JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD
JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD B.Tech II KINEMATICS OF MACHINES Previous Question Paper (August/September - 2022 - R13)
Answer any five questions. All questions carry equal marks.
Main
Give an example for rigid and flexible link.
Answer
A rigid link is a connecting rod in an internal combustion engine, which does not undergo any deformation while transmitting motion. A flexible link is a belt or rope used in a belt drive, which transmits power through tension and undergoes partial deformation.
List all the kinematic inversions of a double slider crank chain with examples.
Answer
A double slider crank chain consists of two turning pairs and two sliding pairs. Its inversions are as follows:
- Elliptical Trammel: This mechanism is used for drawing ellipses. It consists of two sliders moving in two perpendicular slots and a connecting link.
- Scotch Yoke Mechanism: This mechanism is used to convert rotary motion into reciprocating motion. It consists of a crank rotating a slider that moves within a slotted yoke.
- Oldham's Coupling: This is used to connect two parallel shafts whose axes are at a small distance apart. The central floating link slides between two flanges attached to the shafts.
Define transmission angle and mechanical advantage of a mechanism.
Answer
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State Grashof’s law for a four bar mechanism.
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State the type of pair formed by the piston and cylinder of an IC engine.
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Explain the completely and successfully constrained motions with suitable example.
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Explain the kinematic inversions of four bar quadrilateral chain with suitable example.
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In a slider - crank mechanism the crank is 500mm long and rotates at 20 rev/s CCW. The length of the connecting rod is 1800mm. When the crank turns 75° from IDC, determine:
The velocity and acceleration of the slider.
Answer
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Angular velocity and angular acceleration of the connecting rod by relative velocity method.
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In a four bar mechanism ABCD, the crank AB=150mm, coupler BC=360mm, rocker CD=400mm, and fixed link AD=600mm. The angle BAD=60°. The crank AB rotates at a constant angular velocity of 12 rev/s CW.
Locate all instantaneous centers for this mechanism.
Answer
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Also determine the angular velocity of the links BC and CD using instantaneous center method.
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What is Pantograph? Explain briefly the function of the same.
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The ratio between the width of front axle and that of the wheel base of a Davis steering mechanism 0.4. At the instant when the front inner wheel is turned by 20°, what is the angle turned by the out front wheel for best steering?
Answer
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Explain the function of a universal coupling with necessary diagrams.
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Explain the Hart’s mechanism with a sketch and prove it is generating a exact straight line.
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Two shafts are connected by a universal joint. The driving shaft rotates at a uniform speed of 1200 r.p.m. Determine the greatest permissible angle between the shaft axes so that the total fluctuation of speed does not exceed 100 r.p.m. Also calculate the maximum and minimum speeds of the driven shaft.
Answer
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A cam with a minimum radius of 30mm is to be design for a knife edge follower for the following data:
- To raise the follower for 40mm during 75° rotation of the cam.
- Dwell for the next 35° of cam rotation.
- Descend of the follower for the next 100° of the cam rotation.
- Dwell for the rest of cam rotation.
Draw the cam profile if the follower moves with simple harmonic motion during the ascend and descend and its axis is passing through the center of the cam.
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State the law of gearing.
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In an epicyclic gear train shown in figure, the number of teeth on gears A and B are 50 and 250. Determine the speed of the arm a. If A rotates at 100 rpm CW and B at 60 rpm CCW.
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