How to make a rubber band powered car?

Question

I have to make a rubber band powered car for 9th grade physics, okay? And it has to have at least 3 wheels, it must be powered by at least 1 or more rubber bands, and it must start from a resting position and can't be catapulted or slung into motion, and it must operate without intervention. HELP PLEASE!!!

Answer 1

Make the back wheel like this.

o-----o

Tie the rubber band in the middle and then tie the other end to the bottom of the car.  Then wind the wheel axle and it will turn.

Answer 2

Try a crank shaft. take the two back wheels wrap a string around them or fishing wire is better. Now tie the other end of the fishing wire to the rubber band. toward the front of the car have a hook to grab one end of the rubber band. Now when you put the car down pull the car backwords. This should wind the fishing wire around the back wheels while stretching the rubber band. Let the car go and it will go foword.

here is a little sketch if you would

() c===-----()

() Wheels

c Hook

= rubber band

- fishing wire

Hope this helps!  Best of luck to you!

Answer 3

This is easy if you can find an erector set.

Build a three or four wheel cart, but with the two-wheeled part facing forward in the direction you want the cart to travel.  Place and attach a small peg along the cart's center line and near the front of the cart.

Now wrap one end of the rubber band around the peg.  Then scotch tape the other end to the middle of the axle running between the two front wheels.  Now turn the wheels so the rubber band wraps around the axle and tightens   Make sure you wrap in the direction that will cause the wheels to rotate forward in the direction you want the cart to move.  That means you will need to rotate the wheels away from the direction so when they unwind they will rotate forward.

Hold on to the wheels as you put the cart down on the ramp/floor and then let go.  As the potential energy in the stretched rubber band is unleashed, the rubber band will unwind and take the wheels with it.  The rotating wheels will propel your cart as required without slinging or catapulting.

Note, if you don't use too much scotch tape, the rubber band will detach from the axle when it reaches the end of unwrapping.  This will allow your cart to coast for a while; otherwises the rubber band will start to rewrap, but in the opposite direction and cause the cart to slow down in a hurry.