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).
Component failures and performance during a 50,000-mile test of a 3.5-litre Bentley.
| Identifier | ExFiles\Box 97\5\ scan0139 | |
| Date | 22th March 1939 | |
| Sg.{Arthur F. Sidgreaves - MD} from Rm.{William Robotham - Chief Engineer} Hs.{Lord Ernest Hives - Chair} c. By.{R.W. Bailey - Chief Engineer} c. Da.{Bernard Day - Chassis Design} c. Mx.{John H Maddocks - Chief Proving Officer} 400b. Rm{William Robotham - Chief Engineer}3/R.22.3.39. 50,000 MILES' TEST - B.V. The average life of a 3½-litre Bentley big-end bearing in customers hands is 50,000 miles. The same bearings lasted less than 15,000 miles on our Chateauroux tests. This indicates the severity of the handling which the car receives from our testers. Previously, 15,000 miles was a standard-isation run. We have got to be careful when we try and run 50,000 of these miles, to treat the failures which occur intelligently, otherwise to get the necessary dura-bility we shall build a car that is too expensive to buy and of no interest to drive. Actually, we consider that any part that does 25,000 miles successfully should have an odds on chance of giving satisfactory service in the hands of the public. If we take the 25,000 miles' run subse-quently to the intermediate examination, failures are confined to - (a) Frame rivets working loose. Total miles run by frame to this point 32,000. The two serious troubles that occurred at more than 25,000 miles and less than 30,000 miles were - (b) Rear road springs broken. (c) Exhaust valve head came off. Curiously enough, these parts are very similar to corresponding pieces that have been used on the Bentley for some years past. The gearbox, though not in its final form, has run 30,000 miles since the strip without failure, also the propeller shaft. The rear axle, which is an entirely new design, was in perfect condition at the intermediate strip, and completed 40,000 miles before the wheel bearings failed. The front suspension parts have a more or less unblemished record. | ||