
Making a Googol:1 Reduction with Lego Gears [video] - DamnInteresting
https://www.youtube.com/watch?v=QwXK4e4uqXY
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syats
The video is very good. i) It teaches basic gear-ratio concepts ii) it
showcases an amazing repertoire of reduction modules, iii) it poses
interesting questions regarding power transmission like: how much power is
being dissipated throughout the system? or.. where is all the power of the
motor going if you leave it running for 1 hour? iv) it motivates borderline
philosophical question like: is the figurine at the end actually moving at all
due to the gears? v) it has really good video editing / camera work

~~~
frabert
On a practical level: no, it's not moving at all since all the movement is
being absorbed by the slack between the gears.

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StavrosK
There's a video of one of these constructions where the last gear is bolted to
a wall or something.

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sgerenser
Might be think of “machine with concrete”
[https://m.youtube.com/watch?v=5q-BH-
tvxEg](https://m.youtube.com/watch?v=5q-BH-tvxEg)

~~~
lumberingjack
I feel like doing the project in Lagos is going to confuse people but when you
put the final gear bedded into concrete that sort of gets the point across

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simoneau
See also "Machine with Concrete", by Arthur Ganson
[https://www.arthurganson.com/concrete-1](https://www.arthurganson.com/concrete-1)

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dmos62
I remember this art installation that was spinning gears setup in a high gear
ratio and the last gear was cemented. When looking at it you couldn't help but
picture the gears and the motor starting to grind against the resistance of
the cemented gear, but the reality was that that wouldn't happen for many many
years.

~~~
zimpenfish
[https://www.youtube.com/watch?v=5q-BH-
tvxEg](https://www.youtube.com/watch?v=5q-BH-tvxEg)

"With the motor turning around 200 revolutions per minute, it will take well
over two trillion years before the final gear makes but one turn."

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rafaelturk
Now put the motor on the back end and watch the first gear spinning at the
speed of light!

\- from youtube Timon Di Mare's comment

~~~
throwaway_pdp09
Were one to do this assuming hypothetical material that wouldn't break up
under the stress, _nor expand due to stress alone_ \- hypothetical like I said
- reversing it would cause relativistic expansion + general weirdness at the
fast end. Wouldn't that expansion cause the gears to hbe forced apart and
rupture, or something? I have a feeling it would somehow not but I can't
imagine what would happen. They must expand, yet still remain engaged, which
seems contradictory.

~~~
zaarn
The material will break eventually. Other gears provide some structural
support against expansion, but that is not what is going to break a gear. IMO
the thing that would break it would simply be the mass of the gear; the fast
acceleration would tear the gear out of it's axis or break it's teeth.

If it doesn't, at some point the material will give, likely away from the
driving gear, and the entire thing will fling itself apart.

~~~
throwaway_pdp09
Of course it would, which is why I talked about a hypothetical material.

If it did not, though, what would relativity make it do?

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ses1984
I'm not a physicist but it's hard to have a thought experiment where you
introduce ideas like ignoring materials strength, because that could be a
factor in what relativity would make it do.

Anyway as you approach the speed of light the energy required to accelerate
approaches infinity, so you would just not get it there because of the energy
requirement.

I think a simpler version of this experiment is a really long rigid rod. What
happens if you pick one end of the rod to be the axis and then you try to
rotate the rod about the axis?
[https://physics.stackexchange.com/questions/455189/rotating-...](https://physics.stackexchange.com/questions/455189/rotating-
rod-in-special-relativity)

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danfromberlin
It's safe to say that any human capable of rotating that lego man, even just a
single degree within his or her lifetime would cause the outer rim of the
input gear to move at orders of magnitude beyond relativistic baseball[0].

[0] [https://what-if.xkcd.com/1/](https://what-if.xkcd.com/1/)

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tzs
I have no idea how the physics of this works.

At first it seems pretty simple--but at that overall reduction a small motion
at the motor end translates to a motion at the far end that is ridiculously
smaller than the Planck length. The motor end is a simple classical physics
system, but that thing is a quantum system on the far end.

I have no idea how to figure out what would actually happen if you let that
run for long enough that the far end should have moved significantly according
to classical physics.

~~~
Akronymus
It will move but in such a small range, that the wobble of the atoms is MUCH
larger over a "short" amount of time, than the effective movement of the axle.
So, at some point, the wobble would just shift slightly.

And tolerances exagerrate that by a LOT.

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omginternets
Ha! I wonder (having no mechanical engineering background) ... is it possible
to to drive e.g. a tank up a hill using a lego motor with a large enough gear
ratio?

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layoutIfNeeded
No, because the plastic gears connected to the drive wheel would snap under
the immense torque.

~~~
omginternets
Right, sure. In my mind, I was more interested in the relationship between
gear-ratios, torque and the displacement of weight.

What if the motor gears were infinitely strong? That is: is the power output
of a small electric motor theoretically sufficient to drive a tank up a hill
with an arbitrarily large gear ratio?

~~~
simias
You can trade torque for speed basically. So yes. "Give me a lever long enough
and a fulcrum on which to place it, and I shall move the world". That being
said it would be so slow that you'd probably break something before you've
moved a millimeter.

The same Youtube channel demonstrates how to use gear reduction to increase
torque and bend a steel bar with legos:
[https://www.youtube.com/watch?v=jRn5waE0qfk](https://www.youtube.com/watch?v=jRn5waE0qfk)

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coinerone
I want to turn the last Gear backwards to see how fast the first Gear is
rotating.

~~~
k_sze
You probably won't be able to turn it at all with bare hands due to the sheer
friction of the first few gear axles at the other end being amplified so much.

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aequitas
The friction of one wormgear is already enought to prevent rotation in the
other direction. But with this many, impossible.

I also doubt if any of the gears except for the first ones rotate at all
before the first gears are worn through, let alone before the battery to run
out.

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amelius
Are these original Lego parts?

~~~
bonzini
Yes, unless noted otherwise he only uses original parts.

For example, in one video he uses Lego-compatible steel axles.

~~~
whywhywhywhy
Anyone know what set the weird giant wheel at 1:35 is from?

~~~
bonzini
[https://rebrickable.com/parts/44556/wheel-22-x-172-with-
fins...](https://rebrickable.com/parts/44556/wheel-22-x-172-with-fins-and-
inner-168-tooth-gear-hailfire-droid-wheel/8/)

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hoppla
Wonder how much energy is required to turn Zeus around a turn.

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theqult
what if you try to spin it the other way around ?

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doublesCs
Now do Googolplex:1

