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).
Comparison of spring deflections, periodicities, tyre pressures, and shock damper settings for the 20 HP and 40/50 HP models.
| Identifier | ExFiles\Box 178\1\ img198 | |
| Date | 28th August 1926 guessed | |
| - 25 - The main dimensions and clearances of the R-R 20 HP. and 40/50 HP. springs are indicated on the attached print. It will be noted that the deflections (static) of the 20 HP. springs are - front 2.00" - rear - 5.125", giving theoretical periodicities of 134 and 83 per minute. The 40/50 HP. on the other hand, has deflections of 3.1 front and 8.00" rear, giving theoretical periodicities of about 110 and 68 per minute. It is significant that although the 40/50 car has the greater spring deflection and the lower periodicity, yet it is generally agreed that this model suffers worst from the rapid shocks transmitted to the passenger by small road inequalities. Also without doubt the 20 HP. car rides better throughout its whole range. (b) Tyre pressures and shock damper settings. [Table Data] Column Headers: 20 HP. | 40/50 HP. | 20 HP. | 40/50 HP. Sub-Header for first two columns: Shock damper setting. lbs. Sub-Header for last two columns: Tyre pressures. Row 1: Front - | 25 | 28 | 45 | 50 Row 2: Rear - | 50 | As required. Normal - 40. | 40 | 45 With hydraulic, double acting, unequal load shock dampers, the front of both cars will be the same - i.e., 75 lbs. load down and 30 lbs. load up. (c) Front spring deflections. A question may arise as to why the deflection on the front springs of R-R cars is so small relatively compared with the rear. contd. | ||