Jefa Steering Autopilot Direct Drive - DD1, 150 KgM

The Jefa Direct Drives are extremely robust, compact units with simple installation. The big advantage of the Jefa Direct Drives is that the rudder feedback arm is mounted on the Drive itself which saves a considerable amount of installation and system tuning time. The 150 KgM output torque is good for boats from 30 feet up to 45 feet. The Direct Drive controls the rudder using a drag link which can be used directly on the existing tiller arm, via the quadrant or and independent tiller arm. The unit can be mounted in any orientation, even upside down. These units are built for 24hr continuous operation and have a total weight of 12kg

Available in 12V only.

The drive can be separated in 5 main parts: The electric motor, the two step spur gearbox, the planetary gearbox, the electro-magnetic clutch and the final spur reduction gearbox. The Jefa direct drive has multiple advantages over existing integrated drive units.

Electric Motor: The flat wound electric motor (pancake motor) used in the Jefa drive units is carefully selected for this application. Pancake motors have multiple advantages over normal electric DC motors:

• A large flat wound rotor to achieve a high starting toque and an immediate response to the autopilot speed control signal.
• A motor efficiency of 72,5% to achieve a minimal power consumption and maximal mechanical power output (compared to max. 50% efficiency of a normal DC motor).
• Compact main dimensions compared to achievable output.
• Aluminium motor housing in stead of sheet steel plate to avoid corrosion.

Planetary gearbox: To achieve a correct rudder travel speed (hard over time) the electric motor has to be reduced in speed with a factor 750:1. Some autopilot drive producers use a worm reduction box, but the efficiency is extremely low as the gears rub each other. The Jefa direct drive type I uses a combination of a planetary gearbox and spur gear sets (one small gear and one big gear). The planetary gearbox has following advantages:

• The highest possible efficiency compared to any other gearbox.
• All forces are equally spread over 3 gear teeth in stead of one allowing a much compacter and stronger solution.
• The forces and torques from the motor to the output shaft remain in the centre line of the drive unit, resulting in a higher efficiency and extremely reduces the loads on the housing and other internal parts.

Electro magnetic clutch: On the moment the mechanical steering system on the yacht is manually operated, the autopilot drive has to be disconnected from the steering system. This is achieved with the electro-magnetic clutch and controlled automatically by the autopilot junction box. Jefa has developed a unique and patented engagement clutch. The solution is based on two electrically operated spring loaded clutch pins that engage and disengage the outer gear ring of the planetary gear step. This solution has multiple advantages over the existing friction plate clutches:

• Less friction to back drive the unit.
• Lower power consumption (1.4 Amp. at 12 Volt). When the clutch isn't powered, it's disengaged and engaged when powered.
• The clutch doesn't wear in time.
• More compact than any friction clutch.

• When the autopilot is switched off, the helmsman isn't suddenly confronted with the full rudder torque, but has to put loading on the wheel to equalise the forces so the the clutch can disengage, making the manual take over much safer.