### Curriculum Connections

• Science
• Math
• Critical-Thinking Skills

### Background

Every modern invention depends on many inventions before it. Cell phones appeared only after satellites went into orbit. Antibiotics and vaccines followed the microscope. The internal combustion engine made motor vehicles possible. Like these inventions, the modern bicycle appeared after all the necessary technology fell into place — steel, pneumatic (inflated) tires, ball bearings, and so on.

Primitive bicycle models of the early 1800s had no pedals; people pushed along with their feet on the ground. Many of the first pedaled bicycles in the 1870s had extremely large front wheels and tiny back wheels, no gears or chains, pedals attached to the center of the front wheel, and a dizzying six-foot-high seat. Why such a high seat? The rider had to pedal exactly as fast as the front wheel turned. The high seat brought the rider's pedaling legs in line with the pedals and the wheel. The introduction of gears and chains controlled the rate of pedaling, and so bicycle wheels shrank and became equal in size. The rider sat in between the wheels at a reasonable height instead of high on top of the front wheel.

The velocipede ("foot speed"), as the early bicycle was called, went through rapid design changes thanks to advances in materials and machine parts. Inventors filed hundreds of patents. There were 30 patents alone for a split-skirt outfit that allowed Victorian women to maintain modesty while riding! Though we still ride a two-wheeler with a saddle and handlebars, the modern bicycle now comes in a wide array of models. The specialized designs make the bicycles more efficient at certain functions. Examples:

• Long-distance bikes have large, thin tires (to achieve more distance per pedal and give a smoother ride), comfortable saddles and handlebars, and several gears for going up and down hills.
• Racing bikes such as the state-of-the-art 1996 U.S. Olympic bicycle are very lightweight and aerodynamic with minimal handlebars, no breaks, and a solid rear wheel (to reduce air turbulence).
• Rough terrain or mountain bikes have smaller and fatter wheels (to withstand bumps), shorter handlebars (for better control), and a heavier, sturdier frame.
• Load-bearing bikes have special attachments for carrying objects, fat tires, and a sturdy frame.
• General purpose bikes have medium wheels and tires and a sturdy but not rugged frame.

### Lesson Ideas

1. Bicycle Built for Technology: Worksheet 1 printable shows the parts of an old-fashioned bicycle. Which parts still exist? Which ones don't? Which ones have changed and how? Students will be able to answer these questions by comparing the diagram to their own bicycle at home or at school, or a picture of a modern bicycle.

2. Bicycle Built for Technology: Worksheet 2 printable asks students to compare bicycle designs by measuring the features of different bicycles.

3. Scour old biking magazines for examples of various bicycle designs and have students classify them by purpose: general use, long-distance travel, racing, rough terrain, and heavy cargo. What features do the bicycles in each group have in common? How might these features make the bicycle better at its job? For example:

• What types of bikes have big wheels? How does a big wheel help a long-distance rider? (Cushier ride; more distance per pedal)
• How does a small wheel help a mountain biker? (Easier to turn; lower to the ground for more stability)
• Why are the handlebars different? Hint: Which bikes have to be comfortable and which ones have to be easy to control?
• Are the spokes spread out or close together? How does this affect the flow of air? (An open-spoked wheel lets air through more easily and so is easier to turn left or right.)
• What is the trail size? (See Bicycle Built for Technology: Worksheet 2.) Which type of bikes need to be more stable? Which ones need to be easy to turn?

### Extension Activity

Have students identify, investigate, and make a drawing that shows the many small inventions inside a big invention of their choice, such as in-line skates, skateboards, pencil sharpeners, or even the automobile. They can use "how it works" references such as books by David Macaulay and Stephen Biesty to label the parts. Some smaller inventions date to ancient or prehistoric times: the wheel, gears, steel, and iron, for example. Others, such as the chain (1897) and multiple gears (1889), are more recent.