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48 Axle box roller bearings for an underground trainA car has two bogies. Each axle box roller bearings iscushioned and guided by rubber-metal silent blocks.<strong>The</strong>se are arranged between the axle box roller bearingand the frame opening. <strong>The</strong>y are inclined to the verticaland have an angular cross-section.Machining tolerances<strong>The</strong> bearing inner rings carry circumferential load andare therefore given a tight fit: journal to m6, housingto H7.Operating dataWeight and maximum payload <strong>of</strong> one car: 34,000 kg.Number <strong>of</strong> wheelsets per bogie: 2.Wheelset weight G R : 1,400 kg.Supplementary factor f z : 1.3.Equivalent dynamic load P = 22.6 kN.Wheel diameter D R = 900 mm.Top speed v max = 80 km/h.<strong>Bearing</strong> selectionTwo cylindrical roller bearings are mounted per axlebox: One FAG NJ2318E.TVP2.C3.F2.H25 and oneFAG NJP2318ED.TVP2.C3.F2 (dynamic load ratingC = 430 kN).<strong>Bearing</strong> clearance<strong>The</strong> inner rings increase due to the tight fit: the radialclearance decreases. <strong>The</strong> outer rings are cooled morethan the inner rings due to the air stream during travel.This leads to a further reduction in clearance andtherefore a radial clearance C3 was selected.Lubrication, sealingA lithium soap base grease is used for lubrication. Acombination <strong>of</strong> a felt ring and a labrinth was selectedas a means <strong>of</strong> sealing.<strong>The</strong> labyrinth is provided with two axial webs since theaxle boxes are subjected to extreme dirt.48: Axle box roller bearings for an underground trainFAG 70
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