The document discusses different types of power transmission devices and gears. It describes belt drives, chain drives, and gear drives. It then focuses on different types of gears including spur gears, helical gears, bevel gears, worm gears, and hypoid gears. For each gear type, it provides details on how they work, their advantages, limitations, and applications. The main gear types covered are spur gears, which are the most common and used for low speed applications, helical gears which operate more smoothly for higher speeds, bevel gears which change the direction of rotation, and worm gears which enable high gear reductions.

1. Power Transmission Devices
AEPS PIECES

2. Power Transmission Devices
• Belt drive,
• chain drive,
• gear drive

3. Gears
• Gears are toothed wheel which transmit the power and motion from one shaft to
another by means of successive engagement of teeth.
• Shaft are parallel to each other, two types of gears are mounted on the shaft to
transmit the power : Spur Gear, Helical Gear.
• Shafts are non intersecting and non parallel and non coplanar then power transmitting
gears are: Spiral Gear, Worm and Worm Wheel

4. Spur gears are the most common type
of gears.
Spur gears are cylindrical and have
straight teeth, and are mounted on
parallel shafts.
Used to transmit the rotary motion
between two shaft which are parallel.
It is used at once to create very large
gear reductions
Larger gear: Driven gear- Spur gear /
wheel.
Smaller gear: Driver Gear: Pinion.
Motion of the two gears are always
opposite to each other.
SPUR GEARS

6. • Advantages of spur gears
(i) Easy to manufacture.
(ii) Simple and Cheaper among all types of
gears.
(iii) The spur gears do not create axial load or
thrust on the shaft and the bearings.
(iv) The efficiency of spur gear pair is high
(96% to 99%).
(v) The spur gears are interchangeable.

7. Limitations of spur gears
(i) The contact between the two meshing teeth
is sudden line contact. Due to sudden line
contact, the operation of spur gear pair is
noisy.
(ii) The spur gears are not suitable for high
speed applications.
(iii) The power transmitting capacity of spur gear
pair is lower than the helical gear pair.
•

8. Applications of spur gears
(i) The spur gears are used in automobile gear
boxes, machine tool gear boxes, industrial
gear boxes, etc.
(ii) The spur gears are mainly used for low speed
applications.

9. • The teeth on helical gears
are cut at an angle to the
face of the gear. When two
teeth on a helical gear
system engage, the contact
starts at one end of the
tooth and gradually spreads
as the gears rotate, until the
two teeth are in full
engagement.
Helical Gear

10. • This gradual engagement makes helical gears
operate much more smoothly and quietly
than spur gears. For this reason, helical gears
are used in almost all car Transmission
• Because of the angle of the teeth on helical
gears, they create a thrust load on the gear
when they mesh. Devices that use helical
gears have bearings that can support this
thrust load.

12. Advantages of helical gears
(i) The engagement is gradual, and hence the
operation is smooth and silent.
(ii) Suitable for high speed application.
(iii) The power transmitting capacity of
helical gear pair is higher than that of
identical spur gear pair.
(iv) The efficiency of helical gear pair is high
(96% to 99%).

13. Limitations of helical gears
(i) The helical gears are difficult to
manufacture as compared to spur
gears.
(ii) The helical gears are costlier than
the spur gears
(iii) The helical gears create axial load
or thrust on the shaft and the
bearings.

14. Applications of helical gears
(i) The helical gears are used in high speed
stages of automobile gear boxes, machine tool
gear boxes, industrial gear boxes, etc.
(ii) The helical gears are used in high speed
application like steam and gas turbines.

15. 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.
Straight bevel gear teeth actually have the same problem as
straight spur gear teeth -- as each tooth engages, it impacts the
corresponding tooth all at once.
Bevel gears

16. Spiral Bevel Gear
These spiral teeth engage
just like helical teeth : the
contact starts at one end of
gear and progressively
spreads across the whole
teeth

17. Advantages of bevel gears
(i) The bevel gears can transmit the power/motion
between two shafts which are at right angles.
(ii) The efficiency of bevel gear pair is high (95% to
98%).
(iii) The arrangement is very compact.

18. Limitations of bevel gears
(i) The bevel gears are difficult to manufacture.
(ii) The cost of bevel gears is higher than spur
and
helical. gears.
(iii) The bevel gears are non-interchangeable

19. Applications of bevel gears
(i)The bevel gears are used in differential gear
box of automobiles.
(ii) They are also used in industrial gear boxes
where the input and output shafts are
required at right angles.

20. 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. This is because the angle on the worm is
so shallow that when the gear tries to spin it,
the friction between the gear and the worm
holds the worm in place.
• This feature is useful for machines such as
conveyor systems, in which the locking feature
can act as a brake for the conveyor when the
motor is not turning
Worm gears

21. Advantages of worm gears
(i) The worm gear drives are compact as
compared to spur, helical, or bevel gear
drives.
(ii) They can be used for high reduction
ratios, as high as 70:1 in small space
(iii) The operation of worm gear drive is
smooth
and silent.
(iv) The provision of self locking can also be
made.
(V) Tooth engagement occurs without shock
hence operation in quieter.

22. Limitations of worm gear drives
1. The efficiency of worm gear drive is low (45% to 95%). The
efficiency
of worm gear drive decreases with increase in reduction ratio.
For the reduction ratio of 70:1, the efficiency is in the range of
45% to 50%.
1. In worm gear drive, due to frictional losses, considerable
amount of heat is generated. Therefore, effective cooling is
necessary.
2. The power transmitting capacity of the worm gear drive is
comparatively low.
3. The worm gear pair is costly as compared to other gear pairs.
4. The worm as well as worm gears are difficult to manufacture.
5. The worm gears are non-interchangeable.

23. Applications of worm gear drives
1. The worm gear drives are used in lifting or hoisting
devices, cranes, lifts, conveyors, etc.
2. They are used in all applications where high
reduction ratio is required.
The other gears used for connecting two non
intersecting and perpendicular axes
shafts are hypoid bevel gears, skew bevel gears and
spiral or crossed helical gears.

24. Gear drive

25. Types of gears
• Parallel axis
• Intersecting
• Non-intersecting and perpendicular
• Non-intersecting and non-perpendicular

27. Parallel axis

29. Parallel gears also classified

30. Intersecting axes gears

31. Non-intersecting and perpendicular

32. Non-intersecting and non-perpendicular

33. THANK YOU