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
Gear reductions work this way: You have two gears, one of them is small and the other is big, but both share the same size of ‘knobs’ (idk the terminology). So you have the big gear with 24 knobs and a small one has 6, that is a ratio of 4:1, because it takes 4 full rotations of small gear to rotate the big one once (each knob has it’s match, but the small ones are lapping before they meet their match, so they have multiple, in this case 4 knobs matched to each of them).
To make a ridiculously high gear ratio, you hard attach big and small gears in pairs, so when you spin the small gear the big one (having the same rotational velocity) is moving small gear of the next set, and in turn moving next big gear with a ratio. You can imagine it as actually having a chain of ratios 1:1 (fixed together) > 1:4 (interacting) > 1:1 > 1:4…..
Now, this is working pretty easily one way, because when you move in the direction of 1024:1, you’re making one rotation on the first gear, then 1/4th of a rotation on the second, 1/16th on 3rd and so on. When you try to go 1:1024, you’re trying to move 1st gear one time, the second 4 times, 3rd 16 times and so on. (someone do the math)
As you can imagine spinning last gear, by reverse, even a fraction of a googol times would take a lot of energy, not to mention friction between gears and chassis, and rotating each gear in between the last and the first.
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