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).
Preloading specifications for Marles Type Steering on Phantom III & 25 HP models.
| Identifier | ExFiles\Box 95\1\ scan0276 | |
| Date | 7th August 1936 | |
| To By.{R.W. Bailey - Chief Engineer} c. to Wcr. c. to E.{Mr Elliott - Chief Engineer} c. to Ds. c. to EV.{Ivan Evernden - coachwork} c. to Hx. c. to BHC. X 35D Marles Type Steering on Ph.III & 25 HP. We give herewith particulars of the preloading which we recommend for the above steering gears on production. These loads are obtained without any alteration to design, but merely by the tightness of assembly, and refer only to the steering gear itself, so that the figures do not include ball and friction, etc. When the gear is finally assembled, a load of 1 1/4 to 1 1/2 lbs. should be required at the rim of the steering wheel to move it steadily through the central position. This should be obtained as follows:- (1) With the steering cam only assembled in the gear, the load at the wheel rim should be 1 to 1 1/4 lbs. (2) The adjustment of the roller follower on the rockershaft is not important so far as its effect on the load at the wheel rim is concerned, but it should be such that slack does not develop as the gear becomes run in. The adjustment should be such that the roller can just be turned by pressure of the thumb on the outside of the roller. (3) The adjustment of the rockershaft should be such that, with both the cam and rockershaft assembled, the load in the central position is greater than with the cam alone by between 1/4 and 1/2 lb. at the wheel rim. It is very important that this increase of load due to the rockershaft is obtained by pushing the whole rockershaft into engagement with the cam and not by compressing the two conical roller bearings on the rockershaft. The latter method would almost certainly lead to opening of the joint between the two halves of the box. With the first method the increase of load is in the form of a tight spot in the centre of the travel, and does not occur on the locks where there is backlash between the cam and roller. | ||