CRANKSHAFT AND BEDPLATE ALIGNMENT :

The bedplate is first levelled up on the shop floor, usually being in two parts, surfaces planed and main bearing gaps machined. The bedplate is then lined up and rough chocked by the use of spirit levels. Piano wires are mounted along the full length of the bedplate, one port and one starboard, passing over end pulleys and loaded. Micrometer readings are taken between wire and the machined top surface of bedplate at say 1 m intervals, standard allowance being made for the wire sag and the bedplate chocked up until a true horizontal reading is achieved. The bedplate is ready for optical checking.

The bedplate living up is then checked up by sighting through a telescope at one end and a light source at the other end along the line of piano wire. After the bedplate is lined up, the centreline of main bearing bores is lined up by the same method. A dummy shaft is now used to bed into the lower halves of the main bearing bushes after which the crankshaft is bedded to place. The engine would then be assembled, crankshaft deflection taken and the test bed trial carried out.

Engine to shafting alignment is similarly done by lining up aft engine coupling flange to the forward thrust shaft face coupling flange with feelers. Optical telescope is used for lining up, however if a complete line up of crankshaft, intermediate shafts and tailshaft can not be sighted, two lines of sight have to be used, each extended to give as much overlap as possible.

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