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).
Letter comparing the durability of two types of 9-leaf road springs and providing thickness specifications.
| Identifier | ExFiles\Box 154a\2\ scan0120 | |
| Date | 12th June 1939 | |
| 1305 c. Roy {Sir Henry Royce} /Les. Rm {William Robotham - Chief Engineer} /AFM. {Anthony F. Martindale} 6/MH. {M. Huckerby} 12th. June, 1939. Messrs. Thos.Firth & John Brown Ltd., Atlas & Norfolk Works, SHEFFIELD, 1. Dear Sirs, Road Springs. We have now tested the two types of 9 leaf springs supplied. The type of spring which has been made from the 25 sets by the addition of a thin helper leaf is the more durable. we enclose a drawing of it (FB.4364) and we want future supplies to be made to this drawing. The life of the spring on our machine was 16 hours when the 2nd. and 8th. leaves failed, but the main leaf did not fall until 22 hours. The 9 leaf spring with all leaves equal (or nearly equal) lasted only 14-2/3rds. hours, the first leaf to fall being the main leaf. In other words this spring does not last quite so long as the one previously mentioned and moreover, the first failure is the dangerous one. It is important that you do not alter the shaping of the main leaf. The thickness of this was:- Inches Thickness. .251 ...... Front end, central eye .251 .238 .235 .220 ...... Middle .238 .245 .249 .254 ...... Rear End | ||