The Design of Rolling Bearing Mountings

GlossaryAdditivesAdditives are oil-soluble substances added to mineraloils or mineral oil products. By chemical or physicalaction, they change or improve lubricant properties(oxidation stability, EP properties, foaming, viscositytemperaturebehaviour, setting point, flow properties,etc.). Additives are also an important factor in calculatingthe attainable life (cp. also Factor K).Adjusted bearing arrangement/ AdjustmentAn adjusted bearing arrangement consists of two symmetricallyarranged angular contact bearings or thrustbearings. During mounting, one bearing ring (for an Oarrangement, the inner ring; for an X arrangement, theouter ring) is displaced on its seat until the bearing arrangementhas the appropriate axial clearance or the requiredpreload. This means that the adjusted bearingarrangement is particularly suitable for those caseswhere a close axial guidance is required, for example,for pinion bearing arrangements with spiral toothedbevel gears.Adjusted bearing arrangement(O arrangement)Adjusted bearing arrangement(X arrangement)Adjusted rating life calculationThe nominal life L or L h deviates more or less from thereally attainable life of rolling bearings.Therefore, the adjusted rating life calculation takesinto account, in addition to the load, the failure probability(factor a 1 ) and other significant operating conditions(factor a 23 in the FAG procedure for calculatingthe attainable life).Cp. also Modified life in accordance with DIN ISO 281.AlignmentSelf-aligning bearings are used to compensate for misalignmentand tilting.Angular contact bearingsThe term "angular contact bearing" is collectively usedfor single-row bearings whose contact lines are inclinedto the radial plane. So, angular contact bearings are angularcontact ball bearings, tapered roller bearings andspherical roller thrust bearings. Axially loaded deepgroove ball bearings also act in the same way as angularcontact bearings.Arcanol (FAG rolling bearing greases)FAG rolling bearing greases Arcanol are field-provenlubricating greases. Their scopes of application were determinedby FAG by means of the latest test methodsunder a large variety of operating conditions and withrolling bearings of all types. The eight Arcanol greaseslisted in the table on page 179 cover almost all demandson the lubrication of rolling bearings.Attainable life L na , L hnaThe FAG calculation method for determining the attainablelife (L na , L hna ) is based on DIN ISO 281 (cp.Modified life). It takes into account the influences ofthe operating conditions on the rolling bearing life andindicates the preconditions for reaching endurancestrength.L na =a 1 · a 23 · L [10 6 revolutions]andL hna =a 1 · a 23 · L h [h]a 1 factor a 1 for failure probability(DIN ISO 281);for a normal (10%) failure probability a 1 = 1.a 23 factor a 23 (life adjustment factor)L nominal rating life [10 6 revolutions]L h nominal rating life [h]If the quantities influencing the bearing life (e. g. load,speed, temperature, cleanliness, type and condition oflubricant) are variable, the attainable life (L hna1 ,L hna2 , ...) under constant conditions has to be determinedfor every operating time q [%]. The attainablelife is calculated for the total operating time using theformulaL hna =100q 1 +q 2 +q 3L hna1 L hna2 L hna3FAG 178