Conjoined reversal fabrials

[+Oltux72]

@Pagerunner 's thoughts about conjoined fabrials made me look at fabrials.

Looking at Navani's platform, one thing struck my mind. What determines when they can join? With a spanreed, you can demand that both sides can be at rest with respect to each other. But with a reverser fabrial that can obviously be the case only with fabrials at rest. Yet Navani's platforms actually stay connected while they are lifted and lowered.
So is that necessary for a spanreed? We have this from Words of Radiance:

Quote

He would have done it himself, but you could not use a spanreed while moving

This is not as good as it seems, as it may be impossible because a vehicle would be shaking. So what are the exact criteria for using a spanreed?

[Quantus]

15 minutes ago, Oltux72 said:

@Pagerunner 's thoughts about conjoined fabrials made me look at fabrials.

Looking at Navani's platform, one thing struck my mind. What determines when they can join? With a spanreed, you can demand that both sides can be at rest with respect to each other. But with a reverser fabrial that can obviously be the case only with fabrials at rest. Yet Navani's platforms actually stay connected while they are lifted and lowered.
So is that necessary for a spanreed? We have this from Words of Radiance:

This is not as good as it seems, as it may be impossible because a vehicle would be shaking. So what are the exact criteria for using a spanreed?

They use an aluminum box on one end to temporarily suppress the link, as opposed whatever the normal spanreed switching mechanism was.  And switching is really only needed for the horizontal motion, which is a separate system from the lift set, so they can come to a breif halt while the chulls are being reset on the other end.  

[Karger]

25 minutes ago, Oltux72 said:

He would have done it himself, but you could not use a spanreed while moving

I think that is because while moving your pen is moving.  Even if only at walking speed that is more then enough to make writing illegible.  Just bouncing would be annoying but you might be able to get something if you wrote large enough.

[Quantus]

15 minutes ago, Karger said:

I think that is because while moving your pen is moving.  Even if only at walking speed that is more then enough to make writing illegible.  Just bouncing would be annoying but you might be able to get something if you wrote large enough.

Also in the case of spanreeds their getting all that motion through them but are themselves pretty fragile things.  One good bump on one end good easily snap the reed on the other

[+Oltux72]

29 minutes ago, Karger said:

I think that is because while moving your pen is moving.

So what exactly will happen, if you do join them at movement? The Ars Arcanum just says that force is conserved. But she says nothing about momentum. Is the spanreed in the moving vehicle yanked backwards and the other half hurled into the direction the vehicle is moving?

[Karger]

21 minutes ago, Oltux72 said:

So what exactly will happen, if you do join them at movement? The Ars Arcanum just says that force is conserved. But she says nothing about momentum. Is the spanreed in the moving vehicle yanked backwards and the other half hurled into the direction the vehicle is moving?

No.  Different latitudes of the planet move at different speeds and yet this is not an issue.  I suppose if you conjoined while moving and maintained an exact speed you could use one.

[+Oltux72]

6 hours ago, Karger said:

No.  Different latitudes of the planet move at different speeds and yet this is not an issue.

The center of the planet would see it that way. The objects do not. And this is no theoretical diffrence either. You could send a radio signal from a gem on the ground to a gem in a vehicle and you would observe doppler shifting. You would not see that if you sent a signal to a gem further north or south.

Furthermore the users of spanreeds surely are not subject to Coriolis force.

6 hours ago, Karger said:

  I suppose if you conjoined while moving and maintained an exact speed you could use one.

Let me propose a thought experiment. You attach two spanreeds to a rope. One halfway down and one at the end. You start twirling the rope around you. What happens?

[Dracnor]

Isn't the question you are coming to "relativly to what is mesured the movment of a spanreed" ? Remember, there is no such think as absolute movement. right now, relativly to the ground I'm not moving, but relativly to the sun I'm going at thousands of km/h.

If the movment of a spanreed is measured relativly to the ground, then you can't use it in a vehicule - even in a ship (or else the other spanreed would have the same movement as the ship compared to the ground). I don't remember, doesn't jasnah uses a spanreed in her ship before her assassination ?

If it's relativly to the sheet of paper, then they are no problems whatsoever to use it in a vehicule.

10 hours ago, Oltux72 said:

Let me propose a thought experiment. You attach two spanreeds to a rope. One halfway down and one at the end. You start twirling the rope around you. What happens?

Another funky one, inspired by navani's archers tower (cf book 1) and spanreeds. Take a cart, use fabrials to link its movment to another gem (upon activation, like a spanreed). Go in the cart with the gem. Activate the fabrial and move the gem in a straight line (eg by walking in the cart with the gem). What happens ?

[+Oltux72]

32 minutes ago, Dracnor said:

Isn't the question you are coming to "relativly to what is mesured the movment of a spanreed" ?

Yes, that is the main part of the question. The other part is how orientation is transfered

32 minutes ago, Dracnor said:

Remember, there is no such think as absolute movement.

That is the question. Does this apply to arcane questions in the Cosmere? Are they, just for the sake of argument, all relative to Adonalsium's corpse? We cannot a priori rule that out.

32 minutes ago, Dracnor said:

right now, relativly to the ground I'm not moving, but relativly to the sun I'm going at thousands of km/h.

If the movment of a spanreed is measured relativly to the ground, then you can't use it in a vehicule - even in a ship (or else the other spanreed would have the same movement as the ship compared to the ground). I don't remember, doesn't jasnah uses a spanreed in her ship before her assassination ?

Shallan's sister-in-law regarded the use of a spanreed in a ship as impossible. I think for spanreeds movement is measured relative to the other spanreed.

32 minutes ago, Dracnor said:

If it's relativly to the sheet of paper, then they are no problems whatsoever to use it in a vehicule.

The paper and its holder seem to be mere paraphernalia without arcane functions.

32 minutes ago, Dracnor said:

Another funky one, inspired by navani's archers tower (cf book 1) and spanreeds. Take a cart, use fabrials to link its movment to another gem (upon activation, like a spanreed). Go in the cart with the gem. Activate the fabrial and move the gem in a straight line (eg by walking in the cart with the gem). What happens ?

Presumably you cannot move as if you were holding onto the cart.

[Karger]

19 hours ago, Oltux72 said:

Let me propose a thought experiment. You attach two spanreeds to a rope. One halfway down and one at the end. You start twirling the rope around you. What happens?

I personally think you would get a zig zag as the outer will not go faster then the inner.

[+Oltux72]

4 hours ago, Karger said:

I personally think you would get a zig zag as the outer will not go faster then the inner.

But in the end result it won't go faster. Second thought experiment. We take a turning disc. We mount one spanreed at the rim, the other one half way between the nave and the rim, where the other one is. We make the disc rotate and then switch them on. Based on that they work on Roshar, this must work, must it not?

[Karger]

15 minutes ago, Oltux72 said:

this must work, must it not?

what must?

[+Oltux72]

Just now, Karger said:

what must?

The wheel must simply turn without the spanreeds making a difference and the spanreeds must join and you could use them to write a letter.

[theTruthshaper]

I think that Brandon will probably make this like the speed bubbles.

[+Oltux72]

2 minutes ago, The_Truthwatcher said:

I think that Brandon will probably make this like the speed bubbles.

Well, in which way? Speed bubbles have a defined volume and boundaries. The effect of conjoined fabrils lacks both.

[theTruthshaper]

Just now, Oltux72 said:

Well, in which way? Speed bubbles have a defined volume and boundaries. The effect of conjoined fabrils lacks both.

I was talking about the relative speed part. A fabrial would velocities in the frame of a vehicle if it is massive enough

[+Oltux72]

4 minutes ago, The_Truthwatcher said:

I was talking about the relative speed part. A fabrial would velocities in the frame of a vehicle if it is massive enough

While that is possible it does not solve the full problem. To an outside observer different parts of the vehicle move at different speeds. To the spanreeds that is not the case. They see each other as at rest with respect to the other one.

[theTruthshaper]

The thing is that in that case, both the spanreeds have external forces. When spanreeds are used, only of of them does.(I am disregarding the forces along the spanreed right now)

[+Oltux72]

37 minutes ago, The_Truthwatcher said:

The thing is that in that case, both the spanreeds have external forces. When spanreeds are used, only of of them does.(I am disregarding the forces along the spanreed right now)

I am afraid that is not the case. You write with them on paper. Both of them are dragged across paper which will cause friction. Presumably that is the reason they take so much care to level them. You'd ram one of them into the wood, respectively the other one would cease writing, as it is floating through the air.

[theTruthshaper]

4 minutes ago, Oltux72 said:

I am afraid that is not the case. You write with them on paper. Both of them are dragged across paper which will cause friction. Presumably that is the reason they take so much care to level them. You'd ram one of them into the wood, respectively the other one would cease writing, as it is floating through the air.

Hmm, I forgot about friction. Relatedly, why do you think spanreeds have settings for deciding the receiver and the transmitter? The way we understand the fabrials right now, that should not be needed.

[+Oltux72]

52 minutes ago, The_Truthwatcher said:

Hmm, I forgot about friction. Relatedly, why do you think spanreeds have settings for deciding the receiver and the transmitter? The way we understand the fabrials right now, that should not be needed.

Good point. I think, but that is a personal opinion I cannot find textual support for, that it is a social signaling function. "Please write; I am done"

[+Bzhydack]

2 hours ago, The_Truthwatcher said:

Hmm, I forgot about friction. Relatedly, why do you think spanreeds have settings for deciding the receiver and the transmitter? The way we understand the fabrials right now, that should not be needed.

It was in the books. Somewhere in Shalans chapters. One person ends writing, change seting by turning the Gem, and let write other person. But this can be simply signal, to prevent interrupting each other.

[+Oltux72]

2 hours ago, Bzhydack said:

It was in the books. Somewhere in Shalans chapters. One person ends writing, change seting by turning the Gem, and let write other person.

Yes, exactly. But is that a convention or is there a technical reason?

2 hours ago, Bzhydack said:

But this can be simply signal, to prevent interrupting each other.

Yes, or worse, breaking the spanreed, which is not exactly cheap. However, that is an assumption. I have found nothing in the text pointing to that conclusion. Have you?

I think this deserves a thread of its own.

[Karger]

9 hours ago, Oltux72 said:

The wheel must simply turn without the spanreeds making a difference and the spanreeds must join and you could use them to write a letter.

I don't think so.  I think the inner spanreed would actually make small circles as it went forwards faster.

[theTruthshaper]

9 hours ago, Oltux72 said:

The wheel must simply turn without the spanreeds making a difference and the spanreeds must join and you could use them to write a letter.

I am pretty sure that this will lead to the shattering of the gems. We know that happens when there is too much load on them