Q4. A valve is fitted with two close coiled helical springs, each of the same material and with the same free length. The outer spring has 14 coils, mean diameter 120 mm and wire diameter 8 mm. The inner spring has 20 coils of wire diameter 5 mm.
Each spring is to have the same shear stress when the springs are compressed.
Calculate EACH of the following:
(a) The mean coil diameter of the inner spring;
(b) The stiffness of the combined springs.
Note: Modulus of Rigidity for spring material = 70 GN/m2
Q4. A solid steel shaft of 80 mm diameter is connected to a hollow steel shaft by a shear pin of 10 mm diameter fitted diametrically through the solid and hollow shafts. The inside diameter of the hollow shaft is 80 mm. The shear stress in the pin must not exceed 60 MN/m2. Calculate EACH of the following:
(a) The maximum power that can be transmitted at a speed of 300 rev/min;
(b) The minimum outside diameter of the hollow shaft so that its angle of twist does not exceed 0.10 per meter length when transmitting the maximum power.
Note: Modulus of Rigidity for shaft material = 80 GN/m2
Q6. An “I” section beam is loaded as shown in Fig Q7. Calculate EACH of the following:
(a) The maximum stress due to shear in the beam;
(b) The maximum bending moment on the beam;
(c) The maximum bending stress in the beam.
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