The document discusses different types of gears including spur gears, helical gears, herringbone gears, rack and pinion gears, bevel gears, worm gears, and planetary gears. It describes the design and function of each gear type, their advantages and disadvantages, and common applications. Spur gears transmit power between parallel shafts and are used in machines, power plants, and automobiles. Helical gears operate more quietly than spur gears and are used in automobile transmissions. Planetary gears can produce different gear ratios and are commonly used in automatic transmissions.

2. Gears

3.  Introduction to Gears
 Types of Gears
 Design of Gears according to their Types
 Advantages And Disadvantages
 Applications

4.  Power transmission is the movement of energy
from its place of generation to a location
where it is applied to performing useful work
 A gear is a component within a transmission
device that transmits rotational force to
another gear or device

5. 1. According to the position of axes of the
shafts.
a. Parallel
 1.Spur Gear
 2.Helical Gear
 3.Herringbone Gear
 4.Rack and Pinion
b. Intersecting
 Bevel Gear
c. Non-intersecting and Non-parallel
 worm and worm gears

6.  Teeth is parallel to axis
of rotation
 Transmit power from
one shaft to another
parallel shaft
 Used in Electric
screwdriver, oscillating
sprinkler, windup alarm
clock, washing
machine and clothes
dryer

8.  The teeth on helical gears are cut at an angle
to the face of the gear
 This gradual engagement makes helical gears
operate much more smoothly and quietly than
spur gears
 One interesting thing about helical gears is
that if the angles of the gear teeth are correct,
they can be mounted on perpendicular shafts,
adjusting the rotation angle by 90 degrees.
 Helical Gear is used in Automobile gear box
because it produces less noise than spur gear

10.  To avoid axial thrust, two
helical gears of opposite
hand can be mounted side
by side, to cancel resulting
thrust forces
 Herringbone gears are
mostly used on heavy
machinery.

11.  Rack and pinion gears
are used to convert
rotation (From the
pinion) into linear
motion (of the rack)
A perfect example of
this is the steering
system on many cars

12.  Bevel gears are useful when the direction of a
shaft's rotation needs to be changed
 They are usually mounted on shafts that are 90
degrees apart, but can be designed to work at other
angles as well
 The teeth on bevel gears can be straight, spiral or
hypoid
 locomotives, marine applications, automobiles,
printing presses, cooling towers, power plants, steel
plants, railway track inspection machines, etc.

14.  A worm drive is a cylindrical gear with a shallow spiral
thread that engages the worm gear in a non-intersecting,
perpendicular axes configuration.
 Worm gears are used when large gear reductions are
needed. It is common for worm gears to have reductions
of 20:1, and even up to 300:1 or greater
 The gear ratio is the "size of the worm gear - to - 1"
 The worm can easily turn the gear, but the gear cannot
turn the worm
 Typical worm drives can only be turned in one direction
due to self-locking depends on the lead angle, the
pressure angle, and the coefficient of friction
 Worm gears are used widely in material handling and
transportation machinery, machine tools, automobiles etc

15.  One of the newest designs for differentials is called the
Torsen differential. It uses a combination of worms and
worm gears that make each wheel independent of the other
wheels. These differentials are found in Hummers, large
earth-moving vehicles and some off-road vehicles.

17. A gear train is two or more gear working
together by meshing their teeth and turning
each other in a system to generate power and
speed
 It reduces speed and increases torque
 Electric motors are used with the gear systems
to reduce the speed and increase the torque

18.  Simple gear train
 Compound gear train
 Planetary gear train
Simple Gear Train
 The most common of the gear train is the gear pair
connecting parallel shafts. The teeth of this type can
be spur, helical or herringbone.
 Only one gear may rotate about a single axis

20.  For large velocities,
compound
arrangement is
preferred
 Two or more gears
may rotate about a
single axis

22.  Nearly all automatic transmissions rely on planetary
gear sets to transfer power and multiply engine
torque to the drive axle.
 A simple planetary gear set consists of three parts:
a) sun gear,
b) Planet carrier
c) ring gear
 All gears in a planetary gear set are in constant
mesh. The torque flow through a planetary gear set,
both input and output, occurs along a single axis.

23.  In this train, the blue gear has six times the diameter
of the yellow gear
 The size of the red gear is not important because it is
just there to reverse the direction of rotation
 In this gear system, the yellow gear (the sun) engages
all three red gears (the planets) simultaneously
 All three are attached to a plate (the planet carrier),
and they engage the inside of the blue gear (the ring)
instead of the outside.

24.  Because there are three red gears instead of
one, this gear train is extremely rugged.
 planetary gear sets is that they can produce
different gear ratios depending on which gear
you use as the input, which gear you use as the
output, and which one you hold still.

25.  They have higher gear ratios.
 They are popular for automatic transmissions
in automobiles.
 They are also used in bicycles for controlling
power of pedaling automatically or manually.
 They are also used for power train between
internal combustion engine and an electric
motor

27.  Pitch surface: The surface of the imaginary rolling cylinder
(cone, etc.) that the toothed gear may be considered to replace.
 Pitch circle: A right section of the pitch surface.
 Addendum circle: A circle bounding the ends of the teeth, in
a right section of the gear.
 Root (or dedendum) circle: The circle bounding the spaces
between the teeth, in a right section of the gear.
 Addendum: The radial distance between the pitch circle and
the addendum circle.
 Dedendum: The radial distance between the pitch circle and
the root circle.
 Clearance: The difference between the dedendum of one gear
and the addendum of the mating gear.

28.  Face of a tooth: That part of the tooth surface lying outside
the pitch surface.
 Flank of a tooth: The part of the tooth surface lying inside the
pitch surface.
 Circular thickness (also called the tooth thickness): The
thickness of the tooth measured on the pitch circle. It is the
length of an arc and not the length of a straight line.
 Tooth space: pitch diameter The distance between adjacent
teeth measured on the pitch circle.
 Backlash: The difference between the circle thickness of one
gear and the tooth space of the mating gear.
 Circular pitch (Pc) : The width of a tooth and a space,
measured on the pitch circle.
D
N
P
c


29.  Diametral pitch (Pd): The number of teeth of a gear unit
pitch diameter. The diametral pitch is, by definition, the
number of teeth divided by the pitch diameter. That is,
Where
Pd = diametral pitch
N = number of teeth
D = pitch diameter
N
D
 Module (m): Pitch diameter divided by number of teeth. The
pitch diameter is usually specified in inches or millimeters; in
the former case the module is the inverse of diametral pitch.
m = D/N
Pd 

30. d = Diameter of the wheel
N =Speed of the wheel
ω = Angular speed
velocity ratio (n) =
1
2
2
 
1

2
1
d
d
N
N


31. ADVANTAGES
 Spur gears have high power
transmission efficiency
 They are compact and easy to
install.
 Unlike belt drives,
spur gear drives have no Slip.
 They can be used to transmit
large amount of power (of the
order of 50,000 kW)
DISADVANTAGES
 Spur gear drives are costly when
compared to belt drives
 Spur gears produce a lot of noise
when operating at high speeds.
 They cannot be used for long
distance power transmission.

32. ADVANTAGES
 Helical gears are much less
noisy. The teeth engage a little
at a time rather than the entire
face at once.
 They can handle more load then
a spur gear of equivilant width
and tooth size. They tooth is
effectively longer because it is
diagonal.
 They can be made to engage at
angles. Effeciency is lost as the
angle becomes greater.
DISADVANTAGES
 Helical gears have a higher load
capacity but are expensive to
manufacture.
 They have an axial thrust, This
can however be overcome by the
use of double helical gears by
having teeth with a 'v' shape.

33. ADVANTAGES
 This gear makes it possible to
change the operating angle.
 Differing of the number of teeth
(effectively diameter) on each wheel
allows mechanical advantage to be
changed. By increasing or
decreasing the ratio of teeth
between the drive and driven wheels
one may change the ratio of
rotations between the two, meaning
that therotational drive and torque
of the second wheel can be changed
in relation to the first, with speed
increasing and torque decreasing, or
speed decreasing and torque
increasing.
DISADVANTAGES
 One wheel of such gear is
designed to work with its
complementary wheel and no
other.
 The shafts' bearings must be
capable of supporting significant
forces
 Must be precisely mounted.

34. ADVANTAGES
 Worm gear drives operate
silently and smoothly.
 They occupy less space.
 They have good meshing
effectiveness.
 They can be used for
reducing speed and
increasing torque.
DISADVANTAGES
 Worm gear materials are
expensive.
 Worm drives have high
power losses and low
transmission efficiency.
 They produce a lot of
heat,due to resistance
between them.

35.  Spur Gear:
 Metal cutting machines
 Power plants
 Watches
 Fuel pumps
 Rack and pinion mechanisms
 Rolling mills
 Automobile gear boxes.
 Electric screwdrivers, windup alarm clocks & pumps are just a few
everyday machines where internal gears are used.
 Bevel Gear:
 Bevel gears are used in differential drives, which can transmit power to
two axles spinning at different speeds, such as those on a cornering
automobile.
 Its is used in Mining Machine equipment.
 It also used in Printing press Machine.
 Spiral bevel gears are important components on rotorcraft drive systems

36.  Worm Gear:
 Gates and Conveyor Belts – Typical worm drives can only be turned in
one direction, which means that conveyor belts and security gates lock-up
when not being used, Automatic security gates will often adopt two
worm drives, one to open and another to close.
 Elevators/Lifts – worm gears can often be found in the
machinery of common elevators/lifts because of their
compact size and non-reversible properties.
 Hoisting machines
 Automobile steering mechanisms
 Conveyors.
 Helical Gears:
 Helical gears are also used in machine tools, turbine drives,
feed drives, sand mullers, rolling mills & marine applications
And in Actuators.

37.  Rack and pinion:
 Rack and pinion Mechanism is Commonly used in
Cranes and Actuators
 It is also used in Car steering Mechanism.
 Used in Rack Railways.

38. Gears Use in Automatic Transmission
Epi-cyclic gear or planetary gear is a gear system consisting of one or
more outer gears, or planet gears, revolving about a central, or sun gear.
Typically, the planet gears are mounted on a movable arm or carrier
which itself may rotate relative to the sun gear. It is used in automatic
transmission!