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).
Letter from F.H. Royce discussing proposals for crane motor design, including gearing, A.C. motors, and insulators.
| Identifier | Morton\M6\ img031 | |
| Date | 9th November 1929 guessed | |
| (2) (6) It is proposed that a higher speed and higher rating be given to the motors for crane work so that they can be of small dimensions and light-weight. In standard design there should be available a train of 3 pairs of gears for the alternating current work, and 2 pairs for the continuous current work. The motor shaft is always to be substantial enough, and a bearing of a suitable form used so that the brake and pinion can be completely carried on the motor. (7) Regarding A.C. motors, if these could be made with squirrel cages, so much would be saved in the wiring. I suggest we consider making them with very high resistance squirrel cages - i.e. 50% full load slip. The disadvantage will be the heat inside the case at full load. It would seem that they would give the maximum torque alright, and would run under light load just below the full synchronised speed, but with heavy loads the speed may be reduced to half. This might give somewhat the effect of the continuous current motor, the only loss being the loss of efficiency at full loads. It would be particularly advantageous if the 2 motors on the crab were of this pattern. It might suit also a capstan motor. How we make the high resistance bars, and get rid of the heat, we will keep consider later, after we decide whether such a system would be good. (8) Another scheme has suggested itself to me, that is, we could have a slip ring motor on the crab with any proportionate external resistance coupled to the slip rings permanently. This would be a means of getting the heat outside the case. It may not be quite so cheap as the squirrel cage, but would still save a good many cross wires and much collector gear and space. (9) Instead of the large number of expensive strain insulators can we not use simple standard pot insulators? (Bullers.) Yours very sincerely, (Sgd) F.H. ROYCE. | ||