Q3. A shaft consists of a bronze sleeve 390 mm outside diameter shrunk onto a solid steel shaft of 340 mm diameter. The shaft is to transmit a power of 4.8 MW at a speed of 120 rev/min.
Calculate EACH of the following:
(a) The torque transmitted by the bronze sleeve;
(b) The percentage of the total power which is transmitted by the steel.
Note: Modulus of Rigidity for Bronze = 40 GN/m2
Modulus of Rigidity for Steel = 80 GN/m2.
Q2. A hollow brass tube, 24 mm outside diameter and 12 mm inside diameter is 260 mm long and at a temperature of 18°C. It is then heated to 180°C and then rigidly secured at each end to prevent any contraction. Calculate EACH of the following:
(a) The length of the tube immediately after heating;
(b) The temperature to which the tube must be cooled so that the stress in the brass is 55 MN/m2;
(c) The strain energy in the bar at this lower temperature.
Note: Modulus of Elasticity for Brass = 80 GN/m2
Coefficient of linear expansion of Brass = 16 x 10-6/℃.
Q1. An electric motor is running at 1500 rev/min when the power is shut off. The total frictional resistance to motion is equivalent to a torque of 6 Nm, and forty seconds later the speed of the motor has fallen to 800 rev/min. Calculate EACH of the following:
(a) the moment of inertia (I) of the motor;
(b) the total time taken to come to rest;
(c) the total number of revolutions made after the power is shut off before coming to rest.
Q3. A steel beam is 5 m long and has a symmetrical cross section shown in Fig Q4 and is simply supported at each end. The weight of the beam itself is 480 N per metre length and the maximum allowable bending stress for the beam is 110 MN/m2. Calculate EACH of the following:
(a) the maximum additional uniformly distributed load which can be carried;
(b) the least radius of curvature when carrying the load in Q4(a).
Note: Modulus of Elasticity for Steel = 210 GN/m2
Q2. In a four-ram hydraulic steering gear the centre line of the rams is 1.2 m from the centreline of the rudder stock. The diameter of the rams is 280 mm and the diameter of the rudder stock is 420 mm. Movement of the rudder is limited to 35° on either side and the maximum allowable shear stress in the rudder stock is 70 MN/m2. Calculate EACH of the following:
(a) The maximum allowable torque on the rudder stock;
(b) The pressure to which the relief valves on the rams should be set.
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