Machine Design -II Assignment No - I

Date of issue: 20^th Jan, 2012                                             Last date of Submission: 27^th Jan, 2012

1.     Design a suitable flywheel for a 12 BHP, 2clyinder vertical 4 stroke diesel engine coupled to a 7.5 kW A.C. generator. The normal speed of the engine is 900 rpm.

2.      An Otto cycle engine develops 50KW at 150 rpm with 75 explosions per minute. The change of speed from the commencement to the end of power stroke must not exceed 0.5% of mean on the either side. Design a suitable rim section having width four times the deoth so that the hoop stress does not exceed 4 MPa. Assume that the flywheel stores 16/15 times the energy stored by the rim and that the work done during power stroke is 1.40 times the work done during the cycle. Density of rim material is 7200 kg/m³.

3.      A spring is to be designed which is subjected to a load varying from 0.4 kN to 1 kN.  Assume suitable data.

4.      A punching machine is required to produce 30 holes per minute of 20 mm diameter in a steel plate of 15 mm thickness having ultimate shearing strength of 340 MPa. The actual punching operation last for a period of 36° rotation of punching machine crankshaft. Mechanical efficiency of punching machine is 80%. It rotates at 240 rpm. Design s suitable flywheel for the punching machine.

5.      A semi-elliptical laminated spring 900 mm long and 55 mm wide is held together at the centre by a band 50 mm wide. If the thickness of each leaf is 5 mm, find the number of leaves required to carry a load of 4500 N. Assume a maximum working stress of 490 MPa. If the two of these leaves extend the full length of the spring, find the deflection of the spring. The Young’s modulus for the spring material may be taken as 210 kN/mm².