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).
Technical explanation of the advantages and safety features of the Bijur starter drive system.
| Identifier | ExFiles\Box 40\5\ Scan062 | |
| Date | 16th December 1921 guessed | |
| - 5 - accurate center and secure as silent a starting as if the pinion and flywheel gear ring were two premanently meshing gears. Another advantage of the Bijur construction is the fact that the pinion is mounted directly on the smooth starter shaft. This permits us to furnish drives having as few as 9 and 10 teeth of normal pitch on starter shafts for which other constructions using a threaded pinion would require a greater number of teeth. This permits a considerable increase of the gear ratio between starter and engine, giving a correspondingly greater power margin for the starter. Factor of Safety. As explained above, the use of a clutch in the Bijur drive for transmitting the cranking torque from the starter to the engine has the advantage of throwing the cranking load on the starter gradually, thus avoiding shock and noise. The clutch elements are proportioned in such a manner that the clutch will transmit all values of torque required for cranking all engines on the market for motor cars. Its slipping torque is low enough to permit a slipping of the clutch under abnormal values of torque, such as for instance under a backfire of the engine. The amount of slipping is then very small - say a few degrees - but is sufficient to effectively protect the starter, pinion and flywheel gear ring from breakage under undue strains. The wear of the friction clutch faces is negligible and need not be taken into account. Regarding the possibility of breaking or damaging the teeth due to butting, this is practically eliminated through the operation explained above. When the pinion meets a flywheel tooth, it is never applied against it with a greater strength than the compression of the spring 7, which is proportionned with this point in view. I may add that the danger of breaking the flywheel teeth is so small with the Bijur drive that a number of users of our device are cutting the flywheel teeth directly in the cast iron flywheel, and do not use a separate steel gear ring. In order that | ||