Marine Technology Group

Arneson Surface Drives

 WHAT IS AN ARNESON SURFACE DRIVE

Arneson Surface Drive (ASD)

The Arneson Surface Drive is the undisputed leader of Surface Drive Propulsion Systems.  No other system can come close to the success that has been achieved on vessels equipped with the Arneson Surface Drive.

The ASD system is an articulating Surface Drive Propulsion System where the propeller shaft can be articulated up or down to control the propeller submergence, or moved side to side for vessel steering.

Reliability comes from the intrinsic simplicity of the ASD unit.  Only three moving parts groups.  There are thousands of applications worldwide in all vessel groups with many applications operating with thousands of trouble free operating hours.

Arneson Surface Drives are available for applications running very low power to power requirements over 6,000 HP.

WHAT IS A SURFACE PROPULSION SYSTEM

Surface Propulsion systems all are configured to position the propeller shaft approximately on the surface of the water.  This results in a propeller that operates only partially submerged.  Surface propulsion system offer numerous advantages over other types of propulsion systems.  The primary advantage is efficiency.  Other advantages include optimization of reduction ratios, shallow water capabilities and the elimination of cavitation.

ADVANTAGES OF THE ARNESON SURFACE DRIVE

Efficiency.  Surface propellers are the unequalled leader in efficiency.  The ASD system allows for adjustable submergence of the propeller, allowing the vessel operator to control the absorbed horsepower.  When a surface propeller is trimmed down, the propeller curve shifts to the left on the horsepower curve, allowing the propeller to absorb more horsepower for a given RPM.  This is somewhat crudely analogous to a controllable pitch propeller system.  For the vessel operator, this can mean a 15% or more speed increase for a given RPM when the ASD units are trimmed down.  This allows the propeller and engine to operate at higher efficiency.  Operating costs, including fuel and engine maintenance are thus reduced. 

Shallow water capabilities.  ASD's afford the vessel operator the ability to operate the vessel where the bottom of the hull becomes the navigational limit. (without the ingestion of debris)

Maneuverability.  As the ASD uses direct propeller thrust for steering, the system is extremely maneuverable.

No cavitation.  Surface propellers do not cavitate as they are operating at atmospheric pressure, eliminating all problems such as seen on underwater gear and water jets.

Payload.  Due to the adjustability of propeller submergence, (trim), the ASD system allows the vessel to have a flexible payload over a wide range of displacements.  By trimming the propeller either up or down, the operator can maintain optimum conditions without overloading the engines or sacrificing performance issues to the extent as the other systems do.

Other.  Allows for a more optimum layout in the vessel, reducing shaft angles, moving machinery to the aft end of the vessel.  Propellers can be easily changed in water in case of damage.

COMPONENTS OF AN ASD SYSTEM

The following is a brief description of the various components that in total make the Arneson Surface Drive System.  In many of the sections there are links (underlined words) that will lead to more detailed information.

Arneson Surface Drive.  The ASD in the heart of the propulsion system.  Included with the ASD are the Thrust Tube, Trim Cylinder Steering Cylinder, Mounting Hardware and a special wrench for servicing the ball and socket.  When ordering deadrise angle, transom angle and thickness are required.

Tie Bar.  To provide optimum steering control in multi-ASD installations, The Thrust Tubes must be linked together by a mechanical or hydraulic tie bar.  Mechanical Tie bars are application-specific and manufactured per application.

Order must include hull description, ASD model number, and must specify exact distance between ASD unit centerlines.  Tie bar assembly includes tie bar and end fittings, as required.

Hydraulic tie bar systems are available for catamarans and other special applications.

Electrolysis Kits.  Electrolysis Kits are provided to minimize electrolytic corrosion caused by dissimilar metals.  These kits consist of zinc anodes electrically connected to the various ASD components.  The zinc anodes corrode preferentially to the ASD components through sacrificial action. 

The anodes also reduce the tendency of bronze components to cause corrosion of less noble metal such as aluminum or steel (the "composite electro-potential") by providing protective currents.  Since the anodes protect by sacrificial corrosion, they need periodic inspection and renewal.  Periodic checks of anodes will not only reveal expended anodes, but may warn of other problems such as electrical faults.

 H/RI recommends all vessels be protected with electrolysis kits or other cathodic protection.  For vessels protected by an impressed current corrosion system, please contact the manufacture for recommendations.

Trim and steering indicators are used to display the trim angle (vertical) and steering angle (horizontal) of the ASD unit.

Steering and Trim Indicators.  The trim indicator allows the vessel operator to precisely control the propeller submergence for optimum performance.  The steering indicator allows the vessel operator to know the horizontal position of the ASD unit(s) (propellers).  This is especially important for vessels equipped with Hydraulic Tie Bars.

The trim and steering indicators utilize an electrical sender unit usually mounted inside on the transom of the vessel connected to the ASD unit with a mechanical cable.  An electrical gauge mounted at the control station displays trim and steering position.

Trim and steering indicator kits are available with or without the gauge for the control station.  When ordering a trim or steering indicator kit without gauges, be sure that the impedance (ohms) required by the non-H/RI supplied gauge is compatible with the supplied sender.

Drivelines.  Couplings and Inboard Drivelines are used to transmit the torque of the engine to the Arneson Surface Drive.  Depending on engine size and the ASD unit a variety of couplings and driveline configurations are used.

Steering Systems.  Arneson Surface Drives require the use of a Power Steering System for control.  The selection of various components including helm, pumps, reservoir and valves are dependent on the customer requirements as well as the ASD size. 

Since steering is such an important safety issue, H/RI systems are all engineered for use on the ASD system.  We do not use inferior components or compromise on reservoir and hose sizing for the small amount of money saved.  This is an area where many times people involved in selling ASD systems will try and save cost - usually at the expense of safety.

Propellers.  Surface piercing propellers suitable for use with Arneson Surface Drives are available from a variety of suppliers through H/RI dependent on size and usage.   H/RI can recommend the correct model and style of propeller for your needs.  Special purpose propellers are available on request and may be recommended for some applications

Today there are a variety of propeller styles for surface piercing applications to choose from.  In addition, there are numerous manufacturers that claim to have the best propellers available.  Be cautious – It is easy to get swept up in the enthusiasm of the moment discussing a new application only to have reality many months later catch up in the form of a vessel that will not perform, or even get on plane.  We are involved daily in problems such as these.  Many times a propeller supplier will make recommendations based on what they have on the shelf or have patterns for.  Sometimes gear ratios are compromised for the same reasons or to stay under a torque rating to use a a smaller ASD unit.  These issues almost always lead to a disastrous application.  If you are considering using the ASD system, please contact us at H/RI before finalizing your equipment.  We will perform an analysis on your application and make our recommendations at no charge.  We offer this service to enhance the successful use of the ASD system.

ASD PRODUCT, APPLICATION AND GENERAL INFORMATION

What is an Arneson Surface Drive

Twin Disc ASD Specification Sheet

ASD Interface Drawings

History of Surface Piercing Propulsion

Surface Piercing Propeller Styles

Scrapbook of ASD Equipped Vessels