DESCRIBE ABOUT GEAR

2.  A gear is a rotating machine part having cut teeth, which
mesh with another toothed part to transmit torque.
 Geared devices can change the speed, torque, and
direction of a power source.
 The teeth on the two meshing gears all have the same
shape.
 Gears almost always produce a change in torque, creating
a mechanical advantage, through their gear ratio, and thus
may be considered a simple machine.

3. Following are the different types of gears are as under :-
 Spur gear
 Helical gear
 Herringbone gear
 Rack and pinion
 Bevel gear
 Worm and worm gear

4.  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

5.  In external gearing ,the gears of
the two shafts mesh externally
with each other which is shown in
figure .The larger of these two
wheels is called spur wheel or
gear and the smaller wheel is
called pinion.

6.  In internal gearing ,the
gears of these two shafts
mesh internally with each
other as shown in figure.
The larger of these two
wheels is called annular
wheel and smaller wheel
is called pinion.

7.  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 .
 If the angles of the gear teeth are
correct, they can be mounted on
perpendicular shafts, adjusting
the rotation angle by 90 degrees.

8.  A herringbone gear is a
specific type of double
helical gear,which is side to
side (not face to face)
combination of two helical
gears of opposite hands.
 Herringbone gears are
mostly used on heavy
machinery.

9.  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.

10.  Bevel gears are used for transmitting power at a
constant velocity ratio between two shafts whose axes
intersect at a certain angle.
 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.
 Bevel gear used in marine applications, automobiles,
printing presses,power plants, steel plants etc.

12.  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, automobiles
etc

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