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).
Letter from Adamant Engineering discussing steering gear ratios and helix angles.
| Identifier | ExFiles\Box 28\3\ Scan050 | |
| Date | 14th November 1934 | |
| Messrs. Rolls-Royce Ltd. Contd 2. 14.11.34. 57 say that the lowest gear ratio that it is possible to fit in this steering, which limit is fixed by the strength of material between the tracks on the cam, is just under 4 turns of the wheel for 65° movement, which is equal to a gear ratio of just over 22 to 1. Turning to the question of helix angles, as stated during your recent visit, this gear when fitted with 2¾ turn cam gives a helix angle in the mid position of 11.78°. When fitted with 3¼ this helix angle drops to 9.97°. Reducing the ratio further gives the following helix angles: 3½ turns of the wheel 9.25° helix angle. 3¾ turns of the wheel 8.62° helix angle. 4 turns of the wheel 8.09° helix angle. From our experience of this type of gear, so far as helix angle is concerned, we would not hesitate to recommend a gear with a helix angle as low as 8.09°, as we are quite sure it would be entirely satisfactory, so that it is possible to cut a cam to give any ratio down to 4 turns, which is 22 to 1, although, as already stated, such non-standard gear ratios would have to be specially set-up for each batch of cams, and furthermore, there would have to be a wheel or two make to obtain the ratios. We would like to add that as in other types of gearing the reduction of the gear ratio will also give a reduction in the efficiency, although the efficiency will not go down with the Marles principle as quickly as it does with the ordinary type of gear, such as worm and nut, or worm and wheel.. We trust that the above information will be found to be interesting and of use to you, but we are, as we believe you know, at all times entirely at your service for any further data. Again thanking you, and assuring you of our best attention at all times, We are, Yours faithfully, for ADAMANT ENGINEERING COMPANY LIMITED. A.H.Franck. Director. | ||