8 ms·

A new lightweight lift cable will let buildings soar ever upward

79 points by sethbannon 13y ago

PufferBuffer 13y ago
I wonder how many technologies out there exist, which would allow us to go far beyond our current state of the world, but we simply don't know about them. In a such an interconnected world, it sure feels that innovations are not very well combined to move us forward. Good article, btw.
chiph 13y ago
What's the minimum bending radius for carbon-fiber?
- durkie 13y ago
  it depends entirely on the matrix material, and then after that the mechanics of whatever structure you're building. Pure carbon fiber is far too delicate to be used on its own without a matrix, but the fibers themselves behave very much like a lock of hair.
akkartik 13y ago
Are elevators really the limiting factor? Why can't we setup two staggered half-kilometer shafts?
- jacobparker 13y ago
  I can't comment on the first part (seems weird to me?) but they briefly mention "staged" elevators towards the end of the article (although it does not answer the first question.)
- gaadd33 13y ago
  I assume the people who spend a large amount on the top floors of a very tall skyscraper don't want to have to change elevators halfway there.
- hboon 13y ago
  There are already many buildings that segregate elevator systems into multiple stacked towers such as the Petronas Towers in Malaysia [1]. But in Petronas' case, it can become too complex that even the staff don't always get it right. [1] http://en.wikipedia.org/wiki/Petronas_Towers#Lift_system http://en.wikipedia.org/wiki/Petronas_Towers#Lift_system (note, lift means the same thing here)
jordanb 13y ago
I went to a talk by an SOM architect a few years ago, while Tapei 101 was under construction. He said the principal limiting factor for the height of a super-tall structure is economics. In fact buildings over sixty stories or so don't make much sense in any real-estate market -- not even Manhattan or Hong Kong -- if viewed from the perspective of real estate as a commodity. Where supertalls make economic sense is if they can be turned into a prestige address when the building becomes a landmark. With respect to wire rope, there is already synthetic rope with dramatically better tensile strength, and it's displacing wire rope in many applications. Synthetics have a lot less hardness than steel though, and are subject to abrasion. I don't know if a carbon fiber rope would be harder than a steel rope or not, but I know from experience that CFRP panels are not nearly as hard as steel plate.
- durkie 13y ago
  There are a wide variety of coatings out there that could address this -- especially for an application requiring some flexibility like this, there are a wide variety of polyurethanes that have super high abrasion resistance compared to steel. It would probably also be practical to simply modify the bearing surfaces as well.
  - ars 13y ago
    The abrasion problem is more internal than external. The individual fibers run against each other when the bend (since some bend more than others). Without some elasticity the internal forces will destroy the cable. Not sure how elastic CF is compared to steel. They may be able to help with some clever rope making techniques.
- contingencies 13y ago
  I too saw Taipei 101 under construction... incredible to think it's in a serious earthquake zone. there is already synthetic rope with dramatically better tensile strength, and it's displacing wire rope in many applications The article did mention the use of a dual layer anti-abrasian coating for durability. Honestly though, why increase height and density still further? There are stupendous issues here with efficiency with regards to food, water, and HVAC - if nothing else. My personal view is that cities of the present are essentially anachronisms spawned from 20th century post-industrialism intertia: artifacts of outmoded labour markets, planning laws and now-quaint geospatial efficiencies. As the cost of living in cities rises due to the shortage of land, the requirement for importing food and water, and the artificiality of maintaining a reasonable healthy lifestyle in high density urban environment, my bet is that, broadly speaking, emerging labour markets (our type of industry, for example) based on new technologies for communications and a reformed education system will cause a mass migration of professionals away from cities, back to a more sustainable, decentralized model. Sort of like the green banker-belt outside of London, but on a far larger scale. In short, I believe that while the city will not disappear, its face will change .. and certainly not primarily through ever-taller buildings.
dylangs1030 13y ago
I love when scientific interest articles pop up on the front page like this. It's really amazing to me that one of the things that holds skyscraper maximum height back is the practical concern of lift height. That's simply not the first thing I would think of if someone asked me the question. But while that's cool, I don't think we necessarily should be building taller skyscrapers. They're not very practical. If they were, we'd have quasi-Coruscant cities where all the buildings were as tall as the Empire State Building or Willis Tower. Instead, what tends to actually happen is the buildings become landmarks that attract a lot of attention but comparatively little real estate. Furthermore, when cities expand they generally need to build upwards quickly and forsake extravagance for practicality. If it takes 10 years to build a monolithic structure higher than the skyline, that's a project that's burning money for a long time until it's profitable.
WalterBright 13y ago
Maybe I should patent the idea of putting the motor in the car and doing away with the ropes altogether. I.e. imagine a vertical electric train.
- rogerbinns 13y ago
  The ropes provide energy efficiency. On one end is the lift car, but on the other and going in the opposite direction is a counterweight of similar mass. The lift motor only needs to move the difference in mass. If you put the motor in the car without ropes then it has to be powerful enough to lift the whole car and all occupants. And if you want any hope of energy efficiency you'd need regenerative braking for when going down. This would make the lift car a lot heavier and the electrical system a lot more complicated. Sometimes simpler is better!
  - Someone 13y ago
    Yes, but in either case, energy is lost in accelerating and decelerating mass. If your cable is a mile long, accelerating and decelerating it costs quite some energy, too. Long cable also have problems with swaying and elasticity. Also, a main problem with high rise buildings is loss of floor space at lower heights (the water, electricity, waste, and person traffic of floors 2 to N all have to pass though floor 1) Ropeless elevators can have a huge advantage there, as they allow one to hang multiple elevators in a single shaft that both service the full range of floors. Yes, that requires sophisticated software to prevent lift cars from having to pass through each other too often (some designs allow cabines to do that by making it possible for the cars to move horizontally, too), but it is an active research area. "ropeless elevator" is not on Wikipedia yet; the best (but tangential and possibly slightly commercial) I could find Googling it is http://www.barkermohandas.com/images/Integrated%20Vertical%20&%20Horizontal%20Transport.pdf http://www.barkermohandas.com/images/Integrated%20Vertical%2..., which is about a system with wires that allows one to move cars horizontally by sliding them from one car frame to another using linear motors.
    - versk 13y ago
      Not everything is a software problem, I think you are hugely underestimating how much more power is required for an elevator to self propel vertically upwards compared to a counterweight system. I'm not an expert but I'd have to guess its at least 10x if not potentially much more
ars 13y ago
Is it really that impractical to put the motor in the car? The elevator anyway needs rails on the side, if for nothing else to provide something for the emergency brakes. Use regenerative braking on the way down so you don't need a counter weight - although that does mean you need a much large motor, you might save on energy, but power requirements would still be high.
- dmckeon 13y ago
  Assuming that the weights of the lift car and the passenger load remain about the same, moving the motor to the car saves the weight of the cable, but adds the motor, power contacts, and whatever traction device (cog?) moves the car. edit: completely overlooked counter-weight balance, see: https://news.ycombinator.com/item?id=5887522 https://news.ycombinator.com/item?id=5887522 Adding regenerative braking adds some form of energy storage - batteries, flywheel, compressed air, or whatever. A flywheel might be lighter than batteries, but torque I/O might affect passenger comfort. It would be interesting to see how CF holds up over time. ISTR that Kevlar rope is very strong, but turned out to have unexpected issues with repeated jerky load/unload cycles. Presumably the CF elevator cable would have adequate testing before commercial use.
  - ars 13y ago
    For regenerative I would just dump it back into the grid. There are plenty of other consumers in a skyscraper, the meter would not even flow backward. I'm also wondering this about CF - my understanding is it's strong, but has very poor abrasion resistance. Even if you avoid external abrasion you can't avoid internal as the fibers rub against each other when they bend.
aaron695 13y ago
It seems to be missing the real issue that you generally don't want lifts that go all the way to the top in one run because it uses up to much real estate. You have to have multi-stage lifts else the whole building becomes full of lifts rather than offices etc Much more exciting for projects like loon I would have thought.
- ampersandy 13y ago
  I don't see why that would be a real-estate issue, wouldn't the other stages of the lifts take up just as much space?
  - zalzane 13y ago
    Lifts on the ground floor have to service the entire tower, where a lift that started half way up the tower would only have to serve half as much traffic as the ground floor lift, so you could have like a dozen lifts that go from ground->50%, and 6 lifts that go from 50% to top.
  - aaron695 13y ago
    Because when you stack lifts on top of each other in different parts of the shaft you can have multiple lifts running at once, hence multiple time the efficiency per m2. (High latency though) Lifts are also limited by speeds, if they go too fast they make some people queasy. This is also an issue to contend with since express elevator are limited in the 'express' bit. Edit: to be a bit clearer if you split up a shaft into 4 sections with fours lifts you can have four lifts full of people being moved, hence your bandwidth is 4 times as much. Taken to extreme you have one for every floor http://en.wikipedia.org/wiki/Paternoster http://en.wikipedia.org/wiki/Paternoster
s0rce 13y ago
edit: I take it back, my memory is failing me. Some intermediate-modulus high-strength PAN based carbon fibers have strengths exceeding most synthetic polymers. Here is a comparison I put together a few years back for some research on fibers. https://dl.dropboxusercontent.com/u/3730003/fiber%20strength%20to%20weight%20ratio.pdf https://dl.dropboxusercontent.com/u/3730003/fiber%20strength... This is quite surprising as many synthetic polymers (zylon, spectra/dyneema, kevlar) are much stronger than carbon fiber. There is even a competition to make the strongest rope for potential space elevators: http://www.isec.org/sec/index.php/technical-program/strong-tether-comp http://www.isec.org/sec/index.php/technical-program/strong-t...
jlgreco 13y ago
How tall does a building have to get before all the other "utility" stuff becomes a limiting factor for any reasonable floor-space/building footprint? I imagine the space you need to dedicate on each floor to water/sewage, electrical, ventilation, etc goes up approximately linearly with the addition of floors. You also need to add more elevators as you add more floors, just to service the additional people each floor implies. Add too many floors and eventually some of the floors become little more than shafts running to other floors. I don't really know anything about architecture so maybe my intuition is off. Maybe these concerns are never realized with the number of floors that are practical for other reasons?
- ics 13y ago
  The Burj received some pretty unflattering coverage a year or two ago for their "poop trucks", which were necessary for moving however many tons of feces 30,000+ people produce per day. However in many cases the building "cheats", i.e. the floor area shrinks rapidly the higher you go up and so the strain is better distributed throughout the system. I say cheat only because it's much more challenging to manage a uniform (or close to it) floor area from base to top such as the old WTC. The GE Building at 30 Rock is a good example of a building that used the building code (NYC setbacks, a good topic in itself if you're interested) to its advantage in planning the elevators and ventilation. It was mentioned in another comment above I think but in reality the economics are a much more controlling factor than hard engineering, and most of the engineering problems are about doing X for $YYY rather than XYZ for glory and innovation. Edit: This link might be of interest... http://www.bloomberg.com/news/2013-01-02/double-deck-elevators-rise-as-tallest-towers-test-limits.html http://www.bloomberg.com/news/2013-01-02/double-deck-elevato...
  - crazytony 13y ago
    The problem has more to do with Dubai than with the building. Many buildings in Dubai employ similar schemes because the sewerage system wasn't scaled as the city grew. This is like a lot of things in Dubai: roads, public transport and the airport which is currently being more than doubled.
marcosscriven 13y ago
This reminds me of a book back from the nineties called "Faster" by James Gleick. There was a chapter on lifts being the limit to building height, although I seem to recall it was more down to shaft space rather than cable strength.
thornjm 13y ago
There are a number of suggestions to remove the cables altogether and have the car power itself, but would it not be easier to have the cables removed and still power it through the building? Something like electromagnets, rail gun style?
OnionChamp 13y ago
"The other mile-high club"? Together with the brokeback mountain cover, this is pretty pathetic.
spIrr 13y ago
Promo page for the new technology (called "Ultrarope"): http://download.kone.com/ultrarope/index.htm http://download.kone.com/ultrarope/index.htm
Sami_Lehtinen 13y ago
I have been wondering why elevators aren't just vertical trains. No limit to distance, and several cars could use same tracks. Currently elevator shafts can reserve huge part of floor space. Down going cars could run motors in regenerative mode. So there's no need for heavy counterweights or heavy ropes. Another effeciency trick is trying to get people going to same destination into same car, reducing number of required stops. Might add some latency, but makes overall throughput better.
ams6110 13y ago
Why do tall elevators use cables at all? Why not a system with a motor driven gear wheel on the car engaged with toothed rails on the sides of the shaft. You would not have counterweights but you could recover energy used in lifting on the next descent, and store it in supercapacitors for use on the next lift, which would achieve the same ends.
paul_f 13y ago
Lots of discussion here about ratios of usable space in tall structures. Why don't we solve that by putting the elevators on the outside of the building?
- ams6110 13y ago
  If for no other reason, it would reduce available windows, and offices with windows are high-rent items. That said I have seen a few buildings with exterior "glass elevators" but it seems to be mostly a novelty.
  - paul_f 13y ago
    It's always a novelty before it becomes mainstream. Have the elevators run in tracks of some sort, rather than in a shaft. Elevator won't block the view until it goes by.

79 points by sethbannon 13y ago

I wonder how many technologies out there exist, which would allow us to go far beyond our current state of the world, but we simply don't know about them. In a such an interconnected world, it sure feels that innovations are not very well combined to move us forward. Good article, btw.

chiph 13y ago

What's the minimum bending radius for carbon-fiber?

durkie 13y ago
it depends entirely on the matrix material, and then after that the mechanics of whatever structure you're building. Pure carbon fiber is far too delicate to be used on its own without a matrix, but the fibers themselves behave very much like a lock of hair.

akkartik 13y ago

Are elevators really the limiting factor? Why can't we setup two staggered half-kilometer shafts?

jacobparker 13y ago
I can't comment on the first part (seems weird to me?) but they briefly mention "staged" elevators towards the end of the article (although it does not answer the first question.)
gaadd33 13y ago
I assume the people who spend a large amount on the top floors of a very tall skyscraper don't want to have to change elevators halfway there.
hboon 13y ago
There are already many buildings that segregate elevator systems into multiple stacked towers such as the Petronas Towers in Malaysia [1]. But in Petronas' case, it can become too complex that even the staff don't always get it right. [1] http://en.wikipedia.org/wiki/Petronas_Towers#Lift_system http://en.wikipedia.org/wiki/Petronas_Towers#Lift_system (note, lift means the same thing here)

jordanb 13y ago

I went to a talk by an SOM architect a few years ago, while Tapei 101 was under construction. He said the principal limiting factor for the height of a super-tall structure is economics. In fact buildings over sixty stories or so don't make much sense in any real-estate market -- not even Manhattan or Hong Kong -- if viewed from the perspective of real estate as a commodity. Where supertalls make economic sense is if they can be turned into a prestige address when the building becomes a landmark. With respect to wire rope, there is already synthetic rope with dramatically better tensile strength, and it's displacing wire rope in many applications. Synthetics have a lot less hardness than steel though, and are subject to abrasion. I don't know if a carbon fiber rope would be harder than a steel rope or not, but I know from experience that CFRP panels are not nearly as hard as steel plate.

durkie 13y ago
There are a wide variety of coatings out there that could address this -- especially for an application requiring some flexibility like this, there are a wide variety of polyurethanes that have super high abrasion resistance compared to steel. It would probably also be practical to simply modify the bearing surfaces as well.
- ars 13y ago
  The abrasion problem is more internal than external. The individual fibers run against each other when the bend (since some bend more than others). Without some elasticity the internal forces will destroy the cable. Not sure how elastic CF is compared to steel. They may be able to help with some clever rope making techniques.
contingencies 13y ago
I too saw Taipei 101 under construction... incredible to think it's in a serious earthquake zone. there is already synthetic rope with dramatically better tensile strength, and it's displacing wire rope in many applications The article did mention the use of a dual layer anti-abrasian coating for durability. Honestly though, why increase height and density still further? There are stupendous issues here with efficiency with regards to food, water, and HVAC - if nothing else. My personal view is that cities of the present are essentially anachronisms spawned from 20th century post-industrialism intertia: artifacts of outmoded labour markets, planning laws and now-quaint geospatial efficiencies. As the cost of living in cities rises due to the shortage of land, the requirement for importing food and water, and the artificiality of maintaining a reasonable healthy lifestyle in high density urban environment, my bet is that, broadly speaking, emerging labour markets (our type of industry, for example) based on new technologies for communications and a reformed education system will cause a mass migration of professionals away from cities, back to a more sustainable, decentralized model. Sort of like the green banker-belt outside of London, but on a far larger scale. In short, I believe that while the city will not disappear, its face will change .. and certainly not primarily through ever-taller buildings.

dylangs1030 13y ago

I love when scientific interest articles pop up on the front page like this. It's really amazing to me that one of the things that holds skyscraper maximum height back is the practical concern of lift height. That's simply not the first thing I would think of if someone asked me the question. But while that's cool, I don't think we necessarily should be building taller skyscrapers. They're not very practical. If they were, we'd have quasi-Coruscant cities where all the buildings were as tall as the Empire State Building or Willis Tower. Instead, what tends to actually happen is the buildings become landmarks that attract a lot of attention but comparatively little real estate. Furthermore, when cities expand they generally need to build upwards quickly and forsake extravagance for practicality. If it takes 10 years to build a monolithic structure higher than the skyline, that's a project that's burning money for a long time until it's profitable.

WalterBright 13y ago

Maybe I should patent the idea of putting the motor in the car and doing away with the ropes altogether. I.e. imagine a vertical electric train.

rogerbinns 13y ago
The ropes provide energy efficiency. On one end is the lift car, but on the other and going in the opposite direction is a counterweight of similar mass. The lift motor only needs to move the difference in mass. If you put the motor in the car without ropes then it has to be powerful enough to lift the whole car and all occupants. And if you want any hope of energy efficiency you'd need regenerative braking for when going down. This would make the lift car a lot heavier and the electrical system a lot more complicated. Sometimes simpler is better!
- Someone 13y ago
  Yes, but in either case, energy is lost in accelerating and decelerating mass. If your cable is a mile long, accelerating and decelerating it costs quite some energy, too. Long cable also have problems with swaying and elasticity. Also, a main problem with high rise buildings is loss of floor space at lower heights (the water, electricity, waste, and person traffic of floors 2 to N all have to pass though floor 1) Ropeless elevators can have a huge advantage there, as they allow one to hang multiple elevators in a single shaft that both service the full range of floors. Yes, that requires sophisticated software to prevent lift cars from having to pass through each other too often (some designs allow cabines to do that by making it possible for the cars to move horizontally, too), but it is an active research area. "ropeless elevator" is not on Wikipedia yet; the best (but tangential and possibly slightly commercial) I could find Googling it is http://www.barkermohandas.com/images/Integrated%20Vertical%20&%20Horizontal%20Transport.pdf http://www.barkermohandas.com/images/Integrated%20Vertical%2..., which is about a system with wires that allows one to move cars horizontally by sliding them from one car frame to another using linear motors.
  - versk 13y ago
    Not everything is a software problem, I think you are hugely underestimating how much more power is required for an elevator to self propel vertically upwards compared to a counterweight system. I'm not an expert but I'd have to guess its at least 10x if not potentially much more

ars 13y ago

Is it really that impractical to put the motor in the car? The elevator anyway needs rails on the side, if for nothing else to provide something for the emergency brakes. Use regenerative braking on the way down so you don't need a counter weight - although that does mean you need a much large motor, you might save on energy, but power requirements would still be high.

dmckeon 13y ago
Assuming that the weights of the lift car and the passenger load remain about the same, moving the motor to the car saves the weight of the cable, but adds the motor, power contacts, and whatever traction device (cog?) moves the car. edit: completely overlooked counter-weight balance, see: https://news.ycombinator.com/item?id=5887522 https://news.ycombinator.com/item?id=5887522 Adding regenerative braking adds some form of energy storage - batteries, flywheel, compressed air, or whatever. A flywheel might be lighter than batteries, but torque I/O might affect passenger comfort. It would be interesting to see how CF holds up over time. ISTR that Kevlar rope is very strong, but turned out to have unexpected issues with repeated jerky load/unload cycles. Presumably the CF elevator cable would have adequate testing before commercial use.
- ars 13y ago
  For regenerative I would just dump it back into the grid. There are plenty of other consumers in a skyscraper, the meter would not even flow backward. I'm also wondering this about CF - my understanding is it's strong, but has very poor abrasion resistance. Even if you avoid external abrasion you can't avoid internal as the fibers rub against each other when they bend.

aaron695 13y ago

It seems to be missing the real issue that you generally don't want lifts that go all the way to the top in one run because it uses up to much real estate. You have to have multi-stage lifts else the whole building becomes full of lifts rather than offices etc Much more exciting for projects like loon I would have thought.

ampersandy 13y ago
I don't see why that would be a real-estate issue, wouldn't the other stages of the lifts take up just as much space?
- zalzane 13y ago
  Lifts on the ground floor have to service the entire tower, where a lift that started half way up the tower would only have to serve half as much traffic as the ground floor lift, so you could have like a dozen lifts that go from ground->50%, and 6 lifts that go from 50% to top.
- aaron695 13y ago
  Because when you stack lifts on top of each other in different parts of the shaft you can have multiple lifts running at once, hence multiple time the efficiency per m2. (High latency though) Lifts are also limited by speeds, if they go too fast they make some people queasy. This is also an issue to contend with since express elevator are limited in the 'express' bit. Edit: to be a bit clearer if you split up a shaft into 4 sections with fours lifts you can have four lifts full of people being moved, hence your bandwidth is 4 times as much. Taken to extreme you have one for every floor http://en.wikipedia.org/wiki/Paternoster http://en.wikipedia.org/wiki/Paternoster

s0rce 13y ago

edit: I take it back, my memory is failing me. Some intermediate-modulus high-strength PAN based carbon fibers have strengths exceeding most synthetic polymers. Here is a comparison I put together a few years back for some research on fibers. https://dl.dropboxusercontent.com/u/3730003/fiber%20strength%20to%20weight%20ratio.pdf https://dl.dropboxusercontent.com/u/3730003/fiber%20strength... This is quite surprising as many synthetic polymers (zylon, spectra/dyneema, kevlar) are much stronger than carbon fiber. There is even a competition to make the strongest rope for potential space elevators: http://www.isec.org/sec/index.php/technical-program/strong-tether-comp http://www.isec.org/sec/index.php/technical-program/strong-t...

jlgreco 13y ago

How tall does a building have to get before all the other "utility" stuff becomes a limiting factor for any reasonable floor-space/building footprint? I imagine the space you need to dedicate on each floor to water/sewage, electrical, ventilation, etc goes up approximately linearly with the addition of floors. You also need to add more elevators as you add more floors, just to service the additional people each floor implies. Add too many floors and eventually some of the floors become little more than shafts running to other floors. I don't really know anything about architecture so maybe my intuition is off. Maybe these concerns are never realized with the number of floors that are practical for other reasons?

ics 13y ago
The Burj received some pretty unflattering coverage a year or two ago for their "poop trucks", which were necessary for moving however many tons of feces 30,000+ people produce per day. However in many cases the building "cheats", i.e. the floor area shrinks rapidly the higher you go up and so the strain is better distributed throughout the system. I say cheat only because it's much more challenging to manage a uniform (or close to it) floor area from base to top such as the old WTC. The GE Building at 30 Rock is a good example of a building that used the building code (NYC setbacks, a good topic in itself if you're interested) to its advantage in planning the elevators and ventilation. It was mentioned in another comment above I think but in reality the economics are a much more controlling factor than hard engineering, and most of the engineering problems are about doing X for $YYY rather than XYZ for glory and innovation. Edit: This link might be of interest... http://www.bloomberg.com/news/2013-01-02/double-deck-elevators-rise-as-tallest-towers-test-limits.html http://www.bloomberg.com/news/2013-01-02/double-deck-elevato...
- crazytony 13y ago
  The problem has more to do with Dubai than with the building. Many buildings in Dubai employ similar schemes because the sewerage system wasn't scaled as the city grew. This is like a lot of things in Dubai: roads, public transport and the airport which is currently being more than doubled.

marcosscriven 13y ago

This reminds me of a book back from the nineties called "Faster" by James Gleick. There was a chapter on lifts being the limit to building height, although I seem to recall it was more down to shaft space rather than cable strength.

thornjm 13y ago

There are a number of suggestions to remove the cables altogether and have the car power itself, but would it not be easier to have the cables removed and still power it through the building? Something like electromagnets, rail gun style?

OnionChamp 13y ago

"The other mile-high club"? Together with the brokeback mountain cover, this is pretty pathetic.

spIrr 13y ago

Promo page for the new technology (called "Ultrarope"): http://download.kone.com/ultrarope/index.htm http://download.kone.com/ultrarope/index.htm

Sami_Lehtinen 13y ago

I have been wondering why elevators aren't just vertical trains. No limit to distance, and several cars could use same tracks. Currently elevator shafts can reserve huge part of floor space. Down going cars could run motors in regenerative mode. So there's no need for heavy counterweights or heavy ropes. Another effeciency trick is trying to get people going to same destination into same car, reducing number of required stops. Might add some latency, but makes overall throughput better.

ams6110 13y ago

Why do tall elevators use cables at all? Why not a system with a motor driven gear wheel on the car engaged with toothed rails on the sides of the shaft. You would not have counterweights but you could recover energy used in lifting on the next descent, and store it in supercapacitors for use on the next lift, which would achieve the same ends.

paul_f 13y ago

Lots of discussion here about ratios of usable space in tall structures. Why don't we solve that by putting the elevators on the outside of the building?

ams6110 13y ago
If for no other reason, it would reduce available windows, and offices with windows are high-rent items. That said I have seen a few buildings with exterior "glass elevators" but it seems to be mostly a novelty.
- paul_f 13y ago
  It's always a novelty before it becomes mainstream. Have the elevators run in tracks of some sort, rather than in a shaft. Elevator won't block the view until it goes by.