Rudder Carrier bearings

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The rudder carrier bearing takes the weight of the rudder on a grease lubricated thrust face. The rudder stock is located by the journal, also grease lubricated. Support for the bearing is provided by a doubler plate and steel chock. The base of the carrier bearing is located by wsdge type side chocks, welded to the deck stiffening. The carrier is of meehanite with a gunmetal thrust ring and bush. Carrier bearing components are split as necessary for removal or replacement. Screw down lubricators are fitted, and the grease used for lubrication is of a water resistant type (calcium soap based with graphite).

Weardown

A small allowance is made for weardown, which must be periodically checked. This may be measured either between pads welded on top of the rudder and onto the rudder horn, or between the top of the rudder stock and a fixed mark on the inner structure of the steering gear flat. The latter generally involves the use of a 'Trammel gauge' which takes the form of a 'L' shaped rod ade to fit the new condition of the gear. As wear down occurs it can easily be checked with this gauge. The rudder is prevented from jumping by rudder stops welded onto the stern frame.

Rudder movement stops

Rudder stops are arranged as follows;

Angle from centreline	Position of stop	Note
35o	On telemotor system	Normal limit
37o	On steering gear	Prevents rudder striking external stops
39o	External, on stern frame	emergency stop to protect propeller

These limits refer to rudders of traditional design and is governed by both the physical layout of the rudder and actuator but also due to the stall angles of the rudder. i.e. the angle at which lift ( turning moment ) is reduced or lost with increasing angle of attack. There are designs of rudder such as becker flap which have increased stall angles up to 45^o

Critical profiling of carrier bearing

Reasons for critical contouring of thrust face;
1. for lubrication
2. conical in order to prevent side slip and centralise rudder
3. projected area gives greater bearing area allowing smaller diameter bearing