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).
Comparing Marles and Worm and Nut steering gears, including weights and production issues for P.III, Bentley and Wraith models.
| Identifier | ExFiles\Box 153\2\ scan0234 | |
| Date | 1st February 1937 | |
| -2- type, and will be liable either to sticking when hot, or heaviness when cold. If the P.III had a worm and nut gear, and the parking effort were to be kept at the present figure, we estimate that the turns from lock to lock would have to be increased from 3½ to 4½. The steering of Bentley III is bound to require more effort than Bentley II, owing to larger tyres and greater weight on the front wheels resulting from forward engine mounting, and, as it is particularly desirable to have as high a ratio as possible on a car of this type, we think the high efficiency of the Marles gear would be particularly valuable. We do not consider that there is any appreciable difference between the two types of gear so far as transmission of joggle is concerned. In any case, we do not think that joggles will be a trouble to us in future, as with a suitably designed front suspension they are almost non-existant. (2) Weight. We give below a table of steering gear weights. These include steering wheel, pendulum lever, ball pin, control levers, quadrant and tubes. P.III Marles gear 25/30 48 lbs Bentley II Worm and Nut 49 " Wraith-Marles gear (as designed) 41½ " " " gear (as modified for use on Continental P.III) 37½ " From the above the Marles gear is lighter than the worm and nut, and further reductions in weight will be possible as the number of control tubes is reduced. (3) Ease of Production. We have had a lot of trouble with the production of our Marles gears until recently, due entirely to unjustifiable faults in the parts supplied to us by the Adamant Engineering Co. There is no doubt that one half of this trouble will be eliminated by obtaining the Roller Followers from a ball bearing manufacturer as we are now doing. The remaining source of trouble, namely the cam, has not given trouble since the Adamant Co. improved their methods of production. | ||