We created a generator with Legos that uses gravity to drive it to generate electricity. As you can see in the video we used a motor from a Lego Mindstorm kit and some Lego gears. We used a soda bottle weight and counter weight connected by a string to spin a tire on the generator. The table was about 39 1/2 inches off the ground. I have not calculated the final rear ratio. At the half way point in the video you can hear the Lego gears spinning.
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