| Abstract |
- This study compares production rates and costs for four ground skidding machines and for four harvesting treatments. The four
machine types studied were a Caterpillar 060 crawler (060), Caterpillar 518 rubber tired skidder (RTS), FMC 200 CA (FMC), and
International TD-8E crawler (TD-8E). Two treatments, conventional/whole tree and designated/tree length, were studied, and two, Conventional/tree length and designated/whole tree, were determined through the regression analysis and statistical inference. Conventional versus designated refers to skid road location and
restriction to, while whole tree versus tree length refers to whether the skidded trees contained limbs and tops or not. The study took place in northern Idaho. The stand was two-storied and the overstory was removed to release the advanced understory. The overstory averaged s trees per acre and contained 23.0 cunits (gross) per acre. Two operators were time studied for each of the four machine types to help eliminate operator influence and produce more meaningful comparisons. Eight operators, 483 hours of detailed time study, and 2,270 cunits skidded allowed for many delays and all significant variables to be averaged over machine types and treatments. Regression analysis was used to develop equations to predict delay free elemental times. Indicator variables were employed to
determine significant differences between conventional and designated skid roads and between whole tree and tree length skidding. In addition, significance was determined between independent variables. Delay free turn time was calculated by summing the predicted elemental times. At an average residual skidding distance of 530 feet, the study average, dollars per cunit for conventional/whole tree were calculated to be: D6D, $27.60; RTS, $19.00; FMC, $36.30; TD-8E, $27.70 and for designated/tree length: D60, $27.10; RTS, $21.50; FMC, $31.40; TD-8E, $29.30. For all skidding distances and both studied treatments, the
RTS was the most economical machine type. The FMC was the most expensive, and this is attributed to the low observed mechanical
availability and high operating costs. The D6Dand TD-8E were midway in costs. Lower initial and operating costs made the TD-8E more economical than the D6D for distances less than 500 feet for conventional/whole tree and for distances less than 275 feet for
designated/tree length. Designated/tree length was more economical than conventional/whole tree for the D6D and FMC but not for the RTS and TD-8E. The main reason was that a significant increase in pieces per turn for the D6D and FMC offset the additional sawyer costs required to produce the tree length pieces. The RTS and TD-8E showed no increase in pieces per turn.
Just the restriction to skid roads (designated/whole tree versus conventional/whole tree) is expected to influence costs per cunit by: 060, +$0.40; RTS, +$0.40; FMC, -$0.50; TD-8E, +$0.20.
Mortality and damage to the advanced regeneration was shown to be related to machine impact (visual signs of machine activity within an 1/200th acre plot). Plots not impacted by the machine (timber impacted) averaged 37 percent mortality and damage. Plots that were machine impacted averaged 84 to 91 percent mortality and damage. The conventional/whole tree units averaged 34 percent machine impacted plots, and designated/tree length averaged 21 percent. Overall impact, mortality and damage, averaged 54 percent for the conventional units and 46 percent for the designated units. The eight percent
difference was primarily mortality rather than damage. Percent of area in skid roads was calculated using parameters collected during the damage study and assuming an average skid road width of 10 feet. For all machine types, 17 percent of the conventional units and nine percent of the designated units were calculated to be roaded.
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