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).
Issues with the 20-HP starter motor drive pinion clearance and the recommended fix using packing washers.
| Identifier | ExFiles\Box 75\5\ scan0087 | |
| Date | 21th December 1925 | |
| To BJ. from Hm{Capt. W. Hallam - Head Repairs}/NRC.{N. R. Chandler} C. to BY.{R.W. Bailey - Chief Engineer} C. to Hs.{Lord Ernest Hives - Chair} Hm{Capt. W. Hallam - Head Repairs}/NRC{N. R. Chandler}7/EW21.12.25. 20-HP. STARTER MOTOR DRIVE. It has been found that if the pinion, when at rest in the disengaged position, is more than a certain distance from the teeth on the flywheel, it tends to rotate too much before it has moved endways sufficiently to engage, and this causes uncertain engagement or complete failure to engage, with the result that the teeth on the flywheel are severely damaged. We find that there is a considerable variation in the dimension on existing cars. We consider the dimension from the teeth of the pinion to the teeth on the flywheel, when fully disengaged, should be .200". We have had a case recently in which the pinion frequently failed to engage, although the Bijur Drive was free, and everything in apparently perfect working order. The clearance in this case exceeded .350". This is by no means an isolated case. On fitting packing washers between the motor and the crankcase, so as to reduce the distance between the teeth of the motor pinion and flywheel to approx .200" it was found that the starter engaged definitely and positively every time. In the case of the Bendix D.50907, used on chassis approximately 300 to 1200, it will be noticed that the sliding pinion may come to rest with the D.50899 just in contact with the stop D.50904, or, it may come to rest with the spring D.50898 compressed .150". When setting the wheel and pinion .175" apart, the pinion should be in the latter position, i.e. with the spring D.50904 compressed. We will shortly be able to supply aluminium packing washers to pack out the motor but meanwhile please cut washers out of sheet aluminium to suit. We would add that we believe a great many of the cars in existence will be found to have the pinion more than .200" from the gear ring. Hm{Capt. W. Hallam - Head Repairs}/NRC.{N. R. Chandler} WRE | ||