Design sketches and Engineering drawings

Design sketches

Engineers and designers frequently use quick hand-drawn sketches to illustrate design concepts as well as features associated with a particular product or process. In fact, being able to use sketches to illustrate your ideas is an essential part of becoming an engineer! Sketches are also an excellent way of communicating your ideas to other engineers and designers without having to resort to words or formal engineering drawings. When producing a design sketch there are no `hard-and-fast' rules other than ensuring that the sketch is clear and unambiguous (i.e. not liable to be misinterpreted) and that it is adequately labelled.

Activity 2.20

Produce a design sketch for an entry-level digital camera. The camera is to incorporate an in-built flash unit and an LCD screen. The battery is to be powered by two AA batteries and is to have a USB connection for downloading images to a computer. Make sure that all of these features are identified in your sketch. Present your work in the form of hand-drawn sketches and hand-written notes.

Engineering drawings

Like the graphs that we have just considered, there are many different ways of representing and communicating technical information. To avoid confusion, such information should make use of nationally and internationally recognized symbols, conventions and abbreviations. These are listed and their use explained in the appropriate British Standards. Such standards are lengthy and costly, but a summary is available for educational use. This document is entitled `Engineering drawing practice for schools and colleges' and it has the British Standards reference number PP 8888. The document is abridged from the earlier British Standard BS 308.

Block diagrams

These show the relationship between the various elements of a system. Figure 2.24 shows the block diagram for a simple radio receiver. This sort of diagram is used in the initial stages of conceptualizing a design or to provide an overview of the way in which an engineering system operates.

Activity 2.21

Construct a block diagram showing the arrangement of the braking system of a car. Label your drawing clearly.

Present your results in the form of a printout from a simple drawing or technical illustration package.

Flow diagrams

Flow diagrams are used to illustrate a sequence of events. They are used in a wide variety of applications including the planning of engineering processes and the design of computer software. Figure 2.25 shows a flowchart for the process of drilling a hole. The shape of the symbols used in this flowchart have particular meanings as shown in Figure 2.26. For the complete set of symbols and their meanings you should refer to the appropriate British Standard BS 4058.

Activity 2.22

Your bicycle tyre is flat and may have a puncture or may simply need reinflating. Draw a flowchart for checking the tyre and, if necessary, replacing the wheel. Figure 2.27 will provide you with a starting point. Present your results in the form of a printout from a simple drawing or technical illustration package.