Forestry Forwarder

Overview

A forestry forwarder is the load-carrying half of the cut-to-length harvesting method. A separate harvester fells, delimbs, and bucks trees into logs at the stump; the forwarder then drives onto the cut block, picks the logs off the ground with its own crane, carries them on board, and unloads them in sorted piles at a roadside landing. Unlike a skidder, which drags stems along the ground, the forwarder lifts the full load clear, which protects the soil and keeps the logs clean. The machine is built around an Articulated Frame in two halves: the front carries the engine and cab, the rear carries the crane and load space.

The defining design constraints are flotation, traction, and stability on steep, soft, and broken ground. Eight driven wheels on Bogie Axle tandems spread the weight, and steel band tracks can be fitted over the bogie wheel pairs to lower ground pressure further on wet sites. Operating weight runs 17 to 23 tonnes empty, and a mid-size machine carries 12 to 16 tonnes of logs.

Power and drivetrain

The Power Unit is a turbocharged inline 6-cylinder diesel rated 150 to 210 kW and certified to Stage V emissions through a combined DPF and SCR Exhaust Aftertreatment package. The engine drives a Pump Drive Gearbox gearbox off the flywheel that splits torque between the traction and work hydraulic pumps. A reversible Reversible Cooling Fan periodically blows debris and chaff off the cooler cores, a constant problem in a dusty, needle-laden forest environment.

Propulsion is hydrostatic. A variable Traction Pump and a variable Drive Motor form a closed loop that gives stepless speed control from a crawl up to about 25 km/h, with a Transfer Gearbox providing a low work range and a high transport range. From the transfer case, propeller shafts drive the front and rear bogies. Each Bogie Axle uses a central differential with a hydraulic lock and four Portal Hub Reduction reductions that raise the axle centerline above the wheel centers for ground clearance over stumps and rocks.

Articulated steering and frame

The machine steers by bending in the middle rather than turning its wheels. Two Steering Cylinder units pivot the front and rear frames about the Articulation Joint, a vertical pin joint that also carries an Oscillation Bearing so the two frame halves can roll independently as the bogies climb over obstacles. Articulated steering keeps all eight wheels tracking in the same ruts, which reduces soil disturbance and lets the machine thread between standing trees. The frame halves are heavy welded steel boxes; the rear frame additionally carries the loads of both the crane and the full log payload.

Loader crane and grapple

Loading and unloading is done by the operator with the Loader Crane, a knuckle-boom hydraulic crane mounted on a slewing Crane Column. An inner Main Boom handles lift, an outer Knuckle Boom folds for reach, and a hydraulic Telescopic Extension extends the working radius to between 7 and 10 metres. At the tip, a Log Grapple with two curved Grapple Claw units and a continuous Grapple Rotator picks up logs in any orientation. A load-sensing Crane Control Valve meters oil to each function so several movements can be combined smoothly. An experienced operator sorts logs by species and length while loading, which is why the rotating cab matters so much.

Load space and cab

The logs ride on the Log Bunk, a slatted Load Floor flanked by vertical Load Stake posts and protected from the cab by a steel Headboard. Stakes can carry hydraulic Stake Extension sections to widen the load. The operator works from the Operator Cab, a ROPS and FOPS rated cabin that both levels on side slopes and rotates toward the work so the operator always faces the crane and the load. The cab carries an air-suspended Operator Seat, joystick Control Armrest units, a pressurized Cab Climate Unit system, and a graphical operator display.

Hydraulics and control

A single load-sensing Main Hydraulic Pump supplies the crane, steering, and auxiliary functions, drawing from a Hydraulic Reservoir through return and pressure Hydraulic Filter elements. A gas-charged Hydraulic Accumulator damps the pressure spikes that come from snatching heavy logs. The whole machine runs on a CAN network managed by the Machine Controller, with distributed I/O Module nodes reading Pressure Sensor feedback and driving the valves. Twelve LED LED Work Light units let crews run double shifts through long northern winters.

Variants and use

Forwarders are sized by payload class, from compact 8 to 10 tonne thinning machines that work between standing trees in young stands, up to 18 to 20 tonne final-felling machines for clear-cut blocks. Steep-slope variants add traction winches anchored to a stump uphill. The forwarder almost always works as a pair with a harvester of matching size; together they replace the older chain-saw plus skidder crews across most of the boreal and managed temperate forest world, with lower soil impact and far higher daily output.