|
|
Drive & Control Systems for Forestry Machines
Complete Hydraulics for Full-Tree Harvesting
|
|
|
|
|
|
Full-tree harvesting (FTH) is primarily a North American tree-harvesting principle whereby the tree is handled throughout the harvesting process in its full-length form. The steps within the process include felling, transporting (within the forest),
processing and loading. There are several variations of this process, and consequently several types of machines, depending on terrain conditions and/or tree size. The most common machines are wheeled or track-driven feller bunchers with a special disc saw felling head. Other machines include skidders, delimbers and log loaders.
Feller Bunchers
The feller buncher is used to cut (fell) and then bunch or pile the trees on the ground. Since these machines operate far away from roads on severe terrain, great emphasis is put on the capability of covering long distances and all-terrain mobility. The origins of the feller buncher come from the excavator. However, the hydraulic system, the machine structure, the tractive effort and boom attachment are all significantly different. A feller buncher may be required to perform as many as seven movements simultaneously with each movement being equally as important as the other. Due to the severe terrain conditions in which this machine must operate, as well as heavier loads it must lift, the machine’s structure is significantly stronger then an excavator. The steep slopes in forests require the machine’s tractive effort-to-weight ratio to be one to one or greater. Finally, a high-speed disc saw felling head mounted on the boom is the most contrasting difference between a feller buncher and an excavator. The travel drive is achieved in most cases by a track drive, but machines with wheel drive are also used.
Hydraulic Systems and Components for Full-Tree Harvesting Machines
Also full-tree harvesters employ the complete spectrum of drive and control systems from Rexroth. The control concepts range from simple power regulations to completely microprocessor- controlled systems. Due to the increased reliability and driver comfort, this technology is gaining in importance.
Rexroth Product Range for Full-Tree Harvesters
A11VO pumps with power control, load-sensing and cross-sensing controls are ideal for feller bunchers and log loaders. For the disc saw felling head on feller bunchers, an A10VO or A11VO is the pump of choice, the track drive is powered by a gear box GFT with integrated A6VE motor. Whereas with skidders an A4VG-pump or A6VMmotors with GFT-gearboxes is the ideal solution. The LUDV concept is already accepted in the FTH machines, primarily in feller bunchers. The reasons for this are the possibility of performing several functions simultaneously, also in the case of undersaturation, and the simple installation. M4 load-sensing control valves are used for controlling auxiliary functions and cylinder functions in the disc saw felling head.
To view the first picture (JPEG, 352KB), click here
To view the second picture (JPEG, 361KB), click here
Relevant links for Forestry Machines
Back to Forestry Machines Home Page
|
|
|
|
