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).
Brake proportioning, swerving effects during braking, and proposed cures.
| Identifier | ExFiles\Box 154\3\ scan0007 | |
| Date | 8th December 1926 | |
| -2- Decreased front braking. On 12-MC, you will recall that we altered the proportion of front braking at one time, by changing a lever, so as to give 33% front and 67% rear braking; the proportion which Hives recommends. There was definite increased tendency to skid the rear wheels on ice, emphasized of course by the powerful servo action. To go to the extreme we fitted a non-front brake front axle and still used the servo on the rear only. The car was then unsafe on anything but a dry road. We reached the conclusion that a slightly less proportion of front-braking plus considerably less servo action was a desirable compromise and reached the proportion above, namely 38% front and 62% rear, and 80% of total braking effort. Swerving effect. We have tried to account for this by the ball on the side steering lever moving back relative to the pendulum lever when the brake is applied vigorously, and have suggested this to Hs.{Lord Ernest Hives - Chair} and asked him whether their cars swerve to the right, as ours do to the left. Taking Hs.{Lord Ernest Hives - Chair} figure of 3° total change in "lean" of the front axle when brakes are applied hard, we can only account for .040" foreshortening" of the side steering balls, but it may be much more because there is some distortion of the frame when the brakes are applied. .040 shortening of the centres would account for 140 lbs. on the side steering lever ball with our springs in the side steering tube, so that we can account for the occurrence of the swerve if not for the amount. Proposed cure. The ball is now .550 below the centre of the main leaf. We propose to bend the lever 2" upwards at the end so as to bring the ball 1-1/2" above the main leaf. This may be too much and cause the car to swerve to right, but at least I think it will produce a distinct effect. Oy. MO/E | ||