The Design of Rolling Bearing Mountings

37 Driven and non-steered rear wheel of a rear drive truckThe rear wheel hubs of heavy trucks often feature aplanetary gear. This type of drive provides a relativelyhigh gear ratio in a limited space. As the high drivingtorque is generated directly at the wheel, small differentialgears and light drive shafts are possible.Operating dataWheel load 100 kN; tyre size 13.00-20;r dyn = 569 mm; permissible maximum speed 80 km/h.Bearing selectionWheel bearingsTapered roller bearings FAG 32019XA (T4CC095 accordingto DIN ISO 355) and FAG 33021 (T2DE105according to DIN ISO 355). Since these bearings havea particularly low section height they require only asmall radial mounting space thus allowing light-weightconstructions. The relatively large bearing width andlong rollers result in a high load carrying capacity.The bearings are adjusted against each other in Oarrangement (large spread).Planetary gearsThe outer planet drive increases the driving torque in aminumum space. The planet gear bearing arrangementis of the full-complement type, i.e. it features two rowsof needle rollers. Axial guidance is provided by thrustwashers.Machining tolerancesDirect bearing arrangementwith needle rollers: shaft to h5; housing to G6Tapered roller bearing: shaft to j6; housing to N7LubricationCommon oil lubrication for planet drive and wheelbearings. An oiltight, welded housing protects gearand bearings against contamination.37: Rear wheel of a truck57 FAG