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).
'Phantom Braking' issues caused by overly efficient front brakes and weak springs.
| Identifier | ExFiles\Box 66\5\ scan0109 | |
| Date | 1st March 1927 | |
| X6470 To BY. {R.W. Bailey - Chief Engineer} from Hs {Lord Ernest Hives - Chair} /Rm. {William Robotham - Chief Engineer} c. to MX. {John H Maddocks - Chief Proving Officer} c. to Hm. {Capt. W. Hallam - Head Repairs} c. to EP. {G. Eric Platford - Chief Quality Engineer} HS {Lord Ernest Hives - Chair} /Rm {William Robotham - Chief Engineer} 2/LG4. 3. 27. PHANTOM BRAKING. Trouble has been experienced on two cars in the Test Dept. fitted with the new type axle due to the cross steering tube fouling the undershield when the brakes were applied violently. We have carried out careful comparative tests and are convinced that this trouble is due to too efficient front brakes. If we get very efficient front brakes on the old type axle we can produce the same phenomenon. Weak springs accentuate the trouble. We can definitely say that if the cross steering tube fouls the undershield, the front brakes are too efficient and quite apart from damage to this portion of the car, the car will not be safe to drive in the hands of the average customer as the steering will take charge. We note that the trouble has only occurred on 2 out of 52 of the C2. series on test, and that the brakes on these cars have been dealt with particularly severely. This is exemplified by the fact that the alum. bracket round the rear of the front springs has been broken, shewing that the spring must have been twisted through an abnormally large angle. We consider that the best way to deal with the trouble is to make certain that the servos in the exceptional cases give a standard efficiency, and that the front springs of the car are not on the light side and that the leading toes of the brake shoes are well chamfered off as per sketch. The 4" levers on the front equalising shaft should assist in overcoming the trouble. Hs {Lord Ernest Hives - Chair} /Rm. {William Robotham - Chief Engineer} Sketch attc. to BY's copy. | ||