The present article addresses issues related to the development of a scientifically-based classification of agricultural tractors with consideration of problems associated with international harmonization of testing requirements and classification parameters; it describes the disadvantages of classification of tractors by maximum towing power achieved on a concrete surface, which is used abroad.
The authors state the requirements for towing and power classification of agricultural tractors, which should act as a framework for energy harmonization of sets of tractors with sets of machines independently from developers and manufacturers; and demonstrate the need for harmonization of typical size classification series of towing and power parameters with series of preferred numbers recommended by International Organization for Standardization (ISO).
On the basis of a two-parameter towing and power classification, the studies have been conducted, and the operating weight has been extracted as a basic characteristic having the greatest dynamic range for the sets of tractors.
By means of statistical analysis, simple linear dependencies between the basic characteristic and two other derived characteristics (rated towing force and power take-off (PTO-power) have been determined.
Thus, the article shows that for each towing category, a mean value of operating weight and corresponding mean values of towing force and PTO-power may be taken into consideration. The population of values of the above-mentioned characteristics have been considered as certain typical size series, and it has been determined that the first five terms of the series of mean values of wheeled tractors operating weight in 0.2 - 8 towing categories with a 4K 4a wheel arrangement may be represented by basic series R5, and the subsequent five terms with a 4K 4b wheel arrangement may be represented by basic series R10. In a similar manner, it has been found that for caterpillar tractors, the series of mean values of operating weight for 2-8 towing categories may be presented as consisting of a sample series R20/3 and a basic series R10. The result obtained has made it possible to conclude that the determined relations with series of preferred numbers are indicative of coherence between the proposed towing and power classification of agricultural tractors and natural laws of development of systems having broad limits of variation of basic parameters.