Speaker
Description
In Sweden, approximately 75 million m3sub of timber are harvested each year, predominantly using single‑grip harvesters. Maintaining wood value is essential, and the process begins already at the harvesting stage. The Wood Value Trials is a Swedish comparative study evaluating seven large harvesters from different manufacturers. Each machine felled and processed 30 Norway spruce stems, producing roughly 150 logs per harvester. This study is a part of that trial and focuses specifically on wood damage arising during bucking. It is important to minimize damage levels, as part of the wood is wasted at the saw mill if containing bucking splits, stud- or debarking damage, affecting the economic value.
The three types of wood damage were studied separately:
Splits resulting from bucking were assessed at both ends of each log, except at the butt end of the first log (the felling cut). Splits were measured by cutting discs with a chainsaw, striking the lower third of each disc to detect any hidden splits, and continuing to cut discs until the split terminated. The total split length was calculated by summing up the thickness of the discs. The radial position of the split was recorded as the distance from the log center.
Stud damage caused by the feed rollers was recorded at the top end of the log. Damage depth was measured by cutting across a stud mark with a knife and measuring, in millimeters, the deepest affected fiber.
Bark peeling caused by the delimbing knives was recorded at the top end of the log. The extent of bark damage was measured by placing a measuring tape around the log’s perimeter and recording the width of the peeled area. Damage was classified as either 50% depth or 100% depth (the latter indicating complete removal of inner bark and exposure of wood).
Differences in damage levels were compared among the seven harvesters. The preliminary results indicate differences between all three damage types, suggesting that harvester head design has a measurable effect on wood value. These findings imply that further technical development of harvester heads is important to improve value recovery and reduce revenue losses associated with wood damage.
| Keywords | Harvester; Value; Bucking; Damages |
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