3. (a) Designed a closed coiled helical spring to have spring index of 8. Axial defelction in spring is not to exceed 100 mm under an axial load of 2600 N and shear strees developed in spring is not to exceed 300 N/mm2 . Steel wires are available in diameters of 10, 11, 12, 13, 14 mm (in steps of 1mm). Determine most suitable wire diameter, mean coil diameter and number of coils in spring.
Given G = 84000N/mm2 . 10
(b) A two-cylinder uncoupled locomotive has inside cylinders 70 cm apart, the cranks are at right angles and are each 0.3 m long. The mass of revolving parts per cylinder is 160 kg and the mass of reciprocating parts per cylinder is 180 kg. The whole of the revolving and two-thirds of the reciprocating parts are to be balanced and the balance masses are to be placed in the planes of rotation of the driving wheels at a radius of 80 cm. The driving wheels are 2 m diameter and 1.5 m part.
Find the magnitude and position of the balance masses. The driving crank speed is 300 r.p.m. 15
(c) Draw a neat sketch of a cotter joint and show how its various elements are likely to fail under tensile loading. Give one engineering application of this joint. 5+4+1
(d) What is Bauschingers's effect ? Make a neat sketch of strees-strain diagram and explain how yield strength in compression is reduced than the yield strength in tension. 5
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Engineering Services Examination 2011:Mechanical Engineering Question Paper II (Conventional)