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Silva Fennica 1926-1997
Acta Forestalia Fennica

Articles containing the keyword 'forwarders'

Category : Article

article id 4921, category Article
Simo Hannelius. (1975). Ojitusalueiden kulkukelpoisuudesta puunkorjuussa. Silva Fennica vol. 9 no. 3 article id 4921.
English title: On the trafficability of drained peatlands in harvesting.
Original keywords: puunkuljetus; harvennushakkuu; puunkorjuu; turvemaat; ojitetut suot; metsäkoneet; puustovauriot; kantavuus; routa; koneistuminen
English keywords: soil frost; drained peatlands; thinnings; mechanization; forest haulage; timber harvesting; forwarders; bearing capacity; logging conditions
Abstract | View details | Full text in PDF | Author Info

During the next decade there will be a marked increase in the allowable cut in drained peatlands. At the same time, the mechanization in logging proceeds, and in short-distance haulage the use of forwarders will increase. This study, based on literature and some observations, deals with logging conditions in drained peatlands with special reference to the suitability of heavy logging machines for use in such terrain. In addition, soil frost and the bearing capacity of the frozen peat soil were studied.

Freezing of the soil in a drained peatland area depends prevailingly on the weather conditions during early winter. The factors influencing soil freezing of a drained peatland are completely different from those regulating the freezing of natural peat soils. The frost penetrates in general deeper in the drained than virgin peatland. The topmost peat layer does not, however, freeze uniformly. Generally speaking, the bearing capacity of a drained peat soil is lower than that of undrained peat due to lower water content.

It is concluded that heavy logging machines are probably not fitted for use in drained areas on peatland even if the average soil frost values recorded would suggest it. Moreover, because of their extremely superficial root systems, peatland forests are exposed to damages by heavy machines in thinning operations.

The PDF includes a summary in English.

  • Hannelius, E-mail: sh@mm.unknown (email)
article id 4830, category Article
Matti Kärkkäinen. (1970). Optimaalisesta vinssausmatkasta. Silva Fennica vol. 4 no. 4 article id 4830.
English title: The optimum winching distance.
Original keywords: puunkuljetus; harvennushakkuu; puunkorjuu; ajourat; vintturit; vinssausmatka; korjuukustannukset
English keywords: forest haulage; forwarders; terrain transportation; strip roads; winching distance; harvesting costs
Abstract | View details | Full text in PDF | Author Info

The goal of this study was to develop a mathematical model for determination of the optimal winching distance in different conditions as based on harvesting costs. In the thinned forest the strip roads are parallel and the winching routes perpendicularly to them. A directed felling of trees is used so that it is easy to make loads to be winched. The stems can also be prepared to timber assortments on the stump area and gathered to loads for skidding alongside the winching routes.

After winching the timber is transported using a forwarder mowing on the strip roads. If the stems have not been bucked in the forests, they are to be prepared to timber assortments before the following transportation, because the problem of turning whole stems in a thinned forest has not yet been solved.

In the mathematical model the formation of the costs was described using 18 variables of which 15 had an effect on the optimum winching distance. Some empirical values were estimated concerning these variables, and the corresponding optimum winching distance were computed. The optimum was mainly determined by the quantity of timber harvested per unit area, the size of the winching load, the regression coefficient of the times which were depended on the winching distance.

According to the model, the deviation from optimum winching distance does not cause a very great change in the analysed total costs. When the winching distance is longer, the increase of the costs is smaller than if it is shorter than optimum. In general, the increase of the costs was so small that in practice one obviously can be satisfied with rather approximate methods in determining the suitable winching distance.

The PDF includes a summary in English.

  • Kärkkäinen, E-mail: mk@mm.unknown (email)

Category : Research article

article id 1030, category Research article
Jussi Manner, Tomas Nordfjell, Ola Lindroos. (2013). Effects of the number of assortments and log concentration on time consumption for forwarding. Silva Fennica vol. 47 no. 4 article id 1030.
Keywords: productivity; time study; forest haulage; forwarders; cut-to-length logging; log extraction; terrain transport
Highlights: We analysed the effects of total and forwarded log concentrations (m3 (100 m)–1) and the number of loaded assortments on forwarding; The combination of the number of loaded assortments and their abundance (i.e. forwarded log concentration) affected time consumption most; This knowledge enables improved efficiency by optimizing number and assortment proportions in the various loads required to forward a stand.
Abstract | Full text in HTML | Full text in PDF | Author Info
Forwarding has been carried out for 50 years, but much is still unknown about this work. Its complexity comes from both stand features and essential decision-making. Forwarding time consumption is influenced by e.g. log concentrations and number of assortments. Traditionally, focus has been on the total log concentration (TLC), referring to all logs at the harvesting site. However, we focused on forwarded log concentration (FLC), the load-specific log concentration which depends on the assortment distribution at harvesting site and the load-specific number of assortments. To evaluate the effects of TLC, number of assortments in a load and FLC on the loading and unloading times, a standardized field experiment was carried out. Pile and load sizes were constant, while TLC and FLC were manipulated by varying the pile distribution on the test path. For all work elements, the time consumption per m3 was significantly affected by the number of assortments that were loaded, but only the “driving while loading” work element was also significantly influenced by TLC. However, when untangling the intercorrelation between tested factors, it was found that the time consumption for driving while loading significantly decreased as a function of FLC and was unaffected by the number of assortments in a load. That FLC influences the forwarding time consumption highlights the need to study the effects of combining various assortment proportions in a load. Such knowledge will enable analysis of the most efficient number and assortment proportions to combine in the various loads required to forward a given stand.
  • Manner, Swedish University of Agricultural Sciences, Department of Forest Biomaterial and Technology, SE-901 83 Umeå, Sweden E-mail: (email)
  • Nordfjell, Swedish University of Agricultural Sciences, Department of Forest Biomaterial and Technology, SE-901 83 Umeå, Sweden E-mail:
  • Lindroos, Swedish University of Agricultural Sciences, Department of Forest Biomaterial and Technology, SE-901 83 Umeå, Sweden E-mail:

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