Résumé EN : Taper equations make it possible to solve many different problems concerning tree stem mensuration, since they can be used to generate a three-dimensional stem representation (as a body of revolution). Estimating the centre-of-gravity location along the stem length by taper equations proves a suitable approach for predicting such a biomechanical property, at least as regards tree stems with monopodial branching (e.g., stems of many coniferous species). A validation is performed on Monterey pine trees. Models to expand the same approach to predicting stem mass moments of inertia are developed.
Résumé EN : Existing road and landing spacing models assume that spacing affects only the costs of road construction and skidding. However, costs that are independent of production and fixed on the basis of time will vary with spacing when specified on a "per-unit-volume produced" basis and therefore should be considered in the model. Costs of this nature are labeled overhead, and considering these costs in the model will lower total costs. The relationship of overhead costs to spacing follows the same pattern as the skidding costs and can be added to the cost of owning and operating the skidder in the model. Overhead costs were considered in models pertaining to three unique sets of conditions: skidding to roadside with a single road standard; skidding to roadside with two road standards; and skidding to a landing. In all cases, considering overhead in the model lowered total cost and reduced road spacing. Actual cost savings will depend on harvest conditions but can be significant.
Chengxian Gao, Bruce Hartsough, John A. Miles et Andrew A. Frank
Résumé EN : The forces required to pull wheeled vehicles over idealized terrain obstacles were studied. Scale models and computer simulations were used to evaluate the peak forces for single-axle vehicles equipped with rigid wheels and pneumatic tires. A scale model of a rimless spoke wheel was also tested.The results from the rigid wheel and pneumatic-tired simulations approximated those for the scale models. The rimless spoke wheel model required relatively high towing forces. The computer results indicated that towing forces could be reduced by a factor of three in some situations by using low pressure tires instead of rigid wheels. Even with low pressure tires, it is not possible to pull vehicles over obstacles larger than approximately 1 / 5 of the wheel diameter, if towing forces are not to exceed the vehicle weight.
Résumé EN : Managers of cable yarding systems, confronted with inherently high owning and operating costs in a very competitive economic environment, need timely, inexpensive and accurate estimates of yarding production. Yarding time, and thereby production, depend on the location of the turn relative to the landing to which it must be transported. Among the important location attributes of a turn are distance and slope to the landing. For all of the turns on a setting the frequency distributions of these attributes are described by turn location parameters. Among the turn location parameters (TLPs) used by forest engineers are average yarding distance and average yarding slope.The assumptions under which a relatively new class of TLP estimators has been developed are discussed in this paper. Recognition of these assumptions and full appreciation of the limitations thereby imposed on the use of the estimators are essential to judicious application of the methodology. Formulas and procedures are given for calculation of numerical estimates and, in order to clarify and illustrate their use, an example is given.
Résumé EN : The concern over environmental issues, such as global warming, is growing and will influence consumers in the market place. A significant proportion of our forest is used to manufacture wood building materials.Carbon dioxide (C02) emissions of two representative constructions using wood building materials were compared to emissions for non-wood building materials. The energy required to extract the raw materials, to manufacture and distribute the building materials was used to estimate C02 emissions.The study showed that wooden structures require the least amount of energy and emit less C02 than other building materials. This finding should be included by consumers, designers and builders in comparative evaluation of building materials at the design stage, when decisions are made regarding the type of materials to be used.
W. B. Stuart, W. Michael Aust, Hubert Lacki et Lisa Andrews
Résumé EN : The Adaptive Suspension Vehicle, a proof-of-concept, six-legged robotic walking machine, was subject to a series of field trials to evaluate the maneuverability and trafficability characteristics of walking machines. Maneuverability trials were structured to test performance as a carrier for frame-mounted feller-buncher heads in both thinning and clearcutting applications. The trafficability trials focused on the type and extent of soil disturbance, especially changes in soil bulk density, mechanical resistance, macro- and micro-porosity, the machine was found to impact the soil very differently than wheeled or tracked equipment. Direct comparisons of soil parameters were limited because of time and budget restrictions but seem to indicate that the legged locomotion offered distinct production and soil disturbance advantages, especially on steep slopes and in wetlands.