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"Modern Repair Methods in New B.M.T. Shop" (1927)

ELECTRIC RAILWAY JOURNAL · Vol. 69, No. 3 · January 15, 1927 · pp 108-113.

Modern Repair Methods in New B.M.T. Shop

Section Devoted to Controller, Switch Group, Brush-Holder and Other Detailed Equipment Repairs.

Latest Types of Tools to Insure Rapid and Efficient Repairs to Electric Car Equipment Are Installed in the Shop Devoted to Electrical Repairs for the Brooklyn-Manhattan Transit Corporation.

Selection of the best available practices for repairing electrical equipment of cars has made the new shop of the Brooklyn-Manhattan Transit Corporation outstanding. Devices have been installed to do the work quickly and with a minimum of physical effort. While many of the pieces of apparatus are fairly common in large railway shops, the combination of them in one carefully planned layout is unique. For this reason considerable attention has been given in this article to a discussion of the individual tools and devices.

Armature leads are connected to the commutator bars by the pot-soldering method. All oil, dirt, insulating material and paint are removed when the commutator is repaired and the slots in its neck are cleaned and carefully tinned before the coils are inserted in them. The soldering is done in two General Electric soldering pots installed in section 6 of the shop, which has a concrete floor. Provision is made for two additional pots.

The soldering pots, two of which are shown in the illustration on page 108, are standard equipment in a number of large shops. There are two compartments side by side, one in which the soldering is done and the other a reservoir in which the solder is kept molten by gas flames. The soldering compartment has a hollow center in which the commutator is placed, so that it projects below the solder and does not come in contact with it. A sheet metal ring laid on the opening in the center has a hole of such diameter that it just lets the commutator pass through. A collar of asbestos tape placed around the commutator about 1 in. from the neck makes a solder-tight connection. The space between the asbestos collar and the neck is painted with a mixture of whiting and alcohol to prevent the solder from adhering.

The armature is handled by means of a crane, a hook fastened to the pinion end holding it vertical with the commutator end down. It is placed in position in the pot and then the solder is forced around the neck by depressing a plunger in the reservoir. While the solder is around the commutator the neck is raked with a wire brush to insure good contact and union of the solder and copper. After several minutes the hot solder is drained from the central portion by raising the plunger in the reservoir and the armature is removed. With the pot method of soldering the leads of an entire armature can be soldered in one operation, without danger that any excess solder will work back of the commutator neck.

The frequency with which an armature is tested was detailed in the previous outline of armature work. Three types of testing apparatus are used, the bar-to-bar test equipment, the high-voltage test and the buzzer test.

Two types of bar-to-bar test equipment are used. One has a variable resistance and the other a lamp circuit. In either case an ammeter is connected in series. Leads placed on two adjacent commutator bars are used to explore the coils and locate trouble, a milli-voltmeter giving the indication. The 600-volt shop system is used as the source of supply. High-tension tests are made by the portable transformer box already referred to.

The buzzer test to detect short circuits and grounds is made with standard Westinghouse Electric & Manufacturing Company equipment. This consists of a laminated iron core in which an alternating magnetic flux is set up. The exciting coil is energized from the shop a.c. circuit. The core is mounted on a wheeled stand which readily can be moved up to an armature undergoing repair and on which the tests are to be made. A windlass permits of raising or lowering the cross head which supports the laminated core so that it can be shoved against the armature as it rests on the usual type of winding stand. In this position, with the laminated core energized an alternating flux passes through the armature. If the condition of the armature winding is correct the electromotive forces generated counterbalance each other and no current passes through the winding. A short-circuited or reversed coil will cause a local current and a flux around the slot in which the coil lies. A piece of metal or a knife blade passed around the commutator will then short-circuit in succession each of the coils that have one side under the testing pole. If there are no faults in the winding a decided spark occurs as the knife blade leaves each bar. Absence of spark between two bars indicates a short circuit, an open circuit or a reversed coil in the winding.

A short-circuited or reversed coil due to the local current induced in it will generate a flux, which can be detected by moving a piece of sheet iron held lightly over the surface of the armature core so as to bridge from one tooth to the next successively. The local flux caused by a short circuit or reversed connection will attract the piece of iron when it bridges across the slot containing the defective coil. As the sheet iron is thus caused to vibrate the test has been termed the "buzzer." If no local flux is detected the fault disclosed by the sparking test is due to an open circuit. This testing equipment is suitable only for use with wave-wound (two-circuit) armatures, as the equalizing connectors on lap or multiple-wound armatures would make the entire winding appear short circuited.

For testing equipment the shop is wired for 110 volts alternating current, with outlets in the pedestals of the armature winding section and at other convenient intervals. The alternating current is supplied by a General Electric synchronous converter, installed together with the necessary switchboard equipment at one side of the shop adjacent to the office.

Banding of armatures and turning and slotting of commutators are done in section 7, which is equipped with four special lathes. One of these is a Peerless universal slotting, banding and commutator turning lathe. There are also two Le Courtenay combination banding and turning lathes, one of which is equipped with a commutator slotting attachment. The fourth lathe of this group is a small Peerless slotting and banding lathe, which is used for small armatures such as are used for air compressors. The banding equipment also includes a separate band tension machine made from General Electric Company's design by the railway, which provides for accurately weighing the tension used for banding. With the large size subway motor armatures such as are used by this company, a banding tension of 400 lb. is required. These machine tools are designed particularly for electric railway work and the economy of being able to do banding, commutator turning, commutator slotting and, in fact, all ma- chine work on an armature in one set-up will be appreciated by railway repairmen.

For turning shafts already installed in armatures and for cutting threads on the end of the shaft for the pinion nuts a 26-in. lathe made by the Monarch Machine Tool Company is used. This size is needed in order that the lathe carriage may pass underneath the commutators of the large armatures. This lathe can also be used for turning commutators if the volume of work makes it necessary.

An 8-in. Lo-Swing lathe is used for turning new armature shafts and also for turning the tapers on armature shafts. This lathe has two carriages and two tool posts per carriage. All work on an armature shaft can be done in this lathe except the cutting of threads and keyways. Two machines are provided for keyway work, one a No. 3 Little Giant horizontal key seater and the other a No. 5 vertical key seater. The vertical key seater is used for cutting keyways inside armature spiders and in other places where the keyway is inside an opening. In the table of machine tools now installed in this shop will be found listed several other machines necessary for various repair operations and for keeping the cutting tools in proper condition.

All of the armatures used in rapid transit service for the New York Municipal Railway Corporation have strap-wound coils. After removal from the armatures the coils are taken to section 8 for reclamation. The first operation is removal of the insulation. The coils are bundled up in lots convenient to handle and are put into the potash tank. After immersion for two or three hours, the coils are taken out and one edge of the softened insulation is cut off. They are then returned to the potash tank and left overnight. The insulation can then be scraped off with a knife. After washing, the coils go to a bench for shaping, care being taken not to separate the three coils which go together in winding.

The potash tank is made of sheet steel with a frame and supporting legs of angles. It is 6 ft. long, 30 in. wide and 18 in. deep. Steam pipes are run around the inside of the potash tank. The solution that is used in this tank when put in fresh is made with 6 lb. of potash to 50 gal. of water. The solution is continued in use by adding 1 lb. of potash each day. A small washing tank, 28 in. x 18 in. x 10 in. deep, is provided at one end of the potash tank. The lye solution is kept hot by steam from an 8-hp. flash boiler, manufactured by the P. M. Lattner Manufacturing Company. Steam from this boiler is also used for the hot coil presses installed on the balcony in section 14 immediately above the boiler. This boiler burns gas at a low pressure, regulated automatically to keep the steam pressure at 60 lb.

There are several operations in the straightening of the armature coils. The leads and sides of the coil are straightened in a vise and they are brought back to their original shape by placing them on forms and hammering with a wooden mallet. It is also necessary to remove carefully any rough spots and sharp edges, after which the coils are retaped and are then dipped and baked for reuse.

Field Coil Test Methods. Section 14 of the shop is also used for all field coil repairs, which consist mostly of putting on new insulation and new leads, which are placed on all coils which come in for repairs. After repair, each field coil is given a short-circuit test. In this the field under test acts as a secondary of a transformer, the primary coil of which has a circuit breaker, ammeter and a double-pole, single-throw switch. In making the test, a reading is taken on the ammeter and the switch is closed without a field coil in position for testing. This reading gives the primary current of the transformer when the secondary is open circuited, which will be unchanged if the field coil under test is in good condition. A reading higher than normal indicates that the field coil has a short circuit, the reading varying with the number of turns that are short-circuited. If the test is continued for a sufficient length of time the location of the short circuit will be indicated by heating. Coils are tested for open circuits by grounding one terminal and applying a lamp circuit to the other.

All field coils are impregnated. The coils are dipped twice and baked. They are also subjected to a 2,000-volt test before being returned to service.

All coil winding and taping is done on the mezzanine, which contains the latest type equipment needed for this repair work. This department also contains a large number of hot coil pres:es. These are mounted on an angle framework, with the various valves and piping for steam heating carried underneath. Parts are transported to and from the mezzanine through a hatchway.

Most of the employees in the coil-winding and taping department are women. A restroom is conveniently located in the center section of the mezzanine which is fitted up with space for lockers, etc. The east end of the mezzanine is used for the repair of fare registers and passimeters used in subway service.

On the main floor of the shop, in addition to the department, already described, a space 32 ft. x 40 ft. in the southwest corner is partitioned off as a foreman's office. Near the east end under the balcony a large room has been reserved for equipment and later will be used as a testing laboratory. Provision will be made for tests on all kinds of materials used in electric railway construction and operation. The east end of the shop, supplied with an abundance of light, is used for the repair of controller equipment, contactors, switch groups, line switches, magnets, door-operating equipment, brush-holders and other small parts.

A feature of this shop is the provision of storerooms for supplies located conveniently to the point at which they are used. Section 2 is a small storeroom for controller parts, and at the other end of the room is a storeroom for other parts used in the department of electrical repairs. This has two floors and the material used in the coil winding and taping section is carried on the second floor.

A men's locker and wash room is provided in the center of the shop underneath the mezzanine. This is equipped with four Bradley wash fountains of latest design and two shower baths. The lockers are of all-steel construction, made to the company's specifications. Water for washing purposes is heated by a Ruud automatic multi-coil storage heater, regulated by thermostatic control. At convenient intervals throughout the shop are a number of Halsey Taylor drinking fountains. These have a large ice receptacle, 18 in. diameter x 18 in. high. The fountains are set on a pedestal with the top of the bowl about 40 in. above the floor. The drinking bowl is of porcelain. Water is turned on against a slight spring pressure, and is automatically shut off when the handle is released.

Modern Machines Facilitate Maintenance Work in New Shop for Brooklyn-Manhattan Transit Lines. No. 1. Dipping armatures in soldering pots to solder connections at commutator neck.	No. 2. Banding, slotting and turning operations can all be done in these universal lathes.

No. 3. Applying canvas hood to the pinion end of armature windings.	No. 4. Slotting a commutator by means of an individual slotting machine.

No. 5. Commutators are trued up by taking a slight cut and are then sandpapered and polished.	Testing an Armature for Short Circuits by Means of the Buzzer Test.

Removing Insulation and Straightening Armature Coils.	Strap-Wound Armature Coils Are Tied in Bundles Convenient for Handling and Are Placed In a Lye Tank for Removal of the Insulation. The Solution Is Heated by Steam from a Flash Boiler.

A Large Number of Hot Presses Are Used for Armature Coil Work.	Shaping Coils for Reinsulation.

At Left- All Field Coils Received for Repairs Have New Leads Installed. At Right- Winding New Armature Coils.

Circular Wash Fountains Are Provided for Workmen.

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