Engineers Develop 'Ultrarope' For World's Highest Elevator

HughPickens.com writes: Halfway up the Shard, London's tallest skyscraper, you are asked to step out of the elevator at the transfer floor, or "sky lobby," a necessary inconvenience in order to reach the upper half of the building, and a symptom of the limits of elevators today. To ascend a mile-high (1.6km) tower using the same technology could necessitate changing elevators as many as 10 times. Elevators traveling distances of more than 500m [1,640 ft] have not been feasible because the weight of the steel cables themselves becomes so great. Now, after nine years of rigorous testing, Kone has released Ultrarope — a material composed of carbon-fiber covered in a friction-proof coating that weighs a seventh of the steel cables, making elevators of up to 1km (0.6 miles) in height feasible to build.

Kone's creation was chosen to be installed in what's destined to become the world's tallest building, the Kingdom Tower in Jeddah, Saudi Arabia. When completed in 2020, the tower will stand a full kilometer in height, and will boast the world's tallest elevator at 660m (2,165ft). A 1km-tall tower may seem staggering, but is this the build-able limit? Most probably not, according to Dr. Sang Dae Kim. "With Kingdom Tower we now have a design that reaches around 1 km in height. Later on, someone will push for 1 mile, and then 2 km," says Kim. He adds that, technically speaking, 2 km might be possible at the current time. Anything higher would require new materials and building techniques.

Comments

just put a motor on the elevator itself

[Noah Haders]

i would do away with the motor at the top of the shaft, and instead electrify each individual elevator so it has motive power. seems like the best solution to me.

Re:just put a motor on the elevator itself

[BarbaraHudson]

The cable doesn't arrest the fall - brakes do.

Re: just put a motor on the elevator itself

[pavon]

No, you could use a conductive rail, like a subway, and rack and pinion system to move the elevator. The rack and rail would add a fair bit more total weight to the building compared to a cable. But more importantly, the motors would have to be much much more powerful! Modern elevator systems have a counter-weight balanced on the other side of that cable, which means the motor only has to overcome friction and the small difference in weight between the elevator and counterweight (which varies depending on current payload). The motor on an elevator like Noah is suggesting would have to provide enough force to counteract the entire weight of the elevator + payload + motor + friction, which is at least an order of magnitude more than a traditional elevator.

Re: just put a motor on the elevator itself

[Anonymous Coward]

Calling out a person for behavior you present is not going to change anything.

The main problem with rails is that you need a sliding contact. That means arcing at the contact when the air gaps are eventually going to occur (nothing is 100% flat, and air pockets will eventually get between the contact and the brush). Arcing isn't going to cause immediate failure; but, it will leave a carbon / oxidation residue at the arc site. This means that future electricity will have to flow through a very small scale resistor, generating heat. Eventually the heat will cause pitting, accelerating failure.

This is why most in-wall electrical sockets are designed to scrape the plug slightly on insertion. It is a self-cleaning feature of electrical wall sockets, and any wall socket that doesn't provide some modicum of resistance when inserting a plug should be replaced as soon as possible. A loose wall socket will not clean the prongs on the plug, carbon will build up within the socket, and the heat will eventually lead to arcing that will melt the plug, the socket, or both (possibly starting a fire as a side effect).

The issues of contacts on long electrical rails can be fixed by turning the rails into flexible cables; but, that only recreates the cable problem. Even though an electrical cable could be theoretically lighter than the lift cable, it still has to lift its own weight, and an under-built electrical cable cannot entertain even micro-fractures in electrical conductivity without have an accelerated repair cycle.

Now you know why virtually all elevators use cables for lifting with a fixed motor.

Re: just put a motor on the elevator itself

[ShanghaiBill]

With a magical lightweight power cord, perhaps?

The British already have a twenty mile long extension cord that they use to power the trains going through the Channel Tunnel. They reel it out as each train goes through, and then wind it up afterwards to prepare for the next train. There is no other way to do it, since it is totally impossible to transfer electricity to a moving object through, say, a power rail.

Re:just put a motor on the elevator itself

[ihtoit]

you can build as high as you want as long as you can build a cable long enough to service the elevator. Cable length isn't a problem, the weight of the cable is. In systems such as this very simplified model of a counterweighted elevator http://s.hswstatic.com/gif/bt4... it's assumed that the rope weighs nothing, therefore the counterweight only needs to weigh 25lb - even taking into account the rope's weight, all other things being equal it balances itself. That's handy, scaling up you only need a 400lb counterweight for a lift rated at MGW: 1600lb (ten persons (800lb) + 800lb car). This arrangement does of course necessitate four times the length of cable as the height of the shaft, and with another shaft-length you can actually mount the motor at the bottom, negating the requirement for a counterweight - the motor only has to overcome the weight of the car through the system, which practically means it's pulling against a quarter of it. For some reason that's not really practical, so in this arrangement you'd have a counterweight one side, top-anchor the other end of the rope and have the motor roll the cable somewhere in between. FWIW when you see an elevator car with four cables, you're not seeing four cables, it's one cable. It's this arrangement of three (strictly, four, but the car pulley can be and often is a twin) pulleys, a counterweight and a top anchor. Other setups have the anchor point actually on the roof of the car, still others have the car and the counterweight on their own bottom pulleys, both ends top-anchored and the motor in the middle sharing rope between essentially two double systems.

(grew up in a tower where the elevator spent more time stuck between floors than enough, often with me trapped in it. Hearing firefighters clambering around up there to attach car batteries to the brake solenoids so they can lower the car to the ground after eight hours is a terrifying thing for a four year old. Nerd points for spotting the ropes and asking about them when they were fixing the thing, though).

Re:just put a motor on the elevator itself

[germansausage]

He has it exactly right. The tension on the cable pulls on the elevator brake to release them. If there is no tension on the cable, ie pulley or cable fails, the cable looses tension and the brakes apply.

Re: just put a motor on the elevator itself

[fustakrakich]

Maybe we should apply this great cable technology to subway trains. I do notice the pits on the third rail. They always have to send some poor guy out to sand them out real quick before the next train comes.

Re: just put a motor on the elevator itself

[Anonymous Coward]

Train rails are excessively thick. This coupled with scrubbers around the brushes means that the rail is cleaned prior to contact, and the wear of the (cleaner) rail is minimized. This coupled with the minimal movement of a ground fixed tie and a very large amount of metal to wear through leaves the effective life of the rail in the +10 year range (if not +50 year range).

A building will have few of these advantages. Buildings in the 30+ story range sway. Excessively thick rails get far more expensive to run vertically, so the rail thickness will be minimized. This increases the chance of flex and decreases the amount of rail to wear out by scrubbing or pitting. It isn't that it can't be done, it's just that it can't be done easily, which translates to cheaply.

Re: just put a motor on the elevator itself

[Anonymous Coward]

Induction incurs a lot of losses. Yes, it can travel a small air gap easily; however, it does so with a lot of compromises. Some of the main challenges is heat generation and low power transmission efficiency. Increasing the power can attempt to address the latter but only at a cost of more heat. Also, induction has extra challenges when considering a moving receiver, and if you decide to address these by moving the transmitter, you then have a lift problem to solve for your transmitter.

I'm not saying that it is impossible, but it is far, far cheaper and more reliable at this time to not attempt to use inductive charging on a self-powered elevator.

And keep in mind that we are blessed with elevator brakes that are actively held open. A self-powered electrical elevator car would have a pretty high constant draw to replicate the braking system, as it would have to pull solenoids against the breaking springs.

Finally, current elevators don't lift the car. It is counter balanced with a set of stacked weights. The elevator motor (a fixed mounted motor pulling the cables) only needs to lift the difference between the two weights of the loaded car and the counterbalance weight stack. A fully self-powered car of the kind we are considering would not have a counter balance (because it would lack the connecting cable) and therefore would need even more power to lift the entire mass of the car.

That's a large increase of needed power coupled with a large decrease in power delivery. It is far from a trivial engineering problem to solve, and is unlikely to be solved favorable within our lifetime.

What?/ Just 2 Km? That's it?!

[140Mandak262Jamuna]

So I guess the space elevator is not coming any time soon.

Re:trains don't need rope...

[luvirini]

Trains also do not need to pull straight up.

The real reason for the cables is to allow counterweights to balance much of the load. Thus with counterweight you are lifting only the carried weight, without you are lifting also the elevator chassis and any engine and such, a much larger load.

LSM

[jklovanc]

Linear Synchronous Motor Elevators Become a Reality

Re:LSM

[Warbothong]

Well this is the best thing I've seen! Why haven't these been pushed out into the commercial area?

For the same reason that maglev trains and HyperLoop-style vacuum tubes aren't ubiquitous: sending a dumb carriage along a smart track is far more expensive than sending a smart carriage along a dumb track, since there's much more track than there is carriage.

Narrowboats used to be the best way of moving materials around in-land, but "laying the track" (digging the canals, building the locks, etc.) took a lot of work.

Dumb boats were overshadowed by smarter locomotives: more difficult and expensive to build, but ran on much cheaper tracks.

Locomotives were overshadowed by smarter automobiles: more difficult to invent and require a smarter fuel network, but in some cases don't need *any* track laying.

The same argument applies to lifts: it's much cheaper to have a smart motor at the top and/or a smart carriage, with 660m of dumb shaft and cable, than having 660m of smart shaft.

World's highest dick-waving contest

[localroger]

Highest skyscraper is a hell of an expensive way to show your ability to get an erection. How much of the Burj Dubai is even occupied? Or for that matter even the *cough* whatever they're calling it now in NYC which gets a third of its patriotic 1776 feet from a totally nonfuctional dick-waving spire.

Re:Worthless

[TechyImmigrant]

Or build the building horizontally and put in moving walkways.

Just as much space, at a fraction of the cost and it doesn't have to exist to massage the ego of an oil rich prince who murders atheists for fun.

Re:The rate at which oil prices are dropping ...

[ShanghaiBill]

... we may have use the 2km long ultra strong ultra light cable to dredge the Saudi economy from the bottom of the Persian Gulf.

Nope. The Persian Gulf is very shallow, with an average depth of only 50 meters, and a deepest point of only 90 meters. Citation: Persian Gulf Geography

Armchair engineering at its finest

[mcrbids]

I'm probably going to lose some karma for this...

I, too, could come with a half-dozen answers that would be "far superior" to what 100+ years of the finest minds in the industry could come up with. But in reality, I really, seriously doubt that my designs would hold up because there's a *reason* that things are done the way they are.

Mechanical engineering is a *very old* industry, and any radical, new design would have significant hurdles to pass before it could be accepted and used in a real scenario. The cost of failure is very high and there are real lives on the line.

My first thought was to use something like a caterpillar drive along the sides of the shaft, each of which would operate like a mini elevator for perhaps 10 floors. But, very quickly, I can see that this type of system would have many, many more moving parts and consequently many more points of failure.

So, I think it *might* be best to trust that 100+ years of experience are, in fact, at work, and that we should first understand that there is *real knowledge* at work before assuming that our half-baked and thoroughly unproven ideas hold any merit in reality.... ?

Re:Armchair engineering at its finest

[NoNonAlphaCharsHere]

That has GOT to be the most trollish post I've ever ever ever read here. You have NO IDEA how Slashdot works, do you?

Better Way

[JimSadler]

The RCA building in NYC uses compressed air and the elevator is effectively a dart flying up the shaft. With an accelerometer installed to trip the brake if too rapid a descent occurs there is no need at all for cables.