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Big Mower Manages Crop Residue

Developed to match combine harvester header widths of 16, 24, 30 and 40 feet, the 5.0, 7.3, 9.1 and 12.1 metre width Spearhead StarCut rotary mowers are much more than glorified stubble toppers. These machines are designed to be part of a complete residue management system.

Spearhead is no stranger to wide-area rotary mowers. Remember the company’s 4.6 metre 460 MultiCut of 1990? This particular mower went on to spawn variants that include the 820 MultiCut, big five-rotor machine that stretches to a still significant 8.2 metres.

Introduced in 2005, the 820 MultiCut has the potential to cover in excess of 8.5 hectares per hour. So, is the StarCut 1210 just a further development of the established MultiCut, this time with seven rotors and a 12.1 m operating width?

In fact, apart from some shared design DNA that includes a delta deck shape and shaft drive to each rotor, the StarCut models are otherwise significantly different from Spearhead’s MultiCut topper series. The StarCut cutting deck, for example, is constructed rather like an aircraft wing, with two sheets of steel and an internal frame forming each section.

All hoses and cables are routed through the cutting deck sections to leave both the underside and top of the unit smooth and clutter-free. Then there are the rotors themselves. In place of long blades that pivot at the rotor hub, the StarCut design has rigid blade holders. Pivoting heavy-duty blades are bolted to these carriers, with three blades per rotor.

The design thinking behind the StarCut blade system is that, as it’s only the tip of a rotary blade that actually does the cutting, it makes sense to angle the blade in such a way that the remainder of the blade does not come into contact with the “mown” surface. This reduces the StarCut’s power consumption.

When topping stubble, blade angling also allows the operator to virtually work the tip of the blade at soil level; the blades are designed to cope with soil contact.

Adopting this practice with a “straight” blade is possible but, because it takes power to drive a blade over a surface, fuel use increases if such a practice is followed. Operators of previous generation Spearhead machines were able to mimic this approach and alleviate a degree of blade drag by setting the topper at a slight “nose down” angle. This raised the rear of the unit clear, in effect allowing just the “front” rotor blade to be in work at any one time.

Although this approach could, of course, have been adopted with the StarCut rotor, the aim is to do more than just cut the stubble. Even distribution and a thorough mulch of the crop residues are key design features. To achieve these operational goals, the mower needs to be worked “level” to contain cut material within the deck longer — to improve mulching and even out trash distribution.

A second key difference is that a StarCut rotor is built to cope with much higher volumes of material which, in a cereal crop, allows the stubble to be left longer. It follows that this longer stubble reduces the volume of material passing through a combine’s threshing system and rear straw chopper. This, in turn, can potentially increase harvesting throughput and cut fuel use, too.

To further assist in the mulch of longer stubbles, Spearhead offers a StarCut 6 blade. This brings a second set of three blades. These secondary blade tips then ride above the main blades, but they also extend slightly further forward, reducing stubble height fractionally ahead of the standard blades and also improving mulching. In stubbles of lengths of 350 mm or so, the extra blades are recommended.

As part of the StarCut project, Spearhead has carried out research work in Germany on cereal stubble management. One of the main findings of this work is that longer crop stubbles can be effectively managed with high-output toppers like the 12.1 metre StarCut 1210, and that this can also result in higher combine throughputs and reduced diesel consumption, in effect “paying” for the use of a topper postharvest (see box).

The mower’s wing sections

Tie bars run back from the drawbar to the central wheel set raise/lower pivot, so a towing bracket can be fitted. Trailing a stubble cultivator behind the StarCut is an option that’s capable of further reducing post-harvest costs.

are flat across their top surface, with just the drive shafts and link hydraulic hoses running over the wing pivot points. This makes the StarCut much easier to keep clean — an important feature in Denmark, where StarCut mowers have been used to trim seed grasses prior to heading and seed harvest. When moving between grass varieties, the risk of seed cross contamination is avoided by thoroughly cleaning the mowers between fields.

The Danish grass seed sector also helped determine the height setting system. Seed grasses are cut at progressively different heights through the season, so having a straightforward and accurate height setting system is an important trait. By using simple sectioned collars to set the mower cutting height, operators can quickly alter the height by folding in a fixed number of sections.

In contrast, dealing with high volumes of crop residues calls for a somewhat different

approach. The aim here is to promote maximum decomposition of substantial volumes of material and to distribute this material as evenly as possible. It’s also desirable to shave the stubble as close to ground level as possible, the downside being that soil contamination is inevitable. A complex grass-style mulching deck would quickly clog up in all but the driest of field conditions.

The StarCut system achieves its mulching ability by having a high blade speed and containing material so it is acted upon by all three blades as it passes through the deck. Also, the StarCut 6 blades provide extra mulch capacity in longer straw.

ALL ABOUT EFFICIENCY

The effective and economic treatment of long crop stubbles has one fundamental objective — that’s to improve overall combine harvesting efficiency. The goal is to balance any operational costs and machine throughput savings made at harvest with the investment required to deal with the longer stubble in the peak demand summer/autumn period.

According to Spearhead, there are other advantages to leaving long crop stubbles. Among these pluses is the fact that standing crops dry from the top down. So, in a catchy season, a combine will potentially be able to start work sooner when there is only a need to wait for the top third of the crop to dry.

StarCut performance in corn stubble is also claimed to be good, the machine pulverizing the stalks that could otherwise harbour pests and diseases. The ability of the blades to work close to the soil is also seen as a significant advantage when it comes to working in difficult conditions — not unusual for the corn crop.

One final point: The 1210’s rear towing eye is designed to allow operators to trail a cultivator behind the mower. Now that really does make for a horsepower-hungry, yet still interesting combination.

James de Havilland writes for profi, a leading

European farm machinery magazine. Visit the

website at Grainews readers

can go to and sign

up for a free sample of the magazine.

Rotor drive snakes along the top of the deck, with good access to all grease points. Second to last gearbox has a unique pivot design that allows the outer section to fold in stages.

approach. The aim here is to promote maximum decomposition of substantial volumes of material and to distribute this material as evenly as possible. It’s also desirable to shave the stubble as close to ground level as possible, the downside being that soil contamination is inevitable. A complex grass-style mulching deck would quickly clog up in all but the driest of field conditions.

The StarCut system achieves its mulching ability by having a high blade speed and containing material so it is acted upon by all three blades as it passes through the deck. Also, the StarCut 6 blades provide extra mulch capacity in longer straw.

ALL ABOUT EFFICIENCY

The effective and economic treatment of long crop stubbles has one fundamental objective — that’s to improve overall combine harvesting efficiency. The goal is to balance any operational costs and machine throughput savings made at harvest with the investment required to deal with the longer stubble in the peak demand summer/autumn period.

According to Spearhead, there are other advantages to leaving long crop stubbles. Among these pluses is the fact that standing crops dry from the top down. So, in a catchy season, a combine will potentially be able to start work sooner when there is only a need to wait for the top third of the crop to dry.

StarCut performance in corn stubble is also claimed to be good, the machine pulverizing the stalks that could otherwise harbour pests and diseases. The ability of the blades to work close to the soil is also seen as a significant advantage when it comes to working in difficult conditions — not unusual for the corn crop.

One final point: The 1210’s rear towing eye is designed to allow operators to trail a cultivator behind the mower. Now that really does make for a horsepower-hungry, yet still interesting combination.

James de Havilland writes for profi, a leading

European farm machinery magazine. Visit the

website at www.profi.com.Grainews readers

can go to www.profi-int.com/grainewsand sign

up for a free sample of the magazine.

Rotor drive snakes along the top of the deck, with good access to all grease points. Second to last gearbox has a unique pivot design that allows the outer section to fold in stages.

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