Fabrial Invention Ideas Thread

[SourCandyLime He/Him]

I am making this topic, because I want to share a fabrial invention idea I have, and if any others have an invention, please share it!

My brain has been listening to everything about fabrials, and I understand them enough for this invention

INTRODUCING:
The Climbers (Best name i got)
A pair of gloves and boots, With these babies you can climb MID-AIR.

The gloves each have a conjoined ruby on the back, connected to the ground somewhere. These gloves when activated, will freeze in the air.

The boots follow a similar pattern, and when activated also freeze in the air.

When you put a foot in the air, and freeze the boot, you can then stand on one foot, and link the other boot mid air. or, if your more cautious, you can use the gloves as extra support. These boots and gloves will allow you to literally climb on air, or climb up any wall.

How it works:
Aluminium blocks the rubies from conjoining until moved out of the way, allowing the gloves and boots to move freely until activated.

Please share your invention ideas!

[Quantus he/him]

Logicspren in smokestone create a pulse of stormlight relative to how close another piece of metal is to the gem, and they will switch state if tapped by another piece of metal.  That provides a clock signal function and basic logic gate functionality. It might be the size of a building (or several) but you have all the building blocks of a functional computer akin to those massive functional computers that people have managed to build using Minecraft's Redstone system.  

EDIT: Navani's gravitation-based anti-humdification fabrial should work great for DeSalination and DeCremificaiton of water. It could probably Cold Distillation too, and really any sort of very selective fluid separation and/or purification you may want to do.  That could replace all kinds of large-scale industrial processes we use for filtration, distillation columns, selective membranes, etc.   

Edited July 12 by Quantus

[Dragonheir he/him]

Hello, and welcome to the Shard! 
These are cool. I will share a fabriel idea or two, but first I’ll remind you, @SourCandyLime, to read this thread: 

and to make an introduction post in the introduce yourself subforum (it’s at the very top of the topic lists), containing at the very least which books you’ve read. 
With that out of the way, I have some fabreil ideas: 

Basically Yondu’s (the blue guy from Guardians of the Galaxy. I may have spelled his name wrong) Arrow 

Take either a vanilla or an only up and down reverser fabriel, and connect one of them to an arrow with an attractor fabriel set to angerspren (or something). Counterbalance the other side, and put it somewhere with lots of open space. You now have an arrow that runs around stabbing angry people. (Unless attractor fabriels don’t move when attracted. If so, you can put a water attractor over a tank of water, and you get flight. Throw in some conjoiners for stability, maybe a wind attractor and wind augmenter to keep the atmosphere in and moving, some plants to recycle the air, and boom! Spaceship!) 

Another spaceship drive (their mechanics are mutually exclusive, but one of the two should work)

Take a starspren and put it in a very very long range attractor (that might require extra metals or a different design). Add movable conjoiners and reversers for stabilization, steering, and levitation. (This is just the engine. Hull, life support, and other components should be added.) 
To use: angle stabilizers diagonal to the sun, and turn on. You should move towards it. Adjust path regularly to spin around the sun, using additional momentum to move away from it. Once you’ve reached your desired heading, lock stabilizers to it. You should do this when the sun is between you and your destination, off to the side a little. Turn off your attracter fabriel just as you end up next to the sun, then coast to your destination. If you have a star repeller, engage it then, getting more speed. If you can make a ridiculously long range attractor fabriel, you can use aluminum to block it from attracting the sun, and use that to accelerate to your destination star. Depending upon what exactly windspren and luckspren fabriels actually do, you may be able to alter speed and gravity, which could be used for a third spaceship drive or to enhance whichever of the two works. 

Larger power armor 

Contains spoilers for new fabriel capabilities from RoW 

Spoiler

Take a whole bunch of conjoiner fabriels and use Rayseium to move their half spren to a gemstone however many times larger you want the armor to be. Connect the inside to a control rig that the user wears. Connect the outside to a bunch of half shards, or maybe several suits of dead shardplate, which adjust the suit their wearer, and might be able to cover a mech or another suit of shardplate. Uh oh. That sounds pretty heavy. You’ll have to either enhance the strength of the wearer, potentially using more conjoiner fabriels that are synched with their movements (or just shardplate), or you’ll need to make the main suit very light, using either reverser fabriels (potentially Rayseium modified) or gravity fabriels, which are undiscovered. Plus, you’d need a way to let the user see the world around them. You could use the unknown lightweaving fabriel, something weird with rainbowspen, or maybe a non-magical periscope. If you could do that, though, you’d be able to add additional weapons, such as fabriel flamethrowers, reverser fabriels that stop you from getting knocked over; fearspren attractors which might let pull the opposing soldiers, who are afraid, at you; (I think that’s a proper use of semicolons) rockspren attractors to pull boulders up to the mech’s hand then throw them, and a whole bunch of Rayseium modified conjoiners, connected to blades at the fast end and the mech’s hand at the slow end. When activated, they’d zip around slicing things (you could attach other fabriels to them for even more damage). 

Emotionspren enhancers and diminishers 

These can probably be used to medicate things such as ADHD and depression, using concentrationspren enhancers or gloomspren diminishers. Ones such as gloryspren and joyspren enhancers are probably addictive, though. We’ve seen how well painspren enhancers work as weapons. Something like a high power area caused by a fearspren, hungerspren, exhaustionspren, or captivityspren enhancer, or a gloryspren, joyspren, or passionspren diminisher could be used to make an enemy army surrender, or for riot control. Exhaustionspren enhancers in particular would make a good sedative, and its diminisher would act as a stimulant, although it might make people keep moving past their capacity, which would be bad. 

By the way, does anybody know why there are wavespren, riverspren, and rainspren instead of just waterspren, and what each one might do in a fabriel? Also, what do emotionspren attractors do? And decay, death, life, music, creation, laughter, captivity, and persuasionspren are concepts that would be difficult to imagine the fabriel effects for. 

[SourCandyLime He/Him]

Thank you for telling me about the acronyms @Dragonheir! (Brand new to this site) SadWa don't think thats how attractor fabrials work. If i am not mistaken, it pulls the substance to the item.

Spoiler

WoK, Water attractor allowed the archers to shoot, even though the weeping was going on.

But in answer to your questions about spren, here is my theory on each
Emotion spren attractor would influence people feeling that emotion to go towards the gemstone.
Wave Spren repelers would flaten a surface of water completely. For ships in a storm, they no longer have to worry about waves, because the wave spren is repelling all waves
River spren are tricky. Best i have an Idea for, they would be best used as the fabrial detector found in one of the Rysen Interludes, Blinking when close to a river. (I hope that wasn't a spoiler, I don't want to ruin anyone's expiriance
Rain spren would act like wave spren i would think, either pulling in rain, or repeling rain, kinda like a fabrial umbrella (NEW IDEA!!! Fabrial Umbrella)
Decay would speed up or slow down decomposition, death increase or decrease a life span, Life the opposite of death

Music is an interesting Idea, perhaps it would atract musitions towards it, like how earlier i stated an emotion spren would atract those feeling the emotion. (IDk, speculation, right?)
Creation spren could atract artists, or work as low quality soul casters.
laughter spren, like when you got a whole army to give up, could make someone uncontrollably laugh, or never laugh, 

Spoiler

Leren (can't spell, i read audio books) probably has one of those. Its why they say he surgically removed his sense of humor.

Captivity spren could make someone feel like they are trapped, or to make a prison more 'humane' make them feel free on the flip side.

Pursuasion spren could make people more or less likely to accept new ideas, making them more... gullible so to speak.


I think one of the most important parts of fabrials to remember is that "Spren are based on perseption"
Wavespren are linked to the waves, whatever may be qualifyed as a wave by human perseption.

Spoiler

This stands true until speaking to smarter spren, Honorspren for example in RoW making their own form of honor.

You've just got to take the mostlikely thing to happen, what is the common perseption of waves? what if you pushed it away? I love this talk, because its mostly what ifs.

Now, to another invention!

The Fabrial Umbrella!

Stick this gemstone in a backpack, or anywhere on your person. With a captive Rainspren, and a steel cage, The Fabrial Umbrella will repel all rain within a (unknown as of now) radius!

The Fabrial Umbrella, a better umbrella, without the umbrella.

Edited July 13 by SourCandyLime

[Dragonheir he/him]

1 hour ago, SourCandyLime said:

If i am not mistaken, it pulls the substance to the item.

I was saying that if it’s pulled back, it can be used to move towards things if it’s light, and if it’s not, you get one of those “telekinetic stands on platform and then flies around” tricks, because it’s not pulled down the same amount. Pulling yourself up by your own bootstraps, so to speak. 

1 hour ago, SourCandyLime said:

Wave Spren repelers would flaten a surface of water completely. For ships in a storm, they no longer have to worry about waves, because the wave spren is repelling all waves
River spren are tricky. Best i have an Idea for, they would be best used as the fabrial detector found in one of the Rysen Interludes, Blinking when close to a river. (I hope that wasn't a spoiler, I don't want to ruin anyone's expiriance
Rain spren would act like wave spren i would think, either pulling in rain, or repeling rain, kinda like a fabrial umbrella

I think the rainspren were used for the archery fabriels. The difference between riverspren and wavespren here makes sense. 

2 hours ago, SourCandyLime said:

Music is an interesting Idea, perhaps it would atract musitions towards it, like how earlier i stated an emotion spren would atract those feeling the emotion. (IDk, speculation, right?)

Maybe it actually moves the sound, making it louder between it and the source, but quiet or even silent at other points in its area of effect. 

3 hours ago, SourCandyLime said:

Creation spren could atract artists, or work as low quality soul casters.
laughter spren, like when you got a whole army to give up, could make someone uncontrollably laugh, or never laugh, 

  Reveal hidden contents

Leren (can't spell, i read audio books) probably has one of those. Its why they say he surgically removed his sense of humor.

Captivity spren could make someone feel like they are trapped, or to make a prison more 'humane' make them feel free on the flip side.

Pursuasion spren could make people more or less likely to accept new ideas, making them more... gullible so to speak.

The ability to use creationspren and concentrationspren enhancer fabriels to make yourself more creative and focused could be very helpful to artists, or seen as cheating by some. Very interesting… 

Laughterspren enhancing your sense of humor makes sense. (Nice joke by the way.) The use of captivityspren diminishers by prisons to make people feel free doesn’t sound very humane to me. It just sounds like brainwashing. (Doesn’t mean people won’t market it as humane, though) 

3 hours ago, SourCandyLime said:

I think one of the most important parts of fabrials to remember is that "Spren are based on perseption"
Wavespren are linked to the waves, whatever may be qualifyed as a wave by human perseption.

  Reveal hidden contents

This stands true until speaking to smarter spren, Honorspren for example in RoW making their own form of honor.

You've just got to take the mostlikely thing to happen, what is the common perseption of waves? what if you pushed it away? I love this talk, because its mostly what ifs.

I wonder if you can use a wind or wavespren attractor or enhancer to create a self propelled boat? Probably takes some aluminum, but it might work. 

3 hours ago, SourCandyLime said:

The Fabrial Umbrella!

Stick this gemstone in a backpack, or anywhere on your person. With a captive Rainspren, and a steel cage, The Fabrial Umbrella will repel all rain within a (unknown as of now) radius!

The Fabrial Umbrella, a better umbrella, without the umbrella.

I want one of these, please. And the different waterspren is useful here, because it won’t push a water bottle away, or depending on what counts as water, just shove a human away by their blood. 

[SourCandyLime He/Him]

7 minutes ago, Dragonheir said:

doesn’t sound very humane to me. It just sounds like brainwashing

I agree, thus why I put humane in quotes.

9 minutes ago, Dragonheir said:

I wonder if you can use a wind or wavespren attractor or enhancer to create a self propelled boat? Probably takes some aluminum, but it might work. 

That's a great idea! Though it would act like a motor boat, but instead of fuel, use stormlight, a much cleaner and easily acquired source.

10 minutes ago, Dragonheir said:

Maybe it actually moves the sound, making it louder between it and the source, but quiet or even silent at other points in its area of effect. 

I actually really like that idea more for music spren, though the way it would work would seem counter intuitive, as atracters would quiet sound, pulling it into the fabrial, and repellers would boost sound, shoving it away from the fabrial. These could work as noise canceling headphones! or as a microphone!

 

12 minutes ago, Dragonheir said:

I was saying that if it’s pulled back, it can be used to move towards things if it’s light, and if it’s not, you get one of those “telekinetic stands on platform and then flies around” tricks, because it’s not pulled down the same amount. Pulling yourself up by your own bootstraps, so to speak.

Ah, kinda like magnets, when on a table, if they pull each other they will meet in the middle, or a heavy magnet pulling a light metal will move the metal, but a light magnet attracting a heavy metal will get pulled to the metal, that makes sense!

I still love the idea of a wave canceling fabrial, as it would make sea travel so much safer, and possibly let people sail through highstorms. (though you may need to repel the wind)

17 minutes ago, Dragonheir said:

I think the rainspren were used for the archery fabriels.

I am going to have to go back and check to see if that is stated, though it would make perfect sense to use a rain spren

I am loving this thread!!!!!

[Dragonheir he/him]

12 minutes ago, SourCandyLime said:

That's a great idea! Though it would act like a motor boat, but instead of fuel, use stormlight, a much cleaner and easily acquired source.

Yeah! We could throw in more of those reverser fabriels I seem to use in all my ideas, and some windspren and wavespren diminishers, and let it weather a highstorm, so we can reach the Origin, and find out if there’s actually anything over there. 

16 minutes ago, SourCandyLime said:

I am going to have to go back and check to see if that is stated, though it would make perfect sense to use a rain spren

I don’t think it says outright, but that’s my guess. 

17 minutes ago, SourCandyLime said:

I am loving this thread!!!!!

Me two!  
When I come back from camp, I’ll probably have a few more ideas for you. (Or I might have one tomorrow before I leave.) 

[SourCandyLime He/Him]

I sad this thread died

[Atlas333]

I'm curious if you could capture Voidspren to make some new fabrials (I don't see why not, they act like normal spren even if they're rarer).

Shock glove: capture a storm spren and put it in a gauntlet. Boom! You've got great value storm form but for humans. Alternatively, you could add the gemstone to a net, wire, or fence for other electric-based fabrials.

Investiture alerter: secret spren are able to detect active investiture which would be a very useful fabrial. I imagine it would only be able to glow more in the presence of kinetic investiture (or maybe it would scream like the spren do?) so you might have to play a game of hot-and-cold but you could eventually find it. 

 

A bit more tame idea:

lower-gravity harness: trap a luck spren and attach it to something heavy and it should become lighter (like a chasm fiend does), probably good for delivering heavy cargo.

[Determination]

Take a pair of spanreeds and remove the  conjoined rubies. Roll a couple of metal sheets into cone shapes. Embed one of the rubies in the base of each one.

Fabrial telephone.

[Elite01]

I was thinking about making an amplifier fabrial with contained emotion spren, the idea is that whoever you touch with this glove-fabrial will feel that emotion. If you shook someone’s hand while a joy spren is contained they might be more open to listening to you, if you touched someone with a fear spren they may become intimidated. I like it as a new version of rioting that has a few more limits than an AoE I’ve heard about 

 

The other idea I’ve had is a Fabrial flash bang, but a rainbow spren in the Fabrial and make it amplify through a pewter cage and you could disorient enemies with a flash of color 

[SpiritOfWrath]

This contains stuff from RoW

Spoiler

A dagger! Assassination weapon, where there is a two piece dagger. The switch to disconnect them also turns on conjoined gems on each part with the tip being bigger, and when you stab the handle forwards, the tip flies waaaay forwards reeaally fast. Or you have this on like an arrowhead.

[Determination]

Create a pair of conjoined rubies of grossly mismatched sizes, using the method discovered in Rhythm of War.

Put the small ruby into an aluminum box, and have a windrunner lash the big one into orbit. (This shouldn't actually take much stormlight, probably the only thing keeping them from doing this is the math/physics knowledge.)

Be very careful opening that box when you retrieve your new fabrial engine.

 

Edit: Thinking about this further, given the trouble required to set this thing up, you'd probably want to put the smaller gem into orbit and affix the larger one to a flywheel/gear transmission contraption. That way you can transfer that motion to a whole bunch of independent ruby pairs, using the gear ratio to make whatever speed/torque tradeoffs happen to make sense for the application. Sure beats chulls or weights in a shaft.

Edited Monday at 12:03 AM by Determination
Additional thoughts

[PurpleZebra5]

Levitating platform: Take a pair of conjoined amethysts and isolate vertical motion so that they only move up/down. Then, drop one on top of the other, providing a floating platform. With the correct setup, you could use several pairs of them to move up/down, and if you make them only able to translate motion up/down but move sideways together, it can function as a 0 drag wing. Alternatively, just a fun floaty thing: Take a pair of conjoined amethysts and have the cages balance the weight between the two.

[Determination]

Oh right, the amethysts. I must not understand those correctly because it seems like it's too easy to create totally broken contraptions with those.

For example:

Embed a pair of conjoined amethysts within opposite sides of a large gear, placing them such that the line between them crosses its center of the gear.

An amethyst duplicates its twin's motion in the opposite direction, and the placement of the gems means that both actually rotate the gear in the same direction. So the gear spins itself faster by spinning.

Give the gear a nudge and its rotational velocity should immediately accelerate to infinity. Hook it up to something... very durable... and extract that sweet free energy to power your blimps or rocket gloves or whatever.

[SpiritOfWrath]

On 9/15/2024 at 9:24 PM, Determination said:

Oh right, the amethysts. I must not understand those correctly because it seems like it's too easy to create totally broken contraptions with those.

For example:

Embed a pair of conjoined amethysts within opposite sides of a large gear, placing them such that the line between them crosses its center of the gear.

An amethyst duplicates its twin's motion in the opposite direction, and the placement of the gems means that both actually rotate the gear in the same direction. So the gear spins itself faster by spinning.

Give the gear a nudge and its rotational velocity should immediately accelerate to infinity. Hook it up to something... very durable... and extract that sweet free energy to power your blimps or rocket gloves or whatever.

Nonono put the infinite energy up to smt like a chainsaw. Disposable shard blade!

One note, though. This may “generate” energy, but not really. Remember, gemstones understress crack. Sad. Also, investiture is used up.

[Determination]

1 minute ago, SpiritOfWrath said:

One note, though. This may “generate” energy, but not really. Remember, gemstones understress crack. Sad. Also, investiture is used up.

On Roshar, any fabrial that converts Investiture to mechanical energy might as well be a free energy generator. It's not like you're gonna run out of highstorms.

You bring up a good point with gemstones cracking. We know that it can be mitigated by spreading the load across many gemstones. Perhaps with enough gemstone pairs you can prevent cracking entirely.

Of course, when the gear spins up to infinity, something's gonna break. This machine obviously wouldn't work, but I'm not sure where the mistake is.

Consider rubies. I think what happens is that each ruby in a pair is as hard to move as both rubies, since that's what you end up doing when you push on one: you move both of them. So a spanreed would feel twice as "weighty" as it should.

So what happens if you embed them both in the same object? Moving one moves the other in two ways: the regular mundane way, and the magical conjoined gemstone way. I think these forces all end up balancing out, and the entire object ends up behaving as if the rubies weren't conjoined at all.

But now do the same thing with amethysts: embed them both in the same object. For simplicity let's assume you just glue the halves together.

Assuming the glue holds, you wouldn't be able to move the thing at all. Every force you apply to the object is divided between the halves, then transmitted to the other half and reversed, perfectly opposing that force. This is the essentially the same thing as @PurpleZebra's floating platform.

It gets weird with rotations. If the halves are embedded in an object that rotates on the Z axis, and the Z axis crosses the line between the halves at its midpoint, then (ignoring the fact that they're conjoined for a moment) the halves always move exactly opposite each other in the X and Y directions. It seems that adding the conjoined amethyst force transfer+reversal effect to this system would increase the rotation speed.

But we already determined that the analogous situation with rubies acts as if they're not conjoined at all. I feel like amethysts should work the same. What gives!?

 

[SpiritOfWrath]

3 minutes ago, Determination said:

On Roshar, any fabrial that converts Investiture to mechanical energy might as well be a free energy generator. It's not like you're gonna run out of highstorms.

You bring up a good point with gemstones cracking. We know that it can be mitigated by spreading the load across many gemstones. Perhaps with enough gemstone pairs you can prevent cracking entirely.

Of course, when the gear spins up to infinity, something's gonna break. This machine obviously wouldn't work, but I'm not sure where the mistake is.

Consider rubies. I think what happens is that each ruby in a pair is as hard to move as both rubies, since that's what you end up doing when you push on one: you move both of them. So a spanreed would feel twice as "weighty" as it should.

So what happens if you embed them both in the same object? Moving one moves the other in two ways: the regular mundane way, and the magical conjoined gemstone way. I think these forces all end up balancing out, and the entire object ends up behaving as if the rubies weren't conjoined at all.

But now do the same thing with amethysts: embed them both in the same object. For simplicity let's assume you just glue the halves together.

Assuming the glue holds, you wouldn't be able to move the thing at all. Every force you apply to the object is divided between the halves, then transmitted to the other half and reversed, perfectly opposing that force. This is the essentially the same thing as @PurpleZebra's floating platform.

It gets weird with rotations. If the halves are embedded in an object that rotates on the Z axis, and the Z axis crosses the line between the halves at its midpoint, then (ignoring the fact that they're conjoined for a moment) the halves always move exactly opposite each other in the X and Y directions. It seems that adding the conjoined amethyst force transfer+reversal effect to this system would increase the rotation speed.

But we already determined that the analogous situation with rubies acts as if they're not conjoined at all. I feel like amethysts should work the same. What gives!?

 

Sanderson supports the laws of conservation. So even though stormlight is readily available, the energy required is so incredibly high that perhaps even a Shard wouldn’t be able to power it. But the reason amethyst wouldn’t work is bc of imbalanced forces. Even if they are bound to each other, the parent object can and will rotate when touched. Even if this is minuscule rotation, it’s enough to set off the “ow that gemstone just exploded” rotation. So I doesn’t necessarily cancel out, like you say, but instead gets rid of the source of both forces. (Another note. The forces aren’t divided between the two. Otherwise a spanreed would feel only half as much gravity.)
One interesting thing you bring up, though, is rubies. The forces don’t logically cancel out, but is it much of a stretch to say that at some point in time they have had the same force apply to them? No, absolutely not. But something that is mentioned over and over with spanreed me is frame of reference. Since the entire system is affected by gravity, then the frame of reference adopts gravity, and the spren no longer thinks it’s other half should be affected by the gravity it is feeling. (If any of this makes sense. I get the feeling I’m rambling. Also, soorry if I’m being a joy killer. I do think these ideas are cool.)

[Determination]

57 minutes ago, SpiritOfWrath said:

Another note. The forces aren’t divided between the two. Otherwise a spanreed would feel only half as much gravity.

The force is only "divided" between them in the sense that it's being applied to both of them at once, because in this case they're physically connected in addition to being conjoined magically.

But that's not really necessary to explain why the forces transferred magically between conjoined rubies must always cancel out exactly. The rubies don't move relative to each other, so they never accelerate, hence no net force. This is, of course, all within the frame of reference of the rubies. From an external frame of reference, the rubies would be moving all over the place.

You do bring up a good point about frames of reference being subject to perception with these things. I don't think it would come into play with these examples because the gemstones are all close together and co-moving, but it could certainly have an effect on something like my "orbital fabrial engine" concept from earlier.

1 hour ago, SpiritOfWrath said:

Even if they are bound to each other, the parent object can and will rotate when touched. Even if this is minuscule rotation, it’s enough to set off the “ow that gemstone just exploded” rotation.

You're saying it's practically impossible to keep them from rotating even slightly, and therefore the runaway rotation effect would always happen and that would destroy the gemstones or the object they're embedded in or both?

The solution to that (as mentioned by @PurpleZebra in his floating platform concept) is to use aluminum to isolate planes of motion. If you only allow the object to move on a single axis, then it physically can't rotate at all.

Even without thinking about aluminum, it should still be possible to reason through how it'd behave in an ideal scenario, "spherical cow in a vacuum" style.

1 hour ago, SpiritOfWrath said:

Also, soorry if I’m being a joy killer. I do think these ideas are cool.

Not at all! If my crackpot ideas don't add up, I want to know. Especially with the amethyst engine. I know that thing won't work - that infinite rotational acceleration is a dead giveaway - I'm just not certain if the problem in an unaccounted force, or if the way amethysts are supposed to work is just fundamentally broken...

[Dragonheir he/him]

7 minutes ago, Determination said:

Not at all! If my crackpot ideas don't add up, I want to know. Especially with the amethyst engine. I know that thing won't work - that infinite rotational acceleration is a dead giveaway - I'm just not certain if the problem in an unaccounted force, or if the way amethysts are supposed to work is just fundamentally broken...

I think I know the problem. Conjoined and reversed fabrials behave like they are connected by intangible structures and pulleys, respectively. A wheel with a rope and pulley attached to it at opposite sides will not accelerate indefinitely, thus, neither will the amethysts. (Determining this took me a long car ride several weeks ago, when I came up with it independently.) 

Edited Wednesday at 12:30 AM by Dragonheir
Wrote ruby instead of amethyst by accident

[Determination]

18 minutes ago, Dragonheir said:

Conjoined and reversed fabrials behave like they are connected by intangible structures and pulleys, respectively.

I had noticed that fact for rubies - that you could treat them as if they were attached by an invisible, intangible rod - but I hadn't considered looking at amethysts like pulleys. Very insightful. I think I get it now. Maybe I should go on more long car rides.

So amethysts as pulleys seems to work, you just have to assume a rigid connection to the pulley - thinking about it like a rope or chain connection doesn't describe the opposed motion in both directions along the axis. But a rope/chain model is fine if you're thinking in one direction at a time.

I'm gonna go into detail because this was a tricky one to think about.

The easiest way to show why this disproves the amethyst engine is to consider an even simpler scenario, one without all the rotation business.

Suppose you're standing at the top of Navani's shaft of weights in Urithiru, cranking the winch to raise one of the weights back to the top. The crank pulls down on the chain, which loops around a pulley, and pulls up on the weight, which rises.

Note that if you happened to pick out a chain link on the part of the chain going up to the pulley and another one on the part going down to the weight, you would notice them moving exactly like a pair of amethysts would.

Now imagine a Windrunner is coming up the shaft and, noticing someone is trying to winch up the weight, decides to help out by Lashing it upward, making it weightless.

The weight continues up the shaft on its own inertia, and to prevent the chain from bunching up, you keep winding the crank at the same speed. The chain is still moving exactly as it did before, but it's no longer adding anything to the motion of the weight.

So what about the amethysts so "cleverly" arranged on the gear? The gems are already moving opposite each other, because they're physically connected by the gear. Each gem is magically connected to its twin by the "virtual pulley", but because they are already moving toward the "chain" that would be pulling them along, it doesn't actually add to the motion.

Therefore the amethysts act as if they weren't conjoined at all, just like the rubies!

That was a lot. But the perpetual motion machine is defeated, and the orbital ruby once again reigns supreme among fabrial engines!