first

video recording

system,
"
Phonovision
": by modulating the output signal of his

TV camera

down to the audio
range, he was able to capture the signal on a 10
-
inch wax audio disc using conventional
audio recording technology. A handful of Baird's 'Phonovision' recordings survive and
these were finally decoded and re
ndered into viewable images in the 1990s using
modern digital signal
-
processing technology.
5

In 1926, Hungarian engineer

Kálmán Tihanyi

designed a television system utilizing fully
electronic scanning and display elements, and employing the principle of "charge
storage" within the scanning (or "camera") tube.
6
7
8
9

On December 25, 1926,

Kenjiro Takayanagi

demonstrated a television system with a
40
-
line resolution that employed a CRT display at Hamamatsu Indus
trial High School in
Japan.

10

This was the first working example of a fully electronic television receiver.
Takayanagi did not apply for a patent.
11

By 1927, Russian inventor

Léon Theremin

developed a mirror
-
drum
-
based television
system which used

interlacing

to achieve an

image resolution

of 100 lines.
12

Also in 1927,

Herbert E. Ives

of

Bell Labs

transmitted moving images from a 50
-
aperture disk producing

16 frames per minute over a cable from Washington, DC to
New York City, and via radio from

Whippany, New Jersey
.
citation needed

Ives used viewing
screens as large as 24 by 30

inches (60 by 75

cm). His subjects included

Secretary of
Commerce

Herbert Hoover
.
citation neede
d


Philo Farnsworth

In 1927,

Philo Farnsworth

made the world's first working television system with
electronic scanning of both the pickup and display devices,
13

which he first
demonstrated to the press on 1 September 1928.
13
14

WRGB

claims to be the world's oldest

television station
, tracing its roots to an
experimental stat
ion founded on January 13, 1928, broadcasting from the

General
Electric

factory in

Schenect
ady, NY
, under the call letters W2XB.
15

It was popularly
known as "WGY Television" after its sister radio station. Later in 1928,
General
Electric

started a second facility, this one in New York City, which had the call
letters

W2XBS
, and which today is known as

WNBC
. The two stations were
experimental in nature and had no regular programming, as receivers were operated by
engineers within the company. The image of a

Felix the Cat

doll, rotating on a turntable,
was broadcast for 2 hours every day for several years, as new technology was being
tested by the engineers.

In 1936 the

Oly
mpic Games

in Berlin were carried by cable to television stations in
Berlin and Leipzig where the public could view the games live.
16

In 1935 the German firm of

Fernseh A.G.

and the United States firm Farnsworth
Television owned by

Philo Farnsworth

signed an agreement to exchange their
television
patents and technology to speed development of television transmitters and stations in
their respective countries.
17

On 2 November 1936 the

BBC

began transmitting the world's first public regular high
-
definition service from the Victorian

Alexandra Palace

in north London.
18

It therefore
claims to be the birthplace of television broadcasting as we know it today.

In 1936,

Kálmá
n Tihanyi

described the principle of

plasma display
, the first

flat panel
display

syste
m.
19
20

Mexican inventor

Guillermo González Camarena

also played an important role in early
television. His experiments with television (known as telectroescopía at first) began in
1931 and led to a patent for the "trichromatic field sequential system"

color television

in
1940,
21

as well as the remote control.
citation needed

Although television became more familiar in the United States with the general public at
the

1939 World's Fair
, the outbreak of

World War II
prevented it from being
manufactured on a large scale until after the end of the war. True regular
commercial

television network

programming did not begin in the U.S. until 1948. During
that year, legendary conductor

Arturo Toscanini

made his first of ten TV appearances
conducting the

NBC Symphony Orchestra
, and

Texaco Star Theater
, starring
comedian

Milton Berle
, became television's first gigantic hit show.
citation needed

Amateur television

(
ham TV

or

ATV
) was developed for

non
-
commercial

experimentation, pleasure and public service events by

amateur
radio

operators. Ham TV stations were on the air in many cities before
commercial TV
stations came on the air.
22

In 2012, it was reported that television was growing into a larger component of major
media companies' revenues than film.
23

(4)

Mechanical advantage

From Wikipedia, the free encyclopedia

Mechanical advantage

is a measure of the force amplification achieved by using a tool,
mechanical device or machine system.

Ideally, the device preserves the input power and simply
trades off forces against movement to obtain a desired amplification in the output force. The
model for this is the

law of the

lever
.

Ma
chine components designed to manage forces and
movement in this way are called

mechanisms
.

An ideal mechanism transmits power without adding to or subtracting

from it. This means the
ideal mechanism does not include a power source, and is frictionless and constructed from rigid
bodies that do not deflect or wear. The performance of real systems is obtained from this ideal
by using efficiency factors that take i
nto account friction, deformation and wear.


Mechanical advantage in different gears of a bicycle. Typical forces applied to the bicycle pedal and to
the ground are shown, as are corresponding distances moved by the pedal and rotated by the wheel.
Note that even in low gear the MA of a bicycle i
s less than 1.

Law of the lever

The

lever

is a movable ba
r that pivots on a fulcrum attached to the ground. The lever operates
by applying forces at different distances from the fulcrum, or pivot.


A lever in balance

As the lever pivots on the fulcrum, points farther from this pivot move faster than points closer to
the pivot. The power into and out of the leve
r must be the same, so forces applied to points
farther from the pivot must be less than when applied to points closer in.
1

If

a

and

b

are distances from the fulcrum to poin
ts

A

and

B

and if force

F
A

applied to
A

is the
input force and

F
B

exerted at

B

is the output, the ratio of the velocities of points

A

and

B

is given
by

a/b
, so the ratio of the output force to the input force, or mechanical advantage, is given by


This is the

law of the lever
, which was proven by

Archimedes

us
ing geometric reasoning.
2

It
shows that if the distance

a

from the fulcrum to where the input force is applied (point

A
) is
greater than the distance

b

from fulcrum to where

the output force is applied (point

B
), then
the lever amplifies the input force. If the distance from the fulcrum to the input force is less
than from the fulcrum to the output force, then the lever reduces the input force.
Recognizing the profound implic
ations and practicalities of the law of the lever, Archimedes
has been famously attributed with the quotation "Give me a place to stand and with a lever I
will move the whole world."
3

The use of velocity in the static analysis of a lever is an application of the principle of

virtual
work
.

Speed ratio

The requirement for power input to an ideal mechanism to equal power output provides a
simple way to compute mechanical advantage from the input
-
output speed ratio of the
syst
em.

Power

is the product of force and velocity. The power input to a gear train with a
torque

T
A

applied to the drive pulley which rotates at an angular velocity of

ω
A

is

P=T
A
ω
A
.

Because the power flow is constant, the torque

T
B

and angular velocity

ω
B

of the output
gear must satisfy the relation


which yields


This shows that for an ideal mechanism the input
-
output speed ratio equals the
mechanical advantage of t
he system. This applies to all
mechanical systems

ranging
from robots to

linkage
s
.

Gear trains

Gear teeth are designed so that the number of teeth on a gear is proportional to the
radius of its pitch cir
cle, and so that the pitch circles of meshing gears roll on each
other without slipping. The speed ratio for a pair of meshing gears can be computed
from ratio of the radii of the pitch circles and the ratio of the number of teeth on each
gear, its

gear ratio
.


Two meshing gears transmit rotational motion.

The velocity

v

of the point of contact on the pitch circles is the same on both gears,
and is given by


where input gear

A

has radius

r
A

and meshes with output gear

B

of
radius

r
B
,

therefore,


where

N
A

is the number of teeth on the input gear and

N
B

is the number of
teeth on the output gear.

The mechanical advantage of a pair of meshing gears for which the input
gear has

N
A

teeth a
nd the output gear has

N
B

teeth is given by


This shows that if the output gear

G
B

has more teeth than the input
gear

G
A
, then

the gear train

amplifies

the input torque. And, if the output
gear has fewer teeth than the input gear, then the gear train

reduces

the
input torque.

If the output gear of a gear train rotates more slowly than the input gear,
then the gear train is called

a

speed reducer
. In this case, because the
output gear must have more teeth than the input gear, the speed
reducer will amplify the input torque.

Chain and belt drives

Mechanisms consisting of two sprockets connected by a chain, or two
pulleys connected by a belt are designed to provide a specific
mechanical advantage in a power transmission systems.

The velocity

v

o
f the chain or belt is the same when in contact with the
two sprockets or pulleys:


where the input sprocket or pulley

A

meshe
s with the chain or belt
along the pitch radius

r
A

and the output sprocket or pulley

B

meshes
with this chain or belt along the pitch radius

r
B
,

therefore


where

N
A

is the number of teeth on the input sprocket and

N
B

is
the number of teeth on the output sprocket. For a timing belt
drive, the number of teeth on the sprocket can be used. For
friction belt drives the pitch radius of

the input and output pulleys
must be used.

The mechanical advantage of a pair of a chain drive or timing
belt drive with an input sprocket with

N
A

teeth and the output
sprocket has

N
B
teeth is given by


The mechanical advantage for friction belt drives is given by


Chains and belts dissipate power through friction,
stretch and wear, w
hich means the power output is actually
less than the power input, which means the mechanical
advantage of the real system will be less than that calculated for
an ideal me
chanism. A chain or belt drive can lose as much as
5% of the power through the system in friction heat, deformation
and wear, in which case the efficiency of the drive is 95%.

Example bicycle chain drive

Consider the 18
-
speed bicycle with 7in cranks and 26in wheels. If
the sprockets a
t the crank and at the rear drive wheel are the
same size, then the ratio of the output force on the tire to the
input force on the pedal can be calculated from the law of the
lever to be


Now, consider the small and large front sprockets which
have 28 and 52 teeth respectively, and consider the small
and large rear sprockets which have 16 and 32 teeth each.
Using these numbers w
e can compute the following speed
ratios between the front and rear sprockets