Q8. Explain why, in spite of accurate alignment under static conditions use of flexible couplings and copious supply of lubricant, main reduction gearing in still subject to pitting, scuffing and other tooth damage; B. Discuss the significance of viscosity in relation to the function of marine turbine oils as used in main propulsion installations, stating how the viscosity is controlled and what could cause it to change in service.
Q9. A. Sketch and describe a Pilgrim Nut for securing a propeller to the screw shaft. (8)
B. Describe how this device is used to loosen the propeller on the shaft when removal or inspection becomes necessary. (5)
C. Give four reasons why this method is considered to be superior to all other methods. (3)
Q3. A. Sketch a transmission shaft coupling which enables the propeller shaft to be withdrawn outward.
(a) describe the coupling and the method fitting and dismantling;
(b) state how the grip of the coupling can be checked when fitted;
(c) State what safety precaution should be taken when dismantling the coupling.
Q9. Misalignment of the Main shafting between engine and propeller causes bearing overloads and shaft stress.
a) State the difficulties associated with checking the shaft alignment and the reasons why results are unreliable due to external factors.
b) State the reasons for misalignment
c) Explain with a simple sketch how a bearing load is assessed.
d) Explain how uneven loading could be rectified
e) Why wear down in main bearings is critical to the condition of the condition of the crankshaft and propeller system.
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