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"Careful Overhauling of Motors Prevents Service Interruptions" (1928)

ELECTRIC RAILWAY JOURNAL · Vol. 71, No. 24 · June 16, 1928 · pp 972-977.

Careful Overhauling of Motors Prevents Service Interruptions

By Clarence W. Squier, Associate Editor Electric Railway Journal

At left- One of the bays in the motor overhauling section. The machine for installing armatures in box-frame motors is shown in the foreground. At right- Installing an armature in a box frame motor.

With several cars in a rapid transit train a disabled motor may cause delay and inconvenience to hundreds. Motor overhauling in the Coney Island shops of the Brooklyn-Manhattan Transit Lines is planned to prevent failures on the road. The most modern practices are used.

Highly systematized methods are used throughout the motor overhauling department in the Coney Island shops of the Brooklyn-Manhattan Transit Lines. This work is done in two bays each 20 ft. wide by 100 ft. long. Over each bay is a 5-ton overhead traveling crane controlled from the floor. Motors are lifted off trucks at one end of the section when the trucks go through the shops for general overhauling. The department also does intermediate repairs to motors when it is necessary to remove them from trucks. This section is adjacent to the truck overhauling department so that handling is kept to a minimum.

All motors are of a box-frame type. This is of particular value in standardizing the work. The first thing done when a motor is received in this department is to pull waste from axle caps and armature bearing housings and drain off the oil. The oil and waste are placed in steel drums and go to the oil and waste reclaiming department. Next, for removal of armatures, the motors are placed in a dismantling and assembling machine, of which there are two in the section. One is used for taking out armatures and the other, at the opposite end of the section, is used for assembling.

The machines are of a type quite generally used by electric railways for the purpose. The base has two 9-in. channels 12 ft. 3 in. long. These serve as tracks for the carriage which supports the motor shell. End uprights of 1/2x4-in. steel support a headstock and a tailstock with spindles with coned ends to fit in the centers of the armature shaft. The carriage has a spindle with collars at one side over which the motor axle bearing suspension fits. At the other side the carriage has a supporting framework with a plate to support the nose of the motor. The motor is thus supported on the carriage, the same as it ordinarily is on the car truck. Accompanying illustrations show the construction.

To remove an armature the motor is placed on the carriage, the shaft is centered in the head and tailstocks and locked in position. The pinion end housing is then unbolted and the motor shell as it rests on the carriage is pushed in the direction of the commutator end of the frame. The long spindle passes through the motor shell. The commutator end housing remains with the motor shell, but the pinion-end housing stays on the armature shaft until the pinion is removed. When the motor shell has cleared the armature, the latter is lifted out by the overhead traveling crane and is placed on an armature truck. In handling, a sling with a broad supporting surface is passed around the armature at its center. Pinions are removed by means of a pinion puller, end housings are removed and the armature is sent to the department of electrical repairs for cleaning, testing and repairing if necessary. Several armature trucks are towed together by one of a large fleet of storage battery trucks.

Two general types of armature trucks are used. One is of sheet steel construction with three wheels: The center framework forms a cradle to carry the armature. The second has an angle-iron framework with cast steel ends hollowed out to receive the armature shaft ends. There are four wheels, an 8-in. one on either side at the center and one^4-in. wheel in the center at each end. This latter truck is particularly convenient for handling armatures into and out of the baking ovens.

An armature suction blower is to be installed in the motor overhauling section for cleaning. When this is ready armatures will be cleaned before they are sent to the department of electrical repairs.

The end housings are taken to a motor-driven hydraulic press where the armature bearings are pressed out. Housings and axle caps are then placed in a chemical cleaning tank where they remain for about 1 1/2 hours. There are two tanks each 4 ft. x 6 ft. x 3 ft.6 in. high. One has the chemical cleaning solution and the other has water for rinsing. After cleaning, the housings and axle caps are wiped, inspected and gaged for wear, defects or needed repairs. If they pass the test they are then ready for re-use. All bearings are sent to the babbitting department.

Motor frames are overhauled on work stands. Brushholders are removed and sent to the department of electrical repairs for general overhauling and adjusting. All connections to and between field coils are broken and a careful inspection is made for loose joints. Fields are tested from the 600-volt shop circuit. Any that show signs of short circuits or grounds are removed and sent to the department of electrical repairs. Field coils passing this inspection are not removed from the motor frames. After repair, connections are made again and the entire inside of the frame and the field coils is given a coat of insulating varnish.

Some of the motor frame overhauling is done on stands to raise the parts to a convenient height for the workmen. The stands are 5x8 ft. with a structural steel framework. Each has space for two motors. Special overhauling stands, shown in one of the illustrations arranged so the motor can be turned to any position desired, are used for most of the overhauling. Two circular end plates are bolted to the motor frame by means of the bolt holes used for fastening the armature housings in position. The end plates rest on bottom supports with rollers, so that the motor frame can be rotated readily. The base is 3 ft. 10 3/4 in. long by 3 ft. 4 in. wide and the center of the motor frame is 3 ft. 7 in. above the base, which rests on the floor.

In general the motors now in use on the B.M.T. subway cars have not been in service long enough to have excessively worn axle-cap or armature-housing fits. However, these are all gaged carefully to make certain that there is no excessive wear. In some motors a slight warping has occurred in the motor suspension projectors to which the axle caps fit. When this is enough to cause improper alignment or fit of the axle bearing, low spots are built by welding, the fit for the axle caps is planed off and the frames are rebored. This work is done in the machine shop section.

An accompanying illustration shows a motor frame set up in a planer for machining off the axle cap fit. Another shows a motor frame in the double spindle boring mill having the axle bearing fits bored out. The large 48-in. planer was furnished by the C. A. Gray Company, Cincinnati, Ohio. It has a 12-ft. table and three heads for holding tools, two on the cross rail and the other on the side of the column for facing and side cutting. All heads have automatic feed in either a horizontal or a vertical direction and they can be turned to any angle required by the work. The cross rail and all heads are raised and lowered mechanically. All bearing surfaces have forced-feed lubrication.

The double-spindle horizontal boring mill, furnished by the Giddings & Lewis Machine Tool Company, Fond du Lac, Wis., has special attachments for boring at one time both the axle-cap and the armature-housing fits for the subway type motors. All adjustments are made mechanically. The machine can be used as a single spindle boring mill by removing the extra plate from the table, which carries two boring bars, and by taking of the double spindle boring attachment at the driving end.

The practice of the B.M.T. Lines is to bore armature bearings after they are pressed into housings. The bearings have a thin babbitt lining with cast-in oil grooves. This eliminates handling of the large end housings to cut oil grooves after the bearings are bored. Each bearing is fitted to the armature shaft with which it is to be used. Bearings are pressed into housings with a motor-operated hydraulic press. A gage shows the pressure as each bearing is pressed in. An average pressure of 5 tons is used.

Illustrations show the jig used to insure accurate boring of the bearings after they are pressed into housings. This will take both the pinion end and commutator end housings for three different types of motors, Westinghouse types 300 and 50-L and General Electric type GE-248. The jig really consists of two fixtures, an inner and an outer one, the inner one being used for 50-L housings and the outer one for types 248 and 300 housings. Both fixtures are centered accurately on the face plate of the boring mill by slots and keys. The inside fits into which the housings go were bored out on the machine with which they are used. They are 1/32-in. larger in diameter than the housings.

The inside fixture has three locking arms and three indexed set screws. The locking arms center the housing to be bored and the set screws are then tightened until the index on each is the same. This insures accurate centering of the housing with respect to its fit in the motor shell.

The outside fixture has four gage rings, one for use with each of the four different types of housings that are bored in the jig. The gage rings are centered accurately and locked in position by a set of indexed screws which move centering pins into position by the action of beveled surfaces. When a ring is centered accurately all the indices are the same.

Great care is used in the removal and installation of pinions. Pinions are heated in a hot-water tank so that the bores are expanded previous to installation. All teeth are gaged for wear. A discard gage used to determine the scrapping limit is illustrated. When the top projection touches the end of a tooth, the limit of wear has been reached.

A feature of the motor overhauling section is the provision made for storing parts used in overhauling adjacent to the work. Motor leads are cut to exact dimensions and stored in racks. Locked cabinets contain brush-holders, bearings, connectors and other brass or copper parts. Storage racks are used for housings and axle caps and locked boxes hold the overhauling tools.

Removing a pinion from the hot water tank for installation on armature shaft.	Limit of wear gage for gears and pinions.

Floor plan of the section in the Coney Island shops devoted to motor overhauling.

Details of machine used for removal and installation of armatures in box frame motors.

An armature suction blower is to be installed in the motor overhauling section for cleaning. When this is ready armatures will be cleaned before they are sent to the department of electrical repairs.	Type of armature truck used for running armatures into baking ovens.

Chemical cleaning and rinsing tanks. Housings and axle caps are cleaned here.	Details of rotating motor shell work stand.

Working on a motor shell after installation in the rotating work stand.	Tightening lead cleat with motor shell on one of the stationary work stands.

The line drawing on the left shows assembly of the jig used for boring motor bearings after they have been pressed into housing. The center drawing shows the inner fixture of the jig used for boring armature bearings. In the drawing on the right are shown the details of gage rings used with the outside fixture for boring armature bearings after they have been pressed into housing.

No. 1. Machining a motor axle suspension bearing fit in the large planer.	No. 3. Pressing an armature bearing into a motor housing by means of the hydraulic press.

No. 2. Boring out an axle bearing fit in the double spindle horizontal boring machine.	Boring out an armature bearing after it has been pressed into housing. A special jig is used for centering the housing accurately.

Sources: Electric Railway Journal, McGraw Hill Company, Digitized by Microsoft, Americana Collection, archive.org.