Threshing Floor & Winnowing Set-Up
Lay a clean sealed threshing floor and build simple winnowing gear so grain comes off the field clean, dry and free of the grit that ruins flour and teeth.
- Estimated cost
- $15 – $80 for a floor and baskets
- Skill level
- Beginner
- Time
- 1 – 2 days
Not yet verified
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Tools
- Hoe and rake
- Wooden flails or beating sticks
- Trowel
- Buckets
Short a tool or material? Builders below have often swapped something local in — read Local adaptations before you buy anything.
Materials
- Compacted soil-cement slab, plastered floor or heavy tarpaulin
- Woven winnowing trays and a raised platform or stool
- Graded sieves for grit and broken grain
- Sacks and a raised pallet for storage
Dimensions & cut list
A pedal- or crank-driven fan winnower separating chaff from 100–150 kg of threshed grain an hour. These are the reference sizes from Appropedia / post-harvest practice — scale them to what you have, but keep the ratios.
| Fan blade diameter | 450 mm, four flat blades |
|---|---|
| Fan speed | 600–800 rpm |
| Air outlet slot | 400 × 120 mm |
| Feed hopper | 400 × 300 mm mouth with an adjustable slide gate 400 × 20 mm |
| Drop height, hopper to floor | 900 mmGrain needs the fall time to be crossed by the airstream |
| Grain outlet | First chute at 250 mm from the fan, chaff carries past 600 mm |
Take this list to the yard
- 1Plywood or sheet-metal fan housing
- 1 set16 mm fan shaft with two bearings
- 4Sheet metal or hardwood blades
- 1 setBicycle crank, chainring and chain
- 12 m50 × 50 mm timber frame
Step by step
Step 1 of 6
Build a clean floor
Compact and seal a level circle 4 – 5 m across, or spread a tarpaulin. Threshing on bare soil is where the grit in the flour comes from.
Swipe or use arrow keys
1. Build a clean floor
Compact and seal a level circle 4 – 5 m across, or spread a tarpaulin. Threshing on bare soil is where the grit in the flour comes from.
2. Dry the crop first
Stack sheaves heads-inward and dry until grain cracks rather than dents under a thumbnail. Threshing damp grain bruises it and invites mould.
3. Thresh in batches
Spread a thin layer and beat with flails in a steady rhythm, turning the layer. Small batches thresh far more completely than a deep pile.
4. Winnow with the wind
Work in a steady crosswind. Pour the mix from a tray held high so chaff blows aside while grain falls onto a clean sheet; repeat until it runs clean.
5. Sieve and grade
Pass through a coarse sieve for stalks and stones, then a fine one for dust and broken grain.
6. Dry and store properly
Sun-dry to storage moisture, cool, then bag and stack on pallets clear of walls in a ventilated store.
Why mine failed
The ways this build usually goes wrong, and what fixes it.
Good grain blows out with the chaff
CauseFan speed too high
FixSlow the crank or fit a smaller drive pulley, then adjust with the outlet slot damper. Set it so light chaff just lifts and grain drops straight down.
Chaff stays in the grain
CauseFeed rate too heavy — grain falls as a curtain the air cannot cross
FixClose the hopper slide gate to a thin, steady trickle. A slow continuous feed cleans better than fast bursts.
Fan shaft wobbles and screeches
CauseUnbalanced blades or worn bearings
FixWeigh each blade before fitting so all four match, and pack or replace the bearings. An unbalanced 800 rpm fan destroys its own frame.
Safety notes
- Flails swing wide — keep a clear circle around each thresher and never work face to face at arm's length.
- Wear a dust mask and eye protection when winnowing; chaff dust causes real respiratory problems over a season.
- Do not thresh on tarmac roads; vehicle risk and contamination are both serious.
- Store only fully dried grain. Under-dried grain heats, moulds and produces aflatoxin.
Source & attribution
This plan is our build-step write-up of work documented by Appropedia / post-harvest practice. The original design and documentation belong to them — go read the source before you build.
Threshing and winnowingLocal adaptations
What builders changed to make this work where they live.
Field note · Burkina Faso
Households winnow from a raised platform in the late-afternoon breeze, when the wind is steadiest and the grain is at its driest.
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