Basic Mechanical Engineering (BME) Notes.
Vidyapratishthan’s Kamalnayan Bajaj Institue of Engineering and Technology, Baramati
Department of Mechanical Engineering
Subject Notes of
Basic Mechanical Engineering (BME)
Session-2018-19
(F.E – II and F.E – V)
Subject Coordinator
Dr. Vipin B. Gawande
Assistant Professor
Department of Mechanical Engineering
V.P.K.B.I.E.T, Baramati
Dr. Vipin B. Gawande, Assistant Prof., Dept. of Mechanical Engg., V.P.K.B.I.E.T, Baramati.
Page 1
Basic Mechanical Engineering (BME) Notes.
UNIT-1- (a) Machine Elements
Q-1.
What is machine? How are machine elements classified?
[4]
Machine: - A machine is a device consisting of various elements arranged together, so as to
perform the prescribe task to satisfy human needs.
Example: - Lathe machine uses electrical energy for machining operations like turning,
facing, threading, chamfering etc.
Machine Elements: - is an individual component or a group of components of a machine
which perform a specific function
Types:1) Machine elements used for holding the components
Examples: - Nut and bolts, screw, cotters, keys, couplings, pins, revettes.
2) Machine elements used for transmitting the power
Examples: - Gears, shafts, clutches and brakes, pulleys, belts, chain, sprocket are used to
transmit power from one place to another.
3) Machine elements used for support of other components
Examples: - Bearings, axles, brackets, hangers etc. are used to give support to rotating or
stationary members.
Q 2.
Explain different types of shafts.
[4]
A shaft is a rotating machine element, usually circular in cross section, which is used
to transmit power from one part to another, or from a machine which produces power to a
machine which absorbs power.
In order to transfer power from one shaft to another, various machine elements like pulleys,
gears, crank etc. are mounted on it with the help of keys or splines.
Types
They are mainly classified into two types.
1) Transmission shafts are used to transmit power between the source and the machine
absorbing power; e.g. counter shafts and line shafts.
Dr. Vipin B. Gawande, Assistant Prof., Dept. of Mechanical Engg., V.P.K.B.I.E.T, Baramati.
Page 2
Basic Mechanical Engineering (BME) Notes.
Line shaft is a very long transmission shaft
1(a)
which is directly driven by the prime mover
(or power source) and which is used
distribute power from main power source to
different power consuming devices
Counter shaft is a secondary shaft which is
1(b)
not directly connected to power source but
driven by it through belt, chain or gear drive.
2.
Q-3.
Machine shafts are the integral part of the machine itself.
Write the function of axle.
[2]
It is a non-rotating element which is used to support rotating machine elements like wheels,
pulleys etc.
Axle of railway wagon
Q-4.
Axle of bicycle
Axle of car
What is the difference between shaft and axle?
Refer the following table for difference between shaft and axle-
Dr. Vipin B. Gawande, Assistant Prof., Dept. of Mechanical Engg., V.P.K.B.I.E.T, Baramati.
Page 3
Basic Mechanical Engineering (BME) Notes.
S.No
Q-5.
Shaft
Axle
1
It is rotating element of a machine.
It is non rotating or stationary element of a
machine.
2
It is subjected to bending and torsional
moment.
It is subjected to only bending moment.
3
It is used to transmit the torque and to
support the elements like gears, pulleys,
sprockets etc.
It is used to support the elements like pulleys,
brake drums, wheels etc.
4
Example:- Transmission shaft, Machine
shaft.
Example:- Front axle in four wheelers, axle in
bicycle etc.
Define ball bearing? Write the functions of bearings?
[4]
Bearing is a mechanical element that permits relative motion between two parts while
carrying load.
Example:- In automobiles, bearing is placed between wheel hub and axle.
Functions of bearings:1) It provides physical support to shafts and allows it to rotate with minimum friction, on its
axis in order to reduce loss in power during transmission.
2) Bearings sustain the forces acting on the shaft or axle and transmit them to machine frame
or wheel.
3) It reduces wear between the rotating surfaces and also carry away heat generated during
operation.
Types:1) Sliding Contact Bearing:- In this type of bearing, the rotating
shaft has a sliding contact with the bearing which is held
stationary. Due to large contact area, friction between mating parts
is high, requiring higher lubrication.
Dr. Vipin B. Gawande, Assistant Prof., Dept. of Mechanical Engg., V.P.K.B.I.E.T, Baramati.
Page 4
Basic Mechanical Engineering (BME) Notes.
2) Rolling Contact Bearing:- is a bearing which carries a
load by placing rolling elements (such as balls or rollers)
between two bearing rings called races. The relative motion
of the races causes the rolling elements to roll with very little
rolling resistance.
All rolling contact bearings (ball and roller) have low friction Roller Contact bearing
Ball Bearing
coefficients compared with journal bearings. So they are
called as ‘Anti-friction bearings’.
Q-6.

Write a note on ball bearing.
[4]
Ball Bearings are a type of rolling-element bearing that uses balls to maintain the separation
between the moving parts of the bearing.

The purpose of a ball bearing is to reduce rotational friction and support radial and axial loads.

In most applications, one race is stationary and the other is attached to the rotating assembly (e.g.,
a hub or shaft).
Ball bearings are comprised of four major parts:
 a large ring (outer race),
 a small ring (inner race),
 balls between the rings (steel balls),
and a cage/retainer to prevent the balls from hitting
each other.
Q-6.
What are the different types of ball bearing?
[4]
Ball bearings can be broadly classified into the following
1. Deep-Groove ball bearing
2. Angular-contact ball bearing
3. Self-aligning ball bearing
4. Thrust ball bearing
Dr. Vipin B. Gawande, Assistant Prof., Dept. of Mechanical Engg., V.P.K.B.I.E.T, Baramati.
Page 5
Basic Mechanical Engineering (BME) Notes.
1. Deep-Groove ball bearing
(Fig. a)

They are primarily designed to support high radial load and moderate thrust load.

They have deep raceways that are continuous (i.e. there are no openings or recesses)
over all of the ring circumferences.

They are commonly used in electric motors, compressors, fans, and conveyors.
2. Angular-contact ball bearing

The angular contact bearings (Fig. b) are designed such that the centerline of contact
between balls and raceways is at an angle to a plane perpendicular to the axis of
rotation.

This angle is called “contact angle”. The angular contact ball bearing may be of
single or two rows of balls.

They are meant to carry radial and axial load together or only axial load depending on
the magnitude of the angle of contact
3. Self aligning ball bearing

For assembly of shaft and housing which cannot be made perfectly coaxial, the selfaligning ball bearings are best used.

They consist of two rows of balls on a common spherical outer race (Fig. c).

In such bearings the assembly of inner ring and balls can tilt in the outer ring.

The loss of load-carrying capacity is inherent in this construction, due to non-conformity of
outer raceway with the balls. This is compensated by having large number of balls in the
bearings.
Dr. Vipin B. Gawande, Assistant Prof., Dept. of Mechanical Engg., V.P.K.B.I.E.T, Baramati.
Page 6
Basic Mechanical Engineering (BME) Notes.

Self-aligning ball bearings are used in top drafting rollers and main shaft of ring spinning
machine.
4. Thrust ball bearing

If the contact angle of angular contact bearings exceeds 45°, it is classified as ‘thrust
bearing’.

The maximum value this angle can assume is 90°. In such case, races are on the sideways as
shown in Fig. (d).

Q-7.

Such a bearing cannot take any radial load, and is used only for thrust loads.
Sketch and explain different types of keys.
[6]
A key is a piece of steel inserted between the shaft and hub or boss of the pulley to connect these
together in order to prevent relative motion between them.

It is always inserted parallel to the axis of the shaft.

Keys are used as temporary fastenings and are subjected to considerable crushing and shearing
stresses.

A keyway is a slot or recess in a shaft and hub of the pulley to accommodate a key. A keyway is
usually cut by a vertical or horizontal milling cutter.
Dr. Vipin B. Gawande, Assistant Prof., Dept. of Mechanical Engg., V.P.K.B.I.E.T, Baramati.
Page 7
Basic Mechanical Engineering (BME) Notes.
1. Sunk Key: - The sunk keys are provided half in the keyway of the shaft and half in the
keyway of the hub or boss of the pulley or gear.
The sunk keys are of the following types :
1.1. Rectangular Sunk Key
Rectangular sunk keys are keys whose width and height are not equal.
Dr. Vipin B. Gawande, Assistant Prof., Dept. of Mechanical Engg., V.P.K.B.I.E.T, Baramati.
Page 8
Basic Mechanical Engineering (BME) Notes.
1.2. Square Sunk Key
Square sunk keys are keys whose width and height are equal.
1.3. Parallel Sunk Key
Parallel Sunk Keys are Tapeless Keys having a Rectangular or Square Cross Section.
 It is used when the Rotating Elements like pulley, gears etc, are required to slide along
the shaft.
1.4. Gib Head Sunk Key
Gib Head Keys are Rectangular Keys with head at one end known as Gib-Head.
It is usually provided to facilitate the removal of key.
Dr. Vipin B. Gawande, Assistant Prof., Dept. of Mechanical Engg., V.P.K.B.I.E.T, Baramati.
Page 9
Basic Mechanical Engineering (BME) Notes.
1.5. Feather Sunk Key
A feather key is a parallel key which is fixed
either on the shaft or to the hub and which
permits relative axial movement between
them.
Feather keys are used when the parts
mounted on the shaft are required to slide on
along the shaft such as clutches or gear
shifting devices.
1.6. Woodruff Sunk Key
A woodruff key is a sunk key in the form of
an almost semicircular disk of uniform
thickness.
The key way in the shaft is in the form of
semicircular recess with the same curvature
as that of key.
This key is largely used in machine tool and
automobile construction.
2. Saddle Key :
A saddle key is a key which fits in the keyway of the hub only.

There is no keyway on the shaft

These keys are suitable only for light duty, since they rely on a
friction drive alone.
Dr. Vipin B. Gawande, Assistant Prof., Dept. of Mechanical Engg., V.P.K.B.I.E.T, Baramati.
Page 10
Basic Mechanical Engineering (BME) Notes.
Types:2.1. Hollow Saddle Key:A hollow saddle key has a concave surface at
the bottom to match the circular surface of
the shaft.
It is usually used as a temporary fastening in
fixing and setting eccentrics, cams, etc.
2.2. Flat Saddle Key
A flat saddle key has a flat surface at the and
fits on the flat surface machined on the shaft.
The resistance to slip in case of flat key is
slightly more than that of hollow key with
concave surface.
Therefore flat saddle key is slightly superior
to hollow saddle key as far as power
transmitting capacity is concerned
3. Tangent Keys:Tangent keys are fitted in pair at Right
angles for mating bodies of Rectangular
Cross Section.
These are used in large heavy duty shafts.
4. Round Keys:Round keys are Circular in cross section
and fits into the holes drills partly in the
shaft and partly in the hub.
Dr. Vipin B. Gawande, Assistant Prof., Dept. of Mechanical Engg., V.P.K.B.I.E.T, Baramati.
Page 11
Basic Mechanical Engineering (BME) Notes.
5. Splines:Splines are keys in which tooth like
structure,
is
shape
on
the
outer
circumference of the shaft and inner
circumference of the hub.
The splined shafts are used when the force
to be transmitted is large in proportion to
the size of the shaft as in automobile
transmission
and
sliding
gear
transmissions.
6.Kennedy Keys: Kennedy key consists of two square keys.
 In this case, the hub is bored off the centre and the
two keys force the hub and the shaft to a concentric
position.
 Kennedy key is used for heavy duty applications.
Q-8:-
Write the function of coupling.
[1]
A coupling can be defined as a Mechanical device that connects two rotating shafts to each
other at their ends for the purpose of transmitting torque.
Functions:- Couplings are used for

Transmitting power from one end to another end

Misalignment of the shafts or to introduce mechanical flexibility.

Reduction of shock loads from one shaft to another.

Protection against overloads
Dr. Vipin B. Gawande, Assistant Prof., Dept. of Mechanical Engg., V.P.K.B.I.E.T, Baramati.
Page 12
Basic Mechanical Engineering (BME) Notes.

Q-9:-
To alter the vibration characteristics of rotating units.
Explain different types of Coupling? OR
Explain with neat sketch flange coupling.
[6]
Couplings are classified into two categories-
1) Rigid Couplings:Rigid couplings are used to connect two shafts which are perfectly aligned. Rigid couplings
are further classified into:1. Muff/Sleeve/Box Coupling:2. Split muff or clamp or compression coupling
3. Flange coupling
Flange coupling:- This is a standard form of coupling and is extensively used. It can be
seen in large power machines and is used for heavy loads.
Dr. Vipin B. Gawande, Assistant Prof., Dept. of Mechanical Engg., V.P.K.B.I.E.T, Baramati.
Page 13
Basic Mechanical Engineering (BME) Notes.
Flange Coupling has two similar cast iron flanges.
These flanges have keyways in the hubs, so that the ends of the shafts to be connected can
be keyed to the flanges with separate rectangular sunk type keys. Even the shafts also have
keyways, which are assembled at right angles, so that the key of one shaft does not slide
into the other.
The faces of the two flanges are then held together with the help of bolts and nuts (4 or
more). These may be square headed or hexagonal headed. The bolts should be an exact fit,
so that the power can be transmitted properly from one shaft and flange to another.
It is classified into two types depending upon its shape:
a. Unprotected Flange Coupling:- In this type the bolt and nuts lie outside, and during
rotation of shafts, if failure occurs in nut and bolt, they might hurt the workers. Hence this
type of coupling is known as unprotected flange coupling.
b. Protected Flange Coupling:- In this type of coupling, the shield/cover is provided by
slightly altering the shape of the flanges to cover the nuts and bolts. So the flanges have a
flared and flattened rim i.e. a projected outer ring (shroud) as shown in the figure. This
overhangs over the bolt heads and nuts and thus minimizes accidents and ensures safety,
Hence it is named as a 'Protected Flange Coupling'.
Dr. Vipin B. Gawande, Assistant Prof., Dept. of Mechanical Engg., V.P.K.B.I.E.T, Baramati.
Page 14
Basic Mechanical Engineering (BME) Notes.
Advantages of rigid flange coupling:

High torque transmitting capacity.

Easy to assemble and dismantle.

Simple in construction.

Easy to design and manufacture.
Disadvantages of rigid flange coupling :

It can't tolerate misalignment between the axes of two shafts.

It is used only where the motion is free from shock and vibrations.

It requires more radial space.
2) Flexible Couplings:- This type of couplings are used to connect two shafts consisting of
small misalignment which may be lateral or angular. These are further classified into1. Bushed pin type coupling
2. Oldham’s coupling
3. Universal coupling.
Q10:- Explain construction and working of single plate clutch with neat sketch.
[6]
Clutch is mechanical device which is used to transmit rotating motion or torque from one
shaft to another shaft when required. Clutch provides a temporary connection between input
and output shaft. Clutch lies between the engine and the gear box.
Single plate clutch:A single plate clutch is consisting of various parts; for proper working. They are arranged in
a systematical order. Mainly it consists of a clutch plate with both side friction lining and
some other parts which helps in the proper functioning of a clutch like flywheel, pressure
plate, thrust bearing, hub, springs and input mechanism for engaging and disengaging of
clutch. Clutch plate is attached with the hub between flywheel and the pressure plate and it
moves axially on driven shaft. In singe plate clutch; clutch plate should have both side
friction lining because it is mounted between pressure plate and flywheel, friction is
responsible for the torque transmission. The pressure plate is attached with the flywheel and
Dr. Vipin B. Gawande, Assistant Prof., Dept. of Mechanical Engg., V.P.K.B.I.E.T, Baramati.
Page 15
Basic Mechanical Engineering (BME) Notes.
springs. Pressure plate helps to push the clutch plate towards the flywheel. A lever is
attached to thrust bearings with some mechanism on driven shaft which transmits input and
output motion from clutch pedal.
Advantages:1.
The working of the single plate clutch is smooth i.e. the engagement and
disengagement is very smooth in operation.
2.
Single plate clutches have quick operation and respond fast.
3.
No requirement of coolant because less is generated therefore they are called dry
clutches.
Disadvantages:1.
It has less torque transmitting capacity
2.
It has bigger in size even for transmitting less torque.
3.
It requires high maintenance because they are dry clutches and it is necessary to
prevent them from moisture or any leakage of lubricant/oil in machinery.
4.
Single plate clutches have high wear and tear rate and have less smooth engagement.
Q11:- Explain the working of disc brake with neat sketch.
[4]
Brake is a machine element which is used either to stop the machine or retard the motion of
Dr. Vipin B. Gawande, Assistant Prof., Dept. of Mechanical Engg., V.P.K.B.I.E.T, Baramati.
Page 16
Basic Mechanical Engineering (BME) Notes.
a moving system, such as a rotating rollers or drums or vehicle where the driving force has
ceased to act or is still acting.
Disc brake
Components of Disc Brake:-
1. Wheel Hub: The disc rotor is attached to the wheel hub and it rotates with it. The wheel
of the vehicle is bolted to the wheel hub.
2. Caliper Assembly:
The caliper assembly consist of:(i) Brake pad: It makes contact with the rotor disc and due to the friction between the brake
pad and rotor disc the vehicle speed reduces and it stops.
(ii) Caliper bracket
(iii) Caliper frame
(iv) Piston: It applies the brake force on the brake pads when brake lever is pressed.
(v) Slider pin: It is the sliding pin which slides in the hole when brake is applied.
(vi) Dust boots: It prevents the entry of dust into the caliper pin or slider pin hole.
3. Disc Rotor: It is the rotating part of disc brake. When brakes are applied, a lot of heat is
generated which can decrease the braking efficiency, so the rotor has drilled vent holes on it
Dr. Vipin B. Gawande, Assistant Prof., Dept. of Mechanical Engg., V.P.K.B.I.E.T, Baramati.
Page 17
Basic Mechanical Engineering (BME) Notes.
which dissipates the heat.
Working Principle:1. When brake pedal is pressed, the high pressure fluid from the master cylinder pushes the
piston outward.
2. The piston pushes the brake pad against the rotating disc.
3. As the inner brake pad touches rotor, the fluid pressure exerts further force and the
caliper moves inward and pulls the outward brake pad towards the rotating disc and it
touches the disc.
4. Now both the brake pads pushes the rotating disc and a large amount of friction is
generated in between the pads and rotating disc which slows down the vehicle and finally
let it stop.
5. When brake pad is released, the piston moves inward and the brake pad moves away
from the rotating disc and the vehicle again starts to move.
Advantages:1. It is lighter than drum brakes.
2. It has better cooling ( because the braking surface is directly exposed to the air)
3. It provides uniform pressure distribution
4. Replacement of brake pads are easy.
5. By design they are self-adjusting brakes.
Disadvantages:1. It is costlier than drum brakes.
2. Higher pedal pressure is required for stopping the vehicle. This brake system is installed
with vacuum booster.
3. It is difficult to attach a suitable parking attachment .
Dr. Vipin B. Gawande, Assistant Prof., Dept. of Mechanical Engg., V.P.K.B.I.E.T, Baramati.
Page 18
Basic Mechanical Engineering (BME) Notes.
Vidyapratishthan’s Kamalnayan Bajaj Institue of Engineering and Technology, Baramati
Department of Mechanical Engineering
Subject Notes of
Basic Mechanical Engineering (BME)
Session-2018-19
(F.E – II and F.E – V)
Subject Coordinator
Dr. Vipin B. Gawande
Assistant Professor
Department of Mechanical Engineering
V.P.K.B.I.E.T, Baramati
Dr. Vipin B. Gawande, Assistant Prof., Dept. of Mechanical Engg., V.P.K.B.I.E.T, Baramati.
Page 1
Basic Mechanical Engineering (BME) Notes.
UNIT-1- (b) Power Transmission Elements
Q-1:-
Write notes on –
[4]
1) Flat belt drive 2) V- belt drive
Ans:-
1) Flat Belt Drive:-

They are rectangular in cross section.

Flat belts are easy to manufacture and hence have low
cost.

They can be used for long center distance between the
shafts.

The periodic adjustment of belt tension and
replacement of belts when worn out are easier in the
case of tapes and flat belts.

Flat belts transmit more power, more efficiently than V
Belts when each can be used in the same application.

Cross section of flat belt
Generates more noise than V-belts.
2) V- Belt Drive:
Trapezoidal in cross section where lower width is in
contact with the pulley.

V- belts are made of reinforcement material and hence
higher cost.

They are suitable for short to medium center distance
between shafts.

Precise alignment of pulleys and shafts are critical with
V- Belts.

The V-belt has more friction than the flat belt, therefore
uses more power to turn.

Smooth and quite operation even at high speed.
Cross section of V-belt
Dr. Vipin B. Gawande, Assistant Prof., Dept. of Mechanical Engg., V.P.K.B.I.E.T, Baramati.
Page 2
Basic Mechanical Engineering (BME) Notes.
Q-2:-
Differentiate between: Flat belt drive and V-belt drives. Show their cross sections.
[4]
Refer the points from above question.
Q-3:-
Write a notes on – Types of belt drives
OR
[4]
1) Open belt drive and 2) Cross belt drive.
Ans:-
1) Open Belt Drive :-
Fig. 1- Open Belt Drive
Open Belt Drive with Idler Pulley:-
 Belts become slack due to creep during its service life.
 Therefore, a provision should be made to adjust the belt tension from time to time.
 Different methods are available to adjust belt tensions.
 Adjustment of belt tension can also be carried out using an idler pulley.
 Idler pulley is held against the belt by its own weight.
 In all the cases, the idler pulley should be located next to driver pulley on the loose
side of belt.
 The idler pulley causes increase in frictional contact between the belt and driving
pulley.
 The idler pulley increases the arc of contact between belt and driver pulley, which
reduces belt slippage problems and helps in maximum transfer of power.
Dr. Vipin B. Gawande, Assistant Prof., Dept. of Mechanical Engg., V.P.K.B.I.E.T, Baramati.
Page 3
Basic Mechanical Engineering (BME) Notes.
2) Cross Belt Drive:-
3) Quarter turn/ Right angle drive belt drive
 The two axes of the pulleys are at right angle to each other.
 It is used to drive non-parallel, non intersecting shafts.
4) Compound Pulleys
Dr. Vipin B. Gawande, Assistant Prof., Dept. of Mechanical Engg., V.P.K.B.I.E.T, Baramati.
Page 4
Basic Mechanical Engineering (BME) Notes.
 Main functions of a compound drive are to transmit motion and power to long
distances.
 It can also provide high velocity ratio between the driving and driven shaft.
Q-4:-
Compare between belt drive and chain drive.
[4]
Ans:-
Dr. Vipin B. Gawande, Assistant Prof., Dept. of Mechanical Engg., V.P.K.B.I.E.T, Baramati.
Page 5
Basic Mechanical Engineering (BME) Notes.
Q-5:-
Explain different types of chain drives?
Ans:-
Chains are classified into following types-
[4]
1) Load lifting chains:- are used for
suspending, lowering or raising loads
in material handling equipment. Link
chains are used in low capacity hoists,
winches and hand operated cranes.
2) Hauling
chains:-
are
used
for
carrying materials continuously by
sliding,
pulling
or
carrying
in
conveyors. These are used in lightload, low-speed conveyors
3) Power transmission chains:-
are
used for transmitting power from one
shaft to another.
Q-6:-
Explain different types of gears?
Ans:-
Gears are machine elements, which are required to transmit power between shafts
[4]
rotating at different rotational speeds. By adding teeth of the proper shape on disk,
power can be transmitted without slip at uniform rate.
Types:1) Spur Gear:
Spur gears transmit power through shafts that are parallel.

The teeth of the spur gears are parallel to the shaft axis.

Spur gears tend to be noisier than helical gears because they operate
with a single line of contact between teeth.

Used in- Gear box, machine tools, automobiles, watches etc.
Dr. Vipin B. Gawande, Assistant Prof., Dept. of Mechanical Engg., V.P.K.B.I.E.T, Baramati.
Page 6
Basic Mechanical Engineering (BME) Notes.
2) Helical Gear:
Helical gears have teeth that are oriented at an angle to the shaft.

This causes more than one tooth to be in contact during operation
and helical gears are capable of carrying more load than spur gears.

Due to the load sharing between teeth, this arrangement also allows
helical gears to operate smoother and quieter than spur gears.

Helical gears produce a thrust load during operation.

Used in –high speed gear boxes, rolling mills, steam and gas
turbine for speed reduction.
3) Herringbone gears:
Double helical gears are a variation of helical gears in which two
helical faces are placed next to each other without a gap separating
them.

Each face has identical, but opposite, helix angles.

Employing a double helical set of gears eliminates thrust loads and
offers the possibility of even greater tooth overlap and smoother
operation.

Herringbone gears are mostly used on heavy machinery.
4) Bevel Gears:
Bevel gears are cone shaped gears which transmit motion between
two intersecting shafts.

They are used in applications where a right angle gear drive is
required.

Bevel gears are generally more costly and are not able to transmit
as much torque, per size, as a parallel shaft arrangement.

Bevel gears are used in differential drives, rotorcraft, hand drill,
air preheater etc.
Dr. Vipin B. Gawande, Assistant Prof., Dept. of Mechanical Engg., V.P.K.B.I.E.T, Baramati.
Page 7
Basic Mechanical Engineering (BME) Notes.
5) Worm and Worm Wheel:
Used for large speed reduction, between non parallel, non
intersecting shafts.

Worm is a screw like member and wheel is a helical gear.

The action is very similar to that between a screw and a nut. Hence
the drive is also called as screw gearing

Worm gears produce thrust load and are good for high shock load
applications but offer very low efficiency in comparison to the
other gears.

Worm
drives
are
used
in presses, rolling
mills, conveying
engineering, mining industry machines, on rudders, and worm drive
saws.
6) Rack and Pinion:
Rack is a straight bar with teeth cut perpendicular to the axis.

Rack can be considered as a gear wheel with infinite radius.

The pair is used to convert the rotary motion to rectilinear motion.

Applications:-

Mechanism for moving carriage in a lathe, spindle in drilling
machine and bed in a planning machine
7) Internal Gears:
In internal gear, the teeth are cut on the inside of rim of gear.

Internal gears are often used in applications involving planetary
gear drives and gear couplings.
Dr. Vipin B. Gawande, Assistant Prof., Dept. of Mechanical Engg., V.P.K.B.I.E.T, Baramati.
Page 8
Basic Mechanical Engineering (BME) Notes.
Q-7:-
Compare:- Belt drive, chain drive and gear drive (four points).
[4]
Q-8-
Explain Simple Spur Gear Train? What is gear ratio or speed ratio?
[4]
Ans:-
A gear train is an arrangement of number of gear and these gears successively mesh
Ans:-
each other through which the power can be transmitted between the driving and the
driven shafts.
In a simple gear train, a series of gear wheels are mounted on different shafts and
between the driving and driven shaft, each shaft carrying only one gear, Consider A is
the driving gear, D is the driven gear and B &C intermediate gears. The intermediate
gears will not affect the velocity ratio of driving and driven gear. The intermediate gears
change the direction of rotation of driven gear. Therefore it also known as idler gear.
When numbers of intermediate gears are even , the driven gear rotates opposite
direction of driving gear.
Dr. Vipin B. Gawande, Assistant Prof., Dept. of Mechanical Engg., V.P.K.B.I.E.T, Baramati.
Page 9
Basic Mechanical Engineering (BME) Notes.
Let NA- rpm of the first gear A
TA- number of teeth on gear A
DA- diameter of the gear A
Similarly NB, NC And ND- rpm of gear B, C and D respectively
TB, TC and TD- number of teeth on gear B, C and D respectively
DB, DC and DD- diameter of gear B, C and D Respectively
Speed Ratio or Gear Ratio:- The gear ratio is the ratio of the number of turns the
output shaft makes when the input shaft turns once.
N A TB DB


,
N B TA DA
N B TC DC


N C TB DB
N C TD DD


N D TC DC
and
N A TD DD


N D TA DA
Dr. Vipin B. Gawande, Assistant Prof., Dept. of Mechanical Engg., V.P.K.B.I.E.T, Baramati.
Page 10