electric dodgem
These are quite easy to make but you have to understand the principle
Another version of the same thing

They tend to function better the smaller you make them.
This one I made the whole mechanism as simply as possible from bent wire
One bit of wire forms the 'maypole' and is taped to a plastic bowl
Another bit of wire forms the wheel bearing and also one pole of the battery holder, the other end is soldered to one of the motor terminals. A bit of spring wire forms the switch, it is shown above in the 'off' position; to switch the motor on the spring is clipped against the pole of the battery.
Movie
Another movie
This one has two AAA battteries instead of a single AA. Goes really impressively fast. You can only just see the end of the pivot behind the motor. Wheel is made from a large tap washer with spare cogwheel from motor/gearbox set pressed into centre.
They are easier to make square; doesn't work so well on carpet because no curved rim.
good site for motors etc
similar idea
3D printing
examples of parts made by 3D printing
impressive widget made by 3D printing
tink'n'toymouse
sphero
my email is davidvwilliamson@hotmail.com
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