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).
Gearbox oil ingress, servo drive improvements, and high brake lining wear.
| Identifier | ExFiles\Box 152\2\ scan0270 | |
| Date | 4th November 1940 | |
| Rm{William Robotham - Chief Engineer}/MHR.{M. H. Rigby}S/ET.4.11.40. - 2 - With the latest type of gearbox, one shield is fitted under the oil seal housing, and the other of slightly larger diameter has been sweated on to the spring plate, and also spun into it. The final method of making this spring plate has not yet been decided, as the spinning is not easy, but one suggestion is to spin the plate in two pieces and dip-solder. We shall find out if the plate can be made by pressing. This system will be fitted to 8.B.V and 30.G.VII gearboxes. All the other cars have obsolete gearboxes but those using the rationalised braking system can be fitted with large shields on the gearbox, in front of the servo. One of these is fitted to 3.B.50, but has not yet been tested through the Boyleston water-splash. (c) Oil ingress can occur in three ways:- It can enter at the gearbox end of the servo by running down the side of the gearbox, which can be checked by the special water shield on the latest gearboxes. It can also enter from inside the box, but this should not take place with the latest type oil sealing, as on 8.B.V and 30.G.VII. 3.B.50 has the best arrangement of the old type gearboxes consisting of two special washers between gearbox and spring plate. The third place of entry of the oil is round the outside of the spring plate, and can be permanently cured by Neoprene tape used as for sealing aircraft fuel tanks at the rivets, but Neoprene latex is now unobtainable. A substitute rubber solution is being used on the servo, but is not expected to stay on as well as the Neoprene. It is dirty to put on, does not set so quickly, and causes servo squeak when it gets on the lining. 3.B.50 has a rubber ring fitted with a Jubilee clip, but a moulding should be tried. (d) The servo drive as fitted to the latest gearboxes permits of easier fitting than did the old ones, and the limits are being rearranged to give a still further improvement. We cannot help feeling that three pins are nicer than two, although the three pins, as at present, could be smaller if desired. (e) With the present size of master cylinders and wheel cylinders, it is necessary to have 30° cams to give sufficient front braking, the only other method being to decrease the rear brakes which necessitates a greater pedal effort. 2. High Rate of Lining Wear. The high rate of lining wear on the rear brakes is greatly aggravated by the poor drum cooling, although this may not be the sole trouble. | ||