The propeller
drive shaft is one of the most important parts of the ship.
During construction, the shaft is inserted with millimetric precision
into the ship and interlocked with the engines. However, the rigours
of maritime travel exert all manner of force into the shaft and the
slightest damage will wreck the entire assembly, even trigger an
unfortunate accident. As such, aligning the shaft is a tedious but
important procedure.
A realignment process
begins at the engine mounts. A dead giveaway of a misaligned shaft is
that the mount’s studs are leaning in any direction, indicating a
degree of stress. It is possible to uncover a misalignment by running
the engine up from idle to at least one-third throttle speed. Your
team should note the proper alignment relative to the bearings. This
way, you will see if something is wrong with the shaft, even it is
just 1/8th of an inch off center.
A wobbly shaft can be
noticeable if the power setting is at cruise speed. Check if the
engine tachometer is above 1,200rpms at the time the wobbles are
felt. The shaft-to-bearing alignments will warrant a check as well;
the opening and exit holes at the bearings must be lined up
perfectly. A properly-synced up screw will preserve the transmission
of thrust from the engine to the propellers.
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