Force Alignment of the Ends of Two-Tiered Package Rafting Units during their Formation in Water

Promising technologies for transporting round timber from remote areas involve, after passing through shallow water areas, forming small-sized packages into two-tiered package units without violating their integrity. The devices designed for this purpose are intended to align the ends of two-tiered package rafting units, carried out in order to increase their strength and nontaperity, which allows for a reduction in towing costs along the main part of the route. The aim of the study has been to obtain formulas for calculating the forces required to align the ends of two-tiered package rafting units formed in water and to establish the nature and degree of influence of the main determining factors on these forces. The research method has been theoretical. Analytical formulas have been obtained for calculating the forces required for aligning the ends of logs in the lower and upper packages of two-tiered package rafting units. Determining the value of a, included in the given formulas, is associated with the calculation of integrals, which is undesirable in practical calculations. It has been proven that a depends on the shape coefficient of the packages, on the ratio of their height to the diameter of the logs and on the tier in which the packages are located. Using numerical methods, the values of a have been determined for various combinations of determining factors. Based on the calculation results for the standard shape coefficients, approximating dependencies have been obtained, which make it possible to establish, in practical calculations, a and the end-cutting forces for packages of both tiers. When designing devices, the calculated force for aligning the ends of two-tiered package rafting units consists of the corresponding double forces for the upper and lower packages. The most significant factor influencing the force of alignment of the ends of the logs in a package is the ratio of its height to their diameter. An increase in this ratio in the studied range is accompanied by an increase in the considered force for packages of both tiers by 4.90–5.02 times. The package shape coefficient also significantly influences the output value. Its increase from 1.5 to 2.5 causes a decrease in the alignment force by 75–77 % for the lower packages and by 52–56 % for the upper ones. The relationship between the alignment force and the volume of the package is linear. To align the ends of logs in the upper tier packages, more force is required than in the lower ones.