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).
Specifications for bearings, lubrication, brushes, terminals, and performance of a starting motor.
| Identifier | ExFiles\Box 23\2\ Scan074 | |
| Date | 4th November 1921 | |
| ROLLS-ROYCE - 6 - 4/11/21 7. BEARINGS AND LUBRICATION: The highest grade phosphour bronze bushing is used for both drive and commutator end. A clearance of ".002 to ".003 is provided between the shaft and the bushing. We have tests to show that 6,000 starts can be made with these bearings with such clearances, without lubrication. However, ample lubrication is provided for both end bearings by means of oil wells and wicks. These wells are packed with soft cup grease before the machine leaves our works, and a few drops of oil every 500 miles will give plenty of lubrication. Steel end play washers are used to limit the end play to ".010. 8. BRUSHES AND BRUSH RIGGING: The same brush rigging is used on both the 56 CG motor and the 77 BR generator. The cross connections between brush holder posts on the motor bracket, is made from heavy copper strap, and is carried between posts through a recess in the bracket over the bearing. A ring from micarta sheet insulates the cross over from the bracket. Bracket shunts are used to carry the current from the brush holder posts to the brush. This brush holder construction reduces to a minimum the voltage drop between the motor leads at the terminal, and the brush on the commutator. Morganite CM and Spear Metal B brushes are both used on our standard motors. We notice that the Rolls-Royce lucas motor uses Morganite CM brushes. 9. TERMINALS: One terminal is located on the frame and one on the commutator bracket, to provide simplest and most direct cable connections to the battery and starting switch. The frame terminal is recessed in a channel in order to prevent rotation. Insulation from the frame is secured by a micarta duck channel piece. 10. PERFORMANCE: The 56 CG starting motor is designed to start the Rolls-Royce engine under all temperature conditions, when used with a suitable battery. The maximum efficiency is 68%, and is obtained at approximately 100 R.P.M. cranking speed of the engine. The machine is so designed that high efficiency is obtained at the higher torque values, where it is most needed, as the higher torque and the higher current values are obtained under cold weather conditions. Also, the motor is designed for higher cranking speeds, and in operation the total watts seconds taken from the battery, will be less than that the Rolls-Royce motor now used, as the Westinghouse motor will take more current for less time, and quicker starting of the engine will result. This is particularly true at the higher current and torque values, where the efficiency obtained on the Westinghouse motor, shows up to good effect. The 56 CG motor is designed | ||