Dr. Gadget's Science Machine
How you can make cardboard dragsters and a racing ramp
By Joe Laszlo
 |
| Mililani Mauka Elementary School fifth-graders Michael Tanigawa and Kent Yamada with miniature race cars made of cardboard.
Deborah Booker • The Honolulu Advertiser |
Aloha! This week we're continuing our discussion of wheels and motion. So let's have some fun by making dragsters and having some races!
To build a dragster from simple items around your house, you'll need:
- A piece of cardboard that is 4 by 8 inches long (you can use corrugated cardboard, but a better kind is found on the back of a legal pad).
- A soda straw for your bearings.
- A bamboo skewer for your axles.
- A nail the same diameter as the bamboo skewer.
- Scissors, glue, a pen, a ruler.
- Two pairs of different-size plastic bottle caps for the wheels; the two front ones will need to be matching smaller bottle caps, and the two rear wheels should be matching larger bottle caps.
- Cut the cardboard to the shape shown here, and draw the two lines on it. Score the cardboard along the two lines by going over them repeatedly with a ballpoint pen. Fold the edges down. You should have a streamlined wedge-shaped body (Figure 1).
- Make holes on the front (1 inch back and near the fold) and 1-1/2 inches foreword of the rear end. Make the holes large enough to allow the soda straw bearings to fit through. (Figure 2)
- Cut a 2 1/4-inch piece of straw to create the front bearing. Cut a 3 1/4-inch piece of straw to create the rear bearing. Put each straw through the holes with equal amounts of the ends protruding on each side.
- Cut a 2 3/4-inch piece of skewer to create the front axle. Cut a 3 3/4-inch piece of skewer to form the rear axle.
- Make a hole in the center of each set of the two plastic bottle-cap wheels. To find the center, draw around one of the caps on a piece of paper. Cut out the circle. Fold the paper twice, then unfold it. The center is where the fold lines cross. Make a small hole here. Place the paper onto each of the caps. Mark the centers. Repeat this with the other set of wheels.
- Using the nail, carefully make a hole in each bottle cap (Figure 3).
- Test fit all of the wheels onto the axles.
To assemble the dragster:
Put one small wheel onto the front skewer axle, cap top in. Thread the skewer through the front straw bearing. Put the other small wheel on the other end of the skewer axle.
Repeat with the rear axle.
Use white glue or an electric glue gun to secure the wheels.
The dragster is done! Make several, and let's race them!
Make a cardboard ramp 8 inches wide and 24 to 36 inches long, with the corrugations running long ways. Tape one end to the floor where you will have a long run. Prop up the other end. Put two dragsters or a dragster and another car at the top. Let them go at the same time. Did one go faster and farther? Why did this happen? Because there was less friction between it and the track and floor, and in the wheel bearings. If they went the same speed and distance, their friction was equal.
If one was heavier, did it go farther? The great scientist Galileo said that all things are pulled equally by gravity, so weight has nothing to do with it. Only friction matters.
Until next time, a hui hou!
Write to Dr. Gadget, c/o The Honolulu Advertiser, P.O. Box 3110, Honolulu, HI 96802, or fax 535-8170. You may send e-mail to ohana@honoluluadvertiser.com only if you're 13 or older. "Dr. Gadget's Science Machine" is written by Joe Laszlo, a retired science teacher and winner of a Presidential Award for Excellence in Science Teaching.
