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).
Technical memorandum discussing faults and potential improvements for the Bentley III braking system.
| Identifier | ExFiles\Box 98\3\ scan0018 | |
| Date | 26th March 1938 | |
| 40b 1 By.{R.W. Bailey - Chief Engineer} from Rm{William Robotham - Chief Engineer}/AFM.{Anthony F. Martindale} c. Ds. c. Ds/Hdy.{William Hardy} c. Mx.{John H Maddocks - Chief Proving Officer} BENTLEY III. BRAKES. In its present form the hand brake has a serious fault. On bringing the car to rest, either with the hand brake alone or with the foot brake assisted by the hand brake at the last moment, the hand brake moves nearly 2" after the car has stopped. This means that the hand brake would tighten or loosen itself (according to the direction of motion of the car) by an amount equivalent to 2" of stroke if the ratchet were allowed to engage. This is due to the effect of rear spring movement and axle twist. These two motions tend to counterbalance each other in the forward direction, but are additive in reverse. We provided Hdy{William Hardy}/HB.{C. E. Harcombe} with diagrams giving the rear axle motion and he decided that raising the rear brake rope 1" on the equalizer would be a 40% advantage. We have rigged up this scheme and tested it. We find that a considerable improvement is effected, especially in forward motion. The car is now much the same as our other cars. The faults remaining due to geometry errors are juddering of the rear axle as the car comes to rest (foot or hand-braking) and quivering of the hand brake lever on light hand brake applications. The juddering of the rear axle, due to alternate slipping and gripping of the rear tyres is common to all our cars and is very disconcerting when it occurs as it means a loss of control. Few other makes of cars suffer from it as hydraulic or Bowden wire operated systems cannot act in this way. We have a scheme for mounting the rear 'equalizer' on the end of a tube which would eliminate the trouble on B.III, and put us on equal footing with American practice. By allowing the tube sideways flexibility, it acts as an equalizer and the present equalizer pivot, and double joints or spheres in the transverse rods, can be deleted. Both these features have given trouble on G.B.IV. in France. We have sunk no dies for the rear equalizer forgings. We recommend that details shall show the brake rope raised by 1" for the time being, and that we shall rig up and test our scheme of the compression tube, and get cost figures for it. | ||