Design Decisions

Factor of Safety

Fire extinguisher from CTF3

This fire extinguisher contains ABC chemical powder which can use in different class A, B and C fire, that is class A for “Ash” which is ordinary solid combustibles, class B for “Barrel” which is flammable liquids and gases, class C for “Current” which is energized electrical equipment, class D for “Dynamite” which is for metal as well as class K for”Kitchen” which is oils and fats.

However, the way of usage of fire extinguisher also known as factor of safety. This is because this fire extinguisher must be used by trained people as it need to push out a pin, carry it and press the button then only can put out the fire.


The use of more elements than necessary to maintain the performance of a system in the event of failure of one or more of the element.

· Diverse

Captured by Nigel

The car brake pedal and it handbrake can function as stopping the car as well. Although both are different types, but it can function when the car has emergency happened. Usually, we will press brake pedal to stop the car. But, sometimes emergency happened we can use handbrake to force the car to stop.

· Homogenous

There has 3 light bulbs so if one is broken then still has left 2 bulbs can use.The lightness will be reduced. The light bulbs will not break in one shot, so the failure can be expected as what theory mentioned.

Light in Lab 1

· Active

The arm support rods are there all the times and they will support the umbrella. If the rods break then have another rods can support the umbrella. Active redundancy can allow users to repair it by using string to tie up or tape it with marking tape.

· Passive

G-2 Pilot pen belongs to Nigel.

This pen can refill its own ink by ourself. We just need to buy the refill inks and insert it once there is out of ink.

Flexibility-usability trade-off

Taken from Yan Qing’s hometown

The flexibility is found out from this rice cooker because it provides the buttons of cooking and reheat, timer, menu and keep warm as well as the off button. However, the usability is need time to figure out. As you want to bake cake, you need to turn on and press “MENU” button to “CAKE”, then set timer by pressing the “TIME” button. To set hour(s) and minute(s), you need to press the “HOUR” button and “MINUTE” button respectively. It is time consuming to determine it.


We can use it when it’s raining and sunny day. But, umbrella always cannot fully cover our whole body. During raining, our lower part of body and shoes always get wet, however, when afternoon, our hands or legs also will expose to sunlight too. It is satisfied to us but it still can improve.

Ockham’s Razor

Kettle from Yan Qing’s

Kettle just for boiling the water so the function and the design of kettle should be simple and easy to use. Just plug in the cable and turn on the button then wait the water to boil. Once the water boiled, the button will automatically turn off which means it does not need manually to care it. Before you boil the water, you need to check the water level does not exceed the marking inside of the kettle.

Form Follows Function

Different types of bottles in term of brands, colours and size but the function still the same.

There has different types of bottles used in campus. There has many designs for bottles to attract people as well as promote their design that can give comfort people. But, the function of bottles is just need to fill the water. In the term of form, the size of bottles can effect the volume of water.

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