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45Axle box roller bearings<strong>of</strong> series 120's three-phase current locomotive<strong>The</strong> frame is supported by coil springs and spring seatswhich are integrated in the bearing housing. <strong>The</strong>spring seats are arranged at different heights. <strong>The</strong> bearingis guided by an arm on each side which is linkeddiagonally to the housing. <strong>The</strong> arms are supported byelastic damping springs.Technical dataVehicle weight: 84,000 kgNumber <strong>of</strong> wheelsets: 4Wheelset weight: 2,250 kgAxle load: 22,000 kgSupplementary factor f z = 1.5<strong>The</strong> locomotive reaches top travelling speeds up to200 km/h.<strong>Bearing</strong> selectionPlease refer to example number 42 to determine theequivalent dynamic load P.Cylindrical roller bearings <strong>of</strong> the type NJ and NJPwith the dimensions 180 x 320 x 75 mm are mounted.Dynamic load rating <strong>of</strong> one bearing: C = 735 kN. <strong>The</strong>outer and inner rings <strong>of</strong> both bearings are separated byspacer rings. <strong>The</strong> inner spacer ring is 2 mm wider thanthat <strong>of</strong> the outer rings.<strong>The</strong> axial clearance which arises thereby, is necessary tocompensate for bogie production tolerances. <strong>The</strong> bearingcan always be mounted without preload.Machining tolerances<strong>The</strong> bearing inner rings have circumferential load andare therefore given a tight fit: Journals to p6. <strong>The</strong> housingmaterial, an aluminium cast alloy, has a greater coefficient<strong>of</strong> expansion than cast steel which is why thetolerance field J7 was selected and not the housing toleranceH7 usually taken for cast steel housings.<strong>Bearing</strong> clearanceDue to the tight fit the bearing inner rings expand; theradial clearance becomes smaller. <strong>The</strong> outer ring iscooled more than the inner ring by the wind resistanceduring travel which leads to a further reduction <strong>of</strong>clearance. For this reason bearings with increasedradial clearance C4 have been selected.Lubrication, sealingA lithium soap base grease is used for lubrication. Onthe wheel side the bearing is sealed by a two-web labyrinthseal. A V ring seal protects from contaminants onthe opposite side.45: Axle box roller bearings <strong>of</strong> series 120's three-phase current locomotiveFAG 66
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