The Next Eco Bike

These three are very important factors that impact the type of frame or type of frame materials.

Stiffness

Stiffness is how much a material flexes for the same amount of force applied. For example if we fasten one end of a metal bar and we suspend a weight on the other end, causing the bar to bend temporarily. When you take out the weight, the bar comes back to its original form.

Stiffness has an effect on the riding traits of a bike frame. So it’s very important factor in the bike. Stiffness is determined by the property called “elastic modulus”. Elastic modulus is basically a substance’s tendency to become deformed temporarily when a force is put on it.

Strength

Strength is basically the crash-worthiness or durability of the bike, but has no impact on the riding. Strength is a material’s yield strength. If we put a heavier load on the block (similar to the stiffness example), that when we take out this weight the bar remains bent the metal is said to have yielded. Different metals can stand different amounts of forces before being permanently bent.

Weight

The way to decide the heaviness of a volume in the frame materials we use specific gravity. Like Elastic modulus, the specific gravity of a metal is not drastically affected by the addition of alloying elements.

Comparisons

The chart shows if you were to build the same frames from the 3 materials using the same tubing widths and wall thicknesses, that the aluminum frame would be only 1/3 as stiff, and the titanium frame only half as stiff as steel.

The yield portion of the chart shows that the aluminum frame is very much weaker than a steel or titanium frame. That would mean that it would be more vulnerable to damage

The specific gravity values show that the aluminum frame would only weigh 1/3 what the steel frame weighs, while the titanium frame would be roughly half the weight of the steel one.

But changing the tubing dimensions and wall thicknesses can alter these dimension rules.

Choosing different tubing diameters can easily alter stiffness. Strength is mainly linked to the wall thickness, but diameter also plays a role. While both diameter and wall thickness has an effect on Weight. Manufacturers can make trade-offs by picking different tube diameters/wall thicknesses, allowing a frame to be made stiffer, or stronger, or lighter. (Bicycle Frame Materials, 2008)

Materials Used

Nowadays 3 different materials are used while manufacturing bikes. They are:

• Aluminum alloys (series 2000)
• Steel alloys
• Titanium

Steel Frames

Steel frames are very sturdy, simple to work, and inexpensive, but only problem is that it is very dense and heavier than most materials used in the frame. Steel in typical tubing widths is often less firm than jumbo tubing (i.e. aluminum tubing) in other materials used for the frame. This permits for some shock absorption giving the rider a less harsh ride contrasted to more rigid tubings such as extra-large aluminum tubing. But for commuter bikes it doesn’t mater as they are only cycling in pavements.

Inexpensive steel bicycle frames are made of milder steel and aren’t butted. The process of butting means that the wall depth of the tubing changes from thick to thin in the middle designed for extra strength and to make it lighter. Even though it reduces weight it still increases the cost so they don’t do it in cheap frames. On the other hand, expensive bicycle frames are made of high strength steel alloys, which can be easily worked into lightweight tubing. But people don’t need bikes using high strength steel alloys as commuter bikes. High strength steel alloys are only necessary for professional cyclists or mountain bikers.

A high-quality steel frame is lighter than a regular steel frame. This lightness makes it easier to travel uphill, and to go faster on the flat land. But since we are building commuter bikes it doesn’t mater as they are only cycling in pavements. And pavements don’t usually go uphill. (Bicycle Frame, 2008)

Aluminum alloys (series 2000)

One thing about it is that there is plentiful of Aluminum in this world. 8.8% of the earth’s crust is made up of Aluminum. And it is the most abundant metallic element in the world. Aluminum is a metal that is silvery-white in color. It has the density of 2.70 g/cm3. And is non-toxic, and can be easily welded or cast. Aluminum alloy series 2000 (a alloy consisting of aluminum and copper) has a lesser density and inferior strength contrasted to steel alloys. But it also has a better strength-to-weight ratio than steel giving it way less weight than steel. Its disadvantages are that an aluminum frame doesn’t possess the same feel as a steel bike frame. And aluminum has a different strongest wall thickness to tubing diameter than steel. Diameter: wall thickness of aluminum frame is at its peak at 200:1, whereas steel is 12:1. But it is usually ignored as if it were built proportionate to that then the tubing thickness would be as thick as a pop can (not good for a good bike). (Chemical Elements 5-13, 2008)

Titanium

Titanium is possibly the most foreign and costly metal normally used for bicycle frame. It merges many attractive characteristics of both aluminum and steel, including a high strength: weight and excellent corrosion resistance. Reasonable amount of stiffness, which allows for titanium frames to be built with regular tube sizes similar to a conventional steel frame. As many titanium frames are much more expensive than similar steel alloy frames, cost make them a luxury for many cyclists. And anyways it is absolutely unnecessary to spend so much on a commuter bike. (Titanium, 2004)

Best option would be……

After all this research I figured the best material for the frame would be aluminum alloy (2000 series), which is an alloy of copper and aluminum. They are very strong and corrosion resistant and can be worked with easily. The reason I chose aluminum is because Steel is very heavy and dense and all its benefits are not necessary in a commuter bike and also takes a lot of energy to create and Titanium is very costly to the consumers and nobody will buy it. And also aluminum can be recycled and to be eco-friendly we can even use Recycled Aluminum.

Production

The first step in the production of aluminum is to acquire pure alumina. Alumina (pure aluminum oxide) generally is prepared by the Bayer process. And once pure alumina is acquired Hall method is completed to get pure aluminum

Bayer process

Finely ground bauxite is mixed under pressure with NaOH in large tanks. The impurities form red mud, which is then filtered out. The left over liquid is a sodium aluminate solution. The liquid is then seeded with crystals of aluminum hydrate. As the solution cools, crystals of aluminum hydrate turns into alumina. The alumina is removed and washed and heated to 1093.3° C (2000° F) in rotary kilns to remove the water and it merges out as a white powder.

Hall Process

In the second half of the procedure called Hall Method, the oxygen in the alumina is removed by the use of electricity. After all this is done, pure aluminum remains. (Chemical elements 5-13, 2008)

Or

Another method would be to just melt recycled aluminum and remove all impurities and use that. That’s why aluminum bike frames would be really cheap and eco-friendly.

Works Cited

• “Bicycle Frame Materials.” Spring 1952. HARRIS CYCLERY. 5 Nov. 2008 .
• Newton, David E. Chemical Elements : From Carbon to Krypton. Ed. Bridget Travers and Rob Nagel. Farmington Hills: UXL, 1998. 5-13.
• University of California, comp. “Titanium.” Periodic table of elements. 04 May 2004. University of California for the US Department of Energy. 5 Nov. 2008 .
• Keller, Fred. “Aluminum.” Encyclopedia Americana. 2008. Grolier Online. 3 Nov. 2008 http://ea.grolier.com/cgi-bin/article?assetid=0011670-00.
• Bell, Trudy E. “Bicycle Frame.” Encyclopedia Americana. 2008. Grolier Online. 3 Nov. 2008 .