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).
Investigation into starter motor slipping due to worn teeth, poor cork discs, and excess oil, detailing solutions.
| Identifier | ExFiles\Box 40\5\ Scan181 | |
| Date | 24th June 1927 guessed | |
| contd :- -4- have become very much worn, the pinion load works back until only .250" of the teeth are in operation. We presume that in time on an owners' car the teeth of the flywheel will wear to the same degree and probably cause failure of the starter motor. During our tests we found that by increasing the spring D.51133 to 10 lbs. and reducing the spring D.51144 to 8+ lbs. we obtained an all-round improvement of the starter unit. In investigating the slipping under load condition the chief and primary cause is as stated previously - the poor surface of the cork discs. Under present conditions and in the event of not being able to obtain better cork, we find that by increasing the initial load of the spring D.51376 from 31.5 lbs. to 50 lbs. we obviate the slipping. Our explanation of this is that the slipping occurs before the pinion is fully engaged, when the load applied to the clutch discs is little more than 38.5 lbs. which is insufficient for the load imposed upon the starter in this position. By increasing the strength of the spring to 50 lbs. we prevent this slipping, and the rating of the spring is not too high to prevent the nut winding up to its full movement, thereby getting the max. load imposed upon the clutch discs when pinion is fully engaged. In further investigation, we cured the slipping caused by excess oil getting on the clutch, by having 6 grooves grouned on the face of the operating bush D.51134 which wipes the excess oil off and is thrown clear by the centrifugal force when the motor revolves. This is now on production and giving good results. With this scheme the unit is well lubricated with Prices Motorine C. oil which facilitates the working contd:- | ||