Wheeldrive pedestal mounting

[Derek - Raymarine - Moderator]

In some installations, the wheel mounted drive unit ( for the ST4000 wheeldrive or the SPX-5 Wheelpilot or the EV100 Wheeldrive) has to be mounted with the motor in the upper position closer to the compass and therefore may trigger excess deviation in the wet card compass mounted on top of the binnacle or in the pedestal.

The deviation seen in the wet card compass is caused by the permanent magnets in the motor and is usually a constant value, causing a constant offset in the heading displayed. This permanent deviation can be allowed for and a marine compass adjuster can compensate for the deviation caused - usually there are adjustable magnets attached to the wet card compass unit, the compass adjuster will swing the boat and move these adjustable magnets to correct the local deviation and this will enable the compass to function normally, with the corrected headings.

It should be noted that given the need for accurate heading information for navigation purposes, the ship's compass accuracy should be checked periodically and the local compass adjuster will swing the boat to check for sources of deviation onboard, such as engines, loudspeakers, etc all of which will cause local deviation, the adjuster will then set up the compass and provide a completed 'Deviation Card' once finished.

Local Deviation caused by equipment onboard a boat will change over time too, so just because the vessel's compass has been swung by a professional adjuster once, does not mean it is still accurate some months later.

More information about Compass deviation can be found here

If you find that the deviation changes, for example, when operating the autopilot drive the compass card swings erratically, then the only way to solve this is to relocate the autopilot drive motor in relation to the compass.

Whilst it is possible to create an additional slot in the backplate of the drive unit, enabling the drive unit to be rotated and to move the drive motor as far from the wet card compass as possible, it should be noted that the existing slots are reinforced. Any new slot created would not be reinforced and so could be liable to stress cracking and premature failure, modifying the backplate of the wheeldrive is not something we would either support or warranty.
The preferred solution would be to have a local machine shop make a custom torque restraint with the pin offset to enable the motor to clear the side of the pedestal.

There are a wide range of pedestal designs, which have also changed over the years, the location of the existing reinforced slots in the back of the Wheel Drive backplate have been chosen based on our wide experience of applications and are appropriate for the vast majority of customers.

Raymarine has not created an offset torque restraint pin, since one size would not cover each exception. In the event that the specific installation will require some local adjustment, Raymarine suggest a stainless steel fabrication be fabricated based on the specifics of these exceptional installations.

RAYFAQ#