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Show me the rotaries

Rumors of a new combine with rotary technology are causing buyers to wonder 'why rotary, why now? And are all rotaries created equal?' We'll show you how each company's rotary stacks up.

Not since Nissan's Infiniti has a single silhouette generated so much speculation about a machine and its maker. The automobile manufacturer broadcast only glimpses of a car for months before revealing its identity.

Recently, Deere has attempted to rouse similar intrigue in farm machinery through its advertising. The ad, published in the May/June issue of Farm Industry News, shows simply the back end of a concept machine in the shadows and the tag line, "a new era of harvesting is taking shape."

Barry Nelson, Deere's manager of public relations, says a new family of combines will be unveiled in Moline, IL, in August at its dealer meeting and will replace the current Ten series. Nelson claims the new family "will offer customers the broadest and best choices of combine configuration in the industry." Production will begin in August.

Rotary rumors. Speculation is that the new combine uses rotary technology in addition to or in place of cylinder-and-concave threshing.

Some observers believe it incorporates components used in the "bi-rotor" combine invented by Kansas farmer Mark Underwood and his cousin Ralph Lagergren. Deere purchased the patent in 1995, but has never commented on its plans to manufacture the unique rotor-within-a-rotor design.

Others guess the new combine has something to do with Deere's CTS II combine made for rice and small grains. CTS stands for cylinder tine separator. The machine uses rotary technology as far as the separating aspect of it and a cylinder and concave in the front end for threshing.

Still, no one knows for sure what the new combine will be. Or, those who do know have been sworn to secrecy and asked to sign confidence agreements.

But if rumors are correct, adding a combine with rotary technology to its lineup would represent a fundamental shift in philosophy for Deere, who has stayed with the cylinder/walker design to thresh corn and beans even when its competitors switched to rotaries in the mid-1970s. (AGCO and Caterpillar make both types.) It also would mean that all major combine makers - AGCO, Case, Caterpillar, Deere, and New Holland - would have a rotary-based combine in their lineups.

The question for combine buyers is why rotary, why now? And, is one company's rotary better than the next?

Two schools of threshing. There are basically two types of combines - conventional (cylinder/concave and straw walkers) and rotary. "Both force an ear of corn through a space that is too small," says Steve Webb, Indiana farmer and Team FIN product tester. "And the only way to get it through is to take the kernels off."

Both types run the crop between a rotating cylinder and concave to rub the grain off. But in the conventional machine, the cylinder is mounted crossways on the combine or perpendicular to the direction of combine travel. The crop is fed into the cylinder "tangentially" and has one chance - about a third of a rotation of the cylinder - to be threshed. Straw walkers and sieves then separate the grain from the chaff.

In a rotary combine, by comparison, the cylinder is larger and typically is mounted lengthwise in the direction of combine travel. The crop is fed "axially" and spins between the cylinder (or rotor) and concave until the grain is both threshed and separated.

"Imagine a spinning squirrel cage," explains Dr. Jonathon Chaplin, agricultural engineer at the University of Minnesota. "If you were to push a piece of paper into the edge of that cage along a tangent, that is how a conventional combine is fed. If you feed the paper in from the end of that cage, around the circumference, that's how an axial is fed. So really, a major difference is how the crop is fed into thecylinder."

Because the direction of flow is more aligned with the cylinder of the axial rotary combine, it can be gentler on grain than a conventional combine, Chaplin says. What's more, the clearance between the cylinder and concave doesn't have to be set as tight because the spiraling grain can travel a greater distance in the threshing area. The result can be gentler threshing and a better quality grain sample.

"When rotary combines first came out, our department did some tests on the rotary and the conventional," says Dr. John Siemens, agricultural engineer with the University of Illinois. "At that time, the rotary combine resulted in less kernel damage to the corn crop. I should say, it was easier to adjust, resulting in less damage than with the conventional combine. So that would be the advantage."

Grain quality has become increasingly important lately as more farmers are growing specialty crops like food-grade corn or soybeans under contract. These contracts specify a certain level of quality. Grain that has too many cracks or chips can be rejected at the elevator.

"In the past, grain quality was kind of acknowledged. Now it is demanded," says Kelly Kravig, marketing manager with Case Corporation, maker of the Axial-Flow combine. "And that has been a significant change over the last 22 years."

That may account for any recent interest in rotary technology. A major reason all manufacturers (except Deere) went to rotary in the first place was a combination of grain quality and capacity, according to Verlin Tinder, product marketing manager for AGCO's Massey Ferguson (MF) combine. "Axial rotary technology allows you to increase capacity without being totally restricted by the overall width of the combine," Tinder says. You can simply make the rotor longer to increase combine capacity.

With a conventional combine, in comparison, in order to widen the cylinder you would have to widen the machine, he explains. You can go only so wide before interfering with road transport.

Rotary roundup. Not all rotary combines are made the same. Some combines have one rotor. Others have two. And, while most rotors are mounted lengthwise, AGCO's Gleaner R series are mounted widthwise. What's more, some rotors are considered part of the threshing system, some are considered part of the separating system, and some are part of both.

So which one is best? We asked the manufacturers of rotary combines what makes their rotary better than the next for corn and beans. Here's what they said: Case: It claims to have built and sold more rotary combines than any other company since it started building them in 1977. Its current series is the 2300 Axial-Flow made up of three models: the 174-hp 2344, 240-hp 2366, and 280-hp 2388.

"The biggest difference is that Case uses a single rotor that provides fewer moving parts," says Case's Kravig. "A lot of competitive designs use multiple rotors or a rotor that is positioned sideways versus lengthwise. That makes for a more complex material flow in the machine or will add more parts, which create more opportunity for grain damage."

Other rotor features include a 3-speed rotor drive in the 2388 for a greater speed range; and a cross-flow fan that delivers uniform airflow across the sieve to increase cleaning capacity. Suggested list for base machine: $130,600 to $166,880 plus grain header.

AGCO: It makes two kinds of rotary combines: the 260-hp MF 8780 and the Gleaner R series consisting of the 185-hp R42, 230-hp R52, 260-hp R62 and 330-hp R72.

The MF 8780, like Case's Axial-Flow, has one rotor. But AGCO claims its rotor is longer. "As it stands now, we use the longest rotor of anybody in the industry so consequently it has more threshing and separating area," says AGCO's Tinder. "As a result, you get a much cleaner grain sample and less chance of grain loss compared to the competition."

Other rotor features include: a hydrostatic rotor drive, allowing the rotor to be hydraulically driven or hydraulically reversed in the event of plugging; and rotor speed control, a new feature that automatically adjusts the output of the hydrostatic pump to maintain a constant rotor speed for the crop being harvested. Suggested list for base machine: $140,000 to $160,000 plus header.

AGCO's Gleaner R series has a single rotor, too. But, unlike other rotors, its rotor is mounted across the combine - perpendicular to the direction of travel - and is transversely fed. This orientation "allows the crop to flow through in a more natural motion rather than being twisted through the cylinder," according to Tom Draper, Gleaner's general marketing manager.

"Another unique feature is accelerator rolls in our cleaning system," Draper adds. "That is the key to both capacity and quality of the sample. The rolls drive grain down onto the grain pan at four times the speed of free fall. That way, we can use more air and increase cleaning capacity." Suggested list for base machine: $117,000 to $178,000 plus header.

New Holland: "We were the first to introduce rotary combines in 1975," claims Steve Geick, New Holland's combine marketing manager. "Since then, we have been working to perfect the rotor technology." For example, its new 9 series - made up of the 240-hp TR89 and 280-hp TR99 - incorporate 33 product improvements over the previous series.

TR stands for Twin Rotor, meaning it uses two rotors instead of one. "That's the secret to providing the highest capacity combines for their size on the market today with the best sample in the business," Geick says. These side-by-side, smaller-diameter rotors generate up to 40% more centrifugal force than larger rotors so that more of the grain gets threshed and separated right up front, he says.

"They use the example of driving a car to explain the centrifugal separating forces," offers Team FIN's Webb, who recently replaced his 20-year-old combine with a '95 New Holland with 800 hrs on it. "You drive a car at 40 mph around a gentle curve and you're alright. You drive the same car at 40 mph around a lot shorter curve, and it tries to go off the road. Well, the car is the kernel of corn."

Suggested list for base machine: $130,000 to $170,000 plus header.

Caterpillar: Cat has two rotary models - the Lexion 480 and 485, both 365-hp - and will unveil a third, smaller rotary this fall for market in 2000.

The Lexion features two rotors, which use centrifugal force to separate the grain from the straw. In addition, an Accelerated Pre-Separation System (APS)-located directly behind a 67-in. feeder house-uses an initial cylinder to separate up to 30% of the grain and feeds the crop to the main threshing cylinder. Between these two cylinders, up to 90% of the grain is separated before the impeller feeds the crop mat to the two separation rotors, according to Ron Havekost, commercial manager for Caterpillar combine group. This design gives the Lexion the highest harvesting capacity in the industry, the company claims.

You can adjust for better grain quality by slowing down the main threshing cylinder and increasing the concave clearance so that more of the threshing can be done with the rotors. Suggested list for base machine: $211,000 to $265,000 plus header.

Matter of adjustment. Manufacturers of convetional combines say both types of combines can hurt the rain. And both can be equally gentle.

The key to grain quality is getting the right concave speed and concave clearance setting, according to Ron Moron, Deere's senior marketing representative for combines. "When the combine is threshing properly is when you are going to see a good job in overall quality of grain," Moron says. Either type can be adjusted too tight and result in poor quality, cracked grain.

With that in mind, Deere has worked to make it easier to make those adjustments on its latest Ten series, which includes the 190-hp 9410, 220 to 240-hp 9510 and 275-hp 9610. For example, a digital cylinder/concave clearance indicator replaces a mechanical one in the previous 9000 series so that you can fine-tune adjustments to the exact number rather than a notch on the dial. Deere also changed the geometry of its concave, nowcalled Generation II, to get more complete threshing at slower cylinder speeds. Suggested list for base machine: $118,096 to $153,724 (header $24,656 to $50,087).

These changes help ensure proper adjustments that result in grain quality that is just as good as any rotary design, Moron says. What's more, its conventional configuration provides consistent performance in a variety of crops and conditions without extensive changeover or loss of horsepower, he adds.

"When you ask 'why buy a conventional versus a rotary,' we will sell it on the all-crops, all-conditions capability," Moron says. "Today, we believe our Ten series delivers a more consistent level of performance in all of the varieties of crops and conditions you can get into, with less tradeoff than what you have to do with competitive rotary combines currently on the market." In support, he cites that Deere's cylinder/straw walker combine has a larger share of the market than any other combine does in North America.

Moron attributes the combine's performance to everything from a wide feeder house that makes for a wide, thin crop mat that can be more easily threshed, to its transverse or "ribbon-flow" feeding that is more natural than typical rotary designs and results in less twisting. Less twisting means less horsepower is required to do the job, Moron adds. And because the crop isn't so tightly confined in a restrictive space, there is less plugging and fewer material handling problems than in a typical rotary machine.

For those reasons, Deere stands by its current design. And, when asked whether conventional models will continue to be manufactured, Moron responded, "Absolutely yes."

Other makers of both types agreed that there will always be conventional combines because certain conditions may demand them. For example, some experts say a conventional machine may be better if you get into tough conditions like weedy wheat or if you want to bale wheat or oat straw because it is able to leave longer stems.

"If you're baling long-stem straw and you have the best quality of straw to work with, then you'd be wise to stay with a straw walker," says Caterpillar's Havekost. "But, if you're working with specialty crops and grain quality is what you really want, then you'd probably want to look at rotary separation."

Soon, we'll know for sure which way Deere decides to go.

Six future features that will change the way you harvest. Although Deere will not give details about its new combine until September, Bob Malcolm, Deere's manager of product planning for harvesting products, did agree to talk about technology being worked on for incorporation in the next five to 10 years. Malcom gives us this look:

1. Grain quality monitors. Today's combine yield monitors measure yield (mass) and moisture only. Monitors coming in the next five to 10 years will be able to measure grain "quality," such as cleanliness, kernel damage and chemical content, Malcolm says. Growers of specialty crops will need such capabilities.

"Crops will move from being what I call a commodity to being a product, and farmers will be operating on a contract to deliver high oil or low phytate corn or a certain kind of soybean," he says. "This contract will say it must have a certain characteristic of chemicals to meet this contract."

2. Ease and convenience of adjustments from the cab. Future designs will allow you to take readings and make combine adjustments - like fine-tuning the sieve and chaffer to the proper opening - from inside the cab.

3. More monitors and controls. Future control systems will cut down on the number of adjustments the operator has to make. "For example, right now farmers have to shut off the machine, get out of the cab, make some checks and change the chaffer or sieve," Malcolm explains. "But as our technology improves because of different sensors on those future machines, those things will be done automatically. Or, it will provide information so the operator can make those checks in the cab versus getting out of the machine."4. Better residue management. The company is looking at crop residue as it relates to combines from two standpoints: Provide a combine and residue disposal system that will allow farmers to collect and sell the residue for alternative uses; and How to handle residue better in the field to eliminate a tillage pass.

5. Grain logistics. "We are looking at ways to make the handling of grain both on board and to and from the storage site more efficient." he says.

6. Increased combine uptime. Uptime refers to the time the combine is employed in the task of harvesting. The industry is researching ways to increase that time to reduce owner's overall operating costs. This area includes everything from product support to faster road speeds.

Technologies to increase a combine's efficiency in the field will also play a role. But that will not mean bigger combines, Malcolm says. "The package size cannot grow. We will try to improve the performance in existing package sizes."

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