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).
Road test report on a reduced diameter Phantom III steering rocker shaft.
| Identifier | ExFiles\Box 95\1\ scan0535 | |
| Date | 15th August 1939 | |
| PHANTOM III STEERING ROCKER SHAFT. We have held up Depot Sheet No. BY.15, which instructs the reduced diameter rocking shaft retrospectively on all Phantom III cars, in order to make road tests on a car with one of these shafts fitted to see whether it had any adverse effects on joggles or low speed wobbles, and to see whether we could twist the shaft by ordinary curb or bank bumping. The shaft tested was a standard shaft reduced to 1.000 diameter on a length of 2.750 between the inner and outer bearings, thus using the same box and bearings. A similar shaft had previously been twisted off in the material test to compare it with the original shaft. The shaft twisted a total of 300° before fracture, as compared with only 15° on the standard shaft, whereas the ball pin load was almost the same i.e. 1¾ tons. On the road, it was impossible to tell any difference, from a handling point of view, on a car with which we were very familiar and on which we had previously done a good deal of running in connection with other work. Low speed wobbles could not be induced even on the worst road surfaces, whilst the car was perfectly normal for joggles at speed. Actually the increased torsional flexibility should be an advantage from the point of view of joggles, and the only question was whether this would enable some of the flexibility to be taken out of the rear end of the side steering tube. It was hard to appreciate any difference, and as the stiffness of the shaft is still enormously high as compared with the rating of the springs in the side steering tube, we think the latter could well be left alone. Attempts were made to twist the shaft by bumping into the bank on the skid pan and against a number of road curbs, any effect being checked by a pointer on the scuttle rail registering against marks placed on the steering wheel at either lock and in the straight ahead position. The wheel being geared up 15 to 1 as compared with the pendulum lever would immediately show any twist on the rocking shaft. These attempts were carried long past the point of accidental impact of the sort which a driver would overlook or forget in the ordinary course of driving (as we had been told has occurred in the past when rocking shafts have been twisted without anyone being aware of accidental damage), but as we did not want to wreck the car, we stopped short of inflicting obvious damage to the remainder of the front suspension. We were quite unable to produce any sign of permanent distortion. These tests have shown definitely that :- | ||