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Bike Shop 3-5 / Week 01 / Thursday
4/6
Week 01 · Meet the Bike

Thursday

Pedals to the back wheel
// A system of parts with jobs
⏱ about 15 min

Thursday: Pedals to the Back Wheel

Rocket points at the pedals. "These push the front wheel, right?"

Raven traces the chain with her finger in the air. "What do you notice? Where does the chain go?"

Rocket follows it with his eyes. "It goes to the back wheel!"

Nova hovers by the gears. "The drivetrain is a relay team," she says. "Who passes the turn to whom?"

Rocket grins and grabs his notebook.

The drivetrain

The drivetrain is the group of parts that makes the back wheel turn.

Your feet push the pedals.

Each pedal is joined to a crank arm.

The crank turns your pedaling into a spinning motion.

The front gear is joined to the crank. It is a wheel with teeth.

The chain wraps around the front gear and a back gear.

The back gears are joined to the hub of the back wheel.

So the chain carries the turning to the back wheel.

THE DRIVETRAIN RELAY
  • Tap a card.
  • Then tap its spot.
11
22
33
44
55
DRIVETRAIN CHECK
  • Read the question.
  • Tap your answer.
Which wheel does the chain turn?
What is the pedal joined to?
What is a gear?
The loop of links that moves the turning back is the ____.
Your feet push the ____.

Many bikes have more than one gear in back.

A gear changer moves the chain from one gear to another.

You will learn much more about gears in week 5.

Safety first
The bike stays still. A grown-up holds it.
Only a grown-up turns the pedals.
Keep hands away from the chain and gears whenever anything turns.
Loose pant legs and shoelaces can get caught in a chain. Tuck them in.
If you touch the chain, wash your hands with soap and water.
Try it
Watch a grown-up turn a pedal slowly while holding the bike still.
Watch the chain move and the back wheel turn.
No bike? Wrap a rubber band around two jar lids and turn one lid.
In your shop notebook, draw the drivetrain. Use arrows to show where the turning goes.

Terrific tracing! Tomorrow we meet the brakes and see how all the parts work as a team.

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