A colleague of mine came up with this ingenious car design for our Maker Club at the public library. It is made from recycled materials and electronic components easily found at a dollar store.

Step 1: Supplies

One oblong piece of strong cardboard 5x7.5 inches
Two empty Bic-type disposable pen tubes
Thin rubber band
One water bottle cap with a hole drilled in its centre
Two large wheels (cardboard or large vitamin bottle caps with holes drilled in the centre)
Two fat rubber bands to put around the large wheels to give them traction (cut the rubber band and hot glue it onto the wheel if it’s too big)
One thin cardboard circle with a hole in the centre that is smaller than the big wheel, but bigger than the bottle cap
Two small wheels (Large lifesavers)
Duct tape
Two popsicle sticks
Two wooden skewers, one six inches, one seven and a half inches, plus an extra wooden skewer (size doesn’t matter for that one). Sharpen the ends of the shorter wooden skewer
Two small pieces of an eraser
One AAA battery holder with exposed wires (if yours does not have this, simply strip off some of the plastic coating on both the wires so that you have about an inch of exposed wire).
One alligator clip.
One toy motor (can buy a small personal fan at the dollar store and take it apart to get the motor or buy one from an electronics store/hobby store) with a ball bearing or small nut soldered onto the end. If you are new to soldering, there are various Instructables on it.
Soldering iron and solder

Step 2: Prepare the Chassis

Duct tape popsicle sticks lengthwise down the cardboard plank to give it strength.

Cover the cardboard with Duct tape on top to give it strength and so that you can tape down and move the motor later without tearing up the cardboard

Hot glue the pen tubes to the bottom of the cardboard (these are your axels)

Step 3: Front Wheels

Push the eraser pieces into the holed of the two large lifesavers. You may have to twist them to make sure they are firmly in place.

With the smooth side of the lifesaver in (if the rough side is facing in, it will bang against the side of your cardboard plank and slow the car down), poke the short wooden skewer into the eraser in the centre of one lifesaver. Make sure to push the skewer all the way through so that just a little bit of wood is sticking out the other side.

Put a blob of hot glue on the end of the wooden skewer that is sticking out of the eraser.

Put the skewer through one pen tube on the bottom of the car.

Put another lifesaver down on a desk, with its rough side down.

Lift the car up and poke the other end of the skewer through the eraser in the lifesaver that is on the desk. Do this gently or you may break the skewer.

Make sure the wheels are not too close to the sides of the car or they will not spin easily.

Put a blob of hot glue on the end of the skewer that is sticking out of the eraser.

Now you should have two small wheels on the front of your car.

Step 4: Rear Wheel #1

Take the longer skewer and push one large wheel onto it

Slide the wheel almost to the end of the skewer

Put hot glue around the end of the skewer to hold the wheel in place

Put the skewer through the other pen tube on the bottom of the car

Step 5: Rear Wheel #2 - the Gear

Gear Assembly:

This piece needs to be glued together on an extra skewer, so that the holes all line up and then you can transfer it to the skewer on the car:

Take the other large wheel and slide it onto the spare wooden skewer.

Run some hot glue around the lip of the bottle cap—be very careful not to let any glue fall in to the centre of the bottle cap where the hole is. Quickly slide the bottle cap with the hot glue onto the extra wooden skewer and glue it to the large wheel.

Put some hot glue around the edge of the top of the bottle cap—be careful not to get the glue too close to the centre hole or it will stick to the skewer and you need to be able to take it off the extra skewer and transfer it to the car.

Slice the thin cardboard piece onto the extra skewer and glue it to the bottle cap top.

When the glue had dried and cooled a little, pull the gear assemble off the extra skewer.

Back to the car:

Slide the gear assembly onto the wooden skewer opposite the other large wheel until it is close to, but not touching the car. There has to be some space so that the wheels can spin freely.

Put a blob of hot glue on the end of the skewer that is sticking out of the gear assembly to hold it in place.

Step 6: Adding the Power!

Twist one wire from the battery pack around an alligator clip—make sure it’s tight or the connection to the motor won’t be good.

Twist the other wire from the battery pack around one of the prongs sticking up out of the motor.

Now comes the tricky part!

You have to tape the motor to the car so that your thin rubber band, when wrapped around the gear assembly, is not too tight or too loose. Too loose and the car won’t move, too tight and you might burn out your motor.

Experiment with it until you feel you have the right distance, then duct tape the motor to the car. You might have to adjust the position later if you find your car is having trouble moving.