338 



ELECTRICAL EQUIPMENT 



A combined guide bearing and spring-thrust bearing has also 

 been developed for carrying moderate weights. These bearings 

 are very economical in the space required and usually do not 

 require oil circulation from a source outside the bearing housing. 



Roller Bearings. This bearing consists also of a revolving and 

 a stationary plate, which, in this case, however, are separated by 



Overflow 



Inlet 



FIG. 200. Assembly of a Roller Suspension Bearing. 



hardened steel rollers, held in a brass retainer and arranged radially 

 to the shaft (see Fig. 200). The oil enters at the inner periphery 

 of the brass cage and discharges between the rolls into the sur- 

 rounding chamber. 



Combination Bearings. Roller bearings for large units are 

 constructed in some cases to incorporate the oil pressure feature 

 also. The latter is combined with the rollers in such a manner 

 that the weight may be lifted off the rollers for ordinary operation 

 and carried by them only in the event that the pressure should 

 accidentally fail. Or it may be carried ordinarily on the rollers, 

 the pressure being held in reserve in case of trouble with the 

 rollers. 



A platform with ladders leading to it should be installed on the 

 top of the machines so as to facilitate the inspection of the bear- 

 ings. Bridges are often provided from such platforms to a gallery 

 running along one wall of the power-house. 



Lubrication. The advent of the adoption of thrust bearings 

 has presented a new engineering problem, that is, the proper 

 design of an oil-circulating and oil-filtering system so that these 



