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).
Design of hydraulic front brakes for the Silver Wraith model.
| Identifier | ExFiles\Box 109\1\ scan0028 | |
| Date | 22th July 1938 | |
| 8686 To Ry. from Rm{William Robotham - Chief Engineer}/AFM.{Anthony F. Martindale} C. Da.{Bernard Day - Chassis Design} C. Hdy.{William Hardy} C. Ly. Rm{William Robotham - Chief Engineer}/AFM.{Anthony F. Martindale}5/MH.{M. Huckerby}22.7.38. SILVER WRAITH - FRONT BRAKES. As the B.III type suspension is to be modified for this car, to increase ground clearance, the B.III brake mechanism cannot be used. The only satisfactory front brake linkage which is universally applicable is the hydraulic linkage and we think we ought to design Silver Wraith with hydraulic front brakes. As the first car is to be produced very soon it seems necessary to play for safety and therefore, the brake unit to use is the Huck' brake which is of proved reliability on millions of cars in America. Again, as we have not at the time of writing demonstrated that this brake can be direct operated by the pedal we shall have to retain the B.III type servo linkage and make the rod to the front brakes actuate a master cylinder. The brake unit SCD.733 is quite satisfactory and can be copied as regards link centres, etc; but the largest possible hydraulic cylinder should be used inside our standard drum, and our standard shoe section should be used. The ends of the shoes will have to be altered. The leverage from pedal to hydraulic cylinder including the servo torque multiplication should be 40:1 but some provision should be made for alterations to this leverage after the car has been tried on the road. The lever operating the master cylinder is the one to alter. The master cylinder has only to feed two cylinders instead of the usual four so it can be quite small. The 1" dia. barrel type master cylinder shown on Sheet 2 of Lockheed's catalogue is the one to use. This needs a separate tank. Silver Wraith is to have hydraulic jacks so a common divided tank to feed both systems can be used. The tank should be 6 pints capacity divided into two portions of 1 pint and 5 pints by a diaphragm directly under the filler as shown on sheet 4 of Lockheed's catalogue. We think a simple standard filter should be incorporated in the feed line to the jacks from the 5 pint partition so as to keep the reservoir fairly clean. The master cylinder will have to be mounted on the frame to keep the gearbox in equilibrium. | ||