Straw Propellor

Ever feel like you've wasted your breath on something? Well now every breath you take is going to spread total wonder and joy with this straw propellor. Also a bit of saliva!

With three straws only you can create this double-spinner of a physics lesson in forces and air pressure. It takes a bit to get started, but once you get the dynamic, you can modify to make some pretty wonderful designs.

The details:

• What: A Straw Propellor!
• Time: ~ 10 minutes first time, 3 minutes after
• Cost: ~ 5 cents
• Materials:
  • 2 large straws
  • 1 skinny straw
  • Tape
• Tools:
  • Scissors
• Concepts: Air Pressure, Forces, Newton's Laws

(Thank you to our propellor model Charlie!)

Start by cutting these two holes spaced apart on the skinny straw. Fold it back, and cut out a triangular wedge so that when it unfolds, it makes two diamonds.

Keep some distance between the two to, because this is where the large straws will go and you don't want them getting tangled with each other.

Tape off one end of the skinny straw so that when you blow in to it, air can only escape out the two holes. Trim off excess tape.

Take your first large straw and cut a through-hole by bending it in half, and making a diagonal cut on both sides of the fold. See the diagram for details and play around with it. It should come out looking like the photo.

Tape both ends of the straw closed so that the straw is squeezed flat. When you look through the through-hole, the flat ends of the straw should be perpindicular to the ground. This is important for getting them to spin.

So again, hold the straw up to eye level so you can see through the through-hole. The ends of the straw should be pinched together and taped such that the flat edge is pointing up and down.

Now it's time to cut notches in the end of the big straw. Cut a triangular wedge on the top-side of the left end of the straw and the bottom-side of the right end of the straw.

This is so that when air gets pushed out the ends of the straw, with the forces going in opposite directions, it will cause the straw to spin.

Check out the first diagram for details on this.

Thread your skinny straw in to the through-hole. I like making a tape stopper around the skinny straw to keep the the large straw in place while it spins.

Go through all the steps with the other large straw and then make a tape stopper so it can spin around the top hole.

Give it a whirl! It's not going to spin itself! It may not look like a lot sitting at the table, but when you spin it, mighty times are had by all.

You can experiment with all sorts of variables including:

• Number of spinning straws
• Length of straws
• Size of Holes
• Orientation of holes

Let us know any great designs you come up with!