Understand how combine components interact to do a better job.
There are discrete steps to set a combine to minimize grain loss and damage when harvesting corn, including:
1. Set concave-to-rotor clearance to the average diameter of shelled cobs from the field to be harvested.
“I want whole cobs coming out the back of the rotor(s),” says Matt Halbrook, AGCO product specialist. “Broken or split cobs indicates the concave is too tight. But broken cobs can also indicate the concave is too wide, that the cobs are tumbling rather than rolling through the concave. Either way, once a cob is broken it’s tough to get the kernels off that broken piece, and grain is going to go out the back of the combine.”
2. Adjust rotor speed in proportion to concave settings.
“For Deere combines, 400 rpm is a good starting spot,” says John Peters, John Deere product marketing manager for combines and headers. “It will vary depending on the concave clearance. If you’re getting grain damage, slow the rotor down in increments of 20 to 25 rpm. If you’re getting full cobs with just a little grain left on them, tweak the rotor speed higher.”
Case IH technician Jason Suhr, a combine specialist with Minnesota Ag Group, says it’s important to understand the relationship of concave clearance and rotor speed.
“Concave clearance is the major factor in getting corn off the cob,” he says. “Rotor speed is how you tune things to get the last few kernels off, or to reduce grain damage.”
3. When possible, use the highest rotor speed that doesn’t cause grain damage.
“Especially in high moisture corn,” Halbrook says. “You need centrifugal force from the rotor(s) to help move grain through all the wet material that’s passing through the concave. More rotor speed not only increases centrifugal force, but also increases the fluffing action to help that grain work free from crop residue.”
4. Keep crop material “level” inside the machine.
“If you’re seeing a string a grain on the ground off one side of the cleaning shoe, do a kill-stop and see if material is distributed evenly across the cleaning augers and chaffer,” Peters says. “If the crop mat is thicker on one side of the chaffer than the other, most of the cleaning fan air takes the path of least resistance and blows through the thinner side, and the overloaded side carries grain out the back.
“On John Deere combines you can raise or lower dividers between the shoe augers to adjust how the rotor distributes material across those augers.”
5. Set sieve to optimize both grain cleaning and air flow to the chaffer.
“If you close the lower sieve too much it can restrict airflow to the chaffer,” Peters says. “It’s like putting your finger over the end of a garden hose. It increases velocity but restricts the volume of air.”
6. Balance chaffer and sieve openings to achieve minimal grain loss and optimum grain sample.
“I close the chaffer (incrementally) until I see grain on the ground, then open it till I don’t,” says Halbrook. “I open the lower sieve until I don’t see grain in the tailings and close it if I start to see trash in the grain tank.
“Some operators are so worried about losing grain that they run their chaffer open and do all their cleaning with the sieve,” he says. “Use the chaffer to clean out the big stuff, the sieve to do the final cleaning, and you’ll optimize the capacity of the combine.”
7. Be cautious when making large adjustments to chaffer and sieve openings.
“If you’ve had the chaffer or sieve open quite a bit for high-moisture corn, or if you’re switching from corn to soybeans, chunks of cob can get wedged in the louvers,” says Halbrook. “If you sit in the cab and push the button to close the louvers against those wedged pieces, you can bend the louvers or damage the actuating mechanism.”
Suhr says newer Case IH combines automatically briefly open louvers whenever the “close” button in the cab is actuated.
“That helps any material in the louvers fall through before they actually reduce their openings,” he says. “It reduces the chances of damaging things.”
