PRECAUTIONS BEFORE TAKING CRANKSHAFT DEFLECTION :

1)   Readings should be taken when the ship is in afloat to get the natural deflection of the floating vessel. To check that no-one is working on the propeller or in the vicinity.

2)                    To check that no-one is working inside the-engine, on crosshead or in cylinder etc.

3)                    To check that all hanging bars or pins are removed and the lifting gear, chain blocks and engine room crane are not attached to any of the running gear.

4)                    To open all indicator cocks.

5)                    Whenever possible, to use a gauge that shows negative readings under compression and positive on expansion.

1 mm drilled at the correct height above the keel. With this centre the reference circle can be drawn for the setting up of the exact boring of the frame. Similarly at the engine room forward bulkhead a small flange in the bulkhead with a small hole drilled at the correct engine height above the keel and at the midship point athwartship.

An electric light is sighted behind the hole in the forward machinery space bulkhead and by looking from the outside the stern frame this light can be seen through the two sight holes. Sighting plates are fitted at aft peak bulkhead, aft machinery space bulkhead and any water - tight bulkhead through which the shaft passes. At these points, the horizontal plate is moved up until the light is masked and a horizontal reference mark is made. The plate is moved vertically down until the light is masked and another horizontal reference mark is made, bisection of these two lines gives the horizontal centre.

The same procedure is repeated using vertical boards moved horizontally port to starboard, bisection of these two lines gives the vertical centre. Crossing point of horizontal centre line and vertical centre line gives the actual centreline.

The optical telescope with eyepiece, cross lines, focus, vertical - horizonal micrometer adjustment is set up in a spherical mounting on a base with adjustment bracket. The telescope is adjusted vertically and horizontally until the light target is perfectly-centred, this becomes the line of sight.

At this stage, the sterntube, tail - end shaft, intermediate shaft and propeller are filted and the line of sight for telescope and target is fixed at the extreme ends. Readings are taken for all intermediate bearings by focusing on a lighted graduated scale held vartically on each bearing in turn. A graph is plotted of any misalignment and the chocking adjusted until a true line is effected.

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