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A ‘Well-Adjusted’ Harvest

Monday, September 1, 2008
filed under: Harvest/Storage

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Veteran sunflower producers are well-versed in setting and tweaking their combines to produce optimum threshing efficiency. For those newer to the crop, however, the following guidelines should prove helpful. Their source is the section on harvesting in North Dakota State University’s Sunflower Production handbook (EB-25 Revised), published in September 2007. The author is Vern Hofman, recently retired extension ag engineer at NDSU.

— Forward Speed —
A combine’s forward speed usually should average between 3.0 to 5.0 miles per hour. The optimum forward speed will vary depending upon moisture content of the sunflower seed and yield of the crop.

Forward speed should be decreased as seed moisture content decreases to reduce the shatter loss as the heads feed into the combine. Faster forward speeds are possible if the moisture of the seed is between 12 and 15%. The higher speeds should not overload the cylinder and the separating area of the combine, except in an extremely heavy crop. Seed having 12 to 15% moisture will thresh from the head very easily as it passes through the cylinder.

— Cylinder Speed —
After the sunflower heads are separated from the plant, they should be threshed at a cylinder speed operating as slow as possible. The normal cylinder speed should be about 300 revolutions per minute (rpm), depending upon the condition of the crop and the combine being used. This cylinder speed is for a combine with a 22”-diameter cylinder to give a cylinder bar travel speed of 1,725 feet per minute.

Combines with smaller cylinders will require a faster speed, and combines with a larger cylinder diameter will require a slower speed. Rotary combines, as well as conventional machines, should have similar cylinder travel speeds. A rotary combine with a 30” cylinder will need to be operated at 220 rpm to have a cylinder bar speed of 1,725 feet per minute. A combine with a 17” cylinder will need to operate at 390 rpm to have a cylinder bar speed of

If a combine cylinder operates at speeds of 400 to 500 rpm, giving a cylinder bar speed of more than 2,500 feet per minute, very little seed should be cracked or broken if the moisture content of the seed is above 11%. Cylinder bar speeds of more than 3,000 feet per minute should not be used because they will cause excessive broken seed and increased dockage. Excess dockage and broken seed may overload the sieves and the return elevator.

— Concave Adjustment —
Sunflower threshes relatively easily. When crop moisture is at 10% or less, conventional machines should be set wide open to give a cylinder-to-concave spacing of about 1.0” at the front of the cylinder and about 0.75” at the rear. A smaller concave clearance should be used only if some seed is left in the heads. If the moisture percentage of the crop is between 10 and 12%, rather than increase the cylinder speed, the cylinder-to-concave clearance should be decreased to improve threshing. If seed moisture exceeds 15 to 20%, a higher cylinder speed and a closer concave setting may be necessary, even though foreign material in the seed increases.

Seed breakage and dehulling may be a problem with close concave settings. Make initial adjustments as recommended in the operator’s manual. Final adjustments should be made based on crop conditions.

Rotary combines should be set to have a rotor-to-concave spacing of about 0.75 to 1.0”. Making initial settings as recommended in the operator’s manual usually is best. Final adjustments should be made based on crop conditions.

— Fan Adjustment —
Oil-type and nonoil (confection) sunflower weigh about 28 to 32 lbs/bu and 22 to 26 lbs/bu, respectively. The seed is relatively light compared with other crops, so excessive wind may blow seed over the chaffer and sieve. Seed forced over the sieve and into the tailings auger will be returned to the cylinder and may be dehulled. Only enough wind to keep the trash floating across the sieve should be used. The chaffer and sieve should be adjusted to minimize the amount of material that passes through the tailings elevator.

When the combine is adjusted correctly to thresh sunflower seed, the threshed heads will come through only slightly broken and with only unfilled seed remaining in the head. Cylinder concaves and cleaning sieves usually can be set to obtain less than 5% dockage. Improper settings will crush the seed but leave the hull intact. Proper setting is critical — especially for nonoil sunflower that is used for the human food market. The upper sieve should be open enough to allow an average seed to pass through on end, or be set at a 1/2 to 5/8” opening. The lower sieve should be adjusted to provide a slightly smaller opening (about 3/8” wide). The final adjustments will depend upon the amount of material returning through the tailings elevator and an estimation of the amount of dockage in the grain tank. Some operators are able to adjust and operate their machine to allow only 2 to 3% dockage in the seed.
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