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The ultimate combine maintenance and adjustment guide

Is running at 100% capacity without suffering grain losses and damage even possible with the day-to-day challenges of getting a crop out of the field on time?

That’s a balancing act even researchers harvesting test plots are challenged to meet. Today’s combines, however, are so well engineered that they can come darn close to those targets, provided you are willing to invest in the day-to-day diligence needed to evaluate your harvester’s performance and to fine-tune its operation to ever-changing field conditions.

Supporting you in that regard is a new generation of advanced electronics. Yield, loss, and capacity monitors wave checkered flags for peak performance. Plus, in-cab adjustments allow on-the-go tweaking, header height and angle corrections are now automatic, and hands-free steering permits you to focus on harvesting like never before.

“All the advanced technology in the world should never replace a talented producer with a keen eye for the performance of the machine during harvest!” states Kelly Kravig of Case IH.

Caleb Schleder of AGCO adds, “Take time to understand all the different jobs a combine performs and how they’re all related to each other.” That knowledge could prevent you making an incorrect adjustment that seemed right at the time. 

For example, let’s say you see whole cobs with kernels attached riding out over the separator. Without first checking to see what’s going on with the entire combine, you automatically increase threshing speed. Now you are getting broken cobs with kernels still attached PLUS damaged grain coming off the chaffer sieve. The cause of nonthreshing, in this case, is a misadjusted corn head feeding slugs of crop into the feeder house and then into the rotor. Those slugs are not getting evenly threshed, which is causing the loss.

This example illustrates the frustration of adjusting a combine without checking out the entire harvest process.

“Adjusting a combine, particularly to tough field conditions, can be complicated,” says Kent Hawk of John Deere. “Understanding the dynamics of a combine and then adjusting – sometimes several times a day – to changing field conditions offers a handsome payoff.”

Those performance dynamics certainly change with the major processing components of a combine that include the head or platform, threshing, separation, the cleaning shoe, and residue-management system.

Yet, it is crucial to remember that the adjustment you make, let’s say to the head, affects threshing, separation, and cleaning. “They are all separate processes but dependent upon each other,” AGCO’s Schleder point outs.

To get your combine at peak performance, here are key areas to focus on.

Pre-season maintenance inspection

Inside the machine
According to Dennis Bollig of Fenton, Iowa, a farmer and president of Dragotec USA, the average farmer runs a lot more acres through a combine now than 20 years ago. “Inspecting a combine often requires taking a guess on whether specific components will make it through the season or not,” Bollig says. “Is it 25% or 50% worn out? What are the chances of having to replace that part? Answer these questions through a thorough inspection. Run the machine and have somebody sit in the cab from a safety standpoint. Somebody’s got to do a walk-around with that machine running who can help you see, hear, or smell if you have potential maintenance issues.”

Bollig encourages farmers to ask whether their last harvest was a wet, drawn-out affair or quick and dry. “It’s important to look back on the conditions you faced the last time your combine was in the field, since that perspective can help you start on the right foot.”

 “With a wet harvest, you’re more likely to pick up more dirt moving between wet fields. Mud can build up in the bottom of an elevator, create more wear on the paddles, and stick to certain parts of the combine. It can fill up the rasp or concave bars in the initial separation and create some grain loss,” Bollig says. “With drier conditions, you have a lot more dirt and dust to clog air filters and you have to watch for the buildup of debris from a fire hazard standpoint. From a temperature standpoint, you’re running in higher ambient temperatures, and you’ve got to make sure you pay close attention to any gearboxes and components that in a cool, wet fall, might be less apt to cause issues.” 

Maintenance troublespots

Massey Ferguson Combine
Particular wear points on a combine that often demand attention are any parts experiencing repeated friction, like the roller chains on a corn head. With any chain that has noticeably loosened, stretched, or become “sloppy,” the likelihood that part will last through harvest’s end lessens. And, the failure of a chain-driven component can have big impacts elsewhere on the combine, making it an important area of focus during a preharvest combine inspection. 

“When a chain continues to run past its prime, it’s stretching quicker, and if somebody’s not maintaining the proper tension, chains are known to start jumping the teeth on the gear driving them,” Bollig says. “That effect sends a shudder through the whole machine, and you can see it affecting bearings. Anything in the vicinity gets the impact of that shudder.”

When inspecting chains, Bollig also suggests making sure you check the gears and pins driving them. In gauging whether those components will last through this fall’s harvest, consider the conditions in which you harvested corn in previous seasons. “If you have a fall during which you have a lot of tough, wet conditions and the stalks are tough, you could have some potential plugging issues that put extra strain on those rollers,” Bollig adds.

The corn head drive system is another area to inspect carefully, both its chains and the sprockets and gears driving them, Bollig points out. Though premature failure is a concern with the drive system, so too is lost efficiency as the components age. “You’ve got to inspect it for wear and make sure you can make an educated guess whether it’s got enough life left in it to run all season. You know your acres and can base it off that. The more it wears, the less efficient it is over time,” he says. “You’re checking sprockets, too. You can put a new chain on, but maybe the sprocket has a lot of wear on the teeth.”

Threshing and auger components

Rasp bar
Even the smallest amount of damage in a concave section or rasp bar (shown at right) can have a considerable influence on your harvest efficiency and potential yield loss.  “Down in the threshing and separation area, people will take a close look at their rotor and concave. You’re looking for damage that may be relatively minor. Maybe you have a small rock or something go through, so you need to replace a concave section,” adds Mark Hanna, Iowa State University Extension engineer. “Down in the cleaning shoe area, check the condition of the sieve. If something’s gotten dinged or banged up, it needs attention. You’re looking for general wear.”

Finally, check the flighting on all augers, Hanna urges. Though damage is less likely in this part of the combine, wear can sometimes leave sharp edges on the flighting, leading to grain damage. “It’s probably in good shape, but it does wear over time. It is something that may need to be looked at,” he adds. “If you have some really sharp edges, you can cut some of the grain. If that’s the case, you’re going to degrade your corn quality.”

Calibrate loss and yield monitors

Combine electronics
Recalibrating monitors should be done at the start of every harvest season, possibly even during the season, notes Deere’s Hawk. “You might want to do a check load, for example, to double-check calibration during the season,” he says.

“With so much technology in the combines, we typically have a yearly inspection done by the dealer. That doesn’t mean he has to do all the work, but you want to get a professional eye to look at it. The same goes for diagnostics,” Bollig says. “It starts with taking it to an expert to hook it up to a computer to test those sensors and diagnostic electronics.”

Starting harvest

Inspecting soybeans
After you have opened up a field but before you get into harvesting that field in earnest, check the ground for field loss, remembering to deduct that loss after finishing the field review behind a combine.

Next, examine the crop to see how easy or hard it is to shell out. Break cobs in half and observe their composition. 

“Cobs with white or soft centers will be harder to thresh than those that are firm and pink,” Schleder explains. “Cob composition certainly has an impact on threshing adjustments.”

For soybeans, look for problems with green stems and how easily pods shell out.

Examine heads and platforms to determine if they are causing losses or smoothly delivering crop to the feeder house.

“Heads and platforms are the primary causes for grain loss,” says AGCO’s Schleder.

A recent development involves running the draper header belt speed too fast. “When side belts run too fast, the left and right swaths merge into a single layer. The denser swath requires more effort to thresh and separate. That can pose a threat to grain quality,” says Jeff Gray of Claas of America. “Belt speed should be optimized (often reduced) to allow the left and right swaths to enter side by side, as indicated by a V-pattern going into the feeder house.”

Adjusting threshing

Adjust threshing
Like an 800-pound gorilla walking a tightrope, threshing requires a balance between rotor speed and concave clearance.

Concave clearance should be adjusted in steps. Start with the widest setting and narrow the spacing until it’s close enough to just thresh out the grain without causing damage. The primary duty of clearance is to regulate the amount of material flowing through the threshing. Running a concave too wide results in grain not being removed from cobs, and that could result in a ricochet effect that damages the grain. Running the concave too tight can cause cracked kernels and broken cobs.

Setting threshing speed is even more crucial for the damage it can inflict. Misadjusted speed is a common mistake, notes AGCO’s Schleder. Signs of excessive threshing include cracked or damaged grain, cobs that are broken excessively, and too many tailings. The place to start when setting threshing speed is at the top of the rpm recommended in the operating manual.

“For example, with Deere combines, I advise starting at 400 rpm and adjusting from there,” say John Deere’s Hawk. “We are harvesting so much more crop (both yield and residue) today. The slower threshing speeds of the past are not fast enough to consume the crop.”

To determine the need for speed adjustment, operate the combine in the field and check for grain damage. If some damage is caused, then back down the speed until damage disappears.

Another major goal is to have a level and even flow of grain coming off the pan or auger deck on to the cleaning shoe. Threshing misadjustments quickly become evident at these locations. Just changing the concave pinch point makes a difference in how well grain and trash are distributed on the pan or deck.

Tweaking the cleaning shoe

Cleaning shoe
When it comes to cleaning shoe adjustments, be mindful that most cleaning takes place with the initial blast of air where the grain comes off the pan.

As such, it’s crucial to have an even feed of grain coming off the pan or deck and onto the chaffer sieve. This allows the air from the cleaning fan to flow evenly through the grain and residue layer. There’s a balancing act occurring between the separator and cleaning system that requires the loss sensors for each to be properly set.

Part of the balancing act here is also to make sure sieve adjustments work in tandem with fan speed.

For example, to counter grain loss off the cleaning shoe, you will often open your upper sieve (chaffer) too wide to try and minimize grain loss by allowing more grain (and chaff) to fall through, Gray has seen.

“This causes more material (including grain) to fall onto the lower sieve. That can overburden the lower sieve resulting in more tailings returning to be rethreshed (whether needed or not) adding stress to the grain traveling within, as well as inconsistent wind flow,” he says.

“To counter the overburden on the lower sieve, farmers will sometimes open the upper sieve, but that could increase foreign matter (FM) in the tank. Increasing the fan speed to penetrate the overburden could generate enough pressure to possibly boost grain loss off the upper sieve, creating a vicious cycle,” Gray notes.

Actually, all that was needed in the first place was optimizing fan speed according to throughput at the given ground speed and adjusting the upper sieve to reduce FM in the sample.

When adjusting fan operation, check that the airflow across the shoe is as uniform as possible. With larger crop flows, however, more air needs to be directed to the front of the chaffer using the adjustable windboard.

If everything is working in unison in the cleaning shoe, tailings in the return auger should be sparse.

Don't forget adjustments to the RMS (residue management system).

Residue management system
“How residue is left behind the machine certainly affects next year’s crop, particularly for reduced-till farmers,” says Case IH’s Kravig.  RMS adjustments have a huge impact on distribution “especially with today’s wider heads and platforms,” adds John Deere’s Hawk.

Overall rules to make adjustments

Each combine make has an optimal match of settings that captures the most yield with minimal damage in the least amount of time. Discovering that sweet spot starts with abiding by these hard-and-fast adjustment rules.

Live with your owner’s manual. “Everything you need to know, starting with initial settings and then a step-by-step analysis of adjustment, is in the book,” says AGCO’s Schleder. “It should be dog-eared and in the cab.”

A pocket-type setting guide is also a very convenient tool if you need a quick reference when the combine is already configured for the crop to be harvested. “But manuals provide greater detail about how and when to change configurations for different crops and conditions and the effect those configurations may have on settings,” says Claas’ Gray.

Adjust operating speed to keep threshing fully charged at all times. Doing so not only boosts harvest speed but also minimizes grain damage, says Deere’s Hawk. “This requires you to consistently monitor engine loading in response to crop conditions since yields can vary a great deal across a field,” he says.

Other general rules to adjusting in the field include:

  • Check the combine’s performance frequently and particularly when field conditions (such as grain moisture content) or varieties (especially with corn) change. Case IH’s Kravig knows operators who save settings to employ in the morning (when crop moisture is the highest), in the afternoon (when the crop is drier), and again late in the day when moisture starts to creep back into the crop.
  • Stop the combine at least once a day in an area representative of the field. Manually disable its residue management system. Operate the combine at acceptable speeds, filling the separator with crop. Shut the combine down, get out of the cab, and starting ahead of the head or platform to determine preharvest loss, examine every major step of the processing. End this process by examining the field, looking for grain loss and even residue distribution.
  • Know why you’re making an adjustment before making that change.
  • Make only one adjustment at a time and in small increments.
  • Evaluate the results of the last adjustment before making another change.
  • “Look, see, and feel how the combine is operating when in the cab,” says AGCO’s Schleder. “You can feel when a combine is operating smoothly. Take time to pay attention to that.”

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