Working under arduous conditions, 9-axle 76-tonne truck-trailer combinations are turning out be popular in Finland.

In Finland, 9-axle, 76-tonne GCW longer truck-trailer combinations are becoming more and more popular since 2013, when the Government approved this new weight limit on the basis of a proposal of the Ministry of Transportation. This is the story of two such monster trucks: a Volvo FH 16 750 timber truck and a Sisu Polar gravel dump truck. The FH 16 combination is made up of a 4-axle truck, powered by a 16.1-litre D 16 K, 750 hp and 3.550 Nm peak torque engine, and a 5-axle trailer. According to Finnish regulation, the 76-tonne GCW is allowed for (at least) a 9-axle combination, provided that, at least, 65 per cent of the mass of the trailer is on axles fitted with twin tyres. The FH 16 750 is thus fitted with several specific technical features for a timber truck. First of all, it’s a full pneumatic suspension (8×4 rigid), with 2nd lift axle. There are also other geometries, say with 4th lift axle instead of the 2nd. The full pneumatic solution, that is gaining more and more success among Volvo timber trucks, now accounts for 85 per cent of Volvo timber truck sale volumes in Finland (where Volvo commands about 50 per cent of the total market share). Five years ago, the percentage of full-pneumatic suspension was no more than five per cent. The full-pneumatic solution allows the driver to lift an axle to increase the grip of driven axles. In addition, the driver can dump air from pneumatic suspension of one of the driven axles to increase the grip of the other axle.

In Finland, the total market for timber trucks ranges between 150 and 250 new trucks, per year. On an average, these trucks are changed every five years, and reach a total mileage of 1,50,000 to 2,50,000 km per year. Other technical features of the FH 16-750 timber truck include a special software for Volvo I-shift automated transmission to cope with extremely demanding conditions of timber transport along narrow and sometimes inadequate forest road. Moreover, the truck is fitted with a Hill-holder system, differential lock, sand splitter device (to increase the grip of driven axles) and a timber crane. Another key feature of the FH 16 750 timber truck is the so-called Volvo dynamic steering. An electronically controlled electric motor is attached to the steering shaft. The electric motor, which works together with the traditional hydraulic power steering, is regulated thousands of times per second by the Electronic Control Unit (ECU). In this way the irregularities of road surfaces, such as compacted snow or ice slabs, are automatically dampened by the system. This, in turn, decreases the driver’s workload, because he does not have to compensate for such irregularities by minor and continuous adjustment of the steering wheel. Along public roads and narrow forest roads, the dynamic steering really makes a difference. Despite the longer dimension (24 m long) and higher center of gravity (4.4 m high), the 9-axle truck-trailer combination proved to be easy to drive and stable.

The 5-axle, twin-tyre trailer followed the truck smoothly, without any problem. In Finland, we experienced a standard working day of a timber truck from Kontio – a world market leader – loghouse production headquarters in Pudasjärvi – 700 km north of Helsinki – to an Arctic pine forest and back. Climate conditions were pretty good, because of the sun and a relatively mild temperature by Finnish winter standards, say -17°C. According to experienced timber truck drivers, the most demanding conditions occur on icy and slippery surfaces when the temperature is around zero, or in deep-frozen conditions when the temperature drops to -35 or even -40°C. In the latter circumstances, the natural rubber of Scandinavian winter tyres becomes hard and friction on slippery surfaces becomes more problematic.

During the empty trip from Kontio headquarters to the Arctic pine forest we got stuck in the soft snow of a narrow forest road. We tried – without any result – to lift an axle; to increase the grip of the driven axles of our 8×4 timber truck. Then, we tried to clear the snow from driven axles using a shovel. We also tried to re-position the trailer, using the timber crane fitted on the truck. Since we got no result, we asked for help. A snowplough finally helped to free us. Loading cut-to-length tree trunks – prepared by an harvester – takes about 30 minutes in standard operating conditions. Roundwoods trucks are typically owned by family enterprises situated in countryside, where the entrepreneur participates actively in production work. According to 2010 statistics, there are about 900 timber trucking entrepreneurs, employing 2,600 truck drivers, with a fleet of 1,700 trucks. The average number of trucks per enterprise is less than two. Roundwood logistics in Finland is controlled by Information and Communication Technology (ICT) systems – owned by wood procurement companies. In general, each company has its own ICT system. ICT systems like LogForce, developed by software house Fifth Element, covers all the planning and vehicle software of the haulage contractor to include transport orders, scheduling, stock management, messaging and map functionality.

Sisu Polar Euro 6 range

The second 76-tonne, 9-axle combination tested in Finland was a 21,89 m long Sisu Polar rock gravel truck-trailer. The 10×4 truck was fitted with a Mercedes-Benz Euro 6, 6-in-line OM 473 15.6-litre engine (with high-performance engine brake), rated at 625 hp (3,000 Nm peak torque). Engine power is transmitted to rear axles by Mercedes-Benz Powershift 3, 16-speed automated transmission – as in the vehicle under test – or by Eaton Fuller RTLO22198B 18-speed unsynchronized manual gearbox (optional). Sisu Polar line-up includes Sisu Rock dump trucks, Sisu Works road maintenance trucks, Sisu Timber (timber truck version), Sisu Roll, demountable trucks and Sisu Carrier, machine transport trucks. In addition to these models, Sisu Work plus is now available, which features a combination of road maintenance and demountable applications. Cab, engine, transmission and core electrical/electronic systems of Sisu Polar are based on Mercedes-Benz Arocs technology. Sisu Polar 10×4 proved to be easy to maneouver, thanks to three steering axles. The first axle can be steered by 30°, the second by 16°, while the fifth can be counter-steered by 13°.

In this configuration, the turning radius of the entire 21.89 m combination is 12.5 m. On uneven surfaces, such as compacted snow, ice slabs, or during tight maneouvers with 76-tonne GCW, the Servotwin steering system with electronic steering power assistance makes a difference in terms of comfort for the driver (because less corrections of the steering wheel are needed) and vehicle handling. OM 473 engine brake, with a maximum braking power of 475 kW, can substitute foundation brakes in 90 per cent of the operating conditions. Despite the full-mechanical suspension system, the driving comfort during on-road applications proved to be quite high. Sisu Polar features two different frame heights: 300 mm U-profile with inner reinforcement, and 460 mm C-profile for heavy duty tasks.

Heavier combinations in Finland

The 76-tonne, 9-axle combinations are not the heaviest ones in Finland. Five special permits regarding 33 m, 80-tonne truck-combinations have been granted so far to ‘Speed to run’ on six different road channels, and one 31 m, 94-tonne to Orpe. Some 10 to 15 more applications by three different companies have been handed to the road safety authority Trafi and to the Ministry of Transport.

Orpe is the only transport company with one permit to run with a 31 m (application was for 102-tonne according to axle weights of 12 axle) 94-tonne, 12 axle timber truck on very specified conditions for a trial period till 31 December, 2019. Only specially trained drivers are accepted, to run on roads and routes accepted by the Ministry. All brakes have to be electric EBS. Transports are forbidden when weather conditions or forecasts by the Meteorological Institute are declared “very bad or very bad road conditions.”

The behaviour of the whole vehicle combination has to be continuously controlled by cameras on the vehicle. A report of the routes driven, vehicle behaviour and road conditions have to be delivered every month to the Trafi. The entire vehicle combination has to be passed on to the authorities for testing for no longer than three days whenever Trafi or the Ministry gives notice.

Speed has five 33 m long, 80-tonne truck combinations running from Helsinki and Kotka harbours, to cities to the north and to the east, on five special routes covering some 120 to 200 km of length accepted by the Trafi and the Ministry of Transport. These trucks will carry two 40 ft ‘Jumbo’ containers or four 20 ft containers.

CV is an associate member of the International Truck of the Year (IToY). Being a part of this association gets the magazine exclusive articles, specially written by IToY jury members.

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