Student Activity - Lean, Mean Cycling Machine
INTRODUCTION
If you have completed the two activities - Bike Bits and Balancing Act, you will know that certain characteristics of materials make them suitable for particular purposes on a bike and that sometimes metals such as steel and aluminium are combined or mixed (alloyed).
If you have a bike it is probably strong but fairly heavy. Try lifting it up steps, it's hard work!. An Olympic racing bike, on the other hand, contains many special combinations of metals that make it very strong and durable yet also extremely lightweight. It must be a lean, mean cycling machine capable of taking the rider around the track at incredible speeds and under great stresses.
Photo: Joanna Buckley
Certain metals and alloys of metals have been used to make this bike light, strong and durable
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Light
In racing, weight is a most important consideration. The lighter the bike, the faster the cyclist con make it go. Modern metals can make a bike that is very light - less than 7kg Compare this to an everyday bike |
Strong
A racing bike is put under a lot of strain on a racing track as the slope is 42 degrees. Imagine how much stress is put on the frame and the wheels when riding at that angle. Particular metals add great strength to a racing bike. |
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Durable
Certain metals are added which protect the paintwork on a racing bike and stop it from rusting. Rust would eventually weaken the bike. |
INVESTIGATION
The aim of this activity is to learn what special metals and other materials a racing bike is made from and identify how each helps make the bike a lean, mean cycling machine.
WHAT YOU NEED
The two tables - Features of a Racing Bike and Characteristics of Certain Metals
Features of a Racing Bike
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PART |
CHARACTERISTICS |
MATERIALS |
|
Pedals |
A special clip is on each pedal. A metal part on the bottom of the cyclist's shoes is clipped onto this to keep his or her feet in place. |
Steel Magnesium alloy, or |
|
Frame |
Metal can be shaped to make a hollow tube for the frame which is lighter, but strong. Diamond or triangular shapedistributes the stresses and strains over the front wheel and the frame. The frame can be moulded so that there are few joints and welds. |
Chromium-molybdenum-manganese steel alloy or Aluminium based alloy. or Carbon fibre. Titanium dioxide in the paint. |
|
Wheels and Tyres |
Wheels are used for movement and control Solid wheels reduce air friction. Inner tube weighs as little as 100gm and are sometimes inflated with helium. Why? (Hint - think of a balloon!) |
Aluminium alloy containing magnesium or chromium. Carbon fibre composite. Silk, cotton. Rubber stabilized with zinc. |
Characteristics of Certain Metals
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METAL |
WHY IT IS USEFUL |
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Iron |
Main metal used in steel making. Soft by itself. Easily corrodes. |
|
Chromium |
When exposed to air, the chromium forms an invisible layer that protects the metals underneath from corrosion (rusting). When alloyed with steel, it increases the strength and hardness. Many different colours can be found in chromium so it is used in paints and pigments. |
|
Aluminium |
Not very strong metal on its own. Lightweight metal which, when mixed with steel, reduces the overall weight of the alloy. Resistant to corrosion. |
|
Titanium |
A metal that is very light in weight. It is very resistant to corrosion. When alloyed with steel, it increases the strength and hardness. Used in paints to give colours a brilliant intensity. |
|
Molybdenum |
A silvery metal that is added to steel, to harden it. It increases the tensile strength at high temperatures and is good for parts that get hot. |
|
Magnesium |
Very lightweight metal. Easily worked. When alloyed with steel, increases its strength and resistance to corrosion. Reduces the weight of the alloy. |
|
Manganese |
Has similar properties to iron. When alloyed with steel, increases its strength and resistance to corrosion |
WHAT TO DO
- An ultralight bike frame is made of steel, with other metals such as chromium, molybdenum and manganese alloyed with it. Why is this necessary?
- In what ways does titanium help make a racing bike a lean, mean cycling machine?
- What shape is the main frame on a racing bike? Why do you think this shape is almost always used for bike frames? Draw a diagram of a bike outlining where this basic shape is used. Look around your school or community for examples of constructions using this basic shape for strength.
- Rusting of bike components can be a problem. Using the information in the tables, explain what measures can be taken to reduce corrosion.
DID YOU KNOW?
Racing bikes have no brakes! The cyclist just has to keep rolling on until the bike slows down enough to stop. Imagine if this was the same on a road or a mountain slope.
Riders' helmets are aerodynamically designed for less wind resistance, and are made from carbon fibre or fibreglass. These are both "composite" materials which are mixtures of two or more materials. They are made from carbon, which forms when coal is heated, or glass strands. The carbon and glass strands can be put under a lot of tension. but are too floppy to use alone, so a resin or "glue" (often nylon) is used to join the fibres together and make them strong.
The result is an extremely lightweight, very strong material.
Have you heard of the 'Super Roo'? This is a specially designed monocoque carbon fibre bike that helped Kathy Watt, Bradley McGee and Stuart O'Grady win three gold medals at the 1994 Commonwealth Games. Scientists and engineers from the Australian Institute of Sport and the Royal Melbourne Institute of Technology designed the bike.
For the latest information on the various cycling events for the Beijing 2008 Games, search the web using keywords 'cycling' and 'Beijing Olympics'.
To view a map where the Roadcycling event will take place, visit:
http://en.beijing2008.cn/cptvenues/sports/cycling/