3. In a modern engineering design , the trend is to design
the prime movers for high power to weight ratio.
The prime movers are designed with high operating
speeds which are usually higher than required by the driven
machines.
The power transmission and speed reduction between the
prime mover and the driven machine can be achieved by
using the following:
1. Belt Drive.
2. Chain Drive.
3. Gear Drives.
INTRODUCTION
4. Belt drives are used to transmit the power from
one shaft to another which are at considerable
distance apart.
• A belt drive consist of three elements:
I. Driving pulley.
II. Driven pulley.
III. Belt.
BELT DRIVES
6. The desirable properties of the materials used for the
belts are:
High coefficient of friction
Flexibility
Durability
Strength
The different materials used are:
Leather
Fabric
Rubber
Polyester or Polyamide
MATERIAL AND CONSTRUCTION OF FLAT BELTS
7. I. Open Belt Drive.
II. Crossed Belt Drive.
III. Open Belt DriveWith Idler Pulley.
IV. Multiple Belt Drive.
V. Quarter Turn Belt Drive.
VI. Compound Belt Drive.
VII. Stepped or Cone Pulley Drive.
VIII.Fast and Loose Pulley Drive.
TYPES OF FLAT BELT DRIVES
8. 1. Open Belt Drive:
• The top side is slack side of the
belt , especially when the
distance is large between two
shafts.
• The pulleys rotate in same
direction.
2. Crossed Belt Drive:
• It is used when the shafts
are parallel and centre
distance is shorter.
• The pulleys rotate in the
opposite direction.
9. 3. Open Belt Drive with Idler Pulley:
• It is used when the shafts are parallel
and when an open belt drive cannot
be used due to small angle of contact
on the smaller pulley.
• The belt tension can be adjusted by
changing the position of idler pulley.
4. Multiple Belt Drive:
• It is used when the power is to
be transmitted from one shaft
to the number of parallel
shafts.
10. 5. QuarterTurn Belt Drive:
• It is used when the axes of the two
shafts are perpendicular and non-
intersecting.
6. Compound Belt Drive:
• It is used when the power is to be
transmitted from one shaft to
another through a number of
intermediate pulleys.
• It gives relatively high reduction
ratio.
11. 7. Stepped or Cone Pulley:
• It is used for changing the speed of
the driven shaft while the driving
shaft runs at constant speed.
• This arrangement is used in Lathes to
achieve the various spindle speeds for
a constant motor speed.
8. Fast and Loose Pulley Drive:
• It is used when the driven shaft is to
be stopped or started whenever
desired without stopping the driving
shaft.
• When the driven shaft is to be
stopped , the belt is pushed on the
loose pulley by means of a shifting
fork.
12. A Chain drive consists of an endless chain running around two sprocket
wheels.
They have features which are common to both, the gear drives and the
belt drives.
CHAIN DRIVES
Chain
Drives
Roller
Chain
Silent
Chain
13. It consists of :
1. Outer link plates
2. Inner Link Plates
3. Pins
4. Bushing
5. Roller
ROLLER CHAINS
14. It consists of a series of toothed link plates that are pin connected to
permit articulation.
Each Link Plate has two straight sided teeth with a space between them
to accommodate the mating teeth of the sprocket.
SILENT OR INVERTED – TOOTH CHAIN
15. COMPARISON BETWEEN BELT AND CHAIN DRIVE
Serial
No.
Comparison Belt Drive Chain Drive
1. Type Of Drive Non-Positive Positive
2 . Elements Of Drive Belt, Driving Pulley
and Driven Pulley
Chain, Driving and
Driven Sprocket.
3. Polygon Effect Absent Present
4. PowerTransmission
Capacity
Low High
5. Transmission Efficiency Low High
6. Space Requirement More Less
7. Lubrication Not Required Required
8. InitialTension Required Not Required
16. Gear can be defined as the
mechanical element used for
transmitting power an rotary motion
from one shaft to another by means of
progressive of projections calledTeeth.
Gears operates in Pairs , the smaller
of the pair called Pinion and the larger
is called Gear.
GEARS
18. 1. Spur Gears:
They are Used for transmitting
Power/Motion between two parallel axes
shafts.
It can be used for reduction ratio up to
6:1.
PARALLEL AXES GEARS
2. Helical Gears:
TheTeeth are cut at an angle,
known as Helix Angle with the axis of
the gear.
It can used for reduction ratio up to
6:1.
19. 3. Herringbone Gears :
It Consists of two identical helical gears
but of opposite hands cut on the same
blank with a small groove between the two
facilitate the gear generation .
It can used for reduction ratio up to 6:1
FURTHER CLASSIFICATION OF PARALLEL AXES GEARS :
a. External Gear Pair :
In external gears mesh externally.(as per
figure)
The pinion and gear always rotate in
opposites direction.
20. b. Internal Gear Pair :
The gear Meshes with an external
pinion.
The gear and pinion rotates in same
direction.
c. Rack & Pinion Gear Pair:
It is used to convert a rotary motion of
Pinion into a linear motion of the rack or vice
versa.
The straight sided rack meshes with the
pinion.
21. Two intersecting axes shafts are
connected by gears known as bevel gears.
Although the bevel gears are made for a
shaft angle of 90 °, they can be produced
for any shaft angle.
The types of bevel gears used for
connecting two intersecting shafts are :
1. Straight Bevel Gears.
2. Spiral Bevel Gears.
The bevel gear pair can be used for
reduction ratio up to 6:1
INTERSECTING AXES GEARS
22. Two non-intersecting & perpendicular
axes shafts are connected by worm and a
worm gear.
In worm gears, the worm is a driving
member whereas worm wheel is a driven
member.
The worm gear drive is used as compact
arrangement for high reduction ratios, as
high as 70:1
NON-INTERSECTING & PERPENDICULAR AXES GEARS
23. They are Connected by Spiral or Crossed
Helical gears
The crossed helical gears have only one
point contact and hence are only suitable for
transmitting small powers.
Non-Intersecting and Non-Parallel Axes Gears
24. A Coupling is a device used to connect two shafts
together at their ends for the purpose of transmitting
power.
The primary purpose of couplings is to join two
pieces of rotating equipment while permitting some
degree of misalignment or end movement or both.
COUPLING
26. 1. Sleeve or Muff:
This consists of a pipe whose bore is
finished to the required tolerance based on
the shaft size.
Based on the usage of the coupling a
keyway in made in the bore in order to
transmit the torque by means of the key.
RIGID COUPLINGS
2. Split or Clamp:
This Coupling maybe used for
heavy duty and moderate
space.
27. 3. Flange:
A flange coupling usually applies to a coupling having two separate cast
iron flanges.
Each flange is mounted on the shaft end and keyed to it.
The faces are turned up at right angle to the axis of the shaft.
The two flanges are coupled together by means of bolts and nuts.
28. 1. Bush PinType:
It can be used only when there is perfect
alignment between the axis of two shafts.
It uses a flexible element like BUSH in it.
FLEXIBLE COUPLINGS
2. Oldham:
An Oldham coupler is a method to
transfer torque between two parallel
but not collinear shafts.
29. 3. Universal or Hooke’s Joint:
A Universal joint or Hooke's joint is a in a rigid rod that allows
the rod to 'bend' in any direction
It is commonly used in shafts that transmit rotary motion.
It consists of a pair of hinges located close together, oriented at
90° to each other, connected by a cross shaft.
