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).
Major failures on the Wraith model after production and the inadequacy of endurance testing procedures.
| Identifier | ExFiles\Box 148\2\ scan0090 | |
| Date | 17th December 1938 | |
| 1260. Copy Ms. c. Rm.{William Robotham - Chief Engineer} c. RHG. BY.16/G.17.12.38. ENDURANCE TESTING OF NEW DESIGNS. Both Rm.{William Robotham - Chief Engineer} and myself are seriously disturbed by the failures which have occurred on Wraith after it had been passed off experimentally and the chassis had actually gone into serious production. The three major failures which we have experienced cover three separate units :- (a). The engine - a head failure occurred due to valve seats cracking. (b). Gear box. The first motion shaft failed. (c). Propeller Shaft. Universal joint failure. In each case no disabilities were experienced in any of these units during the development running or in the endurance running in France, and in fact very considerable total mileage had been covered apart from the fact that on each unit this was also true, for instance :- (a). Cylinder head failure. This was first discovered by Mx.{John H Maddocks - Chief Proving Officer} and individual heads had been run 15,000 miles without cracking. (b). Gearbox. The box in which the 1st. motion shaft failure occurred had run 33,500 miles and the total mileage on all the boxes tested was 165000 miles. (c). Propeller Shaft. This failure was not discovered on the Wraith, it was brought to light by the Bentley V.{VIENNA} test in France. Mx.{John H Maddocks - Chief Proving Officer} had pointed out that lubrication seemed doubtful, and a scheme to improve this had been arranged. From the foregoing it is now amply evident that the standard test of 15,000 miles in France is hopelessly inadequate, this we had recognised already where a departure from our previous experience occurred, as for instance the semi-floating axle and pressed steel wheels, but it was not similarly appreciated as being inadequate for new designs in line with our experience. | ||