STEERING GEAR

(Edited extracts courtesy of A.N.T.A. publications, Ranger Hope © 2008 www.splashmaritime.com.au)

 

Cable Steering

 

A basic tension cable steering system is shown above. Different cable arrangements are common.

Cable steering for modern outboards usually use a semi-rigid push-pull cable inside a sheath.

A gear arrangement below converts the rotary action of the ship’s wheel to the push-pull action on the cable.

Mechanical steering arrangements may use rigid rod and lever mechanisms, in place of cables.

 

Mechanical steering

 

 

Hydraulic Steering

Direct (Hand-Operated) Hydraulic System

 

Force, leverage, and movement of the direct system can be altered by changing the sizes of rams, gears, ratios, and linkages

In this arrangement, the movement of the wheel is transmitted to the rudder stock by the flow of fluid through hydraulic lines.

The manual effort used to move the wheel, produces the hydraulic pressure needed to move the cylinder driving the rudder shaft.

A more detailed diagram of this system is shown below.

Power Assisted System

A power-assisted system (similar to that used with road transport) can be used with marine steering as shown below.

The power assist pump is controlled by signals through the control line from the manual system.

Hydraulic pressure assists the operator. If the power assist should fail, manual steering is maintained, but extra effort is needed.

 

Ram Arrangements

Clearance is needed all round the rams for the sweep of the tiller, and for the resulting sweep of the ram. 

The single ram:

 

Ram linkages must provide sufficient flexibility to allow for this movement.

Dual cylinder installations may be used to increase the steering torque on the rudder.

Dual Cylinder Arrangement for Extra Thrust

Dual cylinder arrangement to cancel side force on rudder post

 

On most installations, a large hydraulic side-force can be exerted on the rudder-post, especially at the extremes of the rudder stroke .

This side-force can be cancelled using two double-acting rams - one pushing,  the other pulling, both from the same side .

 

A typical hydraulic system may have the following components:

A Tank or Reservoir to hold a reserve of oil. The reservoir also helps in cooling, and settling and filtering out contaminants

A Pump supplies oil flow to the actuators

Relief Valves or Regulators to reduce the pump pressure to a safe level

Stainless or Synthetic Gauze Mesh Filters remove larger contaminants from the oil. A ‘filter condition indicator’ may be provided to give an indication of the state of the filter

Direction Valves to control the fluid path.

Actuators to cause an action.  They may consist of two parts; a transmitter (pump) and a receiver (ram). Actuators may be:
- Linear Actuators (rams) which move things in a straight line.
- Rotary Actuators which rotate things
- Semi-Rotary Actuators

Simple telemotor system

The helm attached pump (the transmitter) hydraulically operates a bi-directional electrical pump that operates the double acting ram.

Electro-hydraulic system

An electronic pulse originating at the helm opens and closes solenoids that direct hydraulic fluid to operate the ram.