The Design of Rolling Bearing Mountings

30 Double-step spur gearOperating dataMax. input speed 1,500 min –1 ; gear ratio 6.25:1;output power 1,100 kW at a maximum speed of1,500 min –1 .Bearing selectionThe bearings supporting the three gear shafts are adjusted.Two tapered roller bearings FAG 32224A(T4FD120)*, two tapered roller bearings FAG30330A (T2GB150)* and two tapered roller bearingsFAG 30336 are used. The X arrangement chosenmeans that the cups are adjusted and the adjustingshims inserted between the cup and housing cover determinethe axial clearance. The same gear housing isalso used for gears transmitting higher power. In such acase larger bearings are used without sleeves.Machining tolerancesThe cones are subjected to circumferential load and are,therefore, fitted tightly on the shaft. The cups are subjectedto point load and can, therefore, have a loose fit.The bearing seats on the shafts are machined to m6,the housings to J7.The relatively loose fit in the housing simplifies cupadjustment.Lubrication, cooling, sealingThe lubrication system selected depends on the gearspeed, power, operating time and ambient temperature.For low power and low gear circumferentialspeeds, oil splash lubrication without extra cooling issufficient. Medium power often requires some extracooling. For high power and high gear circumferentialspeeds circulating oil lubrication (possibly with oilcooler) is provided. Detailed information on the rangeof application of lubrication system and oils in questionis available from gear manufacturers.The rolling bearings are lubricated with the same oil asthe gears; for this purpose baffle plates and collectinggrooves are provided in the transmission case to trapthe oil and feed it through the channels to the bearings.Gap-type seals with grooves and oil return channels inthe end covers provide adequate sealing at the shaftopenings. More sophisticated seals such as shaft seals(with dust lip, if necessary) are provided where ambientconditions are adverse.*) Designation according to DIN ISO 35530: Double-step spur gearFAG 46