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).
Unsatisfactory performance of self-lubricated Grapholly bearings in a Phantom II starter motor.
| Identifier | ExFiles\Box 61b\3\ scan0246 | |
| Date | 23th June 1931 | |
| X6079 By.{R.W. Bailey - Chief Engineer} from Hs{Lord Ernest Hives - Chair}/HEW. c. By/RD. c. RHC.{R. H. Coverley - Production Engineer} Hs{Lord Ernest Hives - Chair}/HEW3/AD23.6.31. GRAPHOLLY BEARINGS ON PHANTOM II SEQUENCE STARTER MOTOR. As explained verbally to Mr. Bavis, we have found these self lubricated bearings in their present condition to be unsatisfactory. Firstly, the coefficient of friction appears to be high and this prevents the satisfactory longitudinal operation of the armature on the teazer winding. This sliding motion, as you know, is very critical and is influenced considerably by bearing friction. There is also a suspicion that the coefficient of expansion of Graphite as compared with bronze and steel is considerably variant as the friction appeared worse when the motor was hot, after our load test. We shall probably have to work with a bigger clearance on the armature shaft at the pinion end bearing. Any extra clearance in the comm. end bearing is strongly deprecated as it has been found that unless this bearing clearance is kept at a minimum, the armature is pulled unsymmetrically in its longitudinal motion causing increased frictional effects. Secondly, the floating bush at the pinion end of the motor should also be treated on the outside diameter as well as the inside with the Graphite compound as this bush rotates and partially seizes in its present state owing to there being no lubrication. We are therefore proposing not to fit these bearings on the starter motor on 25-EX for the 10,000 mile test but will carry out further tests on the bench until satisfactory results are obtained. We require for further experiment, pinion end bearings having more clearance to the armature shaft and with a graphite lubricating surface on the outside dia. as well as the inside. The inside dia. of the steel housing could also be arranged without oil grooves. | ||