MACHINE DESIGN-1 MPR MAY 09


337511(37)
B.E.(Fifth Semester) Examination,
April-May, 2009
(Mechanical Engg. Branch)
MACHINE DESIGN-1
Time Allowed : Four hours
Maximum Marks: 80
Minimum Pass Marks: 28


Note :



  • PSG data book and ISI data sheets are to be provided to examinees to solve the problem.


  • Questions should be solved serially. All questions carry equal marks







  1. (a) What are the advantages anddis-advantages of chain drive? 2

    (b)Design a roller chain drive for driving a compressor by 12 kW electric motor running at 1200 rpm. The compressor speed is around 350 rpm. The centre distance is aroun450mm. The compressor operates for 16 hours per dat. 14



    Or


    (c) What are the steps to be followed while designing achaing drive?

    (d) Chain drive has some features of belt drive and some of the gear drive. Explain. 7+7



  2. (a) What is the purpose of using a gile along with a cotter joint? 2

    (b) Two steel rods are to be connected by means of a steel sleeve, and two steel cotters. The rods are subjected to a tensile load of 40 kN. Design the joint by drawing a free hand neat sketch of the joint. The permissible stress in tension (sigma)t = 60MPa, in shear T =50 MPa and in crushing (sigma)c 90 MPa may be assued. 14



    Or


    (c) Enlist the factors which determine the superiority of splines over the keys. 4

    An automobile engine has a capacity of 250 N-m. The clutch is attached to driven shaft by means of six aplines, that is to slide when not under load . Determine the dimentions of the shaft and spline. The material of the shaft and splines is steel and the load is applied with a moderate shock. The maximum pressure on the spline is 8.5 N/mm2. Assume length of the spline is 1.5 times the shaft diameter. 10



  3. (a) What is meant by screwed fastener and what are the applications of screwed fasteners? 2

    (b) A steam engine cylinder of 300mm effective diameter is subjocted a steam pressure of 1.5 N/mm2. The cylinder head is connected by means of 8 bolts having yield strength 0F 320 MPaand endurance limit of 240 MPa. The bolts are tightened with an initial preload of 1.5 times that of steam load. A soft copper gasket is used to make the joint leak proof. Assuming a fatigue stress concentration factor of 1.4 and factor of safety of 2; determine the size of the bolts required. 14.



    Or


    (c) Figure 1 show a screw clamp and nut, calculate (a) the diameter of the screw, (b) the height of the nut and (c) the dimentions of the handle; for maximum clamping force Fc=20 kN force at the end of the level arm = 200 N= W allowable compressive stress for screw = 80 Mpa = (sigma)c Bearing pressure for screw & nut pb= 20 Mpa, coefficient of friction between screw and nut threads = 0.15 = (mu) , Friction torque of pad T2= 40 N-m, allowable binding stress for handle (sigma)b = 90 MPa. 14






  4. (a) Which type of joints is used for longitudinal joint of a boiler and why? 2

    (b) The ends of a cylindrical receiver is closed by a lap joint. The maximum pressure in the receiver is 1N/mm2. The axial length of the receiver is limited 2m, while its storage capacity is 2 m3. Design and sketch the joint.
    The permissible stress in shear T= 60 Mpa
    The permissible stress in cruss of rivet= (sigma)c = 90 Mpa
    The permissible tensile stress for the plate material = 80 Mpa 14



    Or


    (c) A boiler is made by welding the plates longitudinally and circumfenetially as shown in figure 2. The diameter of the boiler is 1 m. The maximum pressure is 1.5 n/mm2. Design both the joint, using single-V butt weld for both the joints. The permissible tensile stress in the plate material is 70 MPA. Also assume the strength of the plate and weld is the same. 14




  5. (a) What are the purpose in machinary for which couplings are used? 2

    (b) It is required to design a bushed pin type of flexible coupling for connecting the motor and centrifugal pump shafts. The details of the duty reqired from the pump are:
    Power to be transmitted = 18.5 kW
    Speed in revolution/minute = 1000
    The diameter and pump shaft are 50 mm and 45mm respectively. Take the bearing pressure on the rubber bush as 0.35 N/mm2 and the working shearing stress in the materials of the pins as 20 N/mm2 . 14



    Or


    (c) Enumeratethe cases of shaft failure; and differentiate between a shaft and an axle?

    A transmission shaft with keyways is subjected to a maximum torsionaal moment of 750 N-m and maximum bending moment of 1200 N-m. The leads are suddenly applied , minor shocks are encountered and the aloowable shear stress is 42 MPa. Find the shaft diameter 4+10