IB Design and Technology Product Design Ergonomics.

Ergonomics The application of scientific information concerning the relationship of human beings to the design of objects, systems and environments

Human factors – ergonomics and anthropometrics All design is carried out to meet a human need and all products or systems must interact in some way with people. Why is so much effort expended in dealing with the human interface between products and systems? Whatever else may be standardised in the design process, the dimensions, capabilities and responses of humans certainly cannot. Ergonmics is multidisciplanary encompassing anthropometrics, psychological factors and physiological factors.

Early Ergonomics The consideration of human factors in design dates back thousands of years even though formal research techniques in the field are relatively new. Look at the picture. What “ergonomic” features are evident in this pre-historic knife blade?

The Development of Tools In more recent centuries many people, such as farmers, weavers, and carpenters, have found that the human factors experience of early generations has produced good, lasting designs. These people have had to make their own tools and they have shaped them so that they are comfortable to use. Tools that are shaped to fit the user will help to make the job easier and more successful.

Compare the pictures of old and modern Braces.

The Human Interface The Brace shown before is a very simple product. It works well because it has been developed to suit the size, shape and ability of the people who will use it. It is vital that you, as a designer, understand this relationship, or interface, between the product being used and the people using it.

Ergonomics – The Study of the Human/Product Interface. Examples of this interface surround us in our daily lives. For example, brushing your teeth involves you, as the person, using the toothbrush, or product. There are interfaces between your hand and the handle and also between your teeth and the bristles.

Person/Product Analysis PersonProductInterface(s)Result(s) YouToothbrush Hairbrush Cups/Mugs Pens/Pencils Lamps Hand/Handle Bristles/Teeth Pressure/Fatigue Plaque Removal

Three Fields of Ergonomics Ergonomics involves three main areas: 1. Physiology - The study of bodily strength, fatigue reaction times, perception of colour, reaction to light, sound, taste, texture and temperature. This field includes Anthropometrics ~ the study of human dimensions such as height, arm length, span of fingers etc. 2. Psychology - The study of behaviour ~ especially in the way we react to heat, light, texture, noise etc. 3. Sociology – The study of the interaction of large numbers of people.

Human Sizes Whether we are at home, at work or just relaxing, it is important that the products we use relate to the actual dimensions of our bodies. It is possible to buy some products, such as spectacles, clothes and sports equipment in various sizes. The vast majority of our products, however, we share with the rest of the population. How does a designer know what shape and size to make all of these products?

“Joe and Josephine” Probably the first scale drawings of humans intended for designers were made by Henry Dreyfuss. The “average American man” – Joe – and the “average American woman” – Josephine - were drawn in a number of situations and these were published in The dimensions of small and large men and women were also marked on the drawings, but it was still found that most of the designs were being done for the “Dreyfuss Average Man” or the “Dreyfuss Average Woman”.

Henry Dreyfuss Dreyfuss' many enduring professional relationships resulted in superior products that were designed to serve a broad range of consumers and avoid short-term solutions.

The Average Person Your task as a designer is to fit your design to the maximum number of people; just because it fits the average person is no guarantee of success. Placing a shelf at the right height for an average person is no guarantee that it will be suitable for the very tall or the very short, the elderly, the very young or the disabled.

Anthropometrics The aspect of ergonomics that deals with body measurements, particularly those of size, strength and physical capacity.

Designing for Groups A constant problem for the designer of mass- produced products is the conflict between designing for as many people as possible and, at the same time, helping the manufacturer to keep down production costs. If you study the physiological factors of design, you will see how this problem may be best resolved. We will analyse the development of a workbench for a school design studio to further these ideas.

Who is it for? The workbench is to be used by a small group. Students similar in height to those shown below could be found in most schools. If you had to design one bench that could be used comfortably by all of them, how would you decide on its height?

How big should it be? Would you make it for the shortest person, and expect the tallest to bend right down? Would you build it so the tallest person could use it comfortably, and expect the shortest to reach up higher?

Size distribution If you look at the group of 7 people shown below, you will notice that the increase is not the same in each case. The three people in the middle are very nearly the same height. The people beside them are a bit shorter and a bit taller respectively, and it is only the ones on the end who differ considerably.

If you were to take a very much larger group – let’s say 1000 women in the age group years – you would notice a similar distribution of heights. That is to say, there would be a great many people around the middle, or average, height, with relatively few who were very tall or very short. If this distribution were represented as a graph it would look like the one following. Note, on this graph, that height is indicated along the horizontal axis with frequency of women at these heights on the vertical axis. Size distribution

Percentile Range The proportion of a population with a dimension at or less than a given value.

The Frequency Graph

Percentiles The graph shows that there are relatively few women in our society who are below 1505mm tall – only 5% of our group.Designers refer to this as the fifth percentile (5%le). Similarly, there are very few women taller than 1710mm – 95% of our group are less than this height. Hence, this is referred to as the ninety- fifth percentile (95%le). By far the majority majority of our group will be nearer the average women’s height of 1610mm tall. This mid-way point is called the fiftieth percentile (50%le) or mean. It is important to remember that no-one is average in every respect. A person who is equal in height with the 50%le may have a width of the 95%le and an arm reach of the 5%le!

Using Percentiles The 5 th to 95 th percentile values are the most used when applying Anthropometric Data. It is usually both uneconomic and impractical to design for the extremes. When designing for a group it should be designed to best suit those who fall between the 5%le and the 95%le. Returning to the workbench problem, it is now clear that it is unsuitable to make it simply to fit the tallest or shortest of such as small group. It should be designed to fit the maximum number of users, with thought given to the 5%le and 95%le.

In the case of the workbench both boys and girls measurements will need to be taken into account. The bench must be low enough to allow a 5%le girl to use it comfortably while being high enough for the 95%le boy to get his knees beneath. There are different sets of measurements for boys and girls and these measurements are available on your Anthropometric Tables. Using Percentiles

Anthropometric Tables (Boys)

Anthropometric Tables (Girls)

Anthropometric Data TASK: Using this table as a guide measure each other and produce a table to show the measurements for A to T for each student. Calculate the 50 th percentile for this class.

Bodily Tolerances As soon as we start to design products which are to be used continuously for prolonged periods of time we also need to start considering bodily tolerances. For example, repeated use of a computer keyboard can cause RSI. Sitting and working in a chair that is at the wrong height can cause back injury. A drivers chair that is comfortable for short journeys may become uncomfortable after a while – affecting concentration and, therefore safety. A machine whose controls involve reaching may be safe to operate at the start of the day but after 8 hours the operator may become tired. Individuals vary in their responses according to psychological factors. One person may find a room too hot while another may not, and the same person may react differently to the same conditions of a different day.

The Telephone Box This is the classic British telephone box as designed by Sir Giles Gilbert Scott in the 1930s. Sketch the box into your book. Identify all aspects of it’s design where anthropometric data would be useful. Suggest whether it would be designed to suit the 5%le, 50%le or the 95%le.