Wheels on the El-forest forwarder are driven individually by separate electric motors, reducing wheel spin and resultant damage to the forest floor.

Wheels on the El-forest forwarder are driven individually by separate electric motors, reducing wheel spin and resultant damage to the forest floor.

Hear the term “forwarder” and you might think of a company that handles freight shipments. But in forestry, a forwarder is tractor-like machine that transports raw timber from the felling site out to a road for collection by a truck. It’s a critical element of the highly mechanized and efficient forest products industry found throughout Scandinavia. The Swedish company El-forest has introduced an environmentally adapted forwarder that reduces damage to the forest floor and cuts fuel consumption.

A forwarder looks similar to a dump truck, except that instead of a rear tipper or platform, it’s equipped with rails to carry logs. Since it has to lift and carry heavy loads over rough terrain, transporters are equipped with large diesel engines to generate the power required to get several tons moving from a standstill. About 350 forwarders are bought each year in Sweden, and the world market encompasses some 1,500 machines per year.

A new forwarder with new technology

Manufacturers have long focused on building forwarders that cause as little damage as possible to the forest floor. Still, a great deal remains to be done. Besides the direct physical impact on the ground-level habitat, forwarders emit diesel fumes and carbon dioxide, and fuel costs are substantial.

“Our new forwarder offers several important environmental advantages,” says Gunnar Bäck, CEO of El-forest. He describes how the idea of developing less damaging forestry equipment started with the inventor Lennart Lundström, whose family has been involved in the timber industry for generations. With a long career working for the electrical engineering firm ABB, Lundström had the background to combine environmental interest with modern technology. The result is a forwarder that the head of state-owned Sveaskog, Sweden’s largest forest owner, calls “the biggest advance in forest machinery in a decade.”

Better fuel efficiency, less ground damage

The El-forest forwarder weighs in a relatively modest 15 tons, but still features a robust frame that can handle up to 14 tons of timber. The six large wheels provide high clearance over uneven terrain while reducing ground pressure. Each wheel is driven via a hub gear by its own 30 kW alternating current motor, and each of the three wheel pairs is steered independently. The second and third wheel pairs follow precisely in the track of the first pair, an engineering trick that Gunnar Bäck calls “100 percent tracking.”

The vehicle has a turning radius of just 6.2 meters, requiring about half of the area of traditional forwarders with articulated steering and differentials like those found in automobiles. This results in much less damage to soil and vegetation. “Our machine individually adjusts the speed of each wheel, so they don’t need to spin to keep up with one another,” Bäck explains.

A Deutz diesel generating 60 kW maintains a constant engine speed, keeping fuel consumption low while charging the batteries that drive the forwarder. The 400-kg battery package is also charged by regenerative braking as the vehicle rolls downhill, when the electric motors act as generators. The combination of the diesel engine and six electric motors provides plenty of power for heavy lifting and pulling. El-forest’s calculations point to 30 to 35 percent lower fuel consumption compared to traditional forwarders, cutting costs and reducing emissions of greenhouse gases. “Our drive technology can be further improved,” Bäck says. “In the future we hope to replace the diesel engine with one driven by biogas or fuel cells.”

Bäck also points to improvements in productivity and the work environment. The El-forest forwarder features a newly developed cab that swings a full 360 degrees, meeting the toughest ergonomic standards for both noise and visibility. The driver also enjoys an effective climate-control system and ergonomically designed seat. Controls and monitors are within easy reach for better comfort and productivity.

First tests

Volvo contributes expertise in steering systems, cab design and engines.

Volvo contributes expertise in steering systems, cab design and engines.

The first commercial machine, bought by Sveaskog in the spring of 2009, has now undergone about 1,000 hours of operational testing. Two more machines are completed and other forestry companies are closely following further development. Holmen AB, a large private concern, is sponsoring work on the El-forest forwarder.

The venture capital firm Volvo Technology Transfer, owned by the automaking company, became the largest shareholder in El-forest in 2007. Volvo brings to the project expertise in a number of areas, including the steering system, cab design and engine choice. The partnership with a major player in the auto and truck industry is crucial for a small firm like El-forest, as the electric hybrid forwarder may someday be included in Volvo’s line of forest machines. If all goes according to plan, series production of the El-forest forwarder will begin during 2010.

Article published in September 2009