Materials Science Reporting: Stronger, Lighter Elevator Cables

This German elevator illustration is from 1405; mass commercialization began in 1852 with Otis’s invention of the ‘Safety Elevator’ which included a counter-weight to the cab.

Reporting on innovations in the materials science field tends to follow the Gartner Hype Cycle – most early reports are vague, full of promises, and ultimately a few years later, nothing has been delivered.  The Economist’s recent article on innovations in elevator cables is a great example to the contrary – it is a real innovation, near to commercialization, overseen by a group that understands technology scale up that has a practical impact on society.

Using the materials science framework of: Process => Structure => Properties => Performance, provides an easy way to appreciate the clarity provided in this article.


We’re not provided with any detail on the rope production process – but we are provided with the most important detail in that the maker is Kone, a Finnish elevator maker.  Unlike other materials science innovations where the primary source is an academic or research laboratory, the source here is an entity that is well familiar with their target industry and understands what it takes to produce material at scale and at a cost that is attractive to their target market.


The structure of the cable is also slim on details – but we’re told that it is swappable with current elevator cable technology.  Reverse compatibility is more important in materials science product adoption than in many other industries.  As a new material flows out into the supply chain, the users just want it to work.  Further, many times a full list of all the characteristics needed for the material to work isn’t available.  The only way a user can find out that it doesn’t work in a certain scenario is when it fails – a scenario not acceptable with an elevator cable.  In the article, The Economist leads with the fact that Kone has a 333 meter deep test shaft to exercise new materials – test rigs that replicate operating scenarios are crucial in the commercialization of new materials.


The article notes that a 400 meter tall lift would require a steel cable that weights 18,650 Kg, while a carbon fiber lift would only weight 1,170 Kg – a 94% reduction in the weight of the cable.  The author states that in combination with the cab, the reduction in weight of the entire assembly is 45% – perhaps that 20,000 Kg cab should also be made of carbon fiber.  Weight is the primary novel property of this new cable.


Many times in materials science, performance is achieved at a needed grade – here the strength of the cable is fixed.  It must be strong enough to support the cab, which means having the appropriate tensile strength and other properties.  There is a fixed performance grade, the major impact is reducing the weight of the cable while maintaining strength.  A stronger cable with no reduction in weight, would not have any benefit.


Tall buildings create a connection with why we care about lighter elevator cables – this connection is crucial in successful commercialization.

Lastly, the reason that this story resonates is because the lighter weight of the cable enables performance of taller buildings.  This human interest component – the thought of buildings rising a kilometer or more, unconstrained by the limits of modern elevator systems, is what gets an institution of The Economist’s caliber involved.  Often times it is the final element of pull – the ability to connect how a new material will enable societal goals, that is the real determinant in how successful a new material can be.

Lighter, high strength cables, could be useful in many industries – the article even touches on the Space Elevator concept.  Cables may not find their way into the main stream via usage in elevators – it could be maritime, construction, automotive or any of a dozen other applications, but buildings may serve as the beachhead market which provide cash flow for their makers until product market fit is found.

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