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Reading Selection, Lesson 10

Bicycle Ingredients

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Racer on modern bike

Bicycles like this one, made partially from carbon composites, are lighter than metal bikes and can be designed to be more aerodynamic than those made from metals.

Compared to cars, bicycles look pretty simple. But this appearance is deceiving. Even an inexpensive bike can be made of more than a hundred different materials. These include several kinds of steel, other metals such as chrome and aluminum, several kinds of rubber, a few oils, and different types of plastic.

Dan Connors is an engineer with Cannondale Corporation, a company in Connecticut that makes bikes. He says choosing the material for each bicycle part always boils down to a trade-off between strength, weight, and price. "You want all the parts to be strong, but they can't weigh too much. Nobody wants to pedal around with a bunch of excess weight," he says. But price is important, too. "You can design the greatest thing in the world. But if that means putting a thousand dollar part on a bike you want to sell for five hundred bucks, you won't get too far," Connors says.
Illustration of the draisienne, the first two-wheeled machine for personal transport.

The draisienne, invented in 1818, was the first two-wheeled machine for personal transport. It had no pedals and was made from iron and wood, the most practical materials available at that time.

The single biggest part of a bicycle is the frame. The first bike frames were made of wood.

Today, most bike frames are made of steel. Steel has a good balance between strength and weight. It is easy to work with. It also doesn't cost much. For more expensive frames, designers often choose aluminum. Aluminum or aluminum alloys can have the same strength as steel, but they weigh less. Aluminum is also cheap to buy. Unfortunately, it is tricky to weld aluminum pieces together, so aluminum frames cost more.

Some very high-priced bikes have frames made of carbon composites. These new materials are made by setting strong carbon fibers in a solid plastic matrix. Frames made of carbon composite can be as strong as steel but weigh only one-third as much, says Connors.

Racer on historic bike

Strength, weight, and cost are important for other parts of a bike, too. Take the gears, for example. The big front gear turned by the pedals does not need to be as strong as the gears on the back wheel. Designers often save a little weight by using aluminum alloy for the front gear, says Connors, but this trick won't work at the back. "You might save a little weight if you put aluminum alloy gears in the back, but the gears would wear out after a couple of months," he says. The back gears are usually made from more durable steel.

Illustration of biker on modern bike.

Modern bikes are composed of varied materials.

Tires are made of rubber. Rubber is flexible and holds air, but by itself, it is not very strong. To compensate for the lack of strength of rubber, bicycle tire makers embed long fibers, often made from nylon, inside the rubber. The fibers help the tire hold its shape and resist punctures.

The ball bearings inside the axles of the wheels are especially hardened steel. They may be sealed with lubricants that have special additives to withstand heat.

You might think that it would be very difficult to improve on something that has been around for more than a hundred years, like the bicycle. Fortunately, new materials are constantly being discovered or invented. This gives engineers like Dan Connors new options for designing bicycles.

QUESTIONS

1. Conduct Web reseach to determine changes in bicycle technology over the last 5–10 years.

2. In the design of bicycles does style ever win out over comfort and cost in the choice of materials? Cite examples.

 

 

 

 

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