The carbon fibre pendants are incredibly light, by comparison with steel versions, but equally strong. The material is known as CFK. Walter Länge explained, “We developed CFK for crawler cranes. It’s standard for the HS 895 HD, and available as an option for the LR 1300. On long boom crawler cranes, weight is essential. On self-erecting crawlers, we can erect an additional six metres of boom using CFK. It is also fatigue proof. With steel bars, there is a limited service life. With CFK, there isn’t. It offers a higher lifting capacity at maximum radius.”

Liebherr carbon-fibre display at Bauma

Liebherr carbon-fibre display at Bauma

Länge continued, “The carbon fibre material was developed by Carbo-Link, a commercial spin-off of the University of Zurich, based at EMPA (the Swiss Federal Laboratory for Materials Testing and Research). It’s produced in the lab at the moment, but is slowly being moved to industrial production. It’s a very high tech process, and very expensive to produce. The more we sell though, the cheaper it will become. We are still far from industrial production: it’s not a simple process, it needs a lot of process control.”

HS 895 CFK

A HS 895 at Bauma 2007, with CFK pendants

This high tech process comes at a cost, and for now will limit the applications the material is put to. Schranz said, “It’s only cost effective on longer booms. Right now, the fibre carbon pendants are only cost effetive on the HS 895. We would normally use heavy steel rope pendants with steel connectors. On this crane, that kind of steel pendant is also expensive, so the cost difference is less: using carbon fibre here is almost cost neutral. On a lift crane, carbon fibre is still very expensive, but we hope costs will come down.”

HS 895 and LR 1300

A HS 895 HD and LR 1300 at Bauma 2007, with CFK pendants

He continued, “Now, we’re gaining experience in the field, under tough operating conditions, so we can tell customers we have a life history of the product. In France, we erected an 895 with just two guys lifting the securing carbon fibre pendants manually, without a support crane.”

LR 1300 pendants

CFK pendants on the lower boom of an LR 1300

Finding the best way to use the material was no easy task, and Liebherr’s development team had some steep obstacles to overcome. “The main problem we faced was the termination point,” said Länge, “You have very high stresses at the end point. We had to design and fabricate it not to overload at this point. All of these bars also have problems with vortex shedding. This is where wind passes over the bar, making it vibrate. In certain conditions, this can cause the bar to arrive at the harmonic resonance, severely stressing the bar. The spiral design used in some of the bars reduces this.”

CFK display side

A side view of the CFK display at Bauma 2007. Note the spiral pattern on the left pendant, designed to prevent vortex shedding.

Bringing a new material didn’t just present technological challenges, but also forced the firm to ready itself for questions from potential customers. Schranz said, “Lots of people ask, ‘How does it work in low temperatures?’ I say, it’s the same material as is used on modern planes’ wings. They fly at 12,000 meters altitude where it works at 50 degrees C below zero and nobody asks.” Länge continued the comparison: “On a plane, it will be used on 12 hour flights, where the body wing is under continual stress.”

This initial application isn’t necessarily the end of the story. Länge said, “At the moment, we still use traditional steel pendant straps, we could replace them with carbon fibre, but haven’t yet. We could, potentially, make booms, everything, out of carbon fibre. We’ve looked at a lot of applications where we could use it. We are convinced that high-tech materials will more and more take over. But, still, steel also gets more high-tech.”


Liebherr carbon-fibre display at Bauma Liebherr carbon-fibre display at Bauma CFK pendants on the lower boom of an LR 1300 LR 1300 pendants A HS 895 HD and LR 1300 at Bauma 2007, with CFK pendants HS 895 and LR 1300 A HS 895 at Bauma 2007, with CFK pendants HS 895 CFK A side view of the CFK display at Bauma 2007. Note the spiral pattern on the left pendant, designed to prevent vortex shedding. CFK display side