Steel out, textile in

Giant, kilometre-high skyscrapers, and the extraction of mineral resources from nightmare depths – these both show one thing: the technical requirements demanded of conveyor systems, which must overcome enormous spaces safely and rapidly, are rising at a tearing pace. Recently bearer cables of steel have entered the game, designed to replace heavy steel hawsers.

After aircraft and automotive construction, modern plant technology is increasingly entering the purview of fibre-related basic and industrial research – the experts speak here of developing “machine textile elements” as a replacement for classical materials. For passenger and transport lifts, for instance, textile researchers from Chemnitz are currently developing high-tensile fibre bearer cables, to dislodge the 150 year-old preponderance of steel. Their argument is the steel-hard lightness of these textile cables, which are up to seven times lighter than those made of metal alloys.

Shows fibre-based traction with steel-hard lightness: experimental rig of a lift for permanent tests on textile lift cables (source: ifk).

Shows fibre-based traction with steel-hard lightness: experimental rig of a lift for permanent tests on textile lift cables (source: ifk).

Given the gigantic heights and depths involved, steel bearer cables are reaching their limits due to the very nature of their material since, with every metre that must be conquered, the cable’s dead weight increases and its carrying capacity diminishes. After a particular size this makes it almost impossible to attach any further load at all. That is why future cables must be one thing above all: light(er) – while maintaining equal mechanical resilience.

“The search for machine elements with low dead weight – and thus, of course, also with less drive power – with the same mechanical characteristics as steel, is in full progress”, says Professor Markus Michael from the Institute of Materials Handling Technology and Plastics (ifk) at the Technical University of Chemnitz. Together with his team, and with support from the German Ministry of Education and Research, he is researching the fibre bearer cable as an alternative. This high-tech textile consists principally of thermoplastic (polyethylene) and steel-hard aramid fibres; both are initially spun to yarn, and then to cord, in order to braid the high-tensile cable from it.

High industrial potential

According to Professor Michael, long-term tests are currently being carried out – and they already show one thing: despite its textile-based lightness, the composite material can stand comparison with the mechanical characteristics and tensility of steel. A further plus, he explains, is that, in addition to its load-bearing properties, special functions can be integrated into the fibre bearer cable, such as sensors to warn of overloading or for measuring the surrounding conditions, such as humidity or temperature, or on the state of wear of the material in use. And, he adds, the resources needed for installation and servicing of textile cables are much lower than steel, which will save time in construction and real cash in maintenance.

Even now the industrial sector is showing an appreciable interest, he says – and it comes not just from lift-making firms: hoist gear for helicopters, construction machinery, wind-power turbines, and even – in miniature form – displays in motor vehicles, could soon be lavishly equipped with fibre cables. The declared aim of the researchers – true to the motto, “The way (of the cable) is the goal” – is to make fibre cables in general the standard in as many technical applications as possible.

At Techtextil, on a specially built test-bed at the joint stand of the Technical University of Chemnitz, interested parties will be able to make a close examination of so-called fibre-fibre friction, which is designed to simulate mechanical wear. “Cable tsar” Professor Michael will likewise be there and will be glad to answer any questions about cables.

Illustration (top):

They haul as efficiently as steel cables, but are much lighter: fibre cables in an experimental lift (source: ifk)

Illustration (bottom):

Shows fibre-based traction with steel-hard lightness: experimental rig of a lift for permanent tests on textile lift cables (source: ifk).

Ronny Eckert

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