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 document detailing the requirements for leaf springs, including thickness, primary set, and clips.
| Identifier | ExFiles\Box 49\3\ Scan023 | |
| Date | 2nd February 1921 guessed | |
| Contd. -2- E2/G222.21. the springs were straight when unstressed, then the bottom leaves would have been bent more than the top and a certain amount of grading in leaf thickness would be required to get equal range of stress. Owing, however, to the non-stressed position of the spring being bent in the opposite direction by an amount of about equal to the bump position, then the range of curvature is uniform and the leaves should be of equal thickness. (4) TOP LEAF REQUIREMENTS. The requirements of the top leaf as a radius rod etc. are met by making this leaf thicker and allowing it to have a larger stress range, but not a higher maximum stress than the other leaves. This reduces the efficiency of the spring considered purely as a spring. (5) PRIMARY SET AND LEAF THICKNESS. It is customary to put the leaves of a multiple spring together with a certain amount of primary set on each leaf relative to its neighbour, with the object of preventing the leaves from opening when the spring is assembled. This is a source of efficiency, and it should be regulated with prescribed limits. The detail drg. for the spring maker should show an illustration of the spring with all the leaves in position of no stress, just previous to squeezing together, with the allowable variations specified. The primary set should not exceed .125" between any one leaf, and the next. This practice has the effect of creating an initial stress either positive or negative in each leaf (unless a leaf happens to be situated on the neutral position of not stress) and in consequence it is necessary to grade the leaf thickness to secure that the maximum allowable working stress for the steel shall not be exceeded in the bump position. Spring leaf thicknesses should be graded in steps of not less than .010" and there should be not more than three different thicknesses in the working leaves of a complete spring excluding the top plate. It may be found possible to use only two different thicknesses where the number of leaves is small. (6) LEAF CLIPS. Two leaf clips should be used on each half of the Goshawk rear springs. They will locate the longer leaves sideways while the short leaves will be located by the U bolts securing the spring to the axle. The clips should be fixed on by means of rivets and should be of the type shewn on Lec.1341. Comtd. | ||