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).
Braking performance, specifically rear wheel locking, servo efficiency, and proposed brake mechanism upgrades for a Bentley vehicle.
| Identifier | ExFiles\Box 84\2\ scan0139 | |
| Date | 12th April 1934 | |
| - 3 - E.1/HP.12.4.34. (3) Locking of rear wheels stopping servo. ------------------------------------- The effect of locking the rear wheels first does ensure the driver maintaining steerage control which is often very valuable. If the front wheels are locked the car will proceed forward in a direct line beyond control. The former is the lesser of two evils. We do not agree that the front brakes release when the back wheels lock. There is probably some slight decrease in braking effect but we should say it is due to the difference in friction between the rear wheel skidding and just not skidding. With regard to the comment that it is quite easy to lock the back wheels on a car as light as the Bentley, we think the real answer to this is more consistent maintenance of the existing braking proportions front to rear. We do not think that the rear wheels are easily locked if the servo and the wheel brake linings are working with their optimum coefficient of friction. In the present layout if the servo linings decrease in efficiency the proportion of rear braking becomes greater in addition to the fact that more pedal pressure is required. Actually we anticipate some improvement with the direct pedal application on both front and rear brakes instead of on the rear only as by this means any loss of servo efficiency is equally apportioned between the front and rear brakes and the total braking proportions front to rear will be unaltered. The next 10,000 miles Bentley car has the following features specified affecting the brake mechanism:- 14" front drums. 14" rear drums. Spring plate servo. Needle bearings in bridge piece. Direct application to all four wheels.✓ Spherical bearing equalising shafts.✓ Stiffened shafts in front axle. Variable road wheel damping. There is also the question of an improved friction material for the brake shoes if it is found that the latest material put up by the Ferodo Co. shows up better on test than what we are using. E.{Mr Elliott - Chief Engineer} | ||