> Until recently most textile fabrication processes were limited to the creation of surface-based forms.
If you enjoyed this article, you might enjoy looking at the existing knitting machines, many are fascinating and very accessible. There are models powered by a hand crank[1], or with programmable patterns[2], or open source (open hardware).
Are there croquet machines yet? Googling is really confusing with lots of forum people saying there aren't any true ones, and lots of webshops claiming to sell them.
Wonder if I should braid my wired earphones for storage to prevent tangling. I can keep the cable inside a pouch with the earpieces out but that's not very satisfactory.
My current fascination knitted ropes/cables/cords. These are not the typical ropes that are spun and coiled and held together by friction. These ones made of synthetic fibres look like woven tubes, but the insides aren't hollow. The insides seem packed with more woven tubes.
What I really want to see though, are 3d knitted heavy duty carbon fibre flywheels of optimal shape such that it's under equal radial stress everywhere. The shape is interesting to compute for a solid one.
out of curiosity, what would you want a carbon fiber flywheel for? usually the value of a flywheel is for storing kinetic energy which a low density material like carbon fiber would not be suitable for.
What you lose in mass could be made up in velocity and radial distance. Depends on the breaking strength of the fibres. I haven't done any calculations myself to see if they are more promising than a steel one. A carbon fibre flywheel exploding might be somewhat less dangerous than steel if the bits flying away can crumple dissipatively.
Regarding where can they be used... they are just batteries with a different form factor. You can put them on the grid to have some inertia and be a place to dump or extract energy spikes. They may be commercially viable if rare earth based batteries become very expensive. At a smaller scale one could use them as a mechanical UPS for a building/datacenter. Maybe even to power golf carts, not sure how well they will steer because of the angular momentum.
That was somewhat relevant for data centers years ago when inverters were much more expensive, and even then only for the 20 seconds it took to start the diesel by connecting a simple soft starter to the diesel's induction generator (bringing it up to 50/60 rps (1500/1800 rpm) in about 5 seconds, then waiting for the turbo to spool up before it can deliver full power).
Even on the grid, batteries for sub-hour duration storage are cheap, as long as you place them at an already existing AC/DC converter site like a solar plant (or a modern internally-DC datacenter's centralized grid rectifier (AC/DC converter)).
Or even a HVDC transmission line.
Or a sufficiently modern aluminum/zinc smelter.
Pretty much anything large enough to bother that has at least a boost-PFC on the input. Because with those you could just put them there, beef up the capacitor a bit or better yet, use a native 3-phase PFC that doesn't have strong 100/120 Hz ripple on that capacitor, and then literally just control the already there input transistors to do your grid jobs. If it was the very cheap low efficiency rectifier approach, it also needs the rectifier upgraded to be controlled, so just use it on the higher efficiency ones before upgrading the others. (It's like 1% efficiency difference on 240V, and 2% on 120V power supplies.)
Flywheels can have much higher power density than any kind of battery.
There is no competition between batteries (low power density, high energy density, low storage cycle efficiency) and flywheels (high power density, low energy density, high storage cycle efficiency).
Flywheels (preferably levitated in vacuum) compete only with supercapacitors and superconducting rings (SMES = Superconducting Magnetic Energy Storage).
Supercapacitors/flywheels/SMES have their high-power applications, for which batteries are not appropriate.
Using them where batteries are the right solution is of course not a good choice.
Long time knitter - this is genuinely interesting. I’m trying to think of a killer use case for this, because scaling this up to create something for production looks pretty hard to me, or at least like it’s going to take 5+ years, and that’s if this team works with one of the big Japanese knit-in-the-round hardware companies.
That said, I love the idea of specifying and being able to knit in 3D. We just need a brilliant designer to come up with something that would be really great to have knit and can’t be knit with traditional techniques. And like six revs of the hardware for scale, tensioning, yarn size, etc.
In my other comment I suggested carbon fibre flywheels (for energy storage). A design that stresses the rotor uniformly to near it's breaking point would make a great storage device. If it's possible to add density to the fibres but without compromising strength, even better.
For a solid material with equal strength in all direction the optimal cross section is one with an exponentially decreasing thickness.
To give an intuitive reasoning, the more radially inwards you go there's is more material and velocity on the outside that's straining to break free, so you need larger cross-section to resist that. But now, this extra thickness too has to be supported as you move inwards. One can make this formal as a differential equation and the solution is an exponential profile.
Anyhow, for carbon fibres the optimal geometry will depend on the weave because a fibre has different strength along different directions.
AFAIK, carbon fiber flywheels that are levitated in vacuum and that exceed the energy density of the metallic flywheels have already been made and used in certain experiments, even if I am not aware of any such flywheel being available commercially.
There was also some research for using such flywheels for energy recovery in very heavy vehicles with electric motors, e.g. tanks with a turbo-electric generator, but the use in a vehicle has obvious difficulties. Even if the flywheels are paired, to avoid influencing the mobility of the vehicle, that still causes high internal stresses in the case holding the pair of flywheels when the vehicle rotates, which can lead to fatigue failures.
I chose it as my undergraduate project literally several decades ago.
3D woven ones might be stronger as they might resist laminar separation of circumferential layers more. Going by units, the product of stress and volume has the same units as kinetic energy. So it appears breaking stress and volume might be what limits the stored kinetic energy. This addresses doubt and curiosity raised by one comment (not yours).
Actually this should be a call-for-proposal for Y Combinator, demonstrating carbon fiber knitting.
Carbon fiber is typically woven in a simple fashion, to keep the strands straight because high tensile strength is the key.
But if it can be shown that knitted structures can preserve the tensile strength, that would be interesting indeed.
Think about the recent Titan submersible failure due to carbon fiber construction. What if instead of sheets of carbon fiber that could delaminate, you had a solid knitted carbon fiber shape? You might be able to demonstrate knitting that has more isotopic strength under both compressive and tensile loads.
Symmetrical or vertical knitting layers in the development of textile manufacturing was prototyped using the loom in Lowell, MA. There was labour movement amongst the girls attending lectures by Emerson/Adams.
In addition to directly creating volumes of knitting, rather than sheets or surfaces, this also reduces constraints on stitch connection, since it can depart from the strict structure of alternating row passes.
The Lowell Offering may be in line with the work presented in this paper.
Could this effectively “3D print” soft and deformable objects? How would it compare to other techniques that 3D print soft and deformable objects (I know you can print something like a mesh that is made of rigid material but itself deformable)?
> Until recently most textile fabrication processes were limited to the creation of surface-based forms.
If you enjoyed this article, you might enjoy looking at the existing knitting machines, many are fascinating and very accessible. There are models powered by a hand crank[1], or with programmable patterns[2], or open source (open hardware).
[1]: https://en.wikipedia.org/wiki/Circular_knitting#/media/File%...
[2]: https://machineknitting.fandom.com/wiki/Silver_F370K
and if you need help choosing which is best for your needs...
>> https://www.changhua-knitting-machine.com/how-to-select-the-...
Are there croquet machines yet? Googling is really confusing with lots of forum people saying there aren't any true ones, and lots of webshops claiming to sell them.
There are some simplified crochet patterns that can be mechanized, but for the most part we haven't found a way to generically mechanize crochet.
I don't fully understand why, apparently most patterns require manipulating the yarn in a way that simply requires human dexterity?
No. Machines cannot do that reliably, it's still in the realm of research. Crochet is much less simplifiable compared to knitting
crochet, sir. croquet is a game with balls and mallets ;)
He knows what he said. Now can we have an automated machine for balls and mallets please!
Are you Daniel Craig :) ?
That's a game with balls and mallets. You're thinking of croquettes
Just yesterday I was mentioning about the shared fascination with everything knitting, weaving, knitting, tatting, crocheting and braiding.
https://news.ycombinator.com/item?id=46039952
Wonder if I should braid my wired earphones for storage to prevent tangling. I can keep the cable inside a pouch with the earpieces out but that's not very satisfactory.
My current fascination knitted ropes/cables/cords. These are not the typical ropes that are spun and coiled and held together by friction. These ones made of synthetic fibres look like woven tubes, but the insides aren't hollow. The insides seem packed with more woven tubes.
What I really want to see though, are 3d knitted heavy duty carbon fibre flywheels of optimal shape such that it's under equal radial stress everywhere. The shape is interesting to compute for a solid one.
out of curiosity, what would you want a carbon fiber flywheel for? usually the value of a flywheel is for storing kinetic energy which a low density material like carbon fiber would not be suitable for.
What you lose in mass could be made up in velocity and radial distance. Depends on the breaking strength of the fibres. I haven't done any calculations myself to see if they are more promising than a steel one. A carbon fibre flywheel exploding might be somewhat less dangerous than steel if the bits flying away can crumple dissipatively.
Regarding where can they be used... they are just batteries with a different form factor. You can put them on the grid to have some inertia and be a place to dump or extract energy spikes. They may be commercially viable if rare earth based batteries become very expensive. At a smaller scale one could use them as a mechanical UPS for a building/datacenter. Maybe even to power golf carts, not sure how well they will steer because of the angular momentum.
That was somewhat relevant for data centers years ago when inverters were much more expensive, and even then only for the 20 seconds it took to start the diesel by connecting a simple soft starter to the diesel's induction generator (bringing it up to 50/60 rps (1500/1800 rpm) in about 5 seconds, then waiting for the turbo to spool up before it can deliver full power).
Even on the grid, batteries for sub-hour duration storage are cheap, as long as you place them at an already existing AC/DC converter site like a solar plant (or a modern internally-DC datacenter's centralized grid rectifier (AC/DC converter)).
Or even a HVDC transmission line.
Or a sufficiently modern aluminum/zinc smelter. Pretty much anything large enough to bother that has at least a boost-PFC on the input. Because with those you could just put them there, beef up the capacitor a bit or better yet, use a native 3-phase PFC that doesn't have strong 100/120 Hz ripple on that capacitor, and then literally just control the already there input transistors to do your grid jobs. If it was the very cheap low efficiency rectifier approach, it also needs the rectifier upgraded to be controlled, so just use it on the higher efficiency ones before upgrading the others. (It's like 1% efficiency difference on 240V, and 2% on 120V power supplies.)
Flywheels can have much higher power density than any kind of battery.
There is no competition between batteries (low power density, high energy density, low storage cycle efficiency) and flywheels (high power density, low energy density, high storage cycle efficiency).
Flywheels (preferably levitated in vacuum) compete only with supercapacitors and superconducting rings (SMES = Superconducting Magnetic Energy Storage).
Supercapacitors/flywheels/SMES have their high-power applications, for which batteries are not appropriate.
Using them where batteries are the right solution is of course not a good choice.
Long time knitter - this is genuinely interesting. I’m trying to think of a killer use case for this, because scaling this up to create something for production looks pretty hard to me, or at least like it’s going to take 5+ years, and that’s if this team works with one of the big Japanese knit-in-the-round hardware companies.
That said, I love the idea of specifying and being able to knit in 3D. We just need a brilliant designer to come up with something that would be really great to have knit and can’t be knit with traditional techniques. And like six revs of the hardware for scale, tensioning, yarn size, etc.
Anyway - really cool.
Someone needs to knit a Menger Sponge or Sierpinski Pyramid https://en.wikipedia.org/wiki/Menger_sponge
That is one of the challenges that must be accepted by the solid knitting community… and maybe find a way that it doesn’t collapse on itself.
Yes, I also want to see this.
Use a mirror?
Carbon fibre, maybe? You could get a high continuous fibre content without layer weaknesses. That's got to be interesting.
Yes indeed.
In my other comment I suggested carbon fibre flywheels (for energy storage). A design that stresses the rotor uniformly to near it's breaking point would make a great storage device. If it's possible to add density to the fibres but without compromising strength, even better.
For a solid material with equal strength in all direction the optimal cross section is one with an exponentially decreasing thickness.
To give an intuitive reasoning, the more radially inwards you go there's is more material and velocity on the outside that's straining to break free, so you need larger cross-section to resist that. But now, this extra thickness too has to be supported as you move inwards. One can make this formal as a differential equation and the solution is an exponential profile.
Anyhow, for carbon fibres the optimal geometry will depend on the weave because a fibre has different strength along different directions.
AFAIK, carbon fiber flywheels that are levitated in vacuum and that exceed the energy density of the metallic flywheels have already been made and used in certain experiments, even if I am not aware of any such flywheel being available commercially.
There was also some research for using such flywheels for energy recovery in very heavy vehicles with electric motors, e.g. tanks with a turbo-electric generator, but the use in a vehicle has obvious difficulties. Even if the flywheels are paired, to avoid influencing the mobility of the vehicle, that still causes high internal stresses in the case holding the pair of flywheels when the vehicle rotates, which can lead to fatigue failures.
Right.
I chose it as my undergraduate project literally several decades ago.
3D woven ones might be stronger as they might resist laminar separation of circumferential layers more. Going by units, the product of stress and volume has the same units as kinetic energy. So it appears breaking stress and volume might be what limits the stored kinetic energy. This addresses doubt and curiosity raised by one comment (not yours).
Actually this should be a call-for-proposal for Y Combinator, demonstrating carbon fiber knitting.
Carbon fiber is typically woven in a simple fashion, to keep the strands straight because high tensile strength is the key.
But if it can be shown that knitted structures can preserve the tensile strength, that would be interesting indeed.
Think about the recent Titan submersible failure due to carbon fiber construction. What if instead of sheets of carbon fiber that could delaminate, you had a solid knitted carbon fiber shape? You might be able to demonstrate knitting that has more isotopic strength under both compressive and tensile loads.
Nice idea! Both for woven goods and I guess parts.
Video: https://www.youtube.com/watch?v=cwFmB0L_4HY
Symmetrical or vertical knitting layers in the development of textile manufacturing was prototyped using the loom in Lowell, MA. There was labour movement amongst the girls attending lectures by Emerson/Adams.
In addition to directly creating volumes of knitting, rather than sheets or surfaces, this also reduces constraints on stitch connection, since it can depart from the strict structure of alternating row passes.
The Lowell Offering may be in line with the work presented in this paper.
[1]: https://catalog.hathitrust.org/Record/000549503
Could this effectively “3D print” soft and deformable objects? How would it compare to other techniques that 3D print soft and deformable objects (I know you can print something like a mesh that is made of rigid material but itself deformable)?
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