A wheel rake is a haymaking machine that gathers cut forage into long, narrow rows called windrows. It matters because clean, even windrows help hay dry more uniformly and make baling faster and more efficient. Unlike powered rakes, most wheel rakes use ground contact to rotate their rake wheels, which keeps the machine simple and low in fuel demand.
Farmers use them for hay, straw, and other cut forage crops when speed and field coverage are important.
Understanding Agricultural Machines: Wheel Rakes
Each rake wheel works like a rolling comb. As the tractor pulls the frame forward, the lower spring tines touch the ground and the crop. This contact creates a turning force on the wheel.
The curved path of each tine lifts forage from one side, carries it inward, then releases it in a line. The wheel angle controls how strongly the crop moves sideways.
A small angle moves material gently. A larger angle moves it farther, though it can make the crop bunch up if conditions are heavy.
Correct adjustment depends on the field, not just the machine. Light, dry grass needs a gentle setting because brittle leaves can break off. Thick forage may need more wheel overlap so that no strips remain untouched.
The rake height matters just as much. Tines should skim close enough to collect the crop, yet not scrape through the soil.
Uneven ground makes this harder. Operators often slow down near hollows, ridges, and field edges because bouncing wheels can leave clumps behind or pull dirt into the forage.
Forage quality can change during raking. Leaves usually contain more nutrients than stems, but dry leaves are easy to shatter when they are hit or dragged. This is one reason farmers often rake when the crop has some moisture left, such as in the morning or evening.
Wet crop brings a different problem. Dense, damp rows dry slowly and may develop mould.
The aim is not simply to move every piece of forage. The aim is to form an airy row that can finish drying and can be picked up cleanly.
The row made by the rake must suit the next machine. A baler pickup has a limited width. If the row is too wide, material can spill outside the pickup and be missed.
If it is too narrow, the baler may receive an uneven flow, producing poorly shaped bales. Field capacity gives a useful planning estimate. Capacity in hectares per hour equals working width in metres times travel speed in kilometres per hour, divided by ten.
This is an ideal estimate. Turning time, blocked wheels, rough ground, and crop volume reduce the real amount completed.
Students learning about wheel rakes should connect the machine to forces, motion, and material properties. Friction produces wheel rotation, while spring tines bend and recover as they meet the ground. More downward pressure increases grip, but it also raises the chance of soil contamination and tine wear.
Check wheel bearings, bent tines, frame joints, and tyre condition before use. Keep people away from moving machines, especially during turns and transport. Good operation comes from careful observation of the crop left behind, not from driving as fast as possible.
Key Facts
- A wheel rake gathers cut forage by using angled, spoked rake wheels with spring tines that roll across the field.
- Windrow width depends on rake wheel angle, working width, crop volume, and tractor speed.
- Field capacity can be estimated by C = Wv/10, where C is hectares per hour, W is working width in meters, and v is speed in kilometers per hour.
- Ground-driven rake wheels rotate because friction between the tines and the field surface produces torque.
- Too much tine pressure can drag soil and stones into the hay, lowering forage quality.
- A wider rake covers more area per pass, but it must be matched to crop density and baler pickup width.
Vocabulary
- Wheel rake
- A farm implement that uses angled rotating rake wheels to move cut forage into a windrow.
- Windrow
- A long row of cut crop material arranged for drying, baling, or pickup by another machine.
- Tine
- A flexible metal finger on a rake wheel that contacts and moves the forage.
- Working width
- The total width of field covered by a machine during one pass.
- Hydraulic arm
- A movable machine support controlled by hydraulic pressure to raise, lower, or adjust rake sections.
Common Mistakes to Avoid
- Setting the rake wheels too low, which is wrong because the tines can scrape soil into the hay and increase wear on the machine.
- Driving too fast for the crop conditions, which is wrong because the rake may leave forage behind or create uneven, twisted windrows.
- Ignoring windrow size, which is wrong because a windrow that is too wide or too dense may not fit the baler pickup or may dry unevenly.
- Assuming more tine pressure always improves raking, which is wrong because excessive pressure can damage leaves, especially in legumes like alfalfa.
Practice Questions
- 1 A wheel rake has a working width of 7.5 m and is pulled at 8 km/h. Using C = Wv/10, estimate its field capacity in hectares per hour.
- 2 A field is 18 hectares. If a wheel rake covers 6 hectares per hour, how many hours are needed to rake the field, not including turning time?
- 3 Explain why a farmer might reduce rake wheel pressure when raking dry alfalfa compared with raking heavier grass hay.