This paper describes the exact method, which the author derived, for designing a two-stage leaf spring. The spring consists of a multileaf first stage, and tapered-leaf second stage. Using this method, the following can be determined:
Spring rates and stresses when all physical dimensions are known.
Leaf thickness and stresses for given rates.
In the Appendix of this paper, a sample of a step-by-step calculation is given, which makes the whole problem easier to understand.