At the for'd end of the engine room a light box emitting light through a pin hole is fixed from the design height of the crankshaft.

Using the sighting gear in stern frame boss with solid piece fitted. The stern frame boss is marked off for boring. The solid piece is then exchanged for a sighting piece. A second sighting gear with sighting piece is fitted to the bore hole in the aft peak bulkhead. This is adjusted until the light source can be seen through the boss and aft peak bulkhead sighting pieces.

The sighting piece is replaced by the fixed piece and the bulkhead may be machined. The stern tube is scribed out and the p.c.d. of the bolts which will support the stern tube flange marked off.

A similar procedure us repeated for other bulkheads. When boring out is completed the stern tube is hauled into position, wood packing being fitted under the flange before bolting up at the aft peak bulkhead, the external stern tube nut is screwed up hard making a rigid connection at the after end.


The tail end shaft is now fitted into the stern tube, the flange of the tail end shaft is now the standard by which the remaining line shafting will be aligned. The trailing block (or towing block), of fitted, sometimes an ordinary Plummer block is fitted (bearing material all round) is mow fitted around tail end shaft using feelers and wedging, chocked and bolted sown.
The bearing acts also as an auxiliary thrust with a large clearance so that there is no possibility of it taking over from the main thrust under normal conditions otherwise the towing block would shear.

This takes the form of a split brass ring fitted to the for'd end of the towing block which allows the tail end shaft to be disconnected from the intermediate shaft and hence rotate freely whilst the ship is under extended towing .

The after face of the connecting flange then rides against this brass ring.

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