Tracked Feller Buncher

Overview

A tracked feller buncher is a self-propelled forestry harvesting machine that cuts standing trees at the stump and gathers several stems into a bunch before laying them on the ground. The crawler base lets it work on soft, uneven, and sloped terrain where wheeled machines lose traction. The defining tool is the Disc-Saw Felling Head, a high-speed disc-saw head that severs a tree in a fraction of a second and holds it upright with clamp arms.

Production thinning and clearfell operations use these machines because one operator can fell, accumulate, and pile dozens of trees per hour. The cut bunches are later picked up by a grapple skidder or a forwarder and moved to the landing for processing. Compared with a wheeled feller buncher, the tracked version trades road speed for flotation, traction, and stability, which is why it dominates steep-slope and wet-ground harvest sites. The operating weight runs from 32,000 to 38,000 kg, and the leveling undercarriage keeps the operator and the cutting geometry consistent even as the tracks ride over stumps and brush.

Powertrain and hydraulics

A turbocharged six-cylinder Diesel Engine of 250–310 hp supplies the machine. It uses Common-Rail Injection common-rail delivery at up to 2000 bar, a Turbocharger with a Charge Air Cooler, and Exhaust Aftertreatment to meet Tier 4 Final emissions. Engine power becomes hydraulic flow at two Main Hydraulic Pump units, axial-piston variable pumps that match output to demand through a load-sensing Pump Regulator.

Pump flow reaches the Main Control Valve, a sectional bank where each Control Spool meters oil to one function and each Relief Valve caps the circuit pressure near 350 bar. Pilot Pilot Solenoid valves shift the spools under electronic command. Heat from continuous cutting is removed by the Hydraulic Oil Cooler, and a Hydraulic Filter keeps the oil clean enough for the close-tolerance piston pumps.

Undercarriage and leveling

The Leveling Undercarriage is a high-walker crawler frame that raises the upper structure for ground clearance over stumps and slash. Each side carries a Track Chain Assembly built from forged Track Link sections joined by hardened Track Pin and Track Bushing parts, with bolt-on Track Shoe grousers 600–800 mm wide that hold the ground pressure near 55–75 kPa.

The chain runs over a Drive Sprocket driven by the Travel Final Drive, a planetary travel reduction with a two-speed Travel Motor and a spring-applied Travel Brake. A Front Idler and a Track Adjuster set the chain tension, while a Track Roller set carries the weight and a Carrier Roller supports the top run. Two Leveling Cylinder units tilt the upper frame up to 18 degrees fore and aft so the operator stays level while the tracks follow the slope.

Swing and reach

The upper structure rotates a full 360 degrees on a Slewing Bearing, a large ball bearing with an internal ring gear. The Swing Gearbox drives a Swing Pinion against that ring gear at swing speeds up to 9 rpm, with a Counterweight balancing the reach load. Hydraulic oil crosses the rotation joint through a center Center Swivel Joint so the tracks keep working regardless of where the upper structure points.

Reach comes from the Boom and Stick and stick. The Boom Lift Cylinder pair lifts the box-section Boom Weldment, a Stick Cylinder crowds the stick in and out, and a Tilt Cylinder keeps the felling head vertical against the slope. Hardened Pivot Pin and greased Pivot Bushing parts carry the joint loads.

Felling head

The Disc-Saw Felling Head does the cutting and bunching. A forged Saw Disc of 1.1–1.4 m carries replaceable carbide Saw Teeth and spins at 1100–1300 rpm, driven by the Saw Drive Motor through a speed-increasing Saw Gearbox. The disc shears a stem up to 500–660 mm in well under a second.

Before the cut, a Grab Arm clamps the standing stem and a Gather Arm sweeps it toward the saw, all moved by Arm Cylinder units. After the cut, an Accumulator Arm holds the severed tree so the head can fell and collect several stems before laying the bunch down. A Pocket Knife in the back of the head stops trees from splitting, and a Saw Guard covers the disc during travel. The saw teeth are the highest-wear parts on the machine and are changed on a regular schedule, since dull or chipped teeth slow the cut and raise fuel use. The whole Disc-Saw Felling Head hangs from the Tilt Cylinder wrist, which lets the operator set the stump height and keep the cut square to the trunk on a side slope.

Cab and electrical

The operator works inside a FOPS/ROPS Cab built on a certified ROPS and FOPS Cab Frame with polycarbonate Front Guard Glazing, an air-suspension Operator Seat, and two Control Joystick controls. An Electrical System system runs at 24 V around a CAN-based Machine Control Unit that coordinates engine and hydraulic behavior, reads each Pressure Sensor on the main circuits, and shows status on an LCD Panel. Power routes through a Fuse and Relay Box, with Wire Bundle harnesses and sealed Connector sets carrying signals out to the head and undercarriage.