Total No. of Questions 10]
[Total No. of Pages 4
[5353] 113
T.E. Mechanical/Auto/ Mech S/W
THEORY OF MACHINES II
Time :2½ hours] [Max. Marks :70
Instructions to the candidates:
Neat diagrams must be drawn wherever necessary.
Figures to the right indicate full marks.
Use of logarithmic tables slide rule, Mollier charts, electronic pocket
calculator and steam tables in allowed.
Assume suitable data, if necessary.
P3250
SEAT No.
P.T.O.
[5353] 113 2
The center distance between the meshing gears is 150 mm and the angle
between the shaft axes is 60°. The gear ratio is 2 and the normal circular
pith is 10 mm. The driven gear has a helix angle of 25° determine the
number of teeth on each wheel.
OR
Q4) What is the significance of helix angle in the worm gears?
Obtain an expression for minimum number of teeth to avoid interference
in a rack and pinion.
Q5) Compare stepped and step less regulation of speeds.
A 2.2 tonne racing car has a wheel base of 2.4 m and a track of 1.4 m.
The centre of mass of the car lies at 0.6 m above the ground and 1.4 m
from the rear axle. The equivalent mass of engine parts is 140 kg with a
radius of gyration of 150mm. The back axle ratio is 5. The engine shaft
and flywheel rotate clockwise when viewed from the front. Each wheel
has a diameter of 0.8 m and a moment of inertia of 0.7 kg m2. Determine
the load distribution on the wheels when the car is rounding a curve of
100 m radius at a speed of 72 km/hour to the left and right.
OR
Q6) The turbine rotor of a ship has a mass of 2.2 tonnes and rotate at 1800
rpm clockwise when viewed from the aft. The radius of gyration of the
rotor is 320 mm. Determine the gyroscopic couple and its effect when
the
Ship turns right at a radius 250 m with a speed of 25 km/hour.
ii) Ship pitches with bow rising at an angular velocity 0.8 rad/s
iii) Ship rolls at an angular velocity of 0.1 rad/s.
Explain what is Self-tightening effect in conical displaceable variators?[4]
Q7) An umbrella mechanism is to be designed for the following relationships
between the input and output parameters.
• The displacements of the slider 10 mm, 20 mm, and 40 mm from
the initial position Initial position of slider 100 mm from crank centre
• The corresponding angular displacements of the output crank are
40° and 75° from initial position (i.e. 20° with respect to axis
of slider).
[5353] 113 3
Use Inversion method to determine the dimensions of the basic
mechanism.
Define the following terms
Accuracy points.
ii) Structural error
iii) Function generation
iv) Pole and relative pole.
OR
Q8) Explain Function generation using Relative Pole method for slider crank
mechanism to coordinate three positions of slider and crank.
Design a four link mechanism to coordinate three positions of the input
and output link for the following angular displacements of the input and
output links. Assume the following data: Initial positions of the crank
and rocker are 0° and 50° with respect to horizontal;
θ12 35°φ12 50°:θ13 80°:φ13 80°
Take length of fixed link 100mm and length of the rocker 45 mm.
Q9) Design a cam profile to operate an inline roller follower using following
data
• Base circle of radius of the cam: 30 mm
• Radius of the roller: 10mm
• Maximum lift of the follower: 40 mm
• Angle of ascent: 120°
• Angle of dwell: 30°
• Angle of descent: 80°
• Motion of follower during Ascent: SHM
• The follower immediately falls by 10mm at the end of dwell in highest
position and further descents with Cycloidal motion by 30 mm.
The cam rotates at uniform speed in clockwise direction. Also draw the
pitch circle for the cam designed.
Explain what is Undercutting of cams?
[5353] 113 4
OR
Q10)a) Explain the following advanced cam curves. Mention the application of
each.
• Simple polynomial cam
• polynomial cam
Derive and expression for the cam jump of an eccentric cam operating a
flat faced follower.
Explain the effect on the cam profile by varying
Base Circle Diameter and
ii) Pressure angle