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 .
It transmit exact velocity ratio .
It may be used to transmit large
It has high efficiency.
It has reliable service .
It has compact layout
Advantages of Gear Drive
Disadvantages of Gear Drive
The manufacture of gears
require special tools and
The error in cutting teeth may
cause vibration and noise during
Types of Gears
Teeth is parallel to axis of
Transmit power from one
shaft to another parallel
Used in Electric screwdriver,
oscillating sprinkler, windup
alarm clock, washing
machine and clothes dryer
External & Internal Gear
An external gear is one
with the teeth formed on
the outer surface of a
cylinder or cone.
Conversely, an internal
gear is one with the teeth
formed on the inner surface
of a cylinder or cone.
The teeth on helical gears are
cut at an angle to the face of
This gradual engagement
makes helical gears operate
much more smoothly and
quietly than spur gears
Bevel gears are useful when the
direction of a shaft's rotation
needs to be changed
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.
Hypoid gears resemble spiral
bevel gears except the shaft axes
do not intersect.
Usually require some of the most
viscous types of gear oil to avoid
it being extruded from the mating
Which are normally straight cut
bevel gears in motor vehicle
Worm and Worm Gear
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
Many worm gears have an interesting
property that no other gear set has: the
worm can easily turn the gear, but the
gear cannot turn the worm
Worm gears are used widely in
material handling and transportation
machinery, machine tools,
Rack and Pinion
It is Special case of a spur gear
where it is made of infinite
diameter so that the pitch
surface is a plane .
It is used in a lathe in which the
rack transmits motion to the
A non-circular gear (NCG) is a
special gear design with special
characteristics and purpose.
transmissions), window shade
panel drives, mechanical presses,
high torque hydraulic engines.
A crown gear can only
mesh accurately with
another bevel gear
Sun and Planet Gear
A gear train having a relative
motion of axes is called a
planetary or an epicyclic gear
Important application of
epicyclic gears are in
transmission, computing devices,
wrists watches, hoists, back gear
of lathe etc.
Harmonic Drive Gear
Is a special type of
mechanical gear system that can
improve certain characteristics
compared to traditional gearing
typically used in industrial motion
control, machine tool, printing
machine, robotics and aerospace.
for gear reduction but may also be used
to increase rotational speed, or for
1. Grease lubrication
Grease lubrication is suitable for any gear
system that is open or enclosed, so long as it runs
at low speed.
2. Splash lubrication
Splash lubrication is the normal method for
lubricating spur, helical, bevel and worm gears.
3. Spray lubrication
For the higher speed units (10 to 20 m/s
Lubricant for Gear