Design and calculation

Abstract

Form design—deciding the shapes of the individual components of a machine—is the fundamental part of the design process. It represents the truly creative stage—the creation of a mechanism or structure in the mind’s eye using intuition, thought and imagination. The designer tries to reach the best possible concept without, initially, giving any thought to the relationship of individual dimensions—perhaps with no particular scale in mind. Successful form design is an art and is thus particularly difficult to systematize; yet a great deal can be achieved by improving one’s system. When the beginner fails, it is usually due to an unsystematic approach. He should never attempt to produce shapes before he knows their real purpose. Many designers try to put the cart before the horse, ignoring the fact that every design must dovetail in some way with something which already exists. This should always be clear from the design specification, in which the designer has a foothold from which he can proceed to develop his design. The specification will always identify a part of the mechanism which is the focal point of its function. In a riveting machine, for instance, it will be the point at which the pressure tool compresses and shapes the rivet; in a shaft coupling it will occur where one part engages the other; and in a reciprocating compressor it will be the face of the piston which displaces and compresses the gas.