This video shows a quick little project to make a top spin forever - or as long as the batteries last which in this case could be days. It is based on the work of Roger Wayne Andrews who patented the idea and named it "Novelty Electric Motor". The photo shows Andrew's patented ideas for the spinning top that has been used to produce a novelty toy that you can buy.
It uses a simple little two transistor circuit described here: http://www.trainelectronics.com/Pendulum/article.h...
I simply added two neodymium magnets to the bottom of a plastic top and then rotate this over a wire coil. When the magnet rotates toward the coil it triggers a transistor to supply power to the coil which then repulses the magnet as it rotates over the coil.
It doesn't do much but spin but it should run for days on a set of batteries and shows the power of adding a little bit of energy to a flywheel device.
Hope you enjoy the video.
Update: of course you can always find a better way to build a spinning top. This video shows how to do it without the complicated circuit: