Occasionally, I need to send one of my robots on an errand somewhere on the little island of Kia Ora where I and the other Zoobers work. Sometimes I need a coconut (excellent material for robot heads); other times I need pretty shells from the beach. I can’t send my robots out on a hovercraft, however, because the ground is too rough. Instead, I place them on a Whipmobile, a little car that uses the springy energy of a flexible twig for power.
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SAFETY KID SAYS: “This is one of the more complicated projects in the book, and it requires the use of a glue gun, so you should have a grown-up around to help!” |
Materials
1 piece stiff cardboard, about 4 inches by 6 inches
Two ¼-inch-diameter wooden dowels. One should be 8 inches long and the other should be 4 inches long. You can buy dowels from any hobby or hardware store, and they will probably be happy to cut the dowels to the lengths you need.
4 large wooden spools (see Sources, page 77). Make sure the holes in the spools are larger than the diameter of the dowels so the dowels can turn freely.
1 Cut the cardboard as shown in Figure 1. Make sure that the width of the cut-out portion (shown in Figure 1 as 2.5 inches) is wider than the length of the spool.
2 Center the 8-inch dowel across the width of the cardboard and hot glue it to the cardboard about 1 inch from the top edge, as shown in Figure 2. Wait a minute for the glue to harden.
3 Place 1 spool on either end of the 8-inch dowel.
4 Hot glue the pennies to the 8-inch dowel as shown in Figure 2. This will keep the spools from sliding off the dowel. Wait a minute for the glue to harden.
5 Place the third spool on the 4-inch dowel and hot glue the dowel to the cardboard so the dowel and spool are centered in the cut-out area, as shown in Figure 2. Wait a minute for the glue to harden.
6 Flip the cardboard over and glue the fourth spool in the middle of the cardboard, as shown in the illustration at right.
7 Stick the springy twig in the fourth spool. It should fit snugly. Tie the piece of thread or fishing line to the tip.
8 Tie the other end of the thread around the third spool (the one on the 4-inch dowel) and secure it in place with hot glue.
9 Wind up the spool so that the twig bends, set the whipmobile on the ground, and let it go. Make two or more and have a race!
HOW IT WORKS: Just like in a real car, power from the engine (in this case, a twig) is transferred to the wheel of the Whipmobile, which propels it on its merry way.
Figure 1