## Introduction: Cardboard Ball Chaser

Did you ever have one of those physics challenges where you have to retrieve a ball using no electrical, magnetic or nuclear energy? Here's the basics for one solution.

You will need cardboard, glue, pencils, rubber bands, tape and weights (wrap coins in a roll if nothing else comes to mind).

## Step 1:

Draw circles for pretty big wheels--I used a one gallon paint can and that provides about 7 inch diameter circles.

Cut the wheels.

## Step 3:

Find the center of the wheel. I used a ruler to draw an edge to edge line 140 mm long. I marked the 70 mm point and drew a perpendicular line (90 degrees from first line). Repeat in another spot. The intersection of the perpendicular lines is the center of the circle.

## Step 4:

Cut four 1 1/2 inch wide strips of cardboard. They will be folded in three segments--two inch; five inch; eight inch.

## Step 5:

You will have two pieces (each piece is composed of two pieces) that must be glued together in a rectangle.

## Step 6:

Poke or drill holes in the rectangle. Make sure that the pencils (axles) can turn freely.

## Step 7:

Insert and glue one wheel.

## Step 9:

Repeat for the second axle.

## Step 10:

Cut out the ball catcher.

## Step 11:

Glue the ball catcher to one end of the vehicle.

## Step 12:

Cut a flap (about 4 1/2 inches by 3 inches) and tape to the ball catcher opening.

## Step 13:

Cut and glue triangular support pieces to keep the ball catcher "square" (and away from the wheels).

## Step 14:

When the vehicle passes over the ball, the flap will rise and the ball will remain in place.

## Step 15:

When the vehicle has passed the ball, the flap will drop down. When the wound rubber band reverses the vehicle, the ball will be trapped and pushed back into the starting square.

## Step 16:

I had to add three layers of support onto the rubber band driven wheels to keep them from wobbling and breaking loose from the pencil.

## Step 17:

I also added weight to the front and rear of the car to make it roll and return better.

Wheel size, weight addition, rubber band strength, angle of starting incline--these are all variables that will combine to create success or frustration in the build.

## Step 18:

Enjoy the ride!

Participated in the
Cardboard Speed Challenge