Hay Tedder

Overview

A hay tedder (rotary tedder) speeds field drying of mown grass. A mower leaves the crop in dense swaths in which the bottom layer stays wet for days; the tedder picks those swaths up and scatters the crop across the full field surface in a loose, aerated layer. Exposing all of it to sun and wind can halve wilting time, often the difference between baling hay before rain and losing it. For silage the same machine takes grass from 80% moisture at mowing to the 65–70% target in a single sunny day.

The working width is covered by six overlapping Rotor Spiders, each about 1.4 m in sweep diameter and carrying six Tine Arms tipped with sprung Double Tines of 9–10 mm spring steel. Adjacent rotors turn in opposite directions at roughly 200 rpm, so each pair gathers crop between them and hurls it up and rearward; the tine tips travel near 15 m/s, fast enough to tease apart a wet swath but sprung so they ride over stones and comb the stubble without scalping soil.

How it works

Drive enters through the PTO Shaft at 540 rpm into the Main Gearbox, which splits it left and right along the frame. Hex Drive Shafts carry rotation through the frame tubes to a sealed Rotor Drive Head above each rotor; alternate heads are geared to reverse direction. At each fold joint a dog-type Finger Clutch lets the shafts separate as the wings fold and re-engage on unfolding in any relative position.

Ground following decides job quality. Each rotor rides on its own gauge wheel, set on a castoring Wheel Fork directly under the rotor centre, so tine height tracks the local surface rather than the average of the whole 7.7 m machine. A pinned Height Collar sets clearance in roughly 5 mm steps: tines too high leave wet crop behind; tines too low rake soil and ash into the forage, which shows up later as poor silage fermentation. The Pitch Adjuster on each wheel fork sets rotor pitch, steep for aggressive first tedding of heavy wet swaths, shallow for gentle final turning of nearly dry hay, when leaf shatter in legume crops becomes the dominant loss (lucerne can lose a substantial share of its feed-value-bearing leaves to over-aggressive tedding).

The machine is mounted on a Category 2 linkage through a swinging Headstock Frame: the frame pivots behind the tractor on corners and slopes, steadied by Pivot Dampers and recentered by Stabilizer Springs, so the rotors keep tracking the ground line rather than the tractor's yaw.

Two settings deal with field boundaries and weather. The Border Spreading Device tilts the machine so crop is thrown inward along hedges and watercourses instead of into them. The Night Swath Kit narrows the spread into loose windrows in the evening, reducing the surface area that overnight dew rewets, ready to be spread again next morning.

Transport and safety

For the road, two Fold Cylinders raise the four Wing Frame Sections vertical in about 30 seconds, bringing the machine inside 3.0 m width; mechanical Transport Locks hold the wings independently of hydraulic pressure, and Warning Panels mark the silhouette. In work, the Guard Bow around each rotor keeps people and obstacles out of the tine path.

The characteristic failure of any tedder is a fatigued tine breaking off and hiding in the forage, where it can wreck a baler knotter or, worse, be eaten by a cow. Every tine therefore carries a Tine Saver Clip retainer that keeps a fractured coil attached to its arm, a trivial part that the industry treats as mandatory.

Context

Six-rotor mounted machines around 7.7 m suit the 50–70 hp tractors of typical grassland farms and cover 7–9 ha/h. The same architecture scales from 4.5 m four-rotor models to 17 m trailed machines with ten or more rotors for large forage operations. In a grass-drying chain the tedder works between the mower (or mower-conditioner) and the rotary rake that gathers the dried crop back into windrows for the baler or forage harvester; on many farms it is the cheapest machine in that chain and the one whose timing matters most.