. Electric railway journal . as yet, although a number have been reset. Onlyone of the sixty-six air compressors in service has hadto be rebored on. As shown by the table of maintenance costs, thecharges for electrical repairs are very light. Since theengines were placed in service all armatures have beenrebanded on account of coil shrinkage, but very few ofthem have been rebanded a second time. None of themain motor commutators have been turned on accountof wear, and only two have had to be machined on ac-count of accidental damage. Third-rail shoes, which are of the over-running bracket type
. Electric railway journal . as yet, although a number have been reset. Onlyone of the sixty-six air compressors in service has hadto be rebored on. As shown by the table of maintenance costs, thecharges for electrical repairs are very light. Since theengines were placed in service all armatures have beenrebanded on account of coil shrinkage, but very few ofthem have been rebanded a second time. None of themain motor commutators have been turned on accountof wear, and only two have had to be machined on ac-count of accidental damage. Third-rail shoes, which are of the over-running bracket type, run for about15,000 miles in summer, and for about 3000 miles inwinter before replacement. The main motor brusheshave a very long life, or an average between two andthree years. Some have even lasted for 150,000 miles,being removed then for side burning. Some chippingand breakage, however, has taken place, especially inwinter weather, in which case mileages as low as 3000have been made, this applying only to, say, three or. P. R. R. LOCOMOTIVE MAINTENANCE—ELEVATION OF ENGINE HOUSE four brushes out of the forty with which each motor isequipped. Compressor brushes run about 3000 miles,being generally removed for side burning. During the past year four flashovers occurred, thearc in one case going to the motor frame, and in theother three cases extending only between brushes. Inno case was any damage done to the commutator whichcould not be cleaned up with a file, so that it was notnecessary to remove the armature for any of theseelectrical disturbances. There were also two caseswherein circuit breakers burned up, the breaker havingtripped upon an overload and grounded to the box whichcontains it, the arc being maintained by the groundfrom the circuit-breaker frame. One other unusualcase of repairs was involved when a canopy switch ter-minal became grounded and thus burnt out a numberof the auxiliary circuits. The direct cause was thedisconnection of a terminal screw, which gr
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