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).
Modifications to a pinion unit to improve centralisation and engagement, and an investigation into cork clutch slipping issues.
| Identifier | WestWitteringFiles\Q\2April1927-June1927\ 205 | |
| Date | 1st May 1927 guessed | |
| contd :- -2- being released. To overcome these two faults, our aim was to centralise the unit upon being returned, and to reduce surface friction to a minimum. To obtain this feature and keep to the present design as near as possible, we have made the flat face of the rear stop into a broad 'V', and upon the face of the bronze stop in the pinion unit a raised 'V'. The effect of this arrangement brings the unit to a central position on the thread upon being flung back, and any tendency to cross-bind is corrected. It also prevents the climbing between the two stops, and tests carried out with this scheme it was found possible to use 6 volts with successful engagement as against 9 volts with the present design. Several cases have been found whereby the cork clutch had insufficient friction to convey the inertia of the mass of the unit, and would not run up the thread and so engage. The chief cause of this is the poor coefficient of friction of the cork. It does not appear to be the effect of too much oil, as the cork discs which failed were to all purposes in a moderately dry condition, similar to others which were O.K. In investigating this we found that the outer spring D.51133 was one of the minimum poundage allowed i.e. 6 lbs., and by fitting the maximum spring (i.e. 8 lbs.) it overcame the slipping and engaged without trouble. We find that this spring D.51133 is a controlling feature in the starter unit, as explained further on. We may point out here that we do not consider the quality of the cork discs up to standard requirements. contd :- | ||