An off-road vehicle with a front- and rear-wheel steering capability (4WS) can move sideways, and can avoid obstacles easily, with the same steering phase of both front and rear wheels. With the different steering phase of front and rear wheels, its minimum turning radius is half of that of a vehicle of the same size with only front-wheel steering (2WS). Furthermore, it can make the inner radius difference zero regardless of the wheel base. However, the practical breadth of turning with a minimum radius of a 4WS vehicle is wider than that of an articulated-frame steered vehicle of the same size because the practical minimum inner turning radius of the 4WS is shorter than the inner radii of the inner wheels and the practical minimum outer turning radius is longer than the outer radii of the outer wheels, whereas the practical minimum outer and inner turning radii of the frame-steering whose body is narrower than the overall width equal the outer and inner turning radii of the wheels, respectively. The distance between obstacles in slalom running of a 4WS is 57-62% and 68-71% of that of the 2WS and the frame-steered vehicle of the same size, respectively. The 4WS we tested can efficiently pass through a 48-year-old plantation of hinoki which the same-sized 2WS can not penetrate.
Centralised processing may be an alternative to skidsite processing for some regions of New Zealand where radiata pine plantations now await harvest. However, a pre-emptive cut will generally be necessary to reduce felled stems to lengths which can be trucked to a central processing yard. There are various strategies for determining where a single pre-emptive cut should be placed. The effect on potential stem value has been compared for samples of trees using the bucking simulation program AVIS. All strategies tested reduced stem value but the amount of loss varied with the strategy chosen and the subsequent cutting pattern used in the yard.
The use of a harvester-forwarder system for commercial thinning operations in a Douglas-fir plantation had little detrimental impact on the residual stand. Less than five percent of the sample trees in the residual stand exhibited damage from the thinning operation. Trails occupied less than 20 percent of the harvested area with significant portions of the developed trail, over 13 percent of the harvested area, in lightly disturbed harvester trails. Trail spacing was consistent and averaged 26 metres between trails for the area studied. Changes in bulk density were greater for harvester trails, increasing an average of 25 percent in the first 10 centimetres of soil depth. Bulk densities on forwarder trails averaged 20 percent greater than measurements on adjacent control sites for the first 10 centimetres of soil depth. These bulk density values, when compared against magnitudes from the literature, suggest that little site damage was caused by thinning operations with this system.
This paper presents a hypothetical case in which the positive and negative impacts of intensive forest harvesting (using the full tree method rather than the shortwood method) are evaluated over the long term using financial criteria. The full tree harvesting system collects branch and top material for use as a fuel as well as the roundwood. The analysis shows that the silviculture cost savings and energy biomass value more than offset the loss in long term value due to slower growth of the stand following intensive harvest. This conclusion is robust to changes in discount rate, value of roundwood and volume growth loss. The price of energy biomass had a major effect.
The paper describes a sawmill simulation model developed as a component of an integrated decision support system for hardwood sawmills. Discussions focus primarily on some of the essential features of the simulator and how it can be used as a tool for designing sawmill facilities and in the evaluation of sawing policies and production plans. Further discussed are some of the discrete-event simulation modeling techniques used in developing the simulator.