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).
Modifications to steering boxes based on information from Cadillac and Saginaw.
| Identifier | ExFiles\Box 173\4\ img140 | |
| Date | 25th November 1935 | |
| COPY (Memo. from Da.{Bernard Day - Chassis Design}) DETROIT. 25.11.35. To E.{Mr Elliott - Chief Engineer} from DA.{Bernard Day - Chassis Design} Steering. I have now discussed steering boxes with the engineer (Mr.Kull) from Saginaw, and as a result have to modify in one or two respects the information given me by Cadillacs. The method of cutting the worm with a sort of semi-parallel portion in the centre, which I described the other day, they say they abandoned as not being a success. They now cut the worm form with a single curve, the increased radius of which compared with the radius of the rocker shaft is obtained by using a cutter with a greater number of teeth than the steering ratio - for a ratio of 18.75 to 1 which is a standard with them, they use 22 teeth in the cutter. (I should say they use a Fellowes machine such as was described in 'Machinery' a few weeks ago). But as the ratio gets less, a relatively fewer number of teeth can be used, and they say that for our ratio of 15.3 to 1 they would use sixteen teeth in the cutter. One tight spot in the centre does extend over approximately 90º on either side of the wheel, but it has to be qualified as follows:- 15º either side, very tight springing the gear as it goes over - 45º either side, tight, the remainder - no slack. The slot in the rocker shaft is set at rather less than the angle of helix at the point of contact, so as to even out the difference in angle at the end of the stroke, and the cones of the worm bearings are cut from .002 eccentric with the worm itself. [Diagram Text] .002 (.004 Stroke) Centre of Bearing Cones Centre of Worm The eccentricity is related EXACTLY ½ THE KEY-way SO THAT ITS POSITION IS KNOWN | ||