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).
Technical discussion on reversible and semi-reversible steering systems and their efficiency.
| Identifier | ExFiles\Box 178\1\ img104 | |
| Date | 13th July 1926 guessed | |
| - 5 - reversibility of this type of steering depends entirely on the helix angle of the teeth. (1) Reversible. The simplest example of a reversible steering is that of the bevel and crown wheel type. Reversible steerings can be made about 95% efficient. Their main disadvantage is that obviously they transmit every road shock to the steering wheel. In addition they usually make the car very difficult to control at high speeds. If the only desirable attribute of a steering were lightness, however, they would be ideal. (2) Semi-reversible. These are a compromise and are the type most widely used. They are usually of the worm and segment or screw and nut type. They are just sufficiently reversible to allow the steering to self-centre but at the same time not sufficiently so to transmit too many road shocks to the driver. The very attribute of irreversibility means that the steering reduction gear cannot be highly efficient. The apparent co-efficient of friction between the working teeth dictates the lead angle at which the steering becomes irreversible. This means that a badly made screw and nut might be completely irreversible with a helix angle of 10°, while another carefully manufactured would still be semi-reversible with a helix angle of 8°. Graph II, which shews the efficiency of a screw and nut for various helix angles, demonstrates why it is impossible to exceed an over-all efficiency of about 65% in the reduction gear in the steering sense and yet obtain immunity from road shocks. With a co-efficient of friction of .10, a screw and contd. | ||