## Uses of 1:11 Million Gear Ratio

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jewish_scientist
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### Uses of 1:11 Million Gear Ratio

This gear box has a gear ratio of 1:11,373,076 and only turns in one direction. What is an application of such an extreme reduction?
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ucim
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### Re: Uses of 1:11 Million Gear Ratio

Have you heard of The Long Now? They are developing a clock to run for 10,000 years. I suppose this compact gearset would let you run the century hand of a Long Now watch. If the plastic lasts long enough.

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sardia
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### Re: Uses of 1:11 Million Gear Ratio

jewish_scientist wrote:This gear box has a gear ratio of 1:11,373,076 and only turns in one direction. What is an application of such an extreme reduction?

This is a pair of planetary gears attached together, otherwise known as Epicyclic gearing.
https://en.wikipedia.org/wiki/Epicyclic ... g#Benefits
Planetary gear trains provide high power density in comparison to standard parallel axis gear trains. They provide a reduction volume, multiple kinematic combinations, purely torsional reactions, and coaxial shafting. Disadvantages include high bearing loads, constant lubrication requirements, inaccessibility, and design complexity.[9][10] The efficiency loss in a planetary gear train is 3% per stage.[citation needed] This type of efficiency ensures that a high proportion of the energy being input is transmitted through the gearbox, rather than being wasted on mechanical losses inside the gearbox. The load in a planetary gear train is shared among multiple planets, therefore torque capability is greatly increased. The more planets in the system, the greater the load ability and the higher the torque density.The planetary gear train also provides stability due to an even distribution of mass and increased rotational stiffness. Torque applied radially onto the gears of a planetary gear train is transferred radially by the gear, without lateral pressure on the gear teeth.
That's the benefit.

morriswalters
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### Re: Uses of 1:11 Million Gear Ratio

jewish_scientist wrote:This gear box has a gear ratio of 1:11,373,076 and only turns in one direction. What is an application of such an extreme reduction?
I doubt there is a practical use for that particular gear set. I doubt that there is a material that you could make it out of that would survive his suggested use. Remember that the output is high torque. He can make the gear out of plastic because he never loads it.

Soupspoon
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### Re: Uses of 1:11 Million Gear Ratio

Incredibly high torque sort of reminds me of this. (Though it is to be assumed with the Axle that there is sufficient (improbable) strength throughout the whole Axle, that mechanical failure would occur only on the linkages designed to transfer this torque towards whatever final resistive task overcomes the weakest link. Whilst designing even a torque-'proof' planetary gearbox still leaves a concentrated failure-point in the material of the output shaft (or, without bracing against counter-torque, depending on what the gearbox body associates with, the input one) where it would be vulnerable to sheering if not made of sufficiently strong unobtanium to out-perform the subsequent adamantine linkages.)

Zamfir
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### Re: Uses of 1:11 Million Gear Ratio

A telescope comes to mind. If you want to keep a telescope pointed at a fixed point relative to the stars, it has to rotate with a speed of 1/day, or 1/1440 minutes.

At a gearing ratio of 11 million, you get a drive speed of 7000 rpm. That's in the ballpark for a small electric motor.

I don't know if the telescopes are a real application. I do know that solar panel sun-trackers sometimes use high gear ratio, but not that high. 100,000 or so. I suppose they don't rotate those truly continuously, but in short bursts.

Copper Bezel
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### Re: Uses of 1:11 Million Gear Ratio

Yeah, I'd kinda envision using a stepper motor for that application, really. Itself tied to a reducing gearbox, but still.
So much depends upon a red wheel barrow (>= XXII) but it is not going to be installed.

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morriswalters
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### Re: Uses of 1:11 Million Gear Ratio

Well I looked. At least one of the telescopes at Hawaii uses hydraulic motors. At least 3. Palomar also used multiple motors on the main drive ring at the time of construction, synced together. I speculate that hydraulic motors are used so all three motors turn at precisely the same speed, and that 3 are used so that the torque is split by three. I assume that this keeps the ring from distorting under load.

Edit
I'm trying to decide if Soupspoon is making fun of me or if he is always incoherent. I'll go with making fun at me.

Soupspoon
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### Re: Uses of 1:11 Million Gear Ratio

morriswalters wrote:Edit
I'm trying to decide if Soupspoon is making fun of me or if he is always incoherent. I'll go with making fun at me.

I'm often incoherent, and (checking to see what I might have said to provoke this query) I'm not sure it was making fun of anything, but rather I was riffing on an existing hypothetical to explore possible answers.

But, as I said, I am not always laser-like in my coherence. Take whatever message you want from it. Or none.

morriswalters
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### Re: Uses of 1:11 Million Gear Ratio

I'm often sensitive, maybe even paranoid, don't take me too seriously. And seriously, I have only a vague idea of what you said.

Soupspoon
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### Re: Uses of 1:11 Million Gear Ratio

(Just because you're paranoid, it doesn't mean They aren't out to get you...)

The aforementioned Axle is a fictional technomagical device, perhaps like two cubes, attached face-to-face, that inexorably rotate w.r.t. each other, seemingly with no limit to their torque, no variation in their (slow) rate of rotation and indistructable. They are found by the dwarfs of Discworld deep in the bedrock of the Disc, along with Devices (single cubes of varied and seemingly random function, think of those black cubes from that Eleventh Doctor episode, perhaps). Axles seem to be easy enough (comparatively) to find, due to their unstoppable grinding motion being audible through the rock.

They can be used to drive machinery. Presumably a square 'socket' of iron, or other dwarven alloy, can be plugged over each cube, one anchored stationary and the other on a shaft end. As much torque as can be withstood by the add-ons (given there is apparently no limit to the Axle's power or the sub-Device cube strengths) can thus be harnessed and put through whatever gearing system (and/or other mechanical conversions) can be devised.

By gearing back to high speed, fans can be powered to remove stale (or firedamped?) air from deep excavations, for example. Or pullies can be clutched to raise mining cages. Or perhaps they can operate drills or even tunnel-borers for actual shaft-sinking or traversing. So long as the power requirements do not exceed the finite power-transfer potential of the add-on mechanisms (the Axle seemingly being mystically capable of infinite power).

And so with a high-ratio gear-downer. Assuming that the concentrated link within the gearbox is (finitely) stronger than the (finite) amount of power the real-life device can supply. The internals are going to be stronger (for reasons already given) but extracting the high torque for useful work (maybe, in a twisted analogue of an HVAC power-grid, it would be more efficient to transfer slow-but-steady rotation over extended distances than trying to spin up the same transfer straight from an originally high-rev original source, at the expense of some in-gear mechanical inefficiencies) is going to involve a single axle, thinner than one can make the body, through which enough twistable tension could pass to break it, like anmechanical fuse. But let's assume the whole set-up is designed such that the tapped power (probably going to need at least partial up-gearing at the other end, drawing the torque demand back high) does not exceed the gearbox limits (jams and undue resistances, up-line, break an easier to replace sacrificial link outside of the gearbox).

And that's pretty much where my thinking got to, to prompt my original contribution. It probably could have used more thought, but it seemed good enough at the time.

morriswalters
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### Re: Uses of 1:11 Million Gear Ratio

Okay.

KittenKaboodle
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### Re: Uses of 1:11 Million Gear Ratio

jewish_scientist wrote: What is an application of such an extreme reduction?

Click bait!

I wonder if it counts as a "view" if I only watched 10 seconds of the video?

Copper Bezel
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### Re: Uses of 1:11 Million Gear Ratio

Engineers hate this man!

This one easy trick increases your torque by 11 million times!

17 1/2 applications for reducing gearboxes! No. 8 will shock you!
So much depends upon a red wheel barrow (>= XXII) but it is not going to be installed.

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cephalopod9
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### Re: Uses of 1:11 Million Gear Ratio

The governor on a music box... ( double checks) has a gear ratio about ten thousand times smaller.
Maybe if you wanted a similar mechanism ( https://youtu.be/COty6_oDEkk?t=3m23s ) to work without air resistance, like if you want to play a music box in a vacuum... where no one could hear it...

wumpus
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### Re: Uses of 1:11 Million Gear Ratio

The obvious (to this non-mechanical engineer) issue is at what point does the gearing suffer from stiction.

I'm assuming it is several gearsets that multiply each other. There are two types of friction, static and dynamic. If you have a gear moving without stiction (static friction) moving an object that does, no problem: that's it's job. If you have a gear moving under dynamic friction moving a gear with stiction that in turn moves something with stiction, I suspect you have a problem.

Still, as long as the gear ratio is higher than the ratio of friction with/without stiction, you should get an advantage (basically defined as the inner gears don't break before the final gears). Just expect some unbelievably big friction losses.