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 and potential causes of steering lever failures.
| Identifier | ExFiles\Box 153\4\ scan0156 | |
| Date | 1st June 1943 | |
| To: [redacted] c. Rm{William Robotham - Chief Engineer}/FJH.{Fred J. Hardy - Chief Dev. Engineer} Handwritten note: AH Chassis Handwritten note top right: 1300 Steering Lever Failures. Very many thanks for your memo Ev.{Ivan Evernden - coachwork}8/JH.27.5.43, the information conveyed is appreciated and will undoubtedly be helpful in arriving at a solution of the trouble. There are, of course, quite a number of factors in the problem and one can only hope to arrive at the correct soltuion by taking all the factors into account. It is clear that from the actual data supplied in the form of pictures of cracked and broken levers, that the load which causes the failure is not symmetrical, by which I mean that it does not cause failure at diagonally opposite points on the lever section, and although different cars are involved with different sections of levers, the type of failure persists, that is it is common to all types of the series produced just prior to the war. I of course agree that it is not a single load, but it is clear that it is a repetition of a rather high load which occurs at certain stated intervals, or under certain specified conditions. They are certainly not caused by twisting the road wheels when the car is standing as this would have to be done equally over the life of a car, that is to left or right, and would, therefore, cause failures on both sides of the lever. I had learnt prior to your memo that springs are interposed at the base of the Pendulum Lever in the coupling tube, I had one taken down in the garage to clear this point but these springs will not meet, as you rightly remark, such conditions as are satisfactory for :- (a) Straightforward driving. (b) Severe loads from any particular cause. (c) Specialised loads which are not in the nature of impact but a "follow through" blow. By this I mean a load which is applied steadily and increasingly over a period of time sufficient to react right through to the Pendulum Lever and continue to press the lever steadily instead of a blow which hits the lever and is swung back immediately. That the failure is due to overloads which occur fairly often but which are well below the load necessary to bend the lever is certain, this is clearly demonstrated by the fact that on some of the levers there are three or four cracks, all at varying distances from the centre of the boss of the lever. If it was a regular stress well within the possibilities of the lever, then the stress would be regularly a maximum at one particular section. The fact that three or four cracks occur indicates that the torsional load and the bending moment load did not match up with one another, one being higher than the other at intervals, just how this occurs I am not prepared to say at the moment. continued | ||