Marine Technology Group

ASD Control Systems

HELMS

The selection of helms for Arneson Surface Drives is based on ASD size, number of steering cylinders and the desired number of helm turns lock-to-lock.  The data below is offered for reference and general guidance only.

All H/RI steering systems that require the use of a helm (verses electronic steering control) use the Char-Lynn, non-load reaction steering unit (helm).  With this unit, cylinder ports are locked thus holding them in the position in which the operator released the steering helm.

When adding multiple helms, Double Piloted Check Valves (DPCV) are required to eliminate any feedback.  These check valves are located between each helm and the cylinders.

EMERGENCY HELMS

Some steering systems require emergency and redundant back up for either personal or regulatory preferences.  Many of the Steering Cylinder Control Manifolds by H/RI incorporate features that allow the connections of emergency helms.  Typically these helms are not intended to furnish standby steering, but rather come-home capabilities.

DUAL STEERING CYLINDER APPLICATIONS

Most twin and all three or more ASD equipped vessels will use the twin cylinder configuration.  Where steering cylinders are mounted in opposing directions, the steering system is considered balanced -- it will take the same amount of turns lock to lock in either direction. 

Due to the ASD steering and trim geometry, binding pressures between the opposing steering rams when the drives are trimmed can occur.  The use of a Steering Cylinder Control Manifold with relief is recommended to avoid damage to either the ASD system or the vessel.

Char-Lynn Helm Details
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SINGLE STEERING CYLINDER APPLICATIONS

Single steering cylinders are used on single engine applications as well as on certain twin-ASD installations. Typically for twin-ASD applications the single steering cylinder is mounted between the ASD units.  Inboard yoke pins are required for twin ASD, single steering cylinder applications.

The use of a single steering cylinder results in a non-balanced steering system.  The following table shows the approximate difference between turning right or left, lock to lock.  This is based on steering mounted on the starboard side of ASD.

Char-Lynn Helm Details
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