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).
Data table comparing different types of 25 HP steering gear.
| Identifier | ExFiles\Box 28\3\ Scan088 | |
| Date | 7th January 1935 | |
| 44094 Hs{Lord Ernest Hives - Chair}/FJH.{Fred J. Hardy - Chief Dev. Engineer}12/KW.7.1.35. 25 HP. STEERING GEAR DATA. Type of Steering Gear. R.R. Marles 15/1 Marles 17.5/1 Marles 20.5/1 Standard .. Pendulum Lever Length - ins. 8.250 7.600 10.15 9.50 10.15 9.50 10.15 9.50 Mid. Position Box Ratio 12.5/1 12.5/1 15/1 15/1 17.5/1 17.5/1 20.5/1 20.5/1 Lock to Lock Box Ratio 11.9/1 11.8/1 14.75/1 14.75/1 17.2/1 17.2/1 20/1 20/1 Turns of Wheels including comp. of S.S.Tubes Springs. 2.31 2.50 2.36 - 2.80 2.98 3.23 3.43 Turns of Wheel without comp. S.S.Tube Springs 2.15 2.31 2.20 2.34 2.58 2.77 2.98 3.20 Movement of Pend. Lever including comp. of Springs. 70.5° 77° 56° - 56° 59.5° 56° 59.5° Movement of Pend. Lever without comp.of Springs. 65° 70.5° 51.5° 55.5° 51.5° 55.5° 51.5° 55.5° Mid. Position Helix Angle. 8.45° 8.45° 11.78° 11.78° 9.97° 9.97° 8.62° 8.62° Mid. Position Ratio Stg.Wheel to Road Wheels. 12.1/1 13.15/1 11.8/1 12.63/1 13.8/1 14.7/1 16.2/1 17.3/1 | ||