The modern engineer is rarely faced with a simple problem. Most of the simple ones have been solved already. In earlier days each step in a process would be done by a separate machine or each force in a structure well smothered by redundant members.

Today's relentless economic pressures dictate the use of multi-stage machines with intricate controlling systems to lift speed and precision beyond anything the human hand or eye could ever approach. There is no unsophisticated engineering left; or there shouldn't be.

Our grandfathers, and even our fathers, could visualise and invent total machines. Today we usually cannot hold in our mind's eye the total requirements of a design, much less how to achieve them.

Where do we start? Where, so to speak, does the vital centre of design gravity lie? If we try to start everywhere we get nowhere. We must decide which is the horse and which the cart, otherwise we may find the horse asleep in it or under it. If there is any general answer to this problem, perhaps we may find it by examining where, in fact, are the points where successful designers have chosen to begin over a wide field and see if any common strategy emerges.

We will first have a look at one of the commonest machines in industrial use, i.e. the production line where materials are put in at one end and a saleable product comes out at the other.