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).
Leaf spring failures, comparing stress tests on B.V. and 25/30 chassis springs.
| Identifier | ExFiles\Box 100\1\ scan0238 | |
| Date | 13th May 1939 | |
| HH6, + 1305 To By.{R.W. Bailey - Chief Engineer} from Rm{William Robotham - Chief Engineer}/FWK. c. to Da.{Bernard Day - Chassis Design} c. to Da{Bernard Day - Chassis Design}/DB.{Donald Bastow - Suspensions} Rm{William Robotham - Chief Engineer}/FWK.3/JH.13.5.39. LEAF SPRING FAILURES. We have recently carried out some tests in an attempt to determine the cause of the short life of the B.V. rear road springs both on the bump and in France. The failures appear to be due to local over-stressing on the tension side of the leaves. Since the leaves in question are ground we do not think the break-ages can be attributed to decarburization. Firths say that our latest B.V. road spring is more highly stressed that any production spring they have ever made for us in the past - namely 80,000 lb/sq.in. However we give below the average stresses of the main leaf of the front spring of the 25/30 chassis and compare it with the B.V. rear spring. As can be seen there is a negligible difference in stress range. The 25/30 chassis however was never bumped with 3" cams. | | B.V. | 25/30. | | :--- | :--- | :--- | | Stress on full bump. | 78,000 lb/sq.in. | 85,500 lb/sq.in. | | Stress due to nip. | 35,300 lb/sq.in. | 27,600 lb/sq.in. | | Stress range. | 113,300 lb/sq.in. | 113,100 lb/sq.in. | | ||