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A track-type grapple log skidder was dynamically modeled to allow machine modification by computer to determine the effects of these modifications on the operation of the machine in the forest. The model consisted of an undercarriage, power train, log/drag force, and logging equipment (arch and grapple). This skidder had three types of logging attachments: winch, swinging boom (grapple), and single-function arch (grapple). Each was modeled and simulated under various conditions. The dynamic model of the skidder can be used to analyze its drawbar pull capability and lateral stability with various log weights and soil types on steep slopes. Validation of this model is needed later.

A procedure for simulating the dynamics of agricultural and forestry machines using mechanical system simulation software is presented. A soil/track interface model including rubber-track and steel-track was introduced as well as equations that can be used to model mechanical and hydraulic power trains commonly found in tracked vehicles. Two rubber-tracked vehicles (agricultural tractors) and two steel-tracked machines (forestry vehicles) were simulated to illustrate the technique, and some analysis results are presented. The examples given in this paper are based on the author’s research over the past several years.

A prototype in-field transport system for high-value crops was designed and built. This system carries a semi-trailer upon two rubber-tracked undercarriages. A mechanism was designed for timely assembly and disassembly of the system. A set of field experiments was conducted to compare the sinkage, motion resistance, and drawbar forces of the rubber-track versus the current pneumatic-tire system. Increased flotation was observed with the prototype system. The motion resistance of the track system was less than or greater than that of the pneumatic-tire system depending on the soil condition. The prototype met performance objectives during assembly, operation, and disassembly of the system.