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).
Technical report on leaf spring design, discussing clips, rebound leaves, housing, and performance comparisons.
| Identifier | ExFiles\Box 49\3\ Scan024 | |
| Date | 2nd February 1921 | |
| Contd. -3- E2/G2.2.21. The clips also perform the duty of preventing the leaves opening, due to axle or brake torque, when the spring is in the rebound position and not carrying much load. Without slings under the back axle, the rebound may be sufficiently great to reverse the load on the spring. (7) REBOUND LEAVES. If it is found that the axle and brake torque is a disadvantage to the spring, it is proposed to try using rebound leaves above the master leaf, and for that reason the width of Goshawk 11 rear springs has been increased from 2.000" to 2.25" so that the depth shall not grow excessive. (8) SPRING HOUSING. The pad on the axle serves to reinforce the weak place in the spring caused by the hole for the centre bolt, when the spring is in the position of maximum stress, i.e. on bump. A clamping plate under the bottom leaf would only serve a similar purpose if the road spring were loaded in the opposite direction to normal, and can therefore be dispensed with. The only possible anti-normal load would be that occurring on one half of the spring due to axle or brake torque with the spring on rebound. (9) SPRING SHEWN ON LEC. 1341. The road spring shewn on Lec.1341 has been roughly got out from the formula which assumes the spring to be one wide single leaf cut up into strips (see page 106 part 1 Unwin) for the purpose of checking N. scheme 727, and for comparison with the 40/50 H.P. Load, stress, and deflection diagrams are shewn for this spring, but it is not suitable for making as shewn, as it yet requires to have its leaves varied in thickness, as per point (5) for primary set which would probably demand an addition to the number of leaves and the total depth to meet the required performance. (10) COMPARISON WITH 40/50 H.P. The amount of steel in the spring should be roughly proportional to the weight of the car. Assuming a 4.5" deep spring for the 40/50 H.P., then the depth of "Goshawk 11" spring should be - car wt. spring cens. leaf width 4.5 x (2 tons / 3 tons) x (53" / 56") x (2.5" / 2.25") = 3.15" or with 50" x 2" Goshawk 11 spring (4.5 x 2 x 53 x 2.5) / (3 x 50 x 2) = 4" shewing old spring to be too short. | ||