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 springing, load, and weight calculations for the 20 HP and 40/50 HP models.
| Identifier | ExFiles\Box 71\2\ scan0117 | |
| Date | 22th January 1926 | |
| Hs{Lord Ernest Hives - Chair}/Rm{William Robotham - Chief Engineer}/LG22.1.26. ------------------ 20 HP. AND 40/50 HP. SPRINGING. The following peculiarities are observed :- VARIABLE LOAD. On the 20 HP. half the weight of the passengers is sprung. On the 40/50 HP. the whole of the passenger weight is sprung. Then 25% is knocked off the rear spring rating so obtained. If half the passenger weight were sprung in the first place as in the 20 HP., it would obviate adding weight on to knock it off later as at present happens. UNSPRUNG WEIGHT. The 20 HP. and 40/50 HP. are both fitted with semi-eliptic front springs and front wheel brakes. When springing the car, however, on the 40/50 all the front spring is considered as un-sprung weight, on the 20 HP. half the front spring as un-sprung weight. ALLOWANCE FOR CHAUFFEUR AND TORQUE. On the 40/50 HP. a total allowance of 150 lbs. is allowed on the O.S. for the chauffeur and torque. On the 20 HP. nothing, ostensibly, because a spare wheel is carried on the N.S. A spare wheel is seldom carried in this position except when a large quantity of luggage is fixed to the rear. LUGGAGE. On the 40/50 100 lbs. of luggage is always allowed for on the rear grid, on the 20 HP. nothing. SPARE WHEELS. When carried on the step on the 40/50 HP. contd:- | ||