Seminar for “Dynamic”
Gear
By
Dalal salah
Mohammed ameen
Nihad Mohammed
Yousif Lokman
Ameen Mustafa
University
of Zakho
2019
January
College of Engineering
Mechanic Department
Out line
• Introduction
• Gears are generally used for one of four different reasons
• Gears –The Purpose:
• The definition of gear
• Type of Gears
• What do gears do?
• Compound Gear Train:
• Calculation
Introduction
A gear or cogwheel is a rotating machine part having cut teeth, or in the
case of a cogwheel, inserted teeth (called cogs), which mesh with another
toothed part to transmit torque. Geared devices can change the speed,
torque, and direction of a power source. Gears almost always produce a
change in torque, creating a mechanical advantage, through their gear ratio,
and thus may be considered a simple machine. The teeth on the two
meshing gears all have the same shape. Two or more meshing gears,
working in a sequence, are called a gear train or a transmission. A gear can
mesh with a linear toothed part, called a rack,
producing translation instead of rotation.
Gears are generally used for one of four different reasons
• To reverse the direction of rotation .
• To increase or decrease the speed of rotation.
• To move rotational motion to a different axis.
• To keep the rotation of two axis synchronized.
Gears –The Purpose:
•
Sports cars go fast (have speed) but cannot pull any weight. Big trucks
can pull heavy loads (have power), but cannot (have power), but cannot
go fast. Gears cause this. Gears increase or decrease the power or
speed, but you cannot generally speaking.
The definition of gear
• Gears are wheels with teeth. Gears mesh together and make
things turn. Gears are used to transfer motion or power from
used to transfer motion or power from one moving part to
another.
Gears are defined by two important items: radius and number of teeth :•
Radius: The gear radius is defined differently depending on the
particular section of the gear being discussed. The two most relevant
measurements, however, are the root radius and the addendum radius.
The root radius is the distance from the center of the gear to the base of
the teeth while the addendum radius (also called the "pitch" radius) is
the distance from the center of the gear to the outside of the teeth.
Gears are defined by two important items: radius and number of teeth :• Teeth: The teeth are the portion of the gear that makes contact with
another gear. In order for two gears to mesh together the pitch must be
the same for all mating pairs. The pitch of a gear is the distance between
equivalent points of adjacent teeth. When the teeth of gears mesh
properly they prevent slipping and can exhibit efficiencies of up to 98%.
History of gears
They have used the gears then ingeniously in chariots for measuring the
speed and other mechanisms. Gears are considered as one of the oldest
equipment known to mankind. The origin of gears goes down to the
Chinese South-Pointing Chariot in the 27th Century B.C. This chariot was
known to pointing to the south no matter how it was turned.
History of gears
Primitive gears shown in Figure below were used in door drive mechanism
in temples and caves, and water lifting mechanisms 2600 B.C. in India and
elsewhere.
History of gears
• Aristotle in the fourth century B.C. mentions in his writings that gears
were being used very commonly in many applications.
• Classical origin of worm gearing was made
by Archimedes 287-212 B.C.
• Water wheel and grain mill described by Vitruvius 40 B.C. had
conversion of motion from horizontal to vertical shaft by gears.
History of gears
• Leonard da Vinci used multitudes of gears in various mechanisms
developed by him 500A.D.
History of gears
• Greek and Roman literatures show extensive usage of gears for forward
motion.
• Toothed gears used for the clocks of Cathedrals and other ecclesiastical
buildings during the middle ages are still preserved in many places.
• Salisbury cathedral still possesses the oldest clock in England made in
1386.
• The Wells Cathedral clock made in 1392 is preserved in Science museum
in South Kensington. Though the iron gears have worn out to some
extent, they still keep good timings
History of gears
• German artist Albrecht Durer’s engravings show a vehicle designed for
the Emperor Maximilian I during 15th century which is shown in
Fig.1.4. That vehicle was driven by worm gears on all four wheels. This
clearly shows that he knew the concept of gearing which helped him in
sketching them accurately. Chariot using worm gears
History of gears
• In 18th century, Industrial Revolution in England led to usage of
cycloidal gears for clocks, irrigation devices, water mills and powered
machines. Fig. 1.5 gives the glimpses of their contribution to engine
application.
• Schematic diagram of Watt’s rotating Engine invented in 1784 is shown
in the figure. It was the first engine to produce power directly on a shaft
Gears are actually a natural product:
• But were the ancient Greeks really the inventors/ Research biologists
at the University of Cambridge are certain that the ancient Greeks
were not the first. The three millimeters small bug Issus coleoptratus, a
lantern bearer like those in Europe and North Africa, uses this
mechanism already for millions of years. The gear is not a human
invention of the ancient Greeks, but a mechanism that arose through
evolution in nature.
Type of Gears
Spur Gear
• Teeth are straight and parallel to shaft axis.
Transmits power and motion between
rotating two parallel shafts.
• features
( 1 ) Easy to manufacture.
( 2 ) Relatively easy to produce high quality
gears.
( 3 ) There will be no axial force.
( 4 ) The commonest type.
• Applications
Transmission components
Helical Gear
• Teeth are twisted oblique to the gear axis
• features
( 1 ) Has higher strength compared
with spur gear.
( 2 ) Effective in reducing noise and
vibration compared with spur gear.
( 3 ) Gears in mesh produce thrust
forces in the axial directions.
• Applications
Transmission components
Bevel Gear
• One of a pair of gears used to connect two shafts whose axes intersect, and the pitch
surfaces are cones.
• features
( 1 ) Relatively easy to
manufacture.
( 2 ) Provides reduction ratio
up to approx. 1:5..
• Applications
Machine tools, printing press,
etc. Especially suitable for a
differential gear unit.
Worm Gear
• Worm is a shank having at least one complete tooth (thread) around the pitch surface;
the driver of a worm wheel.
• Worm wheel is a gear with teeth cut on an angle to be driven by a worm.
• features
( 1 ) Provides large reduction ratios for a
given center distance.
( 2 ) Quiet and smooth action.
( 3 ) A worm wheel is not feasible to drive a
worm except for special
• Applications
Speed reducers, anti-reversing gear device
making the most of its self-locking features,
machine tools, indexing device, chain block,
portable generator, etc.
Rack & Pinion Gears
• The rack is a bar containing teeth on one face for meshing with a gear. The basic rack
form is the profile of the gear of infinite diameter.
• Racks with machined ends can be joined together to make any desired length.
• features
Changes a rotary motion into a
rectilinear motion.
• Applications
A transfer system for machine
tools, printing press, robots,
etc.
What do gears do?
• In general Gears are used for transmitting power from
one part of a machine to another. In a bicycle, for
example, it's gears (with the help of a chain) that take
power from the pedals to the back wheel.
What do gears do?
• Increase speed
the red gear has to turn round much faster
than the white gear to keep up. So this
arrangement means the red gear turns
faster than the white but with less force.
• Increase force
the white gear will turn round much
slower but with high force.
The driving
What do gears do?
• Change direction
When two gears mesh together, the second one always turns in the
opposite direction. So if the first one turns clockwise, the second one
must turn counterclockwise. You can also use specially shaped gears to
make the power of a machine turn through an angle power through 90
degrees
What do gears do?
•
Gears for speed
we use this type of gear in the car specially
in the speed car and in too much other
machine that need speed
•
Gears for force
we use this type of gears when we need force for
example if we need to make a heavy truck go up
a hill , or a car when it start moving from rest it’s
needs a huge amount of force and very little speed
to get it moving from rest
What do gears do?
• Gear for change direction
we use this type of gear when we need to change the direction of the
rotation and we can make the angle as we want ,EX. in the drill gears
help to make light work of mixing in two different ways—by increasing
speed and changing direction ,and we use this gear in the car
Compound Gear Train:
When there is more than one gear on a shaft it is called a compound train of
gear.
Calculation
𝑁1 𝑇2
𝑠𝑝𝑒𝑒𝑑 𝑟𝑎𝑡𝑖𝑜 =
=
𝑁2 𝑇1
Or we can use
1
𝑁2 𝑇1
𝑇𝑟𝑎𝑖𝑛 𝑣𝑎𝑙𝑢𝑒 =
=
=
𝑠𝑝𝑒𝑒𝑑 𝑟𝑎𝑡𝑖𝑜 𝑁1 𝑇2
𝑁1 = speed of driver in r.p.m
𝑁2 = speed of driven in r.p.m
𝑇1 = Number of teeth on driver
𝑇2 = Number of teeth on driven
Calculation
𝑠𝑝𝑒𝑒𝑑 𝑟𝑎𝑡𝑖𝑜 =
𝑁𝑏𝑙𝑎𝑐𝑘
𝑁𝑠𝑚𝑎𝑙𝑙−𝑟𝑒𝑑
𝑇𝑠𝑚𝑎𝑙𝑙−𝑟𝑒𝑑
=
𝑇𝑏𝑙𝑎𝑐𝑘
𝑁𝑠𝑚𝑎𝑙𝑙−𝑟𝑒𝑑 = 𝑁𝑏𝑖𝑔−𝑟𝑒𝑑
𝑁𝑠𝑚𝑎𝑙𝑙−𝑟𝑒𝑑
𝑇𝑤ℎ𝑖𝑡𝑒
=
∗ 𝑁𝑤ℎ𝑖𝑡𝑒
𝑇𝑏𝑖𝑔−𝑟𝑒𝑑
𝑁𝑏𝑖𝑔−𝑟𝑒𝑑
𝑇𝑤ℎ𝑖𝑡𝑒
𝑠𝑝𝑒𝑒𝑑 𝑟𝑎𝑡𝑖𝑜 =
=
𝑁𝑤ℎ𝑖𝑡𝑒
𝑇𝑏𝑖𝑔−𝑟𝑒𝑑
𝑁𝑏𝑖𝑔−𝑟𝑒𝑑
𝑠𝑝𝑒𝑒𝑑 𝑟𝑎𝑡𝑖𝑜 =
𝑇𝑤ℎ𝑖𝑡𝑒
=
∗ 𝑁𝑤ℎ𝑖𝑡𝑒
𝑇𝑏𝑖𝑔−𝑟𝑒𝑑
𝑁𝑏𝑙𝑎𝑐𝑘
𝑇𝑤ℎ𝑖𝑡𝑒
∗ 𝑁𝑤ℎ𝑖𝑡𝑒
𝑇𝑏𝑖𝑔−𝑟𝑒𝑑
𝑁𝑏𝑙𝑎𝑐𝑘 𝑇𝑠𝑚𝑎𝑙𝑙−𝑟𝑒𝑑 𝑇𝑤ℎ𝑖𝑡𝑒
𝑠𝑝𝑒𝑒𝑑 𝑟𝑎𝑡𝑖𝑜 =
=
∗
𝑁𝑤ℎ𝑖𝑡𝑒
𝑇𝑏𝑙𝑎𝑐𝑘
𝑇𝑏𝑖𝑔−𝑟𝑒𝑑
𝑇𝑠𝑚𝑎𝑙𝑙−𝑟𝑒𝑑
=
𝑇𝑏𝑙𝑎𝑐𝑘
Calculation
𝑠𝑝𝑒𝑒𝑑 𝑜𝑓 𝑡ℎ𝑒 𝑓𝑖𝑟𝑠𝑡 𝑑𝑟𝑖𝑣𝑒𝑟 𝑝𝑟𝑜𝑑𝑢𝑐𝑡 𝑜𝑓 𝑡ℎ𝑒 𝑛𝑢𝑚𝑏𝑒𝑟 𝑜𝑓 𝑡𝑒𝑒𝑡ℎ 𝑜𝑛 𝑡ℎ𝑒 𝑑𝑟𝑖𝑣𝑒𝑛𝑠
𝑠𝑝𝑒𝑒𝑑 𝑟𝑎𝑡𝑖𝑜 =
=
𝑠𝑝𝑒𝑒𝑑 𝑜𝑓 𝑙𝑎𝑠𝑡 𝑑𝑟𝑖𝑣𝑒𝑛
𝑝𝑟𝑜𝑑𝑢𝑐𝑡 𝑜𝑓 𝑡ℎ𝑒 𝑛𝑢𝑚𝑏𝑒𝑟 𝑜𝑓 𝑡𝑒𝑒𝑡ℎ 𝑜𝑛 𝑡ℎ𝑒 𝑑𝑟𝑖𝑣𝑒𝑟𝑠
1
𝑇𝑟𝑎𝑖𝑛 𝑣𝑎𝑙𝑢𝑒 =
𝑠𝑝𝑒𝑒𝑑 𝑟𝑎𝑡𝑖𝑜
𝑠𝑝𝑒𝑒𝑑 𝑜𝑓 𝑙𝑎𝑠𝑡 𝑑𝑟𝑖𝑣𝑒𝑛
𝑝𝑟𝑜𝑑𝑢𝑐𝑡 𝑜𝑓 𝑡ℎ𝑒 𝑛𝑢𝑚𝑏𝑒𝑟 𝑜𝑓 𝑡𝑒𝑒𝑡ℎ 𝑜𝑛 𝑡ℎ𝑒 𝑑𝑟𝑖𝑣𝑒𝑟𝑠
𝑇𝑟𝑎𝑖𝑛 𝑣𝑎𝑙𝑢𝑒 =
=
𝑠𝑝𝑒𝑒𝑑 𝑜𝑓 𝑡ℎ𝑒 𝑓𝑖𝑟𝑠𝑡 𝑑𝑟𝑖𝑣𝑒𝑟
𝑝𝑟𝑜𝑑𝑢𝑐𝑡 𝑜𝑓 𝑡ℎ𝑒 𝑛𝑢𝑚𝑏𝑒𝑟 𝑜𝑓 𝑡𝑒𝑒𝑡ℎ 𝑜𝑛 𝑡ℎ𝑒 𝑑𝑟𝑖𝑣𝑒𝑛𝑠
Calculation
𝑇𝑏𝑖𝑔−𝑟𝑒𝑑 = 42
𝑇𝑏𝑙𝑎𝑐𝑘 = 48
𝑇𝑤ℎ𝑖𝑡𝑒 = 31
𝑇𝑠𝑚𝑎𝑙𝑙−𝑟𝑒𝑑 = 36
Calculation
What if the black gear rotate 1 time per minute
what happen to the white gear?
𝑇𝑠𝑚𝑎𝑙𝑙−𝑟𝑒𝑑 = 36
𝑇𝑤ℎ𝑖𝑡𝑒 = 31
Driven
𝑇𝑟𝑎𝑖𝑛 𝑣𝑎𝑙𝑢𝑒 =
𝑠𝑝𝑒𝑒𝑑 𝑜𝑓 𝑙𝑎𝑠𝑡 𝑑𝑟𝑖𝑣𝑒𝑛
𝑝𝑟𝑜𝑑𝑢𝑐𝑡 𝑜𝑓 𝑡ℎ𝑒 𝑛𝑢𝑚𝑏𝑒𝑟 𝑜𝑓 𝑡𝑒𝑒𝑡ℎ 𝑜𝑛 𝑡ℎ𝑒 𝑑𝑟𝑖𝑣𝑒𝑟𝑠
=
𝑠𝑝𝑒𝑒𝑑 𝑜𝑓 𝑡ℎ𝑒 𝑓𝑖𝑟𝑠𝑡 𝑑𝑟𝑖𝑣𝑒𝑟
𝑝𝑟𝑜𝑑𝑢𝑐𝑡 𝑜𝑓 𝑡ℎ𝑒 𝑛𝑢𝑚𝑏𝑒𝑟 𝑜𝑓 𝑡𝑒𝑒𝑡ℎ 𝑜𝑛 𝑡ℎ𝑒 𝑑𝑟𝑖𝑣𝑒𝑛𝑠
𝑇𝑟𝑎𝑖𝑛 𝑣𝑎𝑙𝑢𝑒 =
𝑇𝑏𝑙𝑎𝑐𝑘 ∗ 𝑇𝑏𝑖𝑔−𝑟𝑒𝑑
𝑁𝑤ℎ𝑖𝑡𝑒
=
𝑁𝑏𝑙𝑎𝑐𝑘 𝑇𝑠𝑚𝑎𝑙𝑙−𝑟𝑒𝑑 ∗ 𝑇𝑤ℎ𝑖𝑡𝑒
𝑁𝑤ℎ𝑖𝑡𝑒 48 ∗ 42
=
1
36 ∗ 31
𝑁𝑤ℎ𝑖𝑡𝑒 = 1.8 r. p. m
𝑇𝑏𝑙𝑎𝑐𝑘 = 48
𝑇𝑏𝑖𝑔−𝑟𝑒𝑑 = 42
Driver
We are finish 
Any Question?
Thank you 
University
of Zakho
2018
November
College of Engineering
Mechanic Department
Grope -A-
Reference
Khurmi, R. et al.; Theory of Machines, 14th ed.; S. Chand & Co. Ltd., New Dehli 2005; ISBN 9788121925242
Helical gears, retrieved 15 June 2009
MacKinnon, Angus (2002). "Quantum Gears: A Simple Mechanical System in the Quantum Regime".
https://khkgears.net/new/gear_knowledge/introduction_to_gears/types_of_gears.html
to: a b c Dynamics, Theory and Applications by T.R. Kane and D.A. Levinson, 1985, pp. 90– 99: Free download
University
of Zakho
2018
November
College of Engineering
Mechanic Department
Grope -A-