Steering System Tutorial

SYSTEM COMPONENTS

1. the helm pump,
2. the cylinder, and
3. the hose or tubing required to connect the cylinder to the helm pump.

1. The Helm Unit

The SeaStar helm pump is an axial piston pump specifically designed for manual steering. It has a built-in lock valve to prevent the steering load from feeding back to the driver. The lock valve will not allow the rudder or drive unit to move until you move it with the steering wheel. The lock valve section of the helm also includes a relief valve. This relief valve provides over-pressure protection for mechanical components and hydraulic hoses and fittings.

2. The Cylinder

The most important differences between the variety of SeaStar steering systems available is the cylinder selection. The SeaStar system has a cylinder for most steering applications.

3. Hoses and Tubes

Required to provide a path for the fluid to flow under pressure from the helm pump to the cylinder.

HOW IT WORKS

The SeaStar system is a two-line system. This makes operation very simple.

1. The steering wheel, which is attached to the helm pump, is rotated in the desired direction (i.e.: a turn to starboard or clockwise rotation).
2. Oil is pumped out the corresponding port from the rear of the helm into the starboard line and then into the cylinder.
3. This causes the cylinder rod, which is attached to the vessels rudder or drive unit, to move (i.e.: rod moves to port) thus causing the vessel to alter course.
4. Oil displaced from the opposite end (i.e.: the port end) of the cylinder flows (i.e.: into the port line) back to the helm pump.
5. For steering in the opposite direction, simply turn the helm the other way.
6. When no course corrections are required, the integral lock valve holds the rudder or drive unit stationary.

SELECTING A SYSTEM

The objective is to match the steering system to the requirements of the vessel. This depends on four things:

1. type of vessel (i.e.: planing or displacement),
2. type of propulsion system in the vessel (i.e.: Outboard, Sterndrive, Inboard, etc.),
3. the number of engines or rudders,
4. the total power of the engines (i.e.: Horsepower).

Next choose a cylinder that best meets these requirements. Once the cylinder has been selected, the size of the helm pump is predetermined. The options left to specify are:

Notes on Steering Response versus Steering effort

Steering wheel effort is directly proportional to the number of wheel turns lock to lock. The number of wheel turns lock to lock is dependent on three things:

1. the volume of the cylinder,
2. the displacement of the helm pump,
3. the allowable movement of the rudder or drive unit.

Less wheel turns lock to lock results in more steering effort. More wheel turns lock to lock results in less steering effort. However, additional factors that can influence steering effort are:

1. vessel speed,
2. rudder size,
3. unusual propellor selections,
4. hull type (i.e.: displacement, planing, etc.), and
5. steering wheel size.

Recommendations made on this web site are guidelines based on average acceptance of steering effort.