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).
Steering roller failures in Bentley 'M' Series and Wraith models, detailing test results.
| Identifier | ExFiles\Box 153\1\ scan0236 | |
| Date | 3rd April 1939 | |
| By.{R.W. Bailey - Chief Engineer} from Rm{William Robotham - Chief Engineer}/FJH.{Fred J. Hardy - Chief Dev. Engineer} c. Hs.{Lord Ernest Hives - Chair} c. Da.{Bernard Day - Chassis Design} c. RHC.{R. H. Coverley - Production Engineer} c. Mx.{John H Maddocks - Chief Proving Officer} c. Ba/Hdy.{William Hardy} c. LA.{L. A. Archer} Rm{William Robotham - Chief Engineer}/FJH.{Fred J. Hardy - Chief Dev. Engineer}1/R.3.4.39. BENTLEY 'M' SERIES & WRAITH. STEERING ROLLER FAILURES. Up to date, two steering rollers FW.911, as fitted to both Wraith and 'M' Series Bentley, have failed in service. Both failures occurred on Bentley chassis - B-154-MR, and both rollers had been fitted to chassis which were delivered to Paris coachbuilders by rail and boat. A further roller has recently been found cracked on an unused chassis similarly delivered to Paris Coachbuilders. As a result of these failures LA.{L. A. Archer} made tests to find a way of reproducing the failures. It was found that by loading the car with sandbags to increase the weight on the front wheels, and reducing the front tyre pressures, some rollers could be broken by turning the steering from lock to lock with the car stationary. The maximum normal load on a steering gear always occurs under these conditions, and the above test was merely a way of making this load greater than normal. The maximum load on an 'M' Series Bentley steering, under standard conditions, is 35 lbs.ft. torque on the steering wheel. The loads required to break rollers on 40 chassis in the Test Dept. were measured with the following results:- 3 Failed at under 40 lbs.ft. 15 " between 40 and 50 lbs.ft. 3 " " 50 " 60 " " 1 " " 60 " 70 " " 18 were satisfactory at 70 lbs.ft., i.e. 100% overload. Three rollers which were known to be original samples supplied by Hoffmanns for experimental cars satisfactorily withstood 70 lbs.ft. A steering gear was rigged up in the Experimental Dept. for the purpose of testing the production stock of rollers. It was originally decided to test at 100% overload, and pass for temporary production use any which | ||