Self-Propelled Forage Harvester

Overview

A self-propelled forage harvester chops standing crops into short, uniform pieces and blows them into a trailer so they can be stored as silage. Unlike a combine, which keeps the grain and spreads the rest, the forage harvester keeps the whole plant: stalk, leaf, and grain are chopped together and fermented as cattle feed. The machine is built around moving an enormous volume of crop very fast, which is why it carries one of the most powerful diesel engines fitted to any farm machine.

The crop moves in a continuous stream. The Crop Header gathers and cuts the standing crop, the Feed Roll Set compress it into an even mat, the Cutterhead chops it, the Kernel Processor cracks the kernels, and the Accelerator & Spout throws the result into a trailer. The Diesel Engine supplies the power, the Drivetrain propels the machine, and the Operator Cab is where the operator works.

Header

The Crop Header is chosen to match the crop. For maize, a wide row-independent header uses Gathering Drums units with steel Gathering Paddle elements that draw whole plants in regardless of how the rows were planted, while rotating Header Knife discs sever the stalks at ground level. For grass, a pickup header lifts a pre-cut windrow off the ground instead. Either way, a Header Auger consolidates the crop into the throat, and the Header Frame & Drive carries a gearbox driving everything and quick-attaches to the feed housing.

Feed Rolls and Metal Detection

Before chopping, the crop must be packed into a dense, even mat so every piece is cut to the same length. The Feed Roll Set do this. A pair of fluted Lower Feed Roll units carry the crop in, while spring-loaded Upper Compression Roll units press down through the Coil Spring elements to compress it. The speed of these rolls, set by the Feed Roll Drive, is the main control over chop length: faster feed against a fixed cutterhead gives longer pieces. Built into the lower roll is the Metal Detector, a magnetic sensor that stops the feed in milliseconds if it senses tramp metal such as a piece of fence wire. This protects both the expensive cutterhead and the animals that would otherwise eat the metal in the silage.

Cutterhead

The Cutterhead is where the chopping happens. The Cutter Drum carries between 12 and 48 hardened Cutter Knife blades in a chevron pattern, spinning at well over 1000 rpm. Each knife slices the crop against the fixed Shear Bar, a scissor action that must be kept sharp and set to a close gap to cut cleanly rather than tear. Because the knives dull through the day, the machine carries an in-cab Knife Sharpener: a traversing stone hones all knives and resets the shear-bar gap in a few minutes without the operator leaving the seat. The Cutterhead Housing is wear-lined and channels the chopped crop onward.

Kernel Processor

When harvesting maize for silage, every grain kernel must be cracked or the starch passes through the animal undigested. The Kernel Processor sits behind the cutterhead for this. Two grooved Processor Roll units run at a deliberate speed difference, so they both crush and abrade every piece passing through. The Processor Gap Actuator sets the gap between the rolls, typically 1 to 4 mm, from the cab to suit how mature the crop is, and the Processor Drive turns the two rolls at their differential speeds. For grass, which has no kernels, the processor is removed to save power.

Accelerator and Spout

The chopped, processed crop has to be thrown several meters up and out into a moving trailer. The Accelerator & Spout does this. When a kernel processor is fitted, the crop has lost the speed it picked up from the cutterhead, so an Accelerator paddle wheel speeds it back up. Adjustable Accelerator Paddle elements fling the crop into the airstream and up the Discharge Spout, a long rotating chute. The Spout Actuators rotate the spout through a wide arc with the Spout Rotate Drive and tilt the deflector with the Flap Cylinder, so the operator, or an automatic fill system, lays the crop evenly across the trailer running alongside.

Engine and Drivetrain

Chopping and throwing this much crop takes huge power, so the Diesel Engine is a large turbocharged diesel of 400 to 800 kW, often with twin Turbocharger units. A high-capacity Cooling Pack with a self-cleaning rotary screen sheds the heat while keeping crop dust out of the radiator. The Drivetrain is hydrostatic: a Hydrostatic Pump feeds wheel motors so the operator sets speed and direction with one lever, power reaches the ground through planetary Final Drive units on the front Drive Wheel pair, and a steered Steered Rear Axle handles tight turns. Most of the engine power goes to the crop flow rather than to driving, since the machine works at modest ground speed but processes hundreds of tonnes an hour.

Cab and Electronics

The Operator Cab is sealed and pressurised against dust, with an air-suspension Seat Assembly and a Multifunction Handle for speed, header, and spout. The Operation Monitor shows chop length, processor gap, and throughput, and a Yield & Moisture Sensor measures yield and moisture for mapping and for dosing silage additive. The Electrical System system runs at 24 V from a belt-driven Alternator, with the Wiring Harness and Machine Controller coordinating the engine, drives, chop length, and the automatic spout fill. The result is a machine that turns a standing field of maize into trailer-loads of cracked, uniformly chopped silage at a pace no other harvest method matches.