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).
Proposing improvements to the Bentley chassis brake system, including larger 14' drums.
| Identifier | ExFiles\Box 84\2\ scan0129 | |
| Date | 22th March 1934 | |
| To Sg.{Arthur F. Sidgreaves - MD} from Hs{Lord Ernest Hives - Chair}/Gry.{Shadwell Grylls} c. to Sor. c. to Rt. c. to Hiv. c. to Day. c. to Em. X206 BRAKES. It is proposed to fit larger brake drums on the Bentley chassis, namely 14" dia. instead of the present 12". We think that when we carry out this alteration we should incorporate other improvements also. The improvements required are of two kinds; those that the customer will appreciate as being an advance on the present car, and those that we appreciate or help us to make a car without the defects that should not exist. Front brake thumps are obviously of the latter category. Larger drums will increase the periods between adjustments. Fading of the brakes when hot will also be less as the drums will absorb the same heat for a less temperature rise and cool more quickly. Maintaining the same effort for a given deceleration allows of a smaller overall ratio. It will be longer therefore before the pedal reaches the boards or the servo the end of its travel. In the present layout the latter happens considerably before the former due to the large amount of sponge in the front brake system. It is a very unpleasant sensation pushing harder on the brake pedal with apparently no result. We already know of the sponge in the axle torsion shafts but have recently discovered that when braking the front axle moves back with respect to the frame, all such movement having of course to be taken up at the servo. We measured this by wiring off the rear brakes, applying the front brakes and then trying to drive the car in 1st gear with a slipping clutch. .090" movement was measured under this condition. More would exist under road conditions of violent braking. | ||