. Electric railway journal . ca to be undercut. Asmall-diameter saw must be used in order to cut theslot to the proper depth and at the same time not cutinto the neck of the commutator. After the slots aresawed it is sometimes necessary to go over them witha small hand-cutter, or scraper, to remove all remain-ing particles of mica. Where commutation trouble is frequent it is goodpractice to use a V-shaped hand tool to round the edges of the under-cut grooves between bars to about ^ This can be done without removing the motorsfrom the car. Clean undercutting of commutators eliminates
. Electric railway journal . ca to be undercut. Asmall-diameter saw must be used in order to cut theslot to the proper depth and at the same time not cutinto the neck of the commutator. After the slots aresawed it is sometimes necessary to go over them witha small hand-cutter, or scraper, to remove all remain-ing particles of mica. Where commutation trouble is frequent it is goodpractice to use a V-shaped hand tool to round the edges of the under-cut grooves between bars to about ^ This can be done without removing the motorsfrom the car. Clean undercutting of commutators eliminates highmica, thus reducing burning of the commutator barsand giving extended life to carbon brushes. By thismeans practically all flashing is prevented and mainte-nance costs are greatly decreased. Making Brushholder Repair To care for the brushholders of the Iailway motorsintelligently it is necessary for the maintainor to befamiliar with the construction and purposes of theirparts. In repairing and replacing a modern railway. CONDITION OF RAILWAY MOTOR CARBON BRUSHESAFTER BEING USED IN VARIOUS TYPES OF SERVICE motor brushholder of the insulated-pin type the follow-ing points should be considered: The brushholder castings and mechanism should haveat least f in. air clearance from the motor frame. The porcelain insulators give sufficient creepage dis-tance over smooth corrugated surfaces to keep thebrushholders from becoming grounded to the frameand should always be kept tight on the pin by puttingpieces of treated linen between the porcelain and should be kept free from carbon dust and dirt toprevent current from leaking over the surface. It isa question if porcelain insulators are necessary, andin some cases they have been left off with satisfactoryresults in service. Railway motor frames, as built today, have machinedpads for supporting the clamping blocks of the brush-holders exactly in the neutral position. On replacingbrushholders the clamping blocks must be seate
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Keywords: ., bookcentury1900, bookdecade1900, bookpublishernewyorkmcgrawhillp
