ThyssenKrupp Unveils Model of the MULTI, a Vertical Mass Transit System


Elevators haven’t changed much in 150 years; the controls got more sophisticated, but they basically remained a box pulled up by a cable, with one cab per shaft. This becomes a real problem as buildings get taller; the multiple shafts end up taking up a lot of valuable real estate, with only one little box in each. The cables get so heavy that you end up spending more energy moving cables than cab. As the buildings sway, the cables start swaying too. The elevators end up being a real limiting factor on the height of our buildings and the density of our cities, and a big factor in the high cost of high buildings.

Andreas Schierenbeck

Lloyd Alter/ Andreas Schierenbeck in Gijon/CC BY 2.0

This is an important urban issue; as ThyssenKrupp CEO Andreas Schierenbeck notes,

With severe restrictions on space, mid to high-rise developments have proved to be the most economically and environmentally viable developments to accommodate these rapidly growing urban populations.

Last year, ThyssenKrupp announced a solution to this problem: the MULTI lift system which gets rid of elevator cables, and instead runs each elevator cab as an independent vehicle on a vertical track, powered by linear induction motors. Because there were no cables, it meant that they could put more than one car in every shaft. In fact, they could put a continuous stream of them in.

They promised a working model within a year, and today at their Dijon Innovation Center, in northern Spain, they delivered.

They weren’t kidding when they said model; my first reaction was to paraphrase Derek Zoolander and scream “what is this, an elevator for ants? It has to be at least.... three times as big!” Because what they have built is a one-third full scale working model. Being fairly small, I asked to ride it but they said no, I could just watch it move.

mechanism in action

Lloyd Alter/CC BY 2.0

And move it does, in the most remarkable ways, unlike any elevator ever built. The cabs rise up on the tracks, powered by the linear induction motors; when they reach the end, top, bottom or any point where they want to move sideways, a section of track rotates and the cab goes sideways.

Watch my terrible video to see how this happens as Research Head Markus Jetter describes it. Note toward the end that Cab 4, resting by the side of the road, joins the fun; this demonstrates how cabs can be taken out of service and have maintenance done while the elevator keeps working.

It also shows how the elevator can run horizontally to connect other buildings, and to change the form of the buildings we build. The engineers at ThyssenKrupp were not trying to solve this problem; they just wanted to be able to switch shafts and run them in a loop. After all, they also make another product, the Accel moving walkway, which is probably a more sensible solution for moving horizontally (and the subject of another post). But the architects and designers who saw the concept just loved the idea of being able to break out of the standard vertical box.

A vertical mass transit system

From an operating point of view, it is much more like a mass transit system on its side than an elevator; a cab comes along every twenty seconds or so, one after another. Don’t try and hold the door, because they are following a sequence where the next cab is coming up behind you. It won’t have any floor buttons, because it is serving as a vertical express train; you get off at what used to be called a sky lobby and transfer to the local that works like a normal elevator. The cabs are slower and smaller, because there are a lot more of them another is almost no waiting, (and since fast elevators have lots of problems) people probably won’t mind. The advantages add up:

In a manner similar to a metro system operation, the MULTI design can incorporate various self-propelled elevator cabins per shaft running in a loop, increasing the shaft transport capacity by up to 50% and making it possible to reduce the elevator footprint in buildings by half... The overall increase in efficiency also translates into a lower requirement for escalators and additional elevator shafts, resulting in significant construction cost savings and increased rent revenues from the greater availability of usable space.

© ThyssenKrupp

There are so many issues that have had to be resolved to make this work. Because linear induction motors are very expensive, and the more weight it has to move the bigger it gets, and because the entire cab has to pivot around a single point, the cab has to be made as light as possible, so it is being built out of carbon fibre. There is also all those usual things that have to be solved, like emergency brakes and controls to keep one cab from running into another, or dealing with what actually happens if some jerk tries to hold a door open.

linear induction motor

Lloyd Alter/CC BY 2.0

Linear induction motors require tight tolerances so everything has to be machined to a high degree of precision. Those powerful magnets in the carbon fibre carrier have to line up perfectly with the coils in the machined aluminum section here.

Reshaping buildings, but also perhaps the urban fabric


Lloyd Alter/ Dario Trabucco/CC BY 2.0

In his presentation, Dario Trabucco of the Council on Tall Buildings and Urban Habitat foresaw big implications on building and urban design. He noted that more and more, designers are looking at horizontal connections to make connections between buildings easier and more convenient. As cities get denser and more crowded, the pressure for alternate ways of moving will increase as the sidewalks get more crowded.

So fact that the elevator can go sideways will affect building design, but its real impact may well be on a larger, urban design scale, making useful horizontal connections between buildings.

silly building design

ThyssenKrupp/Screen capture

When you look at the ThyssenKrupp video, toward the end they visualize a city with crazy Jenga Jacks buildings that jog all over the place, which is fun but not exactly solving a problem of significance. In fact, it is probably giving architects a dangerous tool that lets them do some very silly architecture.

Linked Hybrid

© Steven Holl's Linked Hybrid

Dario Trabucco used the example of Steven Holl’s Linked Hybrid building, linked together with horizontal connections. Imagine how urban and building design might change when the elevators can do this. It will change not only the way our buildings might look, but the way they connect and become part of the urban fabric.


The Shard/Promo image

Whatever one thinks about the trend to ultra-tall buildings, the facts of urbanization and increasing density are all around us. Currently, these buildings are serving only the very rich in cities like London, New York and Shanghai; the buildings are hugely expensive, and I have argued that they are not particularly dense, nor are they particularly good for the cities they are in. One one of the major contributors to the cost and size of the buildings is the space taken up by elevators, with each like a vertical limousine on a dedicated roadway, taking up all that space to deliver a couple of people to their destination.

However, when you think of the elevator as mass transit, one cab after another, delivering people to vertical neighbourhoods serviced by local elevators that are stacked on top of each other, it changes the picture. Tall buildings will always cost more to build, but this technology might make them more accessible and affordable for a wider audience, the kind of people who are used to changing trains.

That’s the kind of super-tall that they could use in cities like London or New York.

At the press conference in Gijon, Andreas Schierenbeck set what is perhaps a more difficult deadline: to make it three times as big, and demonstrate it in their new test tower in Rottweil that was just topped off, on time and on budget. After seeing what they have done so far, I have no doubt that they will pull this off.

Lloyd Alter’s travel and accommodations to attend the press conference in Gijon, Spain, was paid for by ThyssenKrupp, for which he is very grateful.