The Design of Rolling Bearing Mountings

56– 57 Spherical roller bearings as rudder shaft bearingsOperating dataAxial load 115 kN (weight of rudder and shaft), radialload 350 kN (driving force of steering engine andrudder).Bearing selection, dimensioningDue to the heavy loads and unavoidable misalignmentspherical roller bearings are used. They have a highload carrying capacity and are self-aligning. The ruddershaft diameter depends on size and speed of the ship aswell as on the type and size of the rudder used. Thebearing bore and the size of the bearing are determinedby the shaft diameter specified. A spherical roller bearingFAG 23052K.MB.R40.90 or FAG 23052K.MB.C2(radial clearance 150...220 microns) is mounted. Duringmounting the bearing inner ring is pressed ontothe tapered shaft seat so that the bearing operatesunder a light preload. Vibrations can thus be adequatelyaccommodated. The hydraulic method facilitatesdismounting particularly in the case of bearings withC2 bearing clearance. For this purpose the shaft musthave oil ducts and the tapered seat a circular groove.The housings of rudder shaft bearings FAGRS3052KS.1..... or FAG RS3052KW.1..... are made ofwelded shipbuilding steel plates.The static safety of a rudder shaft bearing is checkedbecause of the few slewing motions. An index of staticstressing f s between 4 and 5 is suitable for sphericalroller bearings.Machining tolerancesShaft taper 1 : 12, housing H7.Lubrication, sealingDuring mounting, the cavities of the spherical rollerbearings and housings are completely filled with lithiumsoap base grease of consistency number 2 which containsEP additives.Rudder shaft bearing FAG RS3052KS.1.....The bearing is grease lubricated. It sits in the pot-likehousing which is attached to the housing base plate bysturdy webs. A stuffing box seal is mounted in this baseplate. Its packing runs on a sleeve of seawater-resistantsteel.Due to the separation between the upper half and thebase any spray water which could penetrate runs alongthe side and does not get into the rolling bearing. Thestuffing box can be inspected at any time during operationand if necessary readjusted. The bottom end ofthe bearing is provided with a spring seal. A felt sealand V ring suffice for sealing at the top end. This bearingarrangement with stuffing box seal is maintenancefree.Rudder shaft bearing FAG RS3052KW.1.....Bearing and seal are in one and the same housing andare lubricated with grease. The bearing arrangementcan also be below the waterline. Sealing consists ofthree seawater-proof shaft sealing rings with an intermediategrease chamber. An automatic grease pumpholds the latter under permanent pressure.56: Rudder shaft bearing FAG RS3052KS.1..... 57: Rudder shaft bearing FAG RS3052KW.1.....FAG 80