ENGINEERS' THEORY

Evening Post, Volume CX, Issue 42, 18 August 1930, Page 10

ENGINEERS' THEORY

EFFECTS OF BBOKEN SHAFT (By Telegraph.) (Special to "The Evenirtff Post.") AUCKLAND,.This Day. lv the absence of definite information, marine engineers in Auckland could advance only speculative opiuions as to the possible cause of the mishap to the Tahiti, but the consensus of opinion, was that the tail-shaft had fractured near the stern, and the propeller, still fastened to the broken end of the shaft, had pulled out and was lost. The shafts of the Tahiti pass from the engine-room into a tunnel which runs the width of the ship, and which can be made watertight by the closing of the door in the bulkhead. The tunnel allows of the oiling of bearings1 and may also be used for stores if desired.' Aft of the tunnel is'the aft peak ballast tank, in which the' shafts move in varying quantities of water. From the aft peak tank the shafts pass through the hull to propellers. Specially packed collars round the shafts make the passages through the tank bulkhead and hull watertight.

The engineers said that it was very seldom that a tail-shaft broke cleanly, the usual thing being for the broken ends 'to twist badly, making it impossible for the piece attached to the propeller to go overboard. In the ease of a jagged break the driving end would be 'whirled round at high speed until the engineers could throttle down. It would be possible for tho broken end to crash through the bulkhead and thus allow water to flow into the vessel.

The theory: advanced in the case of the Tahiti is that the bearings through the hull and in the ballast tank bulkhead have been fractured or twisted to such an extent that there has been a free flow of water past the tank into the tunnel abaft the engine-room.

Ono engineer said that if the weather had been rough and the propeller racing frequently, it was possible, although not likely, that the propeller could be wrenched off bodily, and that when the stern of the vessel crashed down on a wave, as the propeller would, be moving in a clockwise direction, it would naturally tend to travel forward while still in the air, and might crash against the stern and cause a severe leak. In this event water might go either to the engine-room or to the hold..