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).
Mechanical efficiency tests on a Marles Type L.7 Steering Gear on Chassis 21-G-IV.
| Identifier | ExFiles\Box 95\1\ scan0143 | |
| Date | 15th November 1934 | |
| Mechanical Efficiency of Marles Type L.7 Steering Gear on Chassis 21-G-IV. We have recently carried out efficiency tests on the Marles Type L.7 Steering Gear fitted to chassis 21-G-IV. As originally tried, this gear had a cam giving a ratio of angular movement in the box of 15:1, and, with the 10.15" pendulum lever used, the ratio of steering wheel to road wheel movement was the same as the standard 20/25 HP. The static mechanical efficiency at mid position of travel was measured before the gear was fitted to the chassis and the maximum in the forward direction was about 58%. This is considerably lower than the efficiency of our own gear and as a result the steering of the car was very heavy, although it improved slightly as it became "run in". The gear was returned to the Makers and fitted with a cam of less helix angle giving a ratio in the box of 17:1. The efficiency of the gear was measured both before "running in" and after it had been "run in" for 7 hours on a rig. The running on the rig consisted of oscillating the pendulum lever end with a stroke of 3" at 280 cycles/min., the steering wheel being removed. The mechanical efficiency of the gear in the forward direction improved from 61% to 65.5% after being "run in", while the reverse efficiency was approximately unchanged. The attached Hm.{Capt. W. Hallam - Head Repairs}1605 shows the figures obtained after being run in and also gives a comparison between two kinds of lubricating oil. The oil recommended by the makers of the gear considerably reduces the reverse efficiency and so should give better results on the car. The improved efficiency of 65.5% mentioned above is not necessarily the ultimate maximum, but is merely the result of 7 hours under the rig conditions. The makers claim efficiencies of 72 - 75% when the gear is thoroughly run in. | ||