Make a robot that wiggles, wobbles and dances around thanks to a homemade cam.

Step 1: Materials List

Cardboard sections (scrap) (5x7ish)
Plastic bottle
Skewer
Hot glue/glue gun
Straws
Scissors
Metallic card stock (or whatever you want to make your robot out of)

Metallic markers
Metallic pipe cleaners

Step 2: Make Your Robot!

Make your robot (or other fun thing) that will wiggle and wobble when you're done. Make sure it ends up around the size of a 3x5 note card. (We used metallic cardstock, metallic sharpies and silver pipe cleaners.

Step 3: Cut Water Bottle Top Off

From tip to cut line should be around 3” tall. We just cut "above the label".

Step 4: Punch Holes

Punch 2 holes in bottom of bottle section on either side around 1/2 way up.

Step 5: Glue Straws

Cut two 1” segments of straw. Put hot glue on outside of bottle holes and insert both straws halfway into the holes. Place skewer inside the straw to ensure that they line up while the glue hardens. This is where the rod for your cam will rest & rotate. Remove skewer once glue hardens.

Step 6: Cut Out Cardboard Pieces, Punch Holes

Cut out two cardboard circles- One 1 ½” diameter, one 1 ¼” diameter. Cut out two cardboard squares- ½” x ½” each. Punch hole in smaller circle (off center!!! very important!!!) and both squares (center).

Step 7: Make the Top of the Mechanism

Cut a section of straw 2” long. Add lots of glue to a 2” straw section and slide it through the drinking hole onto the horizontal circle. Using your fingers, make sure the straw fits firmly onto the cardboard. Hold until glue is hard. Put this into your bottle so that the straw goes through the opening where you would drink.

Step 8: Make the Bottom Part of the Mechanism

Slide one rectangle onto the skewer with a little bit of the skewer sticking out. Glue into place. Line up circle with hole with the center of the bottle’s opening (where you’d drink from) and glue. Add second cardboard rectangle to the opposite side of the skewer, making sure it will make a “sandwich” which will not let the skewer move left to right. Glue. This is your cam.

What’s a cam?

A mechanism A wheel with a projection sticking out. As the wheel turns, the projection turns too, making sliding contact with another part and imparting motion to it. See how one side of our cam (circle) is bigger than the other side relative to the skewer (because the skewer is off centered)? This is the “projection”. As the skewer turns the cam, the height of the circle changes (because it is uneven). As this happens the cam pushes (imparts motion to) our horizontal circle up and down at different heights. Our cam is transforming the nature of the motion from a rotating motion to a vertical motion.

Step 9: Test!

Test the rotation, if the cam circle is too large you may need to modify it by cutting it smaller. If it dips down too low and hits the table, cut off an extra section of your water bottle and make your machine taller. Keep modifying until it works as desired.

Step 10: Add Skewer Segment to Robot

Place skewer into vertical straw to make sure it’s long enough, it should stick out at least 1/4 “. Glue/tape robot onto part of skewer that is sticking out.