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OBJECTIVES:
In this lesson you will study the aerodynamics of cycling.
Aerodynamics affects the speed of both athletes and their equipment.
You will work in teams, design and modify the shape of your
team's helmet to make it more aerodynamic.
Each team will modify an
inexpensive cycling helmet.
You will test
your team's helmet to determine if the drag has been reduced.
You will learn:
about aerodynamic forces and in particular, drag;
how those forces affect cycling performance (speed);
the design of cycling helmets for optimum performance.
You and your team will:
examine the helmet;
determine factors that may reduce the aerodynamic drag on your helmet;
use simple materials (tape, foam, etc.) and modify your helmet;
test your helmet to determine sources of drag on your helmet.
STEPS TO FOLLOW:
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Review the information in the
background section.
(The background section
is thirteen pages long.
Continue to click "Next Page" to see all thirteen pages.)
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Examine the different characteristics of your helmet. Using the Internet and a web browser, look at the designs of other helmets.
Question: Where will you look on the web, i.e. what types of web sites? Write
this information down on your worksheet.
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Cut about 50 short tufts of yarn (about 2 1/4 inches long each).
Cut a piece of transparent tape long enough to reach from the right to left side of the helmet. Place the tape on a flat surface with the sticky side facing upwards.
Space the tufts equal distance from one another and carefully press the tufts down onto the tape. Apply the tape onto the helmet so that the tape attaches to the left and right sides of the helmet (not from the back to the front of the helmet).
Repeat this process, making at least 4 rows of tufts. Be sure to place
some tufts on the backside of the helmet.
Remember the visual signs of drag:
Tufts that move around chaotically are a sign of drag.
Tufts that move in the direction opposite to the airflow are a sign of high
drag.
Tufts that stay in line with the airflow are a sign of lower drag.
Tufts Indicate The Direction Of The Airflow
With Permission and Courtesy Of
Kurt Long, US Navy
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MATERIALS:
Electric Fan Or Blow Dryer
Inexpensive Cycling Helmets For Each Team
One Additional Cycling Helmet To Serve As The Test Model
Yarn - In a Color Which Contrasts With The Bicycle Helmets
Transparent Tape
Mesh Screen (Optional)
Ball (Optional)
You may consider using some or all of the items listed below:
Styrofoam
Duct Tape
Children's Modeling Dough
Glue Guns and Glue Sticks
Rubber Cement Or Other Heavy Duty Glue
Small Safety Hand Saw
Hobby Knife
File
Sandpaper
Fabric Mesh
Pencil
Colored Pens Or Stickers
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Place the fan on a table or chair (or hold the blow dryer in your hand.)
Turn the fan on.
(Optional) The airflow from the fan probably will not be
flowing in straight lines. One technique to straighten the flow
is to place a mesh screen between the fan and the
object you are studying (in our case the helmet).
If you decide to use the screen, position the screen vertically
about
3-6 inches from the fan. Have two people hold both sides of the screen vertically.
Turn the fan on. The air will blow through the holes in the screen and flow
in straighter lines.
Place the helmet on a ball or place it on your fist about 12 inches from the screen. You may have to vary
the distance based on the power of your fan.
Observe how the air
flows over the unaltered helmet. You can alter the angle that the
air strikes the ball by rotating the helmet on the ball.
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On your worksheet,
list and draw the characteristics of your helmet that you would like to change.
Be as specific as possible.
For each feature you propose changing, write down on your
worksheet why you think
it will improve the aerodynamics of the helmet.
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Using the materials supplied (foam, tape), modify your helmet.
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Double check to be sure that nothing will fall off of your modified helmet.
Once you are confident that all of your modifications are securely attached to
your helmet, add tufts to your helmet and repeat Step 4.
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Compare your modified helmet's drag to the other helmets in the class. Which helmet had the least drag and why? Which helmet had the most drag and why?
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