Calculation of the upgraded flat unit strength

Timber floating on small and medium-sized rivers requires the improvement of flat-flow units characterized by high transport and performance indices. The authors present a modernized flat-flow unit which has high transport and performance indices. A simplified design of the unit allows its manufacturing in a flat-flow machine. This is achieved when rows of round timber are stacked between the lower and upper transverse stickers, where the upper transverse stickers previously pressed along the entire length to the round timber in the flat machine are connected to the lower transverse stickers with raft cables. The practical operation of the considered flat raft unit for the initial timber floating requires its key transport and performance indices calculation with the focus on the calculation of the raft unit strength. The calculation method substantiates the geometric parameters of the lower and upper transverse stickers, rings with a ribbed inner surface, chains and lanyards. The justification of the geometric parameters of the lower and upper transverse stickers was based on taking into account all types of stresses arising in the transverse stickers subjected to various external and internal forces, the maximum allowable stress of the wood of the stickers and a set of safety factors. To justify the parameters of the raft cables the authors took into account deformations occurring in rings with a ribbed inner surface, chains and lanyards subjected to maximum force, the maximum allowable stress of the raft cables material and the safety factor. Dependency for calculating the diameter in the upper section of the lower and upper transverse stickers is obtained. Dependencies for calculating the thickness of rings with a ribbed inner surface and the diameter of the welded chain are also obtained, the condition for choosing lanyards is determined. Timber floating based on a modernized flat raft unit implementation with the mandatory calculation of the geometric parameters of the lower and upper transverse stickers and raft cables according to the presented methodology will allow a trouble-free timber floating with high economic efficiency.