Using an IRRI axial flow thresher

Before operating the thresher

Positioning of the thresher

  • vimage27Position the thresher on a level area close to the crop stack to minimize handling and shattering losses.
  • Spread cloth, canvas, or mat underneath the thresher to collect spilled grain from the grain discharge chute or due to shattering during handling.
  • Install the cylinder, cover, and feed tray if dismantled during field transport.
  • Position the thresher so that the straw is thrown with the direction of the wind.  This will eliminate the blowing of straw, chaff, and dust back toward the operator and the threshed grain.

Check the machine

  • vimage28Check each belt's alignment and tension.  Adjust the idler pulley on the blower/cylinder belt to correct tension. Improper alignment and tension are the major causes of premature belt failure.
  • vimage29Check pulley surfaces.  Rough grooves must be smoothened with a fine file if nicked.  Cracked pulleys should be replaced immediately.
  • vimage30Open the cover and check all pegs on the threshing cylinder for tightness.  Loose pegs will damage the machine and can be dangerous to the operators.
  • vimage31Examine the pegteeth for wear.  Maximum wear occurs at the feed end of the cylinder and is more prominent at the leading side in the direction of rotation.  Worn pegs must be rotated 180 degrees or interchanged with those located near the straw paddles.  Badly worn pegs must be replaced or rebuilt by welding.
  • Rotate the threshing cylinder manually at least five revolutions to ensure that there are no obstructions or interferences.
  • Make sure there are no loose or missing bolts and set screws.  Tighten or replace as necessary.
  • Lubricate all bearings with good quality grease  (see maintenance and service section)  The belt idler and oscillating screen eccentric bearings are lubricated for life, thus require no lubrication.
  • Check engine oil and fuel levels.  Follow the engine manufacturer's recommendations.
  • Start the engine and allow it  to warm up.  Feed the thresher with the crop to be threshed for performance checking. Increase cylinder speed if excessive amounts of unthreshed and unseparated grain are observed with the straw. Optimum threshing and cleaning is obtained with cylinder speeds of 600 to 700 rpm.

Operating the thresher

Three to four persons are needed for operation: One or two persons to load the feed tray, one operator who feeds the machine, one person for bagging.

  • Start the engine.
  • vimage33Load the feed tray with harvested crop with the panicle away from the operator, so it is fed panicle first into the thresher.
  • Feed the crop at a uniform rate. Adjust the feed rate to match the condition of the material. Maintain maximum feeding rate without overloading the engine.
  • vimage34Adjust the cleaner to suit the threshing conditions.
  • Adjust blower openings to ensure sufficient air flow needed for winnowing.  Open slowly to provide more air for the cleaner until a small amount of mature grain flows over the wind-board. For threshing dry paddy less air is needed while for wet paddy a higher airflow is required.
  • vimage35Adjust the angle of the wind-board. For dry paddy, the wind-board should be set at its maximum inclination.  For threshing wet paddy, the inclination of the wind-board must be reduced. To obtain extra-clean paddy, set the wind-board at a low inclination and increase the air shutter opening.  This process will blow more grain over the wind-board, but this can be recovered by recycling the separated impurities through the thresher.
  • Always use a stick to remove clinging straw from the oscillating screen to protect hands from possible injury.

Optimizing thresher operation

  • Long straw: briefly hold the crop bundles at the feed opening for partial threshing. Longer cut material reduces machine output and may result in poor threshing and clogging of the machine.
  • Short straw: Recycling the straw if necessary unthreshed loss is high. Panicle-harvested materials (cutting just above the flag leaf) may result in high unthreshed losses because the panicles move rapidly through the thresher without receiving sufficient threshing.
  • vimage36Hard to thresh varieties: Install stripper bars. The stripper bars prevent straw from wrapping around the cylinder and aid in threshing. Use of stripper bars reduces capacity and increases the amount of finely chopped straw that passes through the concave when threshing overly mature crops, thus they should be installed only when necessary.
  • Wet or partially decomposed crop: Reduce feeding rate to avoid overloading. Ensures that the cleaning screen is kept free of clinging straw. Open the cylinder cover periodically to remove straw and chaff accumulation at the lower concave

Maintenance and service

  1. Lubricate cylinder and fan bearings with a good-quality general purpose grease every 25 hours of operation.  Periodically apply a small amount of oil to all hinge points.
  2. Inspect the machine regularly for loose, worn, or damaged pegteeth, concave bars, cylinder, discharge paddles and other parts, and tighten, repair, or replace them immediately.  Missing bolts or nuts must also be replaced.
  3. Reduce belt tensions by loosening the idler pulley and engine mounting bolts when the machine will not be used for an extended period to minimize deterioration.
  4. Check engine crankcase oil level at least every 4 operating hours and follow the engine manufacturer's recommendations for oil change intervals and oil grade.  Be sure the recommended oil level is maintained.
  5. Service the air cleaner, fuel filter, fuel line, carburetor, and spark plug regularly according to engine manufacturer's instructions.

Storage of a threshing machine

  1. Clean the machine thoroughly.
  2. Remove belts and store in a dry place.
  3. Store the machine in a clean, dry location and cover to reduce damage from dust accumulation.
  4. Paint parts that need repainting.
  5. Clean and apply oil to exposed metal surfaces to prevent rusting.
  6. Follow the manufacturer's recommendations on engine storage