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 design and stress calculations for the main plate of a road spring.
| Identifier | ExFiles\Box 43\2\ Scan196 | |
| Date | 28th September 1937 | |
| H O from Gy ROAD SPRINGS. Y3900 Obviously, to get the best use from a strip of steel in bending, it should be bent equally throughout its length. In practice this implies circular bending. Therefore all plates are bent to circular radii. It would be more correct to bend each plate to two radii with a flat in the middle between the spring clip bolts. However, we did not realize this at the time, and it is probably an unnecessary refinement. Main Plate. [Diagram of a leaf spring showing lengths L₁ and L₂, radii R₁ and R₂, and cambers d₁ and d₂] The first step is to decide what maximum bending stress is permissible in the main leaf when it is at maximum bump position. If d₁ is the initial camber of the main leaf (unknown) d₂ is the bump clearance (allow say ¼" compression of rubber) Max. stress in main leaf is found as follows:- (1) R₁ = (L₁ L₂) / (2 d₁) (within necessary limits of accuracy). (2) R₂ = (L₁ L₂) / (2 d₂) Hence find R₂ from d₂ which is known. (3) Stress = (E t) / (2 R₁) + (E t) / (2 R₂) where t = plate thickness. Suppose we make this 100,000 lbs/in². Hence, knowing R₂, find R₁ and from (1) find d₁ (if desired). This gives us the allowable initial camber for the main plate. (We find, however, that it is best to drop any mention of cambers and work to radii only by means of sheet metal radius gauges, and radial quenching forms). [Stamp: RECEIVED 28 SEP 1937] | ||