Rajasthan Technical University 2010 B.Tech Mechanical Engineering Kinematics of Machines (mechanical Engg.) - Question Paper
RTU Kinematics of Machines (mechanical Engg.)
Rajasthan tech. University
B.tech four sem (Main/back)
Year July 2010
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[Min. Passing Marks : 24 | |||||||||||||||||
Attempt any five questions selecting one question from each unit. All questions carry equal marks. (Schematic diagrams must be shown wherever necessary. Any data you feel missing suitably be assumed and stated clearly. Units of quantities used/calculated must be stated
clearly.)
Use of following supporting material is permitted during examination. (Mentioned in form No. 205)
1._NM__2._NIL____________
UNIT - I
1 (a) What do you mean by inversion of mechanism ? Describe with the help of suitable sketches the inversion of a slider crank chain.
6
(b) In the mechanism shown in the fig. 1, the dimensions of the various links are as under :
AB = 30 mm, BC = 45 mm, CD = 40 mm
AD = 65 mm, CE = 40 mm, and z DAB = 75
The crank AB rotates at 600 rpm in counterclockwise direction. Determine the linear acceleration of slider E and angular acceleration of link BC.
4E2053] 11111111111II11 1 [Contd...
* 4 F ? 0 5 3 *
What do you mean by instantaneous centre ? State and prove Arnold Kennedy theorem.
4
2 (a) (b)
(c)
3 '(a)
(b)
4 (a) (b)
5 (a) 4E2053]
What do you mean by coriolis acceleration ? Show that coriolis acceleration is 2 ov. Also suggest the procedure to find the direction of coriolis acceleration.
6
With a neat sketch, explain the working principle of Scott-Russel mechanism.
6
UNIT - II
What will be the effect on power transmission capacity of a belt drive if :
(i) open belt is replaced with cross-belt
(ii) flat belt is replaced with V-belt
(iii) idler pulley is used
(iv) angle of lap is decreased.
Explain with reasons.
8
A belt embraces the shorter pulley by an angle of 165 and runs at a speed of 1700 m/min. Dimensions of the belt are : width = 200 mm and thickness = 8 mm. Density of belt material is 1000 kg/m3. Determine the maximum power that can be transmitted if the maximum permissible stress in the belt is not to exceed 2.5 N/mm2 and coefficient of friction is 0.25.
8
OR
A universal joint is used to connect shaft whose axes are inclined at 20 and the speed of driving shaft is 500 rpm. Find the extreme angular velocities of the driven shaft and its maximum angular acceleration.
8
What is condition of correct steering ? Compare the characteristics of Davis and Ackermann steering mechanism.
8
UNIT - III
A turnbuckle consists of a box nut connecting two rods, one screwed right handed and other left handed, each having a pitch of 4 mm and a mean diameter of 23 mm. The thread is of V-form with included angle of 55 and coefficient of friction may be taken as 0.18. Assuming that rod does not turn, calculate :
(i) Torque required on the nut to produce a pull of 50 kN
(ii) Efficiency of the screw.
8
IIII 111 111 111 III III! 2 lo-**-
(b) State the laws of dry friction.
4
(c) Define the following terms :
(i) Coefficient of friction
(ii) Limiting friction
(iii) Angle of friction
(iv) Angle of repose.
4
OR
6 (a) What do you understand by uniform pressure theory and uniform wear theory ? Which theory is most suitable for (i) bearing design and (ii) clutch design.
8
(b) The thrust of a propeller shaft in a marine engine is taken up by a number of collars integral with the shaft which is 300 mm in diameter. The thrust on the shaft is 200 kN and the speed is 75 rpm. Taking coefficient of friction equal to 0.05 and assuming intensity of pressure as uniform and equal to
0.3 MPa, find the external diameter of the collar and the number of collars required, if the power lost in friction is not to exceed 16 kW.
8
UNIT - IV
7 The air-operated brake designed for use in oilfield operation is shown in fig. 2 to have a torque capacity of 9 kNm. The coefficient of friction is 0.35. Determine the following :
(i) Direction of rotation of drum such that the effort required is minimum.
(ii) The value of coefficient of friction which will make the brake self-locking.
(iii) The torque capacity of the brake if it is accidently used in the direction opposite to that determined in (i).
4E2053] jlJIEIIl HIM 111 IIIIIU * [Contd...
Draw and describe any one belt transmission dynamometers. Discuss its merits and demerits.
8
(a) (b)
Analyze the effect of breaking to front wheel when a vehicle moves up an inclined plane, hence develop the expression for retardation.
8
UNIT - V
9 A cam rotating clockwise with a uniform speed of 300 rpm is to give the roller follower of 15 mm diameter the following motion :
(i) Follower to rise through a distance of 45 mm during 120 cam rotation.
(ii) Follower to dwell for 60 of cam rotation.
(iii) Follower to return to its initial position during next 120 of cam rotation and then remain dwell for rest period. The minimum radius of cam is 30 mm and line of stroke is offset by 15 mm from the axis of the cam and displacement of the follower is to take place with SHM during rise and uniform acceleration / deceleration during return. Draw the cam profile and calculate maximum velocity and acceleration during rise and return.
16
OR
10 In a symmetrical tangent cam operating a roller follower, the least radius of the cam is 30 mm and the roller radius is 15 mm. The angle of ascent is 75 and the total lift is 20 mm. The speed of the cam is 600 rpm. Calculate :
(i) Principal dimensions of the cam.
(ii) Acceleration of the follower at the beginning of lift, where straight flank merges into the circular nose and at the apex of the cone.
16
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