6
Education
®
(d) Determine the gear ratio of your crank fan. Write down the gear ratio in your
notebook and describe, in your own words, what the gear ratio means in
reference to their crank fan.
(e) What is gained by using this gear train? Did your fan turn quickly or slowly?
5. Use the table below to record your findings and repeat steps (4c-4e) with the small
gear as the driver gear and the large gear is the driven gear.
Gears are same size
Large driver gear moving
small driven gear
Small driver gear moving
large driven gear
GEAR TRAIN
FAN SPEED
GEAR RATIO
INCREASED OUTPUT
SPEED
VS. CRANK SPEED
(APPROXIMATE)
SPEED OR INCREASED
OUTPUT FORCE
6. Brainstorm how you can change the design of the crank fan so that the crank and
the fan turn in the same direction in your journal. Hint: What can you add to the
mechanism? This will introduce the concept of the idler gear.
