Materials

Gears are commonly made from everything from plastic to hardened steel. The materials used are based on several factors including weight, load being carried, speed, life expectancy, environment, design safety factor, machinability, and tolerance of finish gear. Generally cast iron, steel, brass and bronze are preferred for manufacturing metallic gears with cut teeth. Steels are most commonly used because of their high strength to weight ratio and low cost, otherwise plastics are used if weight is a concern as well as cost. Because of the size of the cog and gears in my design, plastic could be the better option, but for durability, a steel might do a better job.

Stainless steel is an alloy of Iron, a possible material choice for the cog and gears, as when exposed to oxygen in the atmosphere a thin layer of chromium oxide is formed, protecting the steel and making it resist the conditions combatting stains and rust. The weather of Wellington can be dull and wet, but also with large amounts of wind. Stainless steel generally is resistant against corrosion - but does have the capability of having this effect. The type of stainless steel 'Austenitic',  is a common steel and is the capability to be weldable and formable. Corrosion resistance can be enhances by adding Chromium, Molybdenum and Nitrogen.

Brass is a generic term for a range of mixtures (alloy) of copper and zinc. It has a lovely yellow colour that can range from quite pale to quite red depending on the proportions of copper to zinc. Other metals are often added to modify the characteristics of the brass. Bass could be the better option to choose from for my design as it acts better in weather conditions as it is commonly used in wet areas, such as on boats, it heavy duty would make the size of it possible within its environment and it is also has a yellow/red colour which would add to the design. It is an extremely versatile materials, as there are multiple ways of which it can be shaped. 

Concrete is made up of three basic components: water, aggregate (rock sand or gravel) and Portland cement. Cement, usually in a powder form, acts as a binding agent when mixed with water and aggregates. A fluid mass is formed from these substances when mixed together and is easily folded into a shape. This stone like material has many uses and is weather resistant and its used for footpaths and multiple other things exposed to the elements. This material also does not let light through it, which is why its chosen to be the material used for the dome shape of the design.