Test example 6
Class 1
1. Describe how alignment of shafting between engine and propeller shaft is checked with the vessel afloat. State how alignment is corrected in the case of appreciable hull deflection.
2. (a) Make a simplified sketch of the operating mechanism for a controllable pitch propeller.
(b) Describe briefly how pitch is altered in accordance with telemotor signal.
(c) State what ‘fail safe’ feature is incorporated into the logic of the mechanism.
3. Identify the defects to which propeller shafts are commonly susceptible. Explain how propeller shafts are surveyed in order to detect these defects.
4. (a) Sketch a ‘muff’ (flangeless or sleeve) coupling for connecting adjacent lengths of main transmission shafting.
(b) Describe the manner in which the coupling is mounted on and transmits torque between the adjacent lengths of shafts.
(c) State how astern thrust is accommodated by the coupling.
Class 2
1. With reference to keyless propeller explain the following:
(a) Why have keys and key ways been eliminated?
(b) How is angular slip avoided?
(c) Why does mounting upon and removal from a propeller shaft require a different technique than that employed for propellers with keys?
2. (a) Sketch a coupling enabling external withdrawal of propeller shafts.
(b) Give a general description of the coupling.
(c) Give one advantage and one disadvantage of this coupling compared to the solid flange type.
3. With reference to controllable pitch propellers answer the following:
(a) Explain why the blade attitude assumed upon control failure is considered safe.
(b) Describe how the ‘fail safe’ feature operates.
(c) State how the ship can be manoeuvred when the bridge control is out of action.