Suez Canal University    Faculty of Engineering    Port Said

Production Engng & Mechanical Design Dept

Machine Elements Design 2 nd Year  ( Code : PRD 214 )  Time One Hour

                                                  Mid Year Exam April 2009

Answer All the questions and assume any missing data you find it necessary to complete your answer

Question No. 1                                                    5 Marks

Describe the design procedure of the cotter joint ( Draw a neat sketch to show the general layout of the final design of the cotter joint )

Question No. 2                                                    5 Marks

A rectangular base plate is fixed at each of its four corners by a 20 mm diameter bolt and nut as shown in Fig 1. The plate rests on washers of 22 mm internal diameter and 50 mm external diameter. Copper washers which are placed between the nut and the plate are of 22 mm internal diameter and 44 mm external diameter.

If the base plate carries a load of 120 kN (including self- weight, which is equally distributed on the four corners), calculate the stress on the lower washers before the nuts are tightened.

What could be the stress in the upper and lower washers, when the nuts are tightened so as to produce a tension of 5 kN on each bolt ?

Question No. 3                                                   5 Marks

A shaft supported at the ends in ball bearings carries a straight tooth spur gear at its mid span and is to transmit 7.5 kW at 300 r.p.m. The pitch circle diameter of the gear is 150 mm. The distances between the centre line of bearings and gear are 100 mm each. If the shaft is made of steel and the allowable shear stress is 45 MPa, determine the diameter of the shaft The pressure angle of the gear may be taken as 20°