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 specifications for 850 lb. and 900 lb. springs for the B.50 model, with revised normal positions.
| Identifier | ExFiles\Box 112\1\ scan0118 | |
| Date | 15th March 1939 guessed | |
| 850 lb. & 900 lb. Springs for B.50, Revised Normal Position. 850 lb. spring. | 900 lb. spring. Wire diameter. | 0.631" | 0.640" Mean diameter of coils. | 4.869" | 4.860" Number of effective coils. | 6 1/4 | 6 1/4 Normal load ( at length 7.396" ) | 1466 | 1552 Normal deflection. | 4.640 | 4.630 Normal stress, uncorrected. | 72,200 lb/in² | 73,400 lb/in² Maximum load ( at length 5.621" ) | 2027 lbs. | 2147 lbs. Maximum deflection. | 6.415" | 6.405" Maximum stress, uncorrected). | 99,800 lb/in² | 101,300 lb/in² Maximum stress, corrected. | 118,200 lb/in² | 120,700 lb/in² Free length. | 12.036" | 12.026" Rate. | 316 lb/in. | 335.5 lb/in. Rate at wheel(plain leverage assumed). | 106.2 lb/in. | 112.7 lb/in. Room for packing. | 0.39 | 0.32 | ||