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 comparison of Bijur and Bendix starter motor systems, discussing pinion gears, ratios, and voltage.
| Identifier | ExFiles\Box 40\5\ Scan104 | |
| Date | 19th December 1922 guessed | |
| Oyl-W-121922 -3- regularly use 10, 9 and even 8 teeth. The pinion on 102-CE had 9 teeth and the flywheel, 140, giving a ratio of 15 1/2 to 1, and the running noise was very slight. The motor on 102-CE had the same speed characteristics as the existing standard Bijur motor, and worked perfectly with the 15 1/2 reduction instead of the 25.6 of the standard transmission gear. The curves of this motor are shown in the attached print. The aim of the Bijur Company in letting a small pinion is to maintain a good reduction ratio on cars in which the flywheel diameter has been skimped for road clearance and cost. This is a very general tendency in American cars to reduce the size and cost of the bell housing connecting the flywheel to the gearbox. For best cold-weather starting, the Bijur Company recommends about 10 or 11 to 1 ratio and would prefer to use a 9 or 10 tooth pinion on the Goshawk, if the flywheel diameter could be increased the 1/2" to 5/8" which would be necessary. b - Slow speed motors As compared with most American makers, who have to get rapid acceleration to throw in the Bendix pinion against its stiff spring, the Bijur Company champions the slow speed motor. The Rolls-Royce Goshawk motor curve would suit them better than the Lucas or C A V, but they warn us that with 12 volts and with such a small motor as 4 1/2" diameter, the acceleration is liable to produce quite a shock in engagement. They prefer the 6 volt system for the reason of giving a slower acceleration when the switch is closed. Comments on Bijur system In common with the Bendix pinion, the Bijur pinion has the disadvantage of flicking out of gear, in case of a feeble start. If the foot is held on the starter button, the teeth will rub until the engine slows down enough to permit re-engagement, and the re-engagement is liable to cause a rather severe shock. The instinctive action, however, is to take the foot off the starter button as soon as the engine fires. It is necessary to | ||