Prospects for the Use of Multifunctional Machines in Mountain Forests : Seminar on the Use of Multifunctional Machinery and Equipment in Logging Operations

1993

10 S.

Unselbständiges Werk

200084992

In Norway 25% of the forest land is classified as steep and difficult, but only 5-10% of the annual cut comes from these areas. In 1991, approximately 500.000 Kubikmeter timber was harvested from terrain steeper than 40%. This quantity was distributed on harvesting systems as follows: Manual cutting/farm tractor or forwarder: 230.000 Kubikmeter (46%). Manual cutting/winch or cable cranes: 140.000 Kubikmeter (28%). Cable cranes combined with processors: 100.000 Kubikmeter (20%). Harvesters/forwarders 30.000 Kubikmeter (6%). This table shows that manual cutting still is predominant. Only 26% of the timber is harvested of processed by machine. The farm tractor equipped with a single or double drum winch is the most common terrain transport machine. This is mainly because of the large number of small farm forests where the owners execute most of the forest work with the machinery available on the farm. However, the quantity harvested by machines is increasing in steep terrain. Modern harvesters can operate quite easily in terrain up to 40% steepness, and the practical limit appears to be approximately 50% on smooth hillsides. A special purpose-built machine, the Norwegian 'Tor 987', have in practical trials been working in terrain up to 55% steepness when driving perpendicular to the contour lines. The machine can be tilted sideways, and is therefore able to work on side slopes up to 50% inclination in terrain with a smooth surface. The productivity of 'Tor 987' and other purpose-built harvesters is only slightly influenced by terrain steepness up to 50-55%. Other charcteristics of the terrain and the forest stand are much more important to the productivity of the machines. For mechanized harvesting systems the terrain transport is the 'bottleneck'. Even if modern forwarders have quite good terrain mobility, it is not recommended to drive a fully loaded forwarder in terrain steeper than 40- 45%. The alternatives are skidders, helicopters and cable cranes. When hauling distance exceeds 150m and the terrain steepness is more than 50%, cable cranes are normally used for the terrain transport in Norway. But there is very little productivity to obtain by delimbing the trees before hauling, and tree processing is therefore carried out on the landing area. Modern cable cranes, like the Norwegian 'Owrens Variokran T3', have quite satisfactory productivity. This is vecause of the short time consumption during moving and mounting, high-speed powerful winches and high reliability. It can therefore be justified to combine this cable crane with a processor. The processor can either work continuously as the trees are winched into the landing area, or the trees can be hauled and stored in bunches for later processing. A solid, second hand machine is suitable for this use, because the wear and tear on chassis and driving wheels is minimal when the machine is ...