Main drive

›  Single-propeller  ships

The propeller shaft is held stationary when the vessel is anchored in a stream (e.g. flowing water).

Reasons therefore are:

a.                      Preventing the bearing and the seal on the stem from running dry

b.                      Avoiding noise e.g. for sleeping passengers

c.                      Regulations for vessels transporting dangerous goods

d.                      The propeller shaft is held when a submarine is towed. This is a building regulation of the German Navy

e.                      The propeller is held stationary if there is a risk of divers, nets or ropes become entangled. (a requirement for Authority ships)

f.                         Whilst under sail, the passively rotating propeller should not interfere with manoeuvring.

› Twin- and multi-propeller ships

Reasons for these vessels are:

a.              The propeller shaft is braked to shorten the reversing times when manoeuvring.

b.              Combat ships of the German Navy must have two ways of retaining the shaft/propeller; a force-locking and a form-locking system must be used in each case.

c.               The UVV (Accident Revention Regulation) requires moving parts to be fixed for

maintenance and servicing, if maintenance is neccessary during a voyage.

d.              Braking a marine engine that is highly loaded and has a low moment of inertia. The overrun

time of the crankshaft should be limited, as the lubricating film could be interupted.

e.       When used in combination with couplings or when using common or distributor gearboxes

› Preventing the spin of the disengaged propeller

f.        Retention of the controllable pitch propeller in double-ended ships, to improve manoeuvrability. If the variable pitch propellers in the sail position are exposed to different currents, then this can lead to reversing shaft rotations.