The Engineering Sketch

because they are so versatile. They can be used for the rather mundane task of communicating information, as in subway maps; they can be an inspiring work of art, such as the drawings of Escher; and they can serve as a powerful reasoning tool for problem solving and design, as in the back-of-the-envelope sketch. Furthermore, drawings are often the best tools we have for certain tasks: try describing a complicated device to someone who hasn't seen it before without drawing a picture. As a mechanical engineer, my interest lies in harnessing the drawing, or the sketch to be more imprecise, as a tool for interacting with computer-based design software. Drawings have always been an important tool for engineers. The oldest known technical drawing is a ground plan of the ziggu-rat (a kind of pyramid) at Ur, which was built around 2100 BC.' The drawing was made to scale and carved in stone (thus beginning a long tradition of design specifications being set in stone). By the 15th century , Leonard0 da Vinci had perfected many of the drawing techniques that are now in common practice, including crosshatching, sectioning, pictorial sketching, and isomet-ric sketching. Today, we have CAD tools that can produce photo-realistic, 3D, geometric models of everything from simple parts to complete aircraft. But surprisingly, engineers still prefer to attack the early stages of a design problem as they have for hundreds of years-with paper and pencil. To gain insight into the reasons behind this, it helps to contrast this with another problem where computers are the preferred tool for the early design stages: paper writing. Many people find they cannot write effectively without a word processor. One of the more obvious reasons is speed: with even mediocre typing skills, you can type much faster that you can write. Also, the editing capabilities of a word processor lets you quickly and easily rearrange the text fragments as the ideas develop so that you can focus on the content rather than the process. There are also psychological factors at work the word-processed doc-Drawings are ubiquitous in everyday life Figure 9. A circuit breaker: (a) o pencil sketch; (b) nonfunctional parts stripped away. ument always looks neat, which can impart a sense that something has been accomplished. But, when it comes to making a simple drawing, the computer can become a hindrance. What might take 60 seconds to sketch on paper might …