ScienceMakers Toolkit Manual - The History Makers

Engineering
Materials:
• Center tube from paper towel roll
• 5 feet of surgical rubber tubing
• 3 ft of cloth ribbon (do not use slippery ribbon)
• 2 ft of bell or iron wire
• C-clamp
• Pliers
Instructions:
1. Fold over about 1 inch of the rubber tubing and wrap it tight with a piece of wire. Twist the wire tight with
the pliers and while doing so, form a loop about 1 inch in diameter in the wire.
2. Attach one end of the ribbon to the other end of the rubber tubing with a piece of wire. Twist the wire tight.
3. Slip the wire loop over the screw shaft of the C-clamp. Tighten the clamp to the end of a table.
4. Lay the tubing and ribbon across the table. Place the paper tube on top of the ribbon at its free end and roll
it up snugly in the ribbon.
5. While keeping the ribbon from slipping, pull the paper tube back to stretch the rubber tubing. Release the
tube. The tube will be spun as the ribbon is pulled off, while at the same time it is pulled forward by the
contracting rubber tubing. With enough speed and spin, the paper tube will lift off the table and may fl y a
loop through the air.
What’s Going On?
When the paper tube is released, two motions are imparted to it. The tube is pulled rapidly through the air and
at the same time it is spun. The combination of motions generates aerodynamic lift. When seen from the side,
air is made to fl ow over and under the tube as the tube moves forward. The tube’s surface experiences a small
amount of friction with the air. As it spins, the friction drags air in contact with the tube’s surface around with it.
On the top of the tube, the air being dragged around with the tube and the air fl owing over the tube are traveling
in the same direction. Below the tube, the air being dragged around the tube and the air fl owing under it
are traveling in opposite directions. There, the air piles up and creates a small zone of relatively high pressure.
On top of the tube the pressure is lower. If the tube is moving fast enough through the air and spinning rapidly
enough, the over versus under pressure difference will be greater than the weight of the tube. The tube will begin
fl ying and it will do so as long as its air speed and rotation are maintained. This is aerodynamic lift.
Rotating airfoils have been added to the wings of some high-performance airplanes to increase lift under certain
fl ying conditions. At least one early airplane designer unsuccessfully tried to build a plane with rotating cylinders
instead of wings.
What do you think would happen if the paper tube were rotated in the opposite direction as it moved forward?
Place the ribbon on top of the paper tube and wind it up turning the top of the tube away from the rubber tubing;
this should wind the ribbon in the opposite direction as the fi rst trial. What happened when you stretched and
then released the rubber tubing? Did the tube have any lift? Why or why not?
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Alfred Brothers, Jr. - Video Clip Transcription
Clip 1 - Infl uential Teachers: I was having trouble with math in high school, you know, when I just couldn’t
quite seem to struggle through it. But that’s when the standardized tests helped. I took the SAT’s, and I scored a
700 in math. And my instructor said, “Wait a minute. You can’t score a 700 and have problems with my course.
What’s the problem?” And he also taught at night at Northeastern University. And I said, “I don’t quite get the