Describe the construction of a tail shaft. What metals are used? What test is carried out
and what readings would you expect to find.
The propeller or tail end shaft is the aftermost length of shaft from good quality mild steel of 28
tons tensile strengths. It requires having toughness and being resistant to fatigue. In the past
propeller shaft were commonly made of wrought Iron. The tail end shaft is 10% greater in
strength than the tunnel shafting by reason of the varied stresses to which it is subjected, also to
the liable to corrosion by its contact with sea water.
The shaft is machined over with a taper at the end for taking the propeller. The propeller boss is
of the order of (0.75 inch per feet 1mm per 10mm length) length and has a length of approx. 3
times the shaft dia. The keyway is milled out and has semicircular ends to avoid stress
concentration. To protect the shaft from corrosion and from wear it has a sleeve or lines of
gunmetal shrunk on. This liner may be in one or more lengths and is machined to have the dia of
forward length slightly greater than the after length. The difference in diameter is an aid for
fitting shaft into the stern tube. The working stress induced in a propeller shaft is torsion, going
ahead and astern and which will vary in intensity on the power developed by the engine.
COMPRESSION: while going ahead
TENSION: while going astern
BENDING AND SHEERING: due to the weight of the propeller and its overhang.
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