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Now that you have built the Crank Fan,
let's explore your model!
1. Can you locate and identify the gears?
Watch the gear mechanism in operation as
your turn the crank. Which gear do you think
is the driver gear? Which is the driven gear?
2. This arrangement is called a Spur Gear
System. In this arrangement, the gears fit
together, or mesh, along the same line or
in the same plane. The Spur Gear System
in your crank fan is producing rotational
motion, because it is being used to turn
the fan blades.
3. Attach a small piece of masking tape to the edge of one fan
blade and select a reference point so you can keep track of
the fan blade as it rotates.
(a) Turn the crank to make one rotation. Continue turning the
crank but vary the speed at which it is turned. How can you
make the fan turn faster/slower?
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Crank Fan Activity
(b) Mark the two gear wheels with either a dot sticker or with a
pencil mark. The marks should be made at the point where
the two gears mesh. Now turn the crank one slow turn. What
do you notice?
(c) Could there be a relationship between the size of the gears
and your findings to (b)?
4. (a) What do you think will happen if you use:
(i) a large gear wheel to drive a small gear wheel.
(ii) a small gear wheel to drive a large gear wheel.
5. Discover if your predictions were correct by rebuilding your
models with two gears that are different in size using these
images from page 3.
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