Self-aligning TWIN-PETP roller bearings type 6D


Type 6T000 bearing

The table below shows all key dimensions of the 6D series self-aligning TWIN-PETP roller bearings in GRP tube. The measurement D is the outside diameter of the GRP tube. 
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PART NO.

Bottom Bearing dia. "db"

Top Bearing dia. "dt"

TUBE dia. "D"

HEIGHT "H" *2

WEIGHT *1

WORKING
LOAD (max)

6D030 - 6D045

30 to 45 mm

30 to 45 mm

90 mm

max. 1500 mm

1.9 kg

1300-1800 kg

6D046 - 6D060

46 to 60 mm

30 to 60 mm

110 mm

max. 1500 mm

3.1 kg

2500-3200 kg

6D061 - 6D072

61 to 72 mm

30 to 72 mm

130 mm

max. 1500 mm

3.6 kg

4200-4800 kg

6D073 - 6D095

73 to 95 mm

30 to 95 mm

150 mm

max. 1500 mm

4.5 kg

4900-6200 kg

6D096 - 6D125

96 to 125 mm

41 to 125 mm

180 mm

max. 1500 mm

5.4 kg

6300-8000 kg

6D126 - 6D160

126 to 160 mm

58 to 160 mm

210 mm

max. 1500 mm

6.1 kg

8100-10100 kg

*1: Weight taken with a 800 mm tube.
*2: Longer tubes are available at a surcharge.

6D specification form:
Please click the left icon to open the 6D specification form in Adobe PDF. You can fill in the gray field with the correct info and tick the appropriate boxes. This form is required to guarantee a correct production of your bearing.

The applications for the 6D series bearing:
The 6D series bearings combine a very simple installation with a very smooth operation under all circumstances as the bearing will always be aligned to the rudder shaft. The bearing is made of PETP (also known as Arnite, Ertalyte, Sustodur & Ultradur) in a GRP tube, allowing it to be laminated directly into the hull. It's primarily meant to be used on tiller steered boats, but could be used on wheel steered boats if the tiller arm / quadrant is above the top bearing.
As the bearing is self-aligning, there will be no torque transmitted to the hull, just rudder forces and the bearing will never try to twist out of the hull. The bearing ball can be easily dismounted out of the housing for installation safety or replacement when any damage in the future may happen.

Installing the 6D bearing:

Installation of JEFA Marine composite bearings:

  1. The GRP tube of the 6T bearing is delivered with a shiny resin surface. To achieve a good bonding to the hull it's important to roughen the outside surface with a grinder or sanding machine so no shiny surface is left. This should be done just prior to laminating the bearing to the hull.
  2. Secure the bearing-housing in it's place in the hull. The bearing should be jigged in place firmly so that it won't alter position when worked during lamination and remove the bearing ball to make sure no resin will enter the rollers.
  3. Make sure the hole in the hull is a few millimetres bigger than the bearing outside diameter and tape close the gap at the bottom.
  4. Cast some resin in the gap to close off the hull laminate .
  5. Laminate the hull and bearing creating an outer skin. It can be tapered down beginning just above the self aligning bearing in the bearing tube.
  6. On top of this outer skin there should be a foam ramp or fillet (minimum 200 kilo/m3 density), which encircles the bearing housing. Make a wooden circular tool to create a nice fillet.
  7. Laminate the hull and bearing making sure that the laminate runs up the side of the bearing in full thickness. It can be tapered down over a 100 mm span beginning just above the self aligning bearing in the bearing tube.
  8. There should always be a skin joint around the bearing that is at least three times the bearing housings measurement in diameter, and the laminate should have a minimum thickness of 1.5x(1.8+(LWL/1.8), this thickness is not including the foam ram mentioned bellow. (LWL in Meters).
  9. In stead of using a filled around the first outer skin, one can also make a web of triangles which will be included in the final lamination (see model below).

Please remember that these guidelines represent good practice, however all structural components of a sailing vessel should be engineered by a qualified engineer for the actual case. JEFA MARINE takes no responsibility for any structural failures which might result from the use of these guidelines.


Installation example of the 6D bearing not using a fillet for stiffness but a web structure

6D examples:

Fitting tiller stops to the 6D bearings:
The 6D series bearings standard have no tiller stop arrangement . By adding a flange with stops which can be bolted to the deck, additional tiller stops can be added. There is one flange to work with our tiller heads 25 mm to 40 (6SP035STP) and one to work with our 50 mm tiller head (6SP050STP).

6SP035STP dimensions:
6SP050STP dimensions:

TILLER STOPS

PART NO.

DISCRIPTION

corresponding tiller heads

6SP035STP

Tiller stop up to 40 mm shaft

25 - 40 mm

6SP050STP

Tiller stop up to 50 mm shaft

50 mm