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).
Analysis of starter motor engagement issues, focusing on pinion gear grinding, weak spring D.51133, and friction problems with cork discs.
| Identifier | WestWitteringFiles\Q\2April1927-June1927\ 206 | |
| Date | 1st May 1927 guessed | |
| contd :- -3- In a good many which were examined, there were a number of hard wood-like spots which become polished up and reduce the co- efficient of friction. This is being taken up with the people who supply the cork discs. The trouble experienced with the false engage- ments or crashing, i.e. the pinion teeth rubbing on the edge of the flywheel teeth, and not engaging, is entirely due to the spring D.51133 being on the weak side. It will be seen by looking at the sketch, that when the pinion unit has climbed the thread as far as the flywheel teeth, when starter motor is in position, it leaves the pinion with a free movement of .250" and is con- trolled by the load imposed by the spring D.51133. If the spring is on the weak side, the momentum of the unit is such that the pinion fails to engage at the moment the teeth are opposite, thereby we get the grinding of the two sets of teeth together. Strengthening up the spring D.51133 overcomes this trouble and a satisfactory engagement of the pinion is obtained. If we go a little further into the question of Starter Unit, we find that the question of the strength of this spring D.51133 is further demonstrated. When the pinion is fully engaged the spring D.51133 having a load of 7 lbs. is opposed by the return spring D.51144 of 9½ lbs. therefore we have a force of 2½ lbs. which is trying to push the pinion out of engagement, and with a free unit does actually push the pinion back .250". With this condition and the flywheel teeth slightly taper due to wear, the tendency of the pinion under load is to disengage, and on the Works starter rig where the flywheel teeth contd :- | ||