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Comparison between skid trail penetration characteristics and tractive performance of adapted farm tractor

This paper describes the analysis for determining the possibility to estimate the tractive performance of an adapted farm tractor (AFT) based on soil penetration characteristics measured by cone penetrometer. It has been established by research carried out to date at the Faculty of Forestry in Zagreb that such assessment is possible for friction-cohesive soils, but not for sand so that further target investigations should be conducted. With that purpose, a simplified investigation of tractive performance of the adapted 4x2 farm tractor was carried out with the measurement of the horizontal tractive force and simultaneous wheel slip. Granulometric soil content was completely determined as well as skid trail inclination, its moisture and soil penetration characteristics. Gross tractive coefficient was calculated on the basis of the measured tractor dimensions and the dynamic model of its load during skidding. The research was carried out on the skid trail of Silty Loam granulometric soil content with two moisture degrees. The analysis of the results obtained by exponential regression model showed that the difference between the penetration characteristics of dry and wet soil correspond to the changes of the tractor tractive performance. The difference was also observed in view of forwarder tractive performance determined by some previous investigations on the soil of the same granulometric content.

wood skidding; adapted farm tractor; tractive performance; cone penetrometer characteristics; exponential regression model

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