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).
Spring stiffness, sprung loads, and stamping inconsistencies.
| Identifier | ExFiles\Box 43\2\ Scan143 | |
| Date | 8th May 1926 | |
| Oy1-E-5826 -5- May 8th, 1926 III. Very soft front springs. All the later results on the above car have been obtained with front springs mentioned above having a stiffness when clipped of 340 lbs./in. To find whether we could expect even better results from extremely soft front springs, we made a pair which gave only 285 lbs./in. when clipped to the wide pad. This corresponds to 4-1/4" deflection with 4 passengers. If the riding was improved at all (which is doubtful) it was certainly very slight and did not justify the risk of breakage on such very soft springs. IV. Sprung loads in front. We suggest that once a suitable spring is established for the front of the car, it can be used on practically all cars fitted with conventional coventional coachwork, mudguards, etc. The sprung load in front with four passengers on our fifteen different body types (including Brewsters) varies between 1075 lbs. per wheel and 1110 lbs. per wheel. On the Phantom it appears that we shall have a variation between 1200 lbs. per wheel and 1240 lbs. per wheel. It appears therefore that an 1100 lb. spring is suitable for all Silver Ghosts and a 1200 lb. spring for all Phantoms. (We find also that putting four passengers into a car only increases the load on each front wheel by 80 lbs.) V.{VIENNA} Stamping of Springs. We have found that different effects on identical cars are often due to springs stamped incorrectly. For instance a roadster this week which was supposed to have 1800 lb. rear springs had the correct spring camber and clearances, but did not ride as it should. The springs were stamped "1800 lb." and when tested they showed 1800 flat load, but the average stiffness over a range from 1" positive to 1" negative camber was 667 lbs./in. corresponding to a 2000 lb. spring. We are now making all springs and are stamping them with the nominal load and actual stiffness. | ||