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).
Engine starting issues, starter motors, and post-war 3-speed gearbox design.
| Identifier | Morton\M22\ img271 | |
| Date | 3rd January 1921 guessed | |
| C for '3 & 4 Speed G/Box' War (3) (12) It should be clearly understood that our engine is a large engine and having very close fitting pistons (so that it shall run silently without piston knocks) and cannot be compared with a small engine with more or less loose fitting pistons. It seems therefore almost impossible to expect to avoid starting troubles unless the engine is housed and protected from excessive cold or refilled with hot water. (13) In England there has been many of our early cars were fitted with direct gear starter motors and these have not been a success unless the above mentioned precautions are taken, and we are sure that the comparisons referred to of the fitting by the service station is not a true comparison and will probably vary much in both temperature and condition of battery. (14) After the war we designed for our present chassis a 3 speed gearbox which was much simpler to make, had central levers for left hand steering, and permitted the more standard drive from the motor to the flywheel; this is now 2 years ago. The parts were made and fitted to a car which is at Derby 5EX, and only requires a small amount of experimental work to finish it. The motor also had reducing gear, and a foot operated sliding pinion was adopted, but the scheme was held up owing to the large stock of present parts, and prejudice against a 3 speed box. (15) The reason for the motor not turning the engine in cold weather is entirely caused by the fall of potential of the battery due to the low temperature and the large current asked for. If an attempt is made to turn the engine too fast (which would be the case with a direct Bendix drive) then it would not turn at all as the current even on short circuit will be insufficient to give the required torque. In conclusion, the following recommendations should be followed:- | ||