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).
Analysis report on the failure of a Phantom III rear brake equalizer pivot pin.
| Identifier | ExFiles\Box 92\4\ scan0390 | |
| Date | 4th April 1938 | |
| To By.{R.W. Bailey - Chief Engineer} from Rm{William Robotham - Chief Engineer}/AFM.{Anthony F. Martindale} c. Hs.{Lord Ernest Hives - Chair} WHC. Mx.{John H Maddocks - Chief Proving Officer} GEB. c. Ed.{J. L. Edwards} N. K.{Mr Kilner} Sr. RM{William Robotham - Chief Engineer}/AFM.{Anthony F. Martindale}2/AP.4.4.38 FAILURE OF PHANTOM III. REAR BRAKE EQUALIZER. A broken pivot pin 0.84094 out of the rear equalizer was sent to us from America and the cause of failure asked. We say it was due to the car being jacked up on the equalizer, for three reasons;- (1) Because of the various marks on the broken piece. (2) Because we can reproduce the failure exactly by jacking the car up on the equalizer. (3) Because the normal loads are far too low to cause failure of sound metal. If the car was jacked up the pivot pin would be in double shear due to loads as in sketch (1) attached. This form of loading would produce marks on the specimen as in Fig.(2), namely;- (a) Heavy indents due to the ball bearings at the upper side of the race. (b) Heavy indents due to needle rollers, shape as in Fig. (3) (c) A crack at the point of bending on the upper side of the pin. (d) A clean break at the bottom of the pin. (e) A tear at the upper side of the failure. All these marks may be seen on the specimen from America, also the one broken in the Garage here. The only normal load in the pin is that due to the weight of the equalizer. This might reach 60 lbs. due to an acceleration of 20g feet/sec.2. In practice this pin is almost strong enough to carry the weight of the car, which indicates a very high safety factor. The laboratory have agreed that the failure was not due to fatigue, but due to a high load. RM{William Robotham - Chief Engineer}/AFM.{Anthony F. Martindale} | ||