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  • 1. Björheden, Rolf
    et al.
    Gullberg, Tomas
    Dalarna University, School of Technology and Business Studies, Business Administration and Management.
    Johansson, Jerry
    Dalarna University, School of Technology and Business Studies, Business Administration and Management.
    Systems analyses for harvesting small trees for forest fuel in urban forestry2003In: Biomass and Bioenergy, ISSN 0961-9534, E-ISSN 1873-2909, Vol. 24, no 4-5Article in journal (Refereed)
  • 2.
    Gullberg, Tomas
    Dalarna University, School of Technology and Business Studies, Wood Technology.
    Ekonomisk analys av drivningskostnad för olika maskinsystem vid alternativa skogsbruksmetoder2003Report (Other academic)
  • 3.
    Gullberg, Tomas
    Dalarna University, School of Technology and Business Studies, Wood Technology.
    Kraftutveckling för manuella trädfällningsredskap: Force development for manual tree felling tools2006Report (Other academic)
    Abstract [sv]

    The objective with this study has been to build general models of the mechanics in tree felling with chain-saw and to compare felling torque for different tools. The theoretical models are completed and validated with a comparative study. The study includes a great number of felling tools of which some are used with different methods. Felling torque was measured using a naturally like measuring arrangement where a tree is cut at about 3.7 m height and then anchored with a dynamometer to a tree opposite to the felling direction. Notch and felling cut was made as ordinary with exception that the hinge was made extra thin to reduce bending resistance. The tree was consequently not felled during the trials and several combinations of felling tools and individuals could be used on the same tree. The results show big differences between tools, methods and persons. The differences were, however, not general, but could vary depending on conditions (first of all tree diameters). Tools and methods that push or pull on the stem are little affected by the size of the tree, while tools that press on the stump are very much dependent of a large stump-diameter. Hand force asserted on a simple pole is consequently a powerful tool on small trees. For trees of medium size there are several alternative methods with different sizes and brands of felling levers and wedges. Larger and more ungainly tools and methods like tree pusher, winch, etc. develop very high felling torque on all tree sizes. On large trees also the felling wedge and especially the use of several wedges together develop very high felling torque.

  • 4.
    Gullberg, Tomas
    Dalarna University, School of Technology and Business Studies, Wood Technology.
    Smaller forestry machines (to contribute to more eco-friendly and flexible forestry management systems) - a feasibility study2001Report (Other academic)
  • 5.
    Gullberg, Tomas
    Dalarna University, School of Technology and Business Studies, Wood Technology.
    Studier av integrerat tillvaratagande av hyggrester och markberedning2004Report (Other academic)
  • 6.
    Gullberg, Tomas
    Dalarna University, School of Technology and Business Studies, Wood Technology.
    Studier av ny markberedningsteknik baserad på virkesgrip: Studies of new equipment for soil scarification mounted on a grapple loader1999Report (Other academic)
    Abstract [sv]

    In this report a new small-scale equipment for soil scarification is being evaluated. It is an attachment consisting of two steel pipes with harrow pins that are bolt onto a conven¬tional log grapple. Scarification is done by opening the grapple, placing it to the ground, closing it, lifting and dropping the vegetation and humus layer beside the patch. A simple attachment for mechanical sowing was also tested. Time consumption per patch was 11.4 seconds. Time consumption was about 2.5 seconds higher per patch when sowing was included. Nearly 90% of production time was used to manouver the grapple loader. Productivity was 320 patches per hour when only scarifica¬tion was done and 262 patches per hour when also sowing was included. The average patch size was about 70 dm2. The thin harrow pins loosed the mineral soil but didn’t digg. The equipment was relatively insensitive to stones and stumps because of the dri¬vers possibilities to place the patches as well as the elasticity of the pins. The patches consisted mostly of mineral soil mixed with some remaining humus. Very little mineral soil was removed from the patch.The scarification cost was estimated to be lower than for conventional large scale equipment when the regeneration area is less than one hectar thanks to lower moving and starting costs.

  • 7.
    Gullberg, Tomas
    Dalarna University, School of Technology and Business Studies, Wood Technology.
    Tidsåtgångsmodeller för drivning vid alternativa skogsbrukssätt2003Report (Other academic)
  • 8.
    Gullberg, Tomas
    et al.
    Dalarna University, School of Technology and Business Studies, Business Administration and Management.
    Johansson, Jerry
    Dalarna University, School of Technology and Business Studies, Business Administration and Management.
    A hitch hook device for improved mobility for farm tractor with unpowered trailer2004In: Baltic Forestry, ISSN 1392-1355, Vol. 10, no 1, p. 89-94Article in journal (Refereed)
  • 9.
    Gullberg, Tomas
    et al.
    Dalarna University, School of Technology and Business Studies, Business Administration and Management.
    Johansson, Jerry
    Dalarna University, School of Technology and Business Studies, Business Administration and Management.
    A method for integrated extraction of logging residues and soil scarification on a small scale2006In: Biomass and Bioenergy, ISSN 0961-9534, E-ISSN 1873-2909, Vol. 30, no 12, p. 1035-1042Article in journal (Refereed)
    Abstract [en]

    A new method for integrated haulage of logging residues and soil scarification on a small-scale has been evaluated. The base machine was a farm tractor to which a grapple loader trailer was attached. The grapple loader had an attachment on the grapple used for the integrated recovery of forest energy from logging residues and soil scarification. The machine was in this case, when hauling the logging residues fresh, also used for hauling round wood. It may even be used for, e.g. spreading wood ashes (only simulated). Conventional machine systems with special machines for all four types of work result in very high fixed costs for moving, etc. which makes cost unacceptable for many small sites. Effective time per dry ton of logging residues was 28.4min in the integrated method, of which soil scarification was 14.3min. Average load size was about 1.3ton dry matter (about 2.9m3 solid). The soil scarification plots covered 12% of the surface. Cost calculations show that the integration of several activities results in substantially lower costs for small harvesting sites. For sites of about 1.5ha the cost is about the same as for conventional machines. The studied method creates new possibilities for self-employed forest owners to do the work themselves and, in case of lower personal cost and no moving cost, reduce cost further.

  • 10.
    Gullberg, Tomas
    et al.
    Dalarna University, School of Technology and Business Studies, Business Administration and Management.
    Johansson, Jerry
    Dalarna University, School of Technology and Business Studies, Business Administration and Management.
    Soil Scarification Equipment Mounted on a Grapple Loader2003In: Baltic Forestry, ISSN 1392-1355, Vol. 9, no 1Article in journal (Refereed)
  • 11.
    Gullberg, Tomas
    et al.
    Dalarna University, School of Technology and Business Studies, Wood Technology.
    Johansson, Jerry
    Dalarna University, School of Technology and Business Studies, Wood Technology.
    Liss, Jan-Erik
    Dalarna University, School of Technology and Business Studies, Wood Technology.
    Studie av system EnHar vid uttag av skogsenergi i unga bestånd - Hamrestudien1998Report (Other academic)
  • 12.
    Johansson, Jerry
    et al.
    Dalarna University, School of Technology and Business Studies, Business Administration and Management.
    Liss, Jan-Erik
    Dalarna University, School of Technology and Business Studies, Business Administration and Management.
    Gullberg, Tomas
    Dalarna University, School of Technology and Business Studies, Business Administration and Management.
    Björheden, Rolf
    Transport and handling of forest energy bundles: advantages and problems2006In: Biomass and Bioenergy, ISSN 0961-9534, E-ISSN 1873-2909, Vol. 30, no 4, p. 334-341Article in journal (Refereed)
    Abstract [en]

    Bundling is a technology used to create a compressed and uniform handling unit from logging residues and other small size energy wood. The bundles may be handled and transported with the same equipment that is used for conventional roundwood. Bundles also offer other advantages such as ''cool systems'', good storing characteristics etc. This study deals with some advantages and problems of transport and handling bundled small size energy wood as an alternative to chips. Transport cost, from stump to consumer, is calculated. Two types of material were included in the analysis: bundles and fuel chips. Transport alternatives included transports directly to consumer as well as transports of bundles via a terminal for drying and chipping, and then, in the form of fuel chips directly to consumer with a bulk cargo truck. The study shows that bundles (especially if dry) are cheaper to transport than fuel chips in road transport bins. The useful cargo space is the limiting factor for trucks when transporting dry material. Transport cost decreased until the moisture content reached the critical levels, below 40.9% for chips in road transport bins and below 44.7% for bundles on timber truck. However, there are also other advantages with a dryer material. Chipping cost is lowest in the terminal alternative and highest in the system with chipping loose logging residues in the stand. However, transport via terminal sharply increases the total costs, due to handling and increased transportation work, especially on shorter distances. Transport of uncovered bundles on conventional log trucks can be dangerous because of the risk for pieces of wood falling off. Bundles may also disintegrate during handling. The risk increases if the bundles are not reinforced with e.g. long tops and small trees, or if the strings are damaged during storing. Sisal strings deteriorate and lose their strength after a relatively short period. Thus, they are less suitable than strings of, e.g. polypropylene. Cost savings in transport and chipping indicate an allowed cost for bundling of approximately 4-5Euro/MWh for short to medium transport distances, to be competitive to the chip alternative. Cost estimates of bundling and covering of stacks with paper indicate that the handling cost is about the same as for chips for short to medium transport distances. However, for longer transport distances and through other advantages such as possibilities for return transports, a dryer and more storable material, cooler systems etc. may increase acceptable bundling-cost substantially.

  • 13. Nilsson, Jonaz
    et al.
    Gullberg, Tomas
    Dalarna University, School of Technology and Business Studies, Wood Technology.
    Studie av säkerhetstänkande vid motorsågsanvändning hos självverksamma i Småland: Resultat från Projekt Säker Skog2004Report (Other academic)
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