Design Aspects of Timber Cutting Hydraulics in a Single-Grip Harvester

The cutting function is an essential part of a harvester's work in the cut-to-length method. The quality of cutting is the most significant property of a cut. Trees should be cut without causing longitudinal splits in the end of a log. In cut-to-length method trees are cut with hydraulically driven chain saw. Energy-efficient timber cutting hydraulics is one of the main targets as well as the short duration of a cutting process. The control of chain speed and feed force of a saw bar set certain requirements for the hydraulics of the cutting system. It is also important that the hydraulics works reliably in a harsh forest environment. Therefore the proper system dimensioning is essential. The paper discusses the design of timber cutting hydraulics, especially the boundary conditions and how they affect the design. This includes the influence of the power supply, power transmission line, valves and actuators. The paper also discusses the hydraulic and mechanical restrictions, which are faced, when cutting speed is increased.