The Physics of Bicycles                           2

Gear Exploration

The gears of a bicycle make pedaling more efficient, allowing the cyclist to travel faster and more easily handle steep grades and other obstacles.

What You Need:
To try this activity you'll need the following materials:

• A bike with gears
• A piece of chalk or masking tape
• Paper and a pencil

 A bicycle, masking tape, paper, pencil, and a little curiosity are all you need to find out how the gears of a bicycle work.

To Do:
Shift the gears so that the chain is on the smallest cog in the front, and on the largest cog in the back.

Mark the top of the rear tire with the chalk, or with a piece of tape.

Note the position of the pedals. Have someone hold the bike upright as you turn the pedals one full revolution, so that the pedals return to their original position.

How many times did the rear tire revolve? Write down the number of revolutions. (Note: you may have to have a friend control the rear tire with his hand, so that the tire does not spin freely past the point that the pedals pushed it to.)

Now try the largest gear in front combined with the smallest gear in the rear. How many times does the rear wheel revolve for one turn of the pedals?

Which of these combinations would be better for climbing a hill? Which would be better for a sprint on a flat road? (You can test your guesses later by riding the bike!)

Experiment with the intermediate gear ranges. Make a chart of the number of rear wheel revolutions each combination of gears produces for one pedal revolution. Why do you think bikes have evolved to have more and more gears?

 The Campagnolo Story One of the first and most renowned bicycle parts makers was the Campagnolo family. Tullio Campagnolo (1902-1983) founded the Campagnolo Company, which has made quality parts for over 50 years. Tullio is credited with perfecting the modern parallelogram derailleur, and inventing the quick-release mechanism for wheels. Legend has it that Campagnolo, a pro racer, was leading a race through Italy's snowy Dolomite Mountains when he punctured a tire on a descent. Fumbling with frozen fingers trying to loosen the heavy wing nuts on his wheel, he was passed by a score of riders. Infuriated by this experience, he designed a hollow-axle quick-release mechanism which is used on almost every bike today. The quality of Campagnolo component sets, or "grouppos," has become legendary, along with their cost. Though some questioned whether the sets were worth the price, afficionados would use nothing else. Cost-conscious alternatives were often referred to as "Cramp-and-go-slow" as opposed to the dependable, smooth-shifting Campagnolo. And though the component market has been dominated in the past decade by the giant Japanese company Shimano, "Campy" still finds its niche at the high end of the performance scale.