Riding Mower Development by Dynamic Design Techniques

The Simplicity Cavalier Series of rear engine rider mowers, introduced in 1979, is utilized in this paper to illustrate the engineering development process for achieving improved operator comfort. It is shown that a proposed ISO Standard for hand-arm vibrations offers one method to quantify the subjective “feel” of the operator towards various vibration levels. Such a quantification is necessary to form a basis for comparison of competitive designs. The dynamic design techniques of modal and Fourier analysis, dynamic testing, and finite element analysis are shown to provide improved design of the system for structural and vibration performance. Specific finite element models of the frame and of the steering wheel are described and their use for improved vibration design discussed. Design considerations and trade offs for the engine/vehicle interaction leading to the selected engine configuration for the Cavalier series mowers are discussed. The unique vehicle body suspension on the frame by soft but progressively stiffening mounting arrangement and the resulting vibration performance of the Cavalier mower are described.