In my last blog I raised the question, how the experienced designers manage to estimate accurately many design parameters without complex calculations. Before trying to answer this I want to ask, why is it important?
The dance of design is a complex one. In the simplified analogy to the ballroom dance it looked as if we can make one step at a time, and then calculate our next move. Even in the ballroom the music never stops and we cannot make just one step before calculating our next
Design is never a straight forward process. While designing we must have some imagined picture of the product in our mind and then try to destroy it. If we manage to destroy it we correct the design. If not, we may weaken it a bit, so that it will have just the right strength. Why should we do it? Because being too strong it is probably heavier, or more expansive, or has other extra "payments".
I referred to strength, but we do the same for any other specified feature of the
Why do we calculate?
Engineers are supposed to calculate. We calculate strength and mass flow, temperature rise and heat transfer, fuel consumption and top speed, or just the total weight of a newly designed product.
Do we really have to calculate all these things?
Ancient engineers over the ages did great job designing complex machines and constructions: war chariots and composite bows, aqueducts and towers. They did marvelous designs even before the introduction
When we pass from high school to the university we bring with us the idea of getting answers by calculations. We use analytical formulas, and we are educated to believe that the results are either right or wrong. We are used to having exactly all the relevant data and nothing more, always given with the problem. I remember testing myself for using the right formulas by checking if I used all the data given.
This is not real life. Not even close. Data is never "given", it is
With so much scientific tools, why do designs fail?
Why the unsinkable Titanic sank? Why did the thoroughly tested Columbia space shuttle burned out on return? Why Toyota had to call back thousands of cars designed by expert engineers?
Design might fails because somebody made a stupid mistake in his calculations, like in the old joke about the bridge that fell down because the engineer forgot to multiply by two. It might happen, but it is extremely rare. Most design failures