Design Challenge - November 2011

Christian Knobloch

The Portalharvester is an innovative concept intended to minimise damage to the delicate forest soils typical of central Europe, the UK, Germany – especially around the Baltic Sea – and west of the Adriatic Sea. Scandinavian wheel-based forestry technology is unsuitable for such sites because it causes serious long-term damage to the soil, which affects future tree growth.

The concept employs a novel kind of stepping movement, which is non-bionic and patented. Two tripods are connected by a bridge, or crossbar, along which the cabin moves. Once the cabin slides to one side, the opposite tripod can ‘stride’ into a new position, enabling the machine to move in a zig-zag pattern. The mechanism enables the harvesting machine to reach a stepping distance of up to 8m. With every step, there are only three points of contact with the soil.

In addition, the tangential shear forces that also occur with wheel-based machinery are removed – because the feet of the machine can be placed directly on and off the soil, the Portalharvester applies only vertical compressive forces, further minimising damage to the forest floor. The walking mechanism enables the machine to traverse rocky terrain and to cross obstacles up to 4m wide (for example, water ditches). There is no need for brakes, steering, driving gear and soon, enabling a considerable reduction in the weight of the machine.

The mechanism is simple to control and can rotate through any angle on the spot. The concept could therefore allow a forestry crane with an outreach of 10m to cover an area of up to 500m2, without needing to move across the soil. In addition, the splayed-out feet of the Portalharvester form a large, solid platform that enables it to lift a heavy load despite its relatively light weight. Low-cost transportation will be possible with a simple trailer and a semi-truck.

The concept will be suitable for a lot of alternative applications, too. Because it enables forestry equipment to work in a more sustainable manner, particularly in regard to the forest soil, forest stands in lowland areas with sensitive soils – currently an unserved niche – could now be catered for.

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BIOGRAPHY

Christian is a mechanical and industrial design graduate from the Technical University of Dresden, Germany. He worked for a design firm before starting his postgraduate studies.

CONTACT DETAILS

Email: knobloch@forst.tu-dresden.de

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