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).
Characteristics of Marles steering gear and recommending specific settings for helix angle and box ratio.
| Identifier | ExFiles\Box 28\2\ Scan156 | |
| Date | 20th March 1933 | |
| -2- Hs{Lord Ernest Hives - Chair}/Rn.{Mr Robinson}1/MJ.20.3.33. The characteristics of the Marles steering gear box leverage are shewn in the attached print, therefore possibly if we could get a different characteristic in which the leverage did not fall off so much under load we might use 16 1/2/1 ratio without finding the steering heavy for parking. Summarizing the position for a R.R. Marles Weller type of steering we should recommend :- (1) Helix angle between 10 - 11o. (2) Over-all box ratio of between 16 1/2 - 17 1/2/1. This combination to be used with the (7.750") pendulum lever (now standard). We have reproduced the effect of your 13/1 box ratio on the R.R. Marles by substituting a 10.6" pendulum lever for the 7.750" one with which we have been running, and the steering is altogether too heavy. You can try it on 20-EX. Hs{Lord Ernest Hives - Chair}/Rn.{Mr Robinson} | ||