Elastic Power Car

In this instructable we create an elastic (rubber band) powered car from scrap material. The car uses a few important physics principles to travel and also teaches skill to use the all important GLUE GUN!  There is a lot of variations of elastic powered "cars" and this variation adds a little elegance to the bunch. This one also does not get your fingers caught in a mouse (or rat) trap. I have built three versions to date, all using different chasis and this one, although not the fastest, is the one that travels the longest distance.

Step 1: Materials and Tools

Look at the pic and improvise..  This is a very flexible piece of work that can be modified as you go along. Ignore the soldering iron in the tool picture, it was taken from another instructable.

Main ingredients:
Plastic drinking straws
Bamboo/wooded skewers
Small (25ml) plastic containers
Old/used optical media for wheels
Other plastic caps for wheels (Size does not matter!)
Epoxy glue
Glue-gun glue
Paper clips
Elastic band
Cotton yarn
Paint (optional)

Step 2: Rear Shaft and Lever Assembly

Use three wooden skewers (one cut short) and make a cross as shown in the picture. Stick everything together with epoxy putty. There are other ways to do this, but I found this the easiest and fastest way.

Step 3: Drive Preparation

I melted notches and holes into the plastic cups I selected with a hot nail.

Step 4: Complete the Drive

Use your glue gun to attach the plastics cups (or whatever you chose) to the rear-axle cross assembly.

Step 5: Build the Chassis

Look at the pictures and use your glue gun to assemble the chassis as shown. I have not added any dimensions to this design. Figure it out as you go along.

Step 6: Attach Drive Assembly to Chassis

The drive assembly which will help add stretch to the rubber band is attached to the rear wheels. The drive assebly which is fixed to the rear axel should allow the wheels attached to also rotate freely.

Step 7: Make the Drive Wheels

Make  a hole through the bottle cap with a hot wire. Glue the cap onto the CD/DVD as shown. It should be in the centre. The wheel, when fitted on the axle, should not be able to move. The axle transfers rotational movement to the wheels.

Step 8: Complete Drive Assembly

Trim the drive assembly stop so that it just hooks and stops on the chassis. It will prevent the car from flipping over.

Step 9: Cosmetics

Gather everything you made so far and give it a good spray-paint. This step is not required but I chose to do so for this instructable.

Step 10: Add the Power Source

Tie two rubber bands together. Slip one open end over the lever arm and attach the other end to the chassis as show in the next step. 

Step 11: Power Source Continued

Attach the other end of the rubber band to the opposite side of the chassis using a piece of bent wire (from a paperclip). The lever arm should now be able to be stretched out when rotated.

Step 12: Attach the Wheels

Attach the wheels to the chassis, making sure that the drive wheels remain stationary on their axles and that the wheels on the drive assembly  are able to move freely. Use a plastic tube as spacer to make sure the wheels do not touch the chassis but that they turn with as little friction as possible. (A little lubricating oil may help)

Step 13: Drive Assembly Hookup

Attach a small piece of wire to the drive axle using tape or glue. Tie a loop at each end of a cotton thread. The cotton thread must be long enough to reach from the drive axle to the outstretched tip of the drive arm. 

Step 14: Attach the Drive Thread

Use a piece of plastic tubing (or glue) to secure the one end of the cotton thread to the tip of the lever arm. Remember that the thread must reach from this position to the snatch on the drive axle.

Step 15: Wind It Up & Let It Go!

Hook the free end of the cotton thread to the snatch on the drive axle and wind the wheels until the lever touches the axle. Set the car down on a smooth surface and let it go!