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).
The results of tests on a 1150 lb. spring with different axle clips.
| Identifier | ExFiles\Box 43\2\ Scan089 | |
| Date | 18th December 1925 | |
| Oy4-E-121825 -6- December 18, 1925. 9. The following are the results (averages of up and down) on a Springfield 1150 lb. spring. Deflection Plain Spring Narrow Clip Wide Clip 1" 340 345 375 2" 662 675 722 3" 987 1002 1075 3½" 1155 1172 1257 4½" 1505 1532 1655 5½" 1860 1902 2077 Flattening effect on spring in unloaded position .070" .400 Rating at 1" 340 345 375 Rating at 3" to 3½" 336 340 364 Rating at 4½" to 5½" 355 370 422 A blue print chart is attached showing the effect of the clips. It appears therefore that whereas the narrow axle stiffens the spring very little, the wide axle stiffens it at the flat position 28 lbs. per in. which is equivalent to using a spring of 100 lbs. heavier load. We believe therefore that the wide axle accounts very largely for the harder riding in front and the "joggling" at the rear met with on these cars (and noticed also on Silver Ghosts fitted with front brakes). We had an exactly similar effect when we fitted a number of the Springfield covered cars with 1200 lb. front springs instead of 1100 lb. It was impossible to prevent them joggling the rear passengers, and all these springs had to be changed back to 1100 lbs. We have not yet completed the job by running 12-MC with a Springfield narrow front axle and noting its riding. We shall do this shortly and will let you know the result. The conclusion so far is, however, that if radius rods would allow us to use quite soft front springs and narrow axle pads, they would be well worth the extra expense and complication. Note 1. A further effect of the wide axle is that a length of about 8" at the centre of the spring is practically inactive and tends to rust up solid, while the ends do more than their share of the work, and take a negative camber. We have this effect on 56-MC (an owner's car) which has run 5000 miles. Note 2. Packard have softened their front springs with front brakes, by putting the spring below the axle probably 5" closer to the road than | ||