Potential Energy Road Roller

this is a home made eco friendly toy (made of junk materials) for good clean fun!

Rubber bands and springs store a lot of pottential energy. Here we’ll harness the potential energy in a rubber band to drive a mini road roller!.

I used to make these back in school.. we used to race them.. because of the low speed they had a lot more traction than other "toys" and hence could be raced uphill.. over all kinds of uneven surfaces. 

You will need: 

1) Two bottle caps(plastic, metal or even crown caps can be used
2) One nail to make holes in the caps
3) One hammer to use with the nail
4) A rubber band
5) Two toothpics, or any other sticks of the same length
6) A wax candle
7) A piece of cardboard.. a little bigger than a visiting card
8) A pair of Scissors

Carefully place the nail at the center of the bottle cap..
and hammer it in.
After pulling it out, do the same to the other cap as well.
Now both caps will have holes in their centers.

Measure a piece of the toothpick.. so that its the diameter of the bottle cap..
break  off the extra bit, and then place it with a rubber band as seen below

place the other bottle cap over the end and pull the rubber band out that side

cut off a bit of the candle.. about the same height as a bottle cap
clean the hole with the nail.. 

use a bit of metal wire to pull the rubberband through the candle’s hole.. 
On the other end remove the wire and shove a toothpick through the rubberband to lock it in place..

if you feel the short stick might fall out on its own, you can tape it down.. 
don't do anything to the longer stick though!

Roll the piece of Cardboard around the hammer’s handle so that it curves neatly..
pull the two bottlecaps apart and put the cardboard roll between the two caps..
(the rubberband will be running through the roll)

ALL DONE! the next step shows you how to use it..

To make the road roller move, just wind up the rubberband, by turning the longer stick.. and then place it on the surface and watch it go!