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).
Explanation of a starter pinion and flywheel engagement mechanism, with a comparison to the Bendix Drive system.
| Identifier | ExFiles\Box 40\5\ Scan070 | |
| Date | 16th December 1921 guessed | |
| -3- (about 1/8") which separates the pinion from the flywheel gear ring. The pinion meets a flywheel tooth and stops advancing any further. However, the continued rotation of the starter shaft 1 and threaded sleeve 2 maintain the flanged nut 9 in its normal longitudinal motion forward until, as shown in Sketch No.3 and as explained before, the plate 6 meets the shoulder stop of the threaded sleeve 2. In this forward motion, the nut 9 carries along with it the clutch members and the barrel 5, which slides along the pinion teeth. The spring 7 on the other hand finds itself compressed between the plate 6 and the flange of the pinion member. As soon as the device reaches the position shown in Sketch No.3, the clutch tightens automatically as explained in the case of normal operation. The barrel is therefore forced to turn with the starter shaft, being driven through the nut, clutch and splined plate 6. The pinion, being driven by the notched barrel 5, must also follow. But, as clearly shown on the drawing, the pinion is simply spring pressed forward against the flywheel, with a strength which limited to a safe value by the suitable choice of the spring 7, and is not applied against it solidly. being free to slide longitudinally against this pressure, while rotating, it can therefore ride around the offending flywheel tooth while being rotated by the barrel with the starter shaft. This is further helped by the slanting end of the pinion teeth as shown in the sketch. As soon as the teeth are uncovered, the compressed spring 7 snaps the pinion into mesh and normal cranking takes place. In this manner, it is impossible to "jam" the pinion teeth against the flywheel teeth, and positive and complete meshing of the starter and engine is obtained every time the starting switch is closed. It is not necessary to try more than once in order to obtain meshing. In your letter, you make reference to the Bendix Drive, with which you intend to compare with the Bijur form of drive. I may therefore point out to you a difference of operation under certain conditions. Thus, while the Bendix Drive is manufactured under license from our Company, it differs among other features in that the pinion forms also the nut, since the thread is cut right into the pinion, which rides directly on the threaded sleeve. The result of this construction is that in case a pinion tooth butts against a flywheel tooth, the pinion is screwed against the flywheel like an ordinary nut, and very energetically since this is done by the electric starter. There is therefore the possibility of jamming solidly the starter and engine, which prevents the rotation of either. Or else, the teeth of either flywheel or pinion may be broken or sheared away. This danger, although not completely avoided, is minimized in some degree in the Bendix Drive by giving a rather contd:- | ||