From the Rolls-Royce experimental archive: a quarter of a million communications from Rolls-Royce, 1906 to 1960's. Documents from the Sir Henry Royce Memorial Foundation (SHRMF).
Specification sheet detailing the construction of an armature, frame, field poles, field coils, and brackets.
Identifier | ExFiles\Box 23\2\ Scan073 | |
Date | 4th November 1921 | |
ROLLS-ROYCE - 5 - 4/11/21 that of the 77 BR generator, except bronze sleeve bearings are used. Aluminum brackets reduce the weight. 2. ARMATURE: The armature core is built up from ".028 high permeability sheet steel punchings, and these are pressed on a heat treated knurled shaft. The coils are formed from heavy copper strap, each coil consisting of one turn. The winding is two circuit, which is best suited to this type of motor. This is a four pole motor, and 29 bars and 29 slots are used. The end winding of the armature is supported on a pressed steel piece, and the coils are securely banded with piano wire after armature is wound. After winding the armature is pre-heated in a vacuum tank, and then impregnated with bakelite, after which it is baked for 10 hrs. at 125° C. This process is repeated in the second dip and bake. After the armature is so treated, it becomes in reality, one single unit, as the bakelite serves to bind the whole armature together. Armatures without banding, when so treated will withstand high speed tests of 10,000 to 12,000 R.P.M., without coils throwing out. The banding provides a safety factor in addition to the bakelite. The moulded bakelite commutator is used. The completed armature is ground to diameter and carefully balanced, after which it is checked for grounds and shorts. 3. FRAME: The frame is made from specially selected seamless steel tubing, which has high permeability. The frames are cut to length, windows punched, and diameters turned to size. The frame is then given a coat of #97 enamel and baked. 4. FIELD POLES: The field poles are made from extruded section, and similar in construction to those used in the 77 BR generator, except the pole tips are offset. Offset pole tips improve the locked torque performance. 5. FIELD COILS: A cotton covered copper strap is used in the field coils. Connections are made at the back and front of the frame, so as to provide the most symmetrical and accessible arrangement. These field coils are given two dips and bakes in Sterling varnish. Coil connections on both ends are insulated from the frame by 1/64" micarta sheet. 6. BRACKETS: Brackets are made from aluminum, and are simple plates similar to those used in the generator. The location of the bearings directly under the bracket fits, gives the best mechanical construction. | ||