I honestly don’t get this. I see these absurd gear reduction videos, 25k:1, Googol:1, etc. The first gear is easy to turn but the last barely turns due to gear reduction. They always show themselves trying to turn the last gear by hand and it doesn’t turn easilly. Why is that the case? why can’t the last gear become the first if you turn it first?
In: Engineering
Gears are basically converting force to speed or vice versa.
If you rotate a gear with 20 teeth that’s connected to one with 10 teeth, the 10 toothed gear will rotate twice as fast. But you can’t get a free lunch with physics. In order to spin twice as fast, it has half as much force behind it.
The opposite is true too. If you spin the gear with 10 teeth, the gear with 20 will turn half as fast. But because it’s slower it has twice as much force behind it.
So in your example the ratios are extreme. The gears will have some friction and resistance between them. If you’re spinning the ‘smallest’ gear, you’re converting speed to force. So the last gear will spin very slowly, but has an immense amount of force behind it. Each gear in the train will spin slower, but with more force and each once can easily overpower the friction. But if you go backwards that isn’t the case. The force will decrease gear to gear until eventually it’s just not enough to overcome that friction. So the whole thing will lock up.
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