linear drive type LD100

Jefa 100 KgM autopilot linear drive unit type LD100
The Jefa linear drive is an extremely strong and compact autopilot drive and much more efficient than existing hydraulic and electro-mechanical linear autopilot drive units. With a thrust of 400 Kgs on 250 mm centers it's much stronger than a human being (the max. output torque of 100 KgM is equivalent to 100 Kg force on the end of a 1 meter steering tiller) and is build for 24 hours per day continuous operation with a total weight of only 6,6 Kgs. The combination of the flat wound (pancake) electric motor with the ultra efficient planetary gearbox results in an extremely efficient drive unit to keep the battery charging time to the minimum. The drive can be used on boats from 20 to 40 foot l.o.a. (or up to 100 Kgm rudder torque) equipped with a mechanical steering system that can be back driven.
The direct drive drives the rudder via the existing tiller arm or quadrant or via an independent tiller arm.

Please click on the picture for a larger view.

 Please click on the picture for a larger view
Due to the telescopic draglink, the overall dimensions are as small as possible. The below pictures show the two outer positions and the middle position. Please click on the pictures for a larger view.
Please click on the picture for a larger view Please click on the picture for a larger view Please click on the picture for a larger view
Main dimensions:

 
Please note that the drive can also be mounted upside down when the installation space requires this.
Correct mounting relative to the rudder stock:

The above illustration shows the correct installation geometry of the linear drive. It's very important to check if correct rudder stops are fitted (shown in green) limiting the rudder travel to 2 x 36° (normal for wheel steered systems). The lack of correct rudder stops will cause the direct drive to act as travel limiter, resulting in damage to the internal gears. The linear drive has a maximum travel of 303 mm, so there is 4 mm of spare travel each side assuring a free run.
On most cable steered boats the rudder travel is 2 x 40° and on some tiller steered boats the rudder angle is even bigger. Please revert to the table at the right for the correct pin centres and offset distance in these cases. Please note that the maximum achievable rudder torque will be lower when shorter centres are used. For example: The maximum rudder torque for the 50° setup will be 192/250*100= 77 KgM in stead of the 100 KgM with the 36° setup.
rudder
angle		 pin
centres 		offset
distance
36° 250 202
38° 239 188
40° 229 175
42° 220 163
44° 212 152
46° 204 142
48° 198 132
50° 192 125
Some mounting possibilities:

 
The above illustration shows how a rack and pinion system can be combined with the linear drive on one tiller lever. This solution saves money and space.

 
The linear drive can point port or starboard, in front or aft of the rudderstock.
The construction:

please click the left picture to open a 3D animation which will show all internal components of the linear drive (file will open in your Media Player and is in Windows Media Video (WMV)), alternative formats can be found below.

(best quality)
The above assembly shows the setup of the linear drive. The drive can be separated in 5 main parts: The electric motor, the two step planetary gearbox, the electro-magnetic clutch and the final spur reduction gearbox. The Jefa direct drive has multiple advantages over existing integrated drive units. These advantages will be explained per section of the drive:

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.

Planetary gearbox: To achieve a correct rudder travel speed (hard over time) the electric motor has to be highly reduced in speed. Some autopilot drive producers use a worm reduction box, but the efficiency is extremely low as the gears rub each other. The Jefa linear uses a planetary gearbox which 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 engagement clutch. The solution is based on a electrically operated spring loaded clutch pin 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 (0.7 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. 
The performance:

This performance table shows the relation between the consumed power and the output power and how quick this is done (hard over time). The red line shows the output torque against the needed amperage. The green line shows the hard over time (time to travel 72° of rudder travel) of the drive relative to the output torque. Also visible is the strength of the drive unit related to man power. The unit is much stronger than a human being and can last much longer but one should note that when the unit is operated in the red zone, something is wrong with the trim of the boats and the sails should be adjusted to achieve lower rudder torques. The above table shows that the Jefa linear drive will steer the yacht even in the worst possible conditions. As the drive will mostly operate in the left green zone and will not continuously rotate, the average power consumption on 12 volts is 1 to 2 amps.
Connections:

This illustration shows the minimal components for a working autopilot configuration. Jefa autopilot drives work together with all mayor autopilot electronics. The connection of the Jefa autopilot drive to the autopilot junction box is quite simple. The two 1.5 mm² red and black wires have to be connected to the plus and minus of the autopilot clutch line. This will make sure that when the autopilot user engages the autopilot on the control screen, the clutch will engage and allow the autopilot motor to drive the rudder. The two 2 mm² red and black wires have to be connected to the autopilot drive output connection. Now the Jefa autopilot drive is integrated into the system.
Tiller specification form
Please click this icon to open the tiller lever specification form in Adobe PDF. This is a great help to specify a tiller arm. Please sent the form to us.
Compatibility in 12 Volts.
Following table shows the maximum rudder torques that can be generated by the Jefa linear drive in combination with various autopilot junction boxes. The hard over time (HO-time) states the time it takes the drive to travel the full 72 degrees of rudder travel when the speed control of the pilot is set to maximum speed.
Autopilot junction box 12 Volt version. Max. output (Amp.) Rudder torque (KgM)
Simrad AC12 12 93
Simrad AC20 20 100
Simrad AC40 overpowered, do not use
B&G h1000*² 25 100
B&G h2000 ACP-1 25 100
B&G h2000 ACP-2 overpowered, do not use
Raymarine S1 15 100
Raymarine S2 20 100
Raymarine S3 overpowered, do not use
Raymarine X-10 25 100
Raymarine X-30 overpowered, do not use
Nexus-Silva A-1510 15 100
NKE gyropilot 2 RVP 25 100
Furuno Navpilot 500/511/520 25 100
*² Please use part number h1000-CUW specially made for Jefa drives, equipped with dynamic braking. Don't use the standard h1000.
Pricing

Jefa linear drive unit type LD100

Part No.

Description

Price in Euro

DU-LD-12

Linear drive 100 KgM - 400 Kg thrust, 12 volts

 € 1.409
The direct drive is delivered including a Ø16 mm tiller pin and in some cases you will need a tiller arm.