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).
Experiments on Bakelite self-lubricating bearings for starter motors.
| Identifier | ExFiles\Box 61\1\ scan0196 | |
| Date | 15th January 1932 | |
| To R.{Sir Henry Royce} from Hs{Lord Ernest Hives - Chair}/Wst. C. Sg.{Arthur F. Sidgreaves - MD} WOT. C. E.{Mr Elliott - Chief Engineer} Da.{Bernard Day - Chassis Design} Ev.{Ivan Evernden - coachwork} X6011 Hs{Lord Ernest Hives - Chair}/Wst.6/AM15.1.32. X6011 X6079 BAKELITE SELF LUBRICATING BEARINGS. We have been experimenting for some time on the sequence starter motor with some kind of self lubricating bearing. We have tried various types of brass bearings having graphite let in, with very little success owing to the fact that the bearings become very sticky and the coefficient of friction is high in the dry condition. It has occurred to us (Mr. Brock and ourselves) that a successful self-lubricating bearing could be made by moulding a bush out of powder made by mixing powdered graphite with the ordinary synthetic resin powder used for the bakelite mouldings. The first bush so moulded was made to replace the driving end bush of a P.2. sequence starter motor as the oil in this bush has been known to congeal in very cold weather making the armature longitudinal motion very sluggish. We find the ordinary wood flour filler as used in ordinary mouldings to be unsatisfactory owing to its poor rate of heat conductivity. When tested under load the armature seized up very quickly but after cooling, functioned again normally showing it to be purely a heat effect. The Bakelite Co. were approached and they have supplied us with the new kind of powder with a better heat conductivity using granulated asbestos as a filler instead of wood flour. The percentage of graphite works out at roughly 25%. A bush moulded with this powder has been successfully tested on our starter motor bench rig and has done to date about 2,000 starts satisfactorily. The motor will work for 10 mins. at the rate of approximately 12 starts a minute without any sign of distress due to undue heating of the bearing. We hope also to modify the commutator end bearing similarly and thus make the motor entirely self-lubricating which will enable us also to make it water-proof. We are continuing experiments along this line and there appears to us to be a big field ahead for this type of bush for such things as engine mountings and all the exposed brake rod bushes underneath the car which normally are supplied with the Bijur system. Hs{Lord Ernest Hives - Chair}/Wst. | ||