@i will invent and then when you put your 100 density gears on a mobile object, I'm sure you will be able to make realistic light weight transmission system .(sarcasm)
Since those rings have quadratic attraction, the speed in which objects get pulled are exponential increased, therefore at the centre the amount of attraction (in a sense) is near infinite.
http://www.algodoo.com/algobox/details.php?id=32299
make a slow recharge using this script (you will have to add your own little bit to make it add "energy" though)