Theory of Machines 1 - Dec 2016
Mechanical Engg (Semester 4)
TOTAL MARKS: 100
TOTAL TIME: 3 HOURS (1) Question 1 is compulsory.
(2) Attempt any four from the remaining questions.
(3) Assume data wherever required.
(4) Figures to the right indicate full marks. 1(a) Write short note on elliptical trammel. State and explain the condition for which it will trace circle.(6 marks) 1(b) Write a short note on pantograph, with its application.(4 marks) 2( b) A small connecting rod 250 mm long between the centers, mass 3 kg and has mass moment of intertia of 2.5× 10kg-mm4 about its C.G. C.G. of connecting rod is located at a distance of 175 mm from the small end center. Determine dynamically equivalent teo masses,when any one mass is located at small end. Also find location of the second mass.(6 marks) 2(a) Draw and explain in brief Turning moment diagram of 4-stroke single cyclinder engine. State the utility of this diagram.(4 marks) 3(a) What do you mean by brakes and dynamometers? State the types of brakes and dynamometers.(6 marks) 3(b) What is clutch? State the functions of clutch and give classification of clutchs.(4 marks) 4(a) What is loop closure equation ? Derive the same for offset slider crank mechanism.(6 marks) 4(b) Write a short note on Double Hooke's Joint.(4 marks) 5(a) In a slider crank machanism the stroke of the slider is 200 mm and obliquity ratio is 4.5. The crank rotates uniformly at 400 rpm clockwise, while the crank is apporaching the inner dead centre and away at 30° fro it (IDC). Find velocity and acceleration of piston and the angular velocity and angular accelerationof the connecting rod.(12 marks) 5(b) Explain the method of calculating rubbing velocity at a pin joint when two links move in the same and opposite direction.(3 marks) 6(a) In a four bar mechanism, AB =20 cm, BC = 30 cm, CD = 32 cm and AD = 60 cm. Crank AB rotates at uniform speed of 300 rpm in antilockwise direction. When the crank AB has turned 60°, locate all the instantaneous centres (ICRS) and find the angular velocity of the link B.C.(12 marks) 6(b) State and explain angular velocity ratio theorem.(3 marks) 7(a) The kinematic diagram of one of the cylinders of rotary engine is shown in Fig. 1. The crank OA which is vertical and fixed is 50 mm long. The length of the connecting rod is 125 mm. The line of the stroke OB is inclined at 50° to the vertical. The cylinders are rotating at a uniform speed of 300 rpm in a clockwise direction, about the fixed center O. Determine :
i) Acceleration of the piston inside the cylinder
ii) Angular acceleration of the connecting rod.
!mage(12 marks) 7(b) State whether the following statements are true or false, and justify your answer :
i) We will have to consider 'Coriolis component of Acceleration' while analyzing a normal Scotch yoke mechanism.
ii) Shape of acceleration polygon remains unchanged if we reverse the direction of rotation of input link.
iii) In all mechanism involving Trunnion, Coriolis component must be considered in the acceleration analysis(3 marks) 8(a) The crank reciprocating engine is 250 mm long and connecting rod is 950 mm long. The crank rotates at 200 rpm in clockwise direction. Find velocity and acceleration of piston. Also find angular acceleration and angular velocity of the connecting rod when the crank makes :
ii) 120° with IDC using Kelin's construction method.(12 marks) 8(b) Derive the equation for magnitude of Coriolis component of acceleration.(3 marks)