April 28, 2009 A German mechanical engineer has designed a tree harvester that weighs just over a tenth of conventional vehicles used to fell trees, which causes less damage to forest floor. Industrial tree harvesting vehicles can weigh up to 55 tons. In comparison, the “Striding Harvester” weighs only 7.5 tons. The concept harvester by mechanical engineer and industrial designer Christian Knobloch works by using a small footprint selectively pushing down on the soil as it moves. Through this approach the soil is allowed to recover much faster than if conventional heavy forest equipment was employed.

The Striding Harvester can take 8-meter steps and functions on marshy ground and on inclines of up to 36 percent. It can also step over ditches and other obstacles up to 4.5 meters in width. According to the designer the harvester offers a far more forest-friendly solution than conventional tree harvesting and a faster, greener solution to forest regeneration.

As part of his diploma thesis, Knobloch chose to look at a radical change in the way tree harvesters moved rather than try to improve on the existing techniques of conventional harvesters. He used "constructional-geometrical optimization methods" to come up with the large stepping movement motion of the harvester. He argued that his harvester could reach trees up to 10 meters away and create a working area of 480 square meters. And even though the machine is relatively light, the large base created by the widely spread cantilevered feet enables the crane arm to lift weights far heavier than it.

The telescopic crane arm and cabin of the harvester sit on a bridge with three cantilevered feet on each end that allows the harvester to adapt to the ground surface, says Knobloch. Once a step is taken, a new direction can be chosen and the bridge moves accordingly. As the weight bears down on one of the two legs or bases, the unloaded base can pivot and move.

Knobloch, in collaboration with Professor Jörn Erler, has also developed a simple, inexpensive way to transport felled trees, without damaging the soil.

Christian Knobloch was presented with the Rudi Högner Advancement Award for Industrial Design for his diploma thesis at the third Industrial Design symposium earlier this month.

David Greig