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Ships steering gear arrangement
Ships from at least the 1950s, have been fitted with automatic steering, making
helmsmen redundant for deep sea passages. After the required course is set, the
automatic steering maintains direction; correcting any deviations due to the
weather. The automatic helm is consistent, with none of the fall off in
performance that occurred in heavy weather with manual steering, when the
human helmsman was changed.
Some problems were experienced with the
early versions of automatic steering systems when changing from automatic to
manual steering and vice versa. An incorrect change over was blamed for at
least one collision (the change over involved a hydraulic telemotor system, the
by-pass for which had not been correctly set).
Automatic steering has improved and electrical control of the steering gear
has now become the norm, with the hydraulic telemotor, if installed at all,
being
Summarized below various ship steering gears general guideline:
- Ship Steering gear failures and safeguards
The hydraulic circuit incorporates an arrangement of stop and bypass valves in the chest VC, which enable the gear to be operated on all four or on any two adjacent cylinders but not with two diagonally disposed cylinders.
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- Four-ram electro-hydraulic steering gear mechanism
The hydraulic circuit incorporates an arrangement of stop and bypass valves in the chest VC, which enable the gear to be operated on all four or on any two adjacent cylinders but not with two diagonally disposed cylinders.
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- Enclosed hunting gear
The light construction of the combined control and hunting gears is possible
because the forces concerned are moderate. The self-contained unit is
self-lubricating, and contained in an oil-tight case.
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- Ship steering control mechanism- use of Hydraulic telemotor
The telemotor has become, on many vessels, the stand-by steering control
mechanism, used only when the electric or automatic steering fails. It comprises
a transmitter on the bridge and a receiver connected to the steering gear
variable delivery pump, through the hunting gear.
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- Two-ram electro-hydraulic steering gear with variable
delivery pumps
An arrangement of a two-ram steering gear with variable
delivery pumps may have a torque capacity of 120-650 kNm.
The cylinders for this gear are of cast steel but the rarns comprise a one-piece
steel forging with integral pins to transmit the movement through cod pieces
which slide in the jaws of a forked tiller end.
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- Rudder carrier bearing & Steering gear
The rudder carrier bearing takes the weight of the rudder on a
grease lubricated thrust face. The rudder stock is located by the journal
beneath, also grease lubricated
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- Small hand and power gears - Ship steering systems
A simpler variant of the electro-hydraulic gear, for small ships requiring rudder
torques below say, 150 kNm
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- Four ram gear with servo-controlled axial cylinder pumps
Variants of the servo-controlled swash plate axial cylinder pump
are capable of working at 210 bar. Each pump is complete with its own torque
motor, servo-valve, cut-off mechanism, shut-off valve and oil cooler.
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- Vane type gear - provides security of four ram steering gear
These may be regarded as equivalent to a two-ram gear, with torque capacities
depending on size. An assembly of two rotary vane gears, one above the other,
provides the security of a four ram gear.
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- Details of two ram hydraulic steering gear arrangement
When the main pumps are at no-stroke, the auxiliary pumps dischar.
to the reservoir via a pressure-limiting valve PC20, set at 20 bar, and to t
pump casings. When the main pumps are on-stroke, the auxiliary pump
discharge to the main pump suction.
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