337511(37)
B.E (Fifth Semester) Examination,
Apr.-May., 2008
(Mechanical Branch)
MACHINE DESIGN -I
Time allowed : FOUR Hours
Maximum Marks : 80
Minimum Pass Marks : 28
Note :- Design data book by PSG and ISI. data sheets are allowed. Duration of the paper is 4(four) hours.
1. It is required to design a chain drive with a duplex chain to connect 15kW, 1400rpm electric motor transmission shaft running at 350 rpm. The operation involves moderate shocks.
(i) Specify the number of teeth on the driving and driven sprockets
(ii) Select a proper roller chain
(iii) Calculate the pitch circle diameters of driving and driven sprockets
(iv) Determnine the number of chain links
(v) Specify the correct centre distance.
During preliminary stages, the centre distance can be assumed to be 40 times the pitch of the chain.
OR
A plate made of steel 20 C8 (Sut = 440 N/mm2) in hot rolled and normalised condition is shown in fig (1). It is subjected to a completely reversed axial load of 30 kN. The notch sensitivity factor q can be taken as 0.8 and the expected reliability is 90% the factor of saftey is 2.Determine the plate thickness for infinite life. 16
2. Design a knuckle joint for a tie rod of a circular section to sustain a maximum pull of 70 kN. The ultimate strength of the material of the rod against tearing is 420 MPa. The ultimate tensile and shearing strength of the pin material are 510 MPa and 396 MPa respectively. Determine the tie rod section and pin section. Take factor if safety =6. 16
OR
Design and draw (sketch) a cotter joint to sypport a load varying from 30kN in compression to 30kN in tension. The material used is carbon steel for which the following allowable stresses may be used.
The load is applied statically .
Tensile stress = Compressive stress -5- MPa;
Shear stress = 35 MPa and Crushing stress = 9- MPa. 16
3. A sluice valve used in water pipe lines, consist of a gate raised by te spindle, which is rotated by the hand wheel. The spindle has single-start square threads. The nominal diameter is 36mm, and pitch is 6mm, The inner and outer diametres of the friction collar are 30 mm and 50mm respectively. The cofficients of friction at the threads and collar are 0.15 and 0.20 respectively. The weight of the gate is 7.5 kN, and the frictional resistance to open the valve due to water pressure is 2.5 kN.Using the uniform wear theory for collar friction, calculate :
(i) the torque required to raise the gate, and
(ii) overall efficiency of the mechanism
Or
(a) A steel plate subjected to a force of 3kN and fixed to a vertical channel by mean of four identical bolts is shown in fig. (2). The bolts are made of plain carbon steel 45 C8 (Syt = 380 N/mm2) and the factor of safey is 2. Determine the nominal diameter of the bolt . 
(b) A steel plate subjected to a force of 5kN and fixed to a channel by means of three identical bolts is shown in fig. (3) . The bolts are made of plain carbonm steel 30C8 (Syt = 400 N/mm2) and the factor of safety is 3 . Determine the nominal diameter of the bolts .
4. A steam Boiler is to be designed for a working pressure of 2.5 N/mm2 with its inside diameter 1.6 m . Give the design calculations for the longitudinal and circumferential joints for the following working stresses for steel plate and rivets. 16
In tension = 75 MPa , Om shear = 60 MPa
In crushing =\ 125 MPa.
Assume triple riveted but joint double strap with unequal cover plate .
OR
A welded connection of steel plates as shown in fig (4). is subjected to an eccentric force of 10kN. Determine the throat dimension of the weld if he permissible shear stress is limited to 95 N/mm2. Assume static conditions. 16
5. An intermidiate shaft of gear box , supporting two spur gears A and B and mounted between two bearings C1 and C2 shown in fig (5). The pitch circle diametres of gears A and B are 500 and 250 mm respectively. The shaft is made of alloy steel 20 Mn Cr5 (Sut = 620 and Syt = 480 N/mm2) The factors Kb and Kt of the ASME code are 2 and 1.5 respectively. The gears keyed to the shaft. Determine the shaft diameter . 16
OR
Design a protective type of cast iron flange coupling for steel shaft transmiting 15 kW at 200 r.p.m. and having an allowablr shear stress of 40 MPa. The woeking stress in the bolt should not exceed 30 MPa. Assume that the same material is used for shaft and key and that the crushing stress is twice the value of its shear stress . The maximum torque is 25% greater than the full load torque. The shear stress for cast iron is 14 MPa. 16
