Pedal-Operated Grain Winnowing Machine

After threshing, grain must be winnowed: the lighter chaff separated from the heavier kernels. Villages still do this by tossing grain in the wind — slow, weather-dependent and laborious — while electric winnowers are unaffordable or unusable where power is unreliable. A pedal-operated winnower is the appropriate-technology answer: the operator pedals like a bicycle, a belt drive steps up the speed to a fan, grain falls from a hopper through the air stream, chaff blows aside and clean grain drops into a bin. It is mechanical engineering in direct service of rural life — and a machine-design project where pedalling effort, fan speed, throughput and cleaning efficiency are all measurable on the finished machine, with weighed trials in the manual.

1. The operator pedals the crank at a steady cadence; the chain and belt step the speed up to the fan.
2. Grain mixed with chaff is poured into the hopper and flows down the chute as a thin curtain.
3. The curtain falls through the fan's horizontal air stream.
4. Aerodynamic drag carries the light chaff sideways into the chaff tray.
5. The denser kernels fall nearly vertically into the clean-grain bin.
6. Outputs are weighed per the manual's procedure to report throughput and cleaning efficiency; pulley ratio and chute angle are tuned from the trials.

Tech stack:

• Angle-iron and wood frame fabrication
• Bicycle crankset, chain and belt drive
• Centrifugal fan in sheet-metal housing
• Feed hopper and sloped delivery chute
• Chaff tray and grain collection bin
• Weighing scale for trial measurements

• [Pedal-crank drive] A bicycle crankset the operator pedals at a comfortable cadence — no motor, no fuel, no grid.
• [Chain-and-belt transmission] Chain drive with a stepped belt pulley multiplies pedal speed up to fan speed.
• [Centrifugal fan] A sheet-metal housed fan throws a steady horizontal air stream across the falling grain.
• [Feed hopper and chute] A sloped chute delivers grain as a thin curtain through the air stream for clean separation.
• [Separate collection] Chaff lands in a side tray; clean kernels fall nearly vertically into the grain bin.
• [Weighed trial procedure] The manual's test method weighs outputs to compute throughput and cleaning efficiency.
• [Tunable design] Pulley ratio and chute angle are adjusted from trial results, documented in the manual.

• Working pedal-operated grain winnowing machine
• Fabrication drawings (frame, drive, fan housing, hopper, chute)
• Operation manual with throughput and cleaning-efficiency test procedure
• Project report PDF (winnowing theory, machine design, trial format)
• PPT presentation for final review
• Viva Q&A preparation document (belt drives, fans, separation principles, appropriate technology)

• Throughput is a design target verified by the buyer's weighed trials — actual figures depend on grain condition and operator cadence.
• Handles threshed grain-chaff mixtures; unthreshed material needs prior threshing.
• Manual feed rate affects separation quality; the manual specifies the steady-feed technique.
• Human-powered by design — it will not match electric winnower throughput, which is the accepted trade-off.