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).
The development of a cheaper lighting switch, detailing issues with friction and contact shape.
| Identifier | ExFiles\Box 168a\2\ img422 | |
| Date | 5th April 1939 | |
| 6139 To By.{R.W. Bailey - Chief Engineer} from RM{William Robotham - Chief Engineer}/KC. c. DB.{Donald Bastow - Suspensions} c. By/KD. RM{William Robotham - Chief Engineer}/KC.3/AH.5.4.39. A.A. LIGHTING SWITCH TO Sch.DCD.834. We have done a certain amount of work on the development of the new, cheaper lighting switch Sch.DCD.834, and have reached a point where the main details can be specified. Experiments have been carried out in connection with the contacts, recesses and the spring; the object being to obtain as smooth and decisive a movement as possible with definite location of the contacts in each position. Generally, the object was attained by reducing frictional resistance and obstruction to movement to a minimum, and substituting as far as possible, spring resistance at the same time reducing the bridging distance between recesses. Following is a summary of the points where improvement or alteration was made, and which need corresponding attention when revising the design. FRICTIONAL RESISTANCE. This is largely a matter of getting the clearances right. Friction was found to occur:- (a) Through the moving contact-plate and its carrier, being too close a fit on the D-shaped spindle. (b) Between the periphery of the moving contact and carrier, and the body of the switch. (c) Between the spindle and the aluminium cover. OBSTRUCTION AND SHAPE OF RECESS. This is bound up with the mutual shape of the contacts and recesses. With both contact and recess a spherical shape the slope of the side of the recess was so steep that under the rotational force applied through the spindle, the contact would not climb out. Cont'd.{John DeLooze - Company Secretary} | ||