3. Gears
A gear is a component within a transmission device that
transmits rotational force to another gear or device
The most common situation is for a gear to mesh with
another gear; however, a gear can also mesh with a non-
rotating toothed part, called a rack, thereby
producing translation instead of rotation.
4. Geared devices can change the speed, torque, and direction
of a power source
Types of Gears
Helical gear
This gear is used for machines that require very smooth and
fast rotations. Helical gears are used in almost all car
transmissions.
5. Bevel gear
A bevel gear is a gear that interlocks at a
90o angle. Bevel gears are used in hand drills.
Spur gear
Simplest type
Consists of cylinder or disk with the
teethprojecting radially
Used in
Gear motors and gear pumps
Automobile gear boxes
6. Belts
The belts or ropes are used to transmit
power from one shaft to another by means of
pulleys which rotate at the same speed or at
different speeds.
7. Selection of a Belt Drive
Following are the various important factors upon which
the selection of a belt drive depends:
1. Speed of the driving and driven shafts,
2. Power to be transmitted,
3. Centre distance between the shafts,
4. Space available
8. Types of Belt Drives
The belt drives are usually classified into the following
three groups :
Light drives: These are used to transmit small powers
at belt speeds up to about 10 m/s, as in agricultural
machines and small machine tools.
Medium drives: These are used to transmit medium
power at belt speeds over 10 m/s but up to 22 m/s, as in
Machine tools.
Heavy drives: These are used to transmit large powers
at belt speeds above 22 m/s, as in Compressors and
Generators.
9. Flywheel
A flywheel is a rotating mechanical device that is used to
store rotational energy.
Flywheels have a significant moment of inertia and thus
resist changes in rotational speed.
The amount of energy stored in a flywheel is proportional
to the square of its rotational speed.
Energy is transferred to a flywheel by applying torque to it,
thereby increasing its rotational speed, and hence its
stored energy.
10. Material of Construction
Flywheels are typically made of steel and these are
generally limited to a revolution rate of a few thousand
RPM
Some modern flywheels are made of carbon fiber materials
and employ magnetic bearings, enabling them to revolve at
speeds up to 60,000 RPM
11. Applications
Flywheels are used in reciprocating engines because the
energy source, torque from the engine, is periodic
Delivering energy at rates beyond the ability of a
continuous energy source. This is achieved by collecting
energy in the flywheel over time and then releasing the
energy quickly, at rates that exceed the abilities of the
energy source.
