Mechanical Engg Diploma Topicwise Paper Solution

Draw the profile of cam operating a knife edge follower from following data:
(i)Follower to move outwards through 40 mm during 60o of cam rotation.
(ii)Follower dwells for next 45o.
(iii)Follower to return to its original position during next 90o.
(iv)Follower to dwell for rest of the rotation. The displacement of follower is
to take place with simple harmonic motion during both outward and
return strokes. The least radius of cam is 50 mm. if the cam rotates at 300
rpm.

A crank of slider crank mechanism rotates clock wise at constant speed of 300 rpm.
The crank is 150 mm and connecting rod is 600 mm long. Determine:
(i)
Linear velocity of the mid-point of connecting rod.
(ii)
Angular acceleration of connecting rod at a crank angle of 45o from inner
dead centre position.

(ii) Angular acceleration of connecting rod at a crank angle of 45o from inner
dead centre position:

Neat labeled Sketch of Crank and Slotted Lever Quick Return Mechanism:

Necessity of Balancing:
[1] The high speed of engines and other machines is a common phenomenon now-a-
days. It is, therefore, very essential that all the rotating and reciprocating parts should
be completely balanced as far as possible.
[2] If these parts are not properly balanced, the dynamic forces are set up. These
forces not only increase the loads on bearings and stresses in the various members,
but also produce unpleasant and even dangerous vibrations.
[3] The balancing of unbalanced forces is caused by rotating masses, in order to

Basic Cam Follower Profile:

Modern vehicles always equipped with disc brakes on at least the front two wheels. It
consists of mainly 3 parts,
[1] Rotor
[2] Caliper
[3] Brake pads
In between each piston and disc, friction pad held in position by springs. Higher
applied forces can be used in disc brakes than in drum brakes, because the design of
the rotor is stronger than the design of the drum. Due to this, large resistance is
carried by flat disc. In this, Flat plate disc with flat friction pad are used against heavy

SR
APPLICATION

SUITABLE Mechanisim

i)
Lifting water from well
Pendulum pump (Bull Engine)

ii)
Connecting misaligned shaft
Oldham’s coupling

iii)
Converting rotary motion into
reciprocating motion
Beam Engine (Crank & Lever Msm)

iv)
Maintain constant relative motion
between two rotary elements

Coupling rod of locomotive

Figure: Coupler Rod of Locomotive
(Link AD = Link BC = Crank Link CD = Coupling Rod Link AB = Fixed Link = Frame)
 
Working of Coupler Rod of Locomotive:
It is an example of Double Crank Mechanism in which, Links AD and BC (having equal
length) act as cranks and are connected to the respective wheels. Link CD acts as a
coupling rod and link AB is fixed in order to maintain a Constant center to center
distance between them. This mechanism is meant for transmitting rotary motion
from one wheel to the other wheel.

Difference between Belt and Gear Drive: (Any 04 Points, 01 Mark for each)
Basis
Belt Drive
Gear Drive
Power
transmitting Less
High
capacity
Slip & Creep
Material used
Type of drive
Centre distance between
the shafts
Overload taking capacity
Velocity Ratio
Use
Occurs
Flexible in nature
Slip drive
Medium or large
No
Rigid material used
Positive drive
Very less
Slips when overloaded
Damages
when
overloaded

Displacement Diagram for Simple Harmonic Motion (SHM):

Displacement Diagram for Uniform Acceleration and Deceleration: