tolerances and with the amount of lubrication as recommended by the ICRR's and the loco- motive builder's specifications, there is some question whether the locking screws in the end plate were tightened Sufficiently to prevent them from being loosened by the rotation of the armature shaft. The rotation of the shaft tends to loosen or tighten the plate depending upon the direction of rotation The purpose of the locking screws was to prevent this movement in either direction
A later design uses five cap bolts to secure the end plate to the face of the shaft. This design eliminates any movement between the plate and the shaft caused by the rotation of the shaft However, vibration is still a factor in the loosening of the cap bolts and lockwires are employed to overcome this problem
If the locking screws of the plate were properly tightened, the circular ends of the casehardened screws would dig into the end of the armature shaft to a slight depth to keep the plate from turning If the plate was turned without loosening the properly-secured locking screws, the ends of the screws would mark the end of the shaft and indicate that this had occurred. The marks found on the end of the shaft in this accident were circular and apparent- ly were not produced by a movement of the plate (See Figure 11 )
if the end plate remained properly secured and an excessive lateral force developed from some other source, there probably would have been extensive wear between the end plate and the H-ring The only wear on the end plate was on the rear surface where it had contacted the bearing cover plate Little or no wear was detected on the H-ring The excessive wear found on one side of the bearing caps, collars, oil throwers, and seals indicate that the armature shaft had moved toward the pinion end a distance in excess of that prescribed
The hearings were manufactured from material that complied with the specified SKF requirements. The wear pattern on the various bearing parts and the amount of heat to which the various component parts of the bearings were subjected indicate that the armature had moved an excessive amount towards the pinion end. This movement caused excessive friction on the bearings and their associated parts The friction produced enough heat to cause a lubrication failure. When this occurred, the bearings rapidly deteriorated
C Reconditioning Armature Bearings
The armature bearings Which failed were designed and manufactured by SKF, they were adequate and were manufactured under a satisfactory quality control system. The relative- ly small number of bearing failures on the ICRR indicates no urgent problem
However, the manner in which SKF recondi- tions bearings could create possible problems. Because the records do not identify the length of service of the bearing parts, SKF does not know what quality bearing is resulting from their reconditioning process. Without such a record, it appears that a reconditioned hearing may contain parts of various ages and of various service histories Without such a record, the maintainability and reliability programs for such bearings can not be established.
Reconditioning bearings provides the railroad with a good bearing at a cost below that of a new one However, since some of the parts may have been subjected to more severe service for longer periods than others in the same bearing, service life of the bearing is unknown. Although the rate of failure on the ICRR has been low, it appears that the practice should be analyzed at all levels
D. Evaluation of the Work Performed by Chandeysson Electric Company
During the observations made at the Chandeysson Electric Company’s plant in St Louis, it was found that most of the repair operations were being performed in a manner prescribed by the builder of the traction motor and by the railroad. The use of a radial gauge,
calibrated from 0001 to 0.100, to measure
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