`K. J. Shinners and RT. Schuler 11
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`Today, hay and forage producers have a wide variety of equipment options for raking and merging swaths or
`windrows. Selecting the proper equipment and operating it correctly will help to insure high quality forage and a cost
`effective harvesting system. Several studies have been conducted evaluating the equipment performance and provide
`useful information in selecting the equipment that best fits a specific forage harvesting system.
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`MARKET SEGMENTATION OF RAKES AND RELATED EQUIPMENT
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`Rakes are often used for four purposes: to invert the crop to allow wet hay on the bottom of the swath to be
`exposed to sun and wind, to displace the swath from wet to dry ground, to merge swaths together to match the windrow
`density with harvester or baler capacity, and to narrow the swath into a windrow narrow enough to meet the width of
`the harvester or baler pick-up. The North American market for equipment that is used to rake forage crops after cutting
`can be illustrated as follows:
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`Single Rotor
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`Rotary ------Double Rotor
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`1.....-----••..s:four Rotor
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`Standard Feature
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`Rakes
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`. - - - - - - -4 •-
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`Mounted
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`OXBO EXHIBIT 2001
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`Parallel Bar
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`11 Professors in Biological Systems Engineering Department, University of Wisconsin-Madison.
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`The tractors PTO or hydraulics are generally used to power rotary and parallel-bar rakes. This gives them
`sufficient power to manipulate wet, heavy swaths or windrows that will be harvested as silage. Wheel rakes are not
`powered directly by the tractor. Rather, forward motion of the tractor and the engaging of the wheels in the crop or soil
`drive the wheels and because of this they often have difficulty moving wet, heavy swaths or windrows. Therefore,
`wheel rakes are often limited to raking drier crop that will be harvested as dry hay.
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`Wheel rakes are available in a wide variety of designs that can be generally grouped into the three categories
`above. Because they do not require a powertrain, wheel rakes are the lowest cost segment and are designed to rake
`widths up to 36 ft. This width allows two swaths from a 18 ft. cut mower-conditioner to be merged in a single pass.
`No other rake type offers such size at such low cost. The mounted and single frame wheel rakes are dominated by
`imports from Italy and are low feature and low cost units. These units are not common in the Upper Midwest because
`they lack the needed width or capacity to manipulate swaths from the typical mower-conditioner or windrower. The
`most common type of wheel rakes is the twin frame design. The twin frame rake can be further divided into low, high
`and premium feature rakes. Low feature rakes typically have the wheels mounted on the rear of the frame, must be
`folded manually and also have manual width adjustment. Hay will be rolled in front of the wheels, so locating wheels
`on the rear of the frame limits capacity because of potential for crop interference under the frame. High feature rakes
`typically have wheels mounted in front of the frame to handle larger crop volumes and have hydraulic controls for
`folding and width adjustment. These rakes will also feature articulated frames that allow wide rakes to follow ground
`contours with less crop loss. Premium wheel rakes feature larger diameter wheels with stiffer teeth and larger overhead
`frames to accommodate these larger wheels. These rakes are more typically seen in the arid western US and are
`popular with commercial hay producers. No matter the design, the wheel rake will have springs whose tension can be
`adjusted to change the weight carried on the wheel. If wheel float is set too light, the wheels will float over the crop
`and leave some crop behind. If wheel float is set too heavy, tooth wear will be accelerated and the wheels will dig into
`the ground, creating greater soil and rock contamination. Most designs require that spring tension be adjusted manually
`on each wheel, so this adjustment is often neglected in the heat of the hay making battle. A concern often expressed
`with wheel rakes is the tendency for the hay to be "roped" after the raking operation, which can reduce air movement
`through the windrow and slow the drying rate. Data on drying rate and leaf loss of various rake types will be covered
`later.
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`Parallel-bar rakes were the dominant machines used to manipulate forage crops in the Upper Midwest for many
`years, but sales of these machines are declining annually. Although parallel-bar rakes are considered less aggressive
`than wheel rakes, parallel-bar rakes are more expensive and are not available in wider widths. The parallel-bar rake
`also has a powertrain and many moving parts to maintain. Twin frame parallel-bar rakes are more expensive than
`single frame rakes because they typically have larger baskets and also have added frame, controls and hydraulics.
`Although parallel-bar rakes will continue to have a place in the rake market in the future, the share of these rakes will
`continue to erode toward rotary rakes.
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`Rotary rakes originated in Europe to handle the heavy, wet grasses that are harvested there. Other rake types
`could not handle the tough conditions experienced in Northern Europe. Rotary rakes were introduced to the North
`American market in the 1980's and they have slowly but surely gained market share since that time. Single rotor rakes
`are the most popular. Although mounted or pull-type rotary rakes are available, the pull-type type is dominant in the
`Upper Midwest. The two primary features that differentiate single rotor rakes are the rotor diameter and the number of
`arms. Larger diameter rotors will improve the swath width handled and more arms will increase the capacity. Standard
`feature twin rotor rakes are typically designed to sweep two swaths toward the center forming a single merged windrow
`and the distance between the rotors is not adjustable. The distance between the two rotors, and hence the coverage
`width, is adjustable on the high feature twin rotor rake. Some twin rotor rakes have identical rotors on both sides so
`that all hay is moved in the same direction. This allows merging to the side of the machine, rather than the center, so
`that when the next pass is made, another merged windrow is laid beside the first. This may be done to meet the
`capacity of a self-propelled forage harvester. Four rotor rakes have a retail price of over $40k, so they have limited
`market in the Upper Midwest. These machines would typically be used to merge crop for large self-propelled forage
`harvesters. Rotary rakes have a deserved reputation for creating a well-formed, less roped windrow that allows good
`air circulation and good crop drying. For this reason, these rakes are becoming increasingly popular to merge the crop
`for large square balers because of the need to get hay very dry in these large bales. Care must be taken with this rake
`type not to sweep the ground to aggressively to avoid soil and rock contamination of the windrow. Another important
`adjustment is the rotor to ground speed ratio. The correct combination of tractor gear and engine speed must be found
`so that all the crop is swept into the windrow, but the rotor is not turning so fast that leaves are battered from the stern.
`Rotary rakes are the most expensive rake type discussed because they are the heaviest and require the heaviest frame,
`and the cam-actuated gearbox that drives the rotor is more complicated and expensive. The cam/gearbox can be quite
`expensive to repair if failure occurs.
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`Many forage producers in the Upper Midwest who chop silage know the expense and frustration of running a
`rock into the forage harvester cutterhead. Merging multiple swaths into a single windrow with a rake can add to this
`risk because the crop is dragged along the ground as it is merged. Also, soil contamination into the windrow can lead
`to problems with clostridia fermentation and high ash content in the dairy ration. As forage harvesters have grown in
`capacity, there has been a need for merging more swaths into a single windrow. This has led to the development of a
`machine referred to as a windrow merger. The major difference between this machine and a rake is that the merger lifts
`the crop onto a belt conveyor that is used to move and deposit the swath into the desired position so that the crop is
`never dragged along the ground. The windrow merger can be used for either silage or dry hay although its primary use
`is silage crops. Most machines can deposit crop to the left or right simply by changing the direction of the
`hydraulically driven belt conveyor. Before purchasing a windrow merger, it is important to consider the compatibility
`of the mower-conditioner width, merger pick-up width and the forage harvester or baler pick-up width. Some mergers
`can be configured with a belt extension to help width compatibility. Windrow mergers are configured as either single
`or double windrow machines. Single windrow machines can merge either two swaths into one with one pass or three
`swaths into one by making a return pass on the other side of the new doubled windrow. Double windrow mergers are
`more expensive at retail list price than single mergers because they have much heavier frames and complicated folding
`or swiveling features for transport. Most double windrow mergers can be configured to deposit crop to the left, right or
`to the left and right simultaneously. Operating by depositing to the left or right exclusively provides the option of
`merging either three or five windrows into a single windrow. Lifting two and depositing onto a third merges three
`windrows. Lifting another two on the return pass on the other side and depositing on the newly tripled windrow merges
`five windrows. Windrow mergers are configured with either conventional tine-type pick-up or tine-belt pick-up similar
`to a windrow pick-up for a grain combine. Some mergers also have optional inverter shield that can be mounted on the
`output of the cross-conveyor to help invert crop for better drying.
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`Windrow inverters pickup one windrow and lay it on the ground up side down. They are configured quite
`similar to windrow mergers with a conventional or belt-type pick-up, cross-conveyor belt and inverter shield at the
`conveyor output. The primary differences between a merger and inverter is that the inverters have a narrow pick-up
`width that can only accommodate a narrow windrow and the inverter is quite a bit lighter-duty than a merger. The
`inverter is not intended as a merging device. Rather, the inverter is intended to move an already formed windrow off of
`wet ground and invert it for faster drying to dry hay moisture.
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`The final type of hay manipulation tool that should be mentioned is the tedder. The modem tedder was
`developed in Europe and most tedders that are sold in the Upper Midwest are imported from Europe. Tedders are used
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`to spread crop into a swath as wide as the cut width of the mower-conditioner. This not only aerates the swath, but
`more importantly it allows all the sunlight that is striking the field to be used to dry the crop. When crop is placed in a
`narrow windrow, much of the sunlight strikes bare ground and does not aid in the crop drying. Besides good crop
`conditioning, the most important factor in achieving fast forage drying is the width of the formed swath. If tedding
`offers so many benefits, why isn't it a common practice in the Upper Midwest? There are several reasons for this.
`First, tedding is an aggressive action and is acceptable for grasses where leaf loss is less of a concern. But for alfalfa
`there is concern that tedders will cause unacceptable leaf loss, especially if the tedding is done when the crop is
`partially dry and the leaves are brittle. Second, tedding adds an additional step in the hay making process: cutting,
`tedding, raking and baling. Third, a tedder adds an additional machine expense to the already substantial line-up of hay
`making equipment. Lastly, sometimes it is beneficial to lay the crop in a narrow swath so that damp ground can be
`dried out. This will allow a dry location for a raked windrow to be placed. There are so many different designs and
`configurations of tedders available that it is not possible to cover all of them here. The most common types in the
`Upper Midwest are pull-types with two or four rotors. These are relatively simple machine with relatively low retail
`list price. The larger six rotor machines are more complicated and much more expensive because of the folding
`requirements for transport. Six rotor machines are often fully mounted, so they require a fairly large tractor to operate.
`Although there are some downsides to using a tedder, forage producers in the Upper Midwest, especially those with
`alfalfa-grass mixtures, who are looking for fast drying to dry hay moisture may find the tedder quite beneficial.
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`Another tedder design, sometimes referred to as a fluff er, does not move the windrow nor changes its width. The
`machine has parallel rake bars that engage the windrow at a faster rearward speed than the forward travel speed. This
`action causes the forage in the windrow to be moved rearward and slightly upward resulting in a aerated windrow that
`allows air to move through it for improved drying. This machine can be helpful in increasing the drying rate after a
`heavy rainfall.
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`MACHINE PERFORMANCE STUDIES
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`Rakes and related equipment can be evaluated based on field losses, drying rates, windrow shape and condition,
`ability to move heavy swaths and ability to create windrow free of rocks and other debris typically found in the field.
`When evaluating this equipment the forage producer must evaluate their situation to ensure high quality forage and to
`meet their needs with respect to their yields and cutting and harvesting equipment size.
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`Losses and Drying Rates
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`This equipment should be selected and operated based on the criteria to create minimal losses and maintain
`rapid field drying which will ensure high quality forage. The manner in which the equipment handles the swath impacts
`the level ofloss and the resultant windrow. Handling methods range from picking up the swath and laying it down to
`rolling the swath across the ground surface.
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`Most of the research has involved the losses and drying rates associated with these machines. In numerous
`cases the forage quality was evaluated which may be related to the losses, usually high quality leaves, and drying rate.
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`In a study by Savoie et al. (1982), a parallel-bar rake was compared to a rotary rake in conditioned and non(cid:173)
`conditioned alfalfa. They found no difference in the drying rate but the rotary rake had slightly higher losses. Raking
`was done near 40 percent moisture, wet basis. They found tedding increased the drying rate slightly but the results
`were not very consistent. During good drying conditions, tedding did not appear to be beneficial but may be beneficial
`after a heavy rain, which creates a windrow that was dense and matted.
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`Using artificial stubble, Buckmaster (1993), evaluated a parallel-bar and a wheel rake. The parallel bar rake had
`about two percentage units less loss throughout a forage moisture range of five to fifty-five percent, wet basis. In an
`Ohio study reported by Claas, three rakes (wheel, rotary and parallel-bar) were compared with respect to drying rate
`based on moisture content as forage dry down approached baling moisture. In the first cutting for a orchard grass(cid:173)
`alfalfa mix, the rotary rake had the lowest moisture (20.9 percent) while the wheel rake had the highest moisture (25.0
`percent). The parallel-bar rake was intermediate. For the second cutting alfalfa, the rotary rake had lower moisture
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`(20.4 percent) than the other two rakes (22.5 percent for the parallel-bar and 23.0 percent for the wheel rake). In a third
`cutting of alfalfa of a orchard grass mixture, the differences in moisture between rake types were not significant.
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`Garthe et al. (1988) compared a parallel-bar rake with a windrow inverter and found no difference between the two
`devices in terms of drying rate or crop quality (based on crude protein content). Shearer et al. (1992) compared a
`parallel-bar rake with two different windrow inverters. They found no difference between the three machines with
`respect to the drying rates or losses. In a study of several rakes and a windrow inverter, Hoover (1996) found that the
`inverter and the parallel-bar rake had significantly less loss than the other rake types which included a wheel rake and
`several rotary rakes. In this study, the drying rate among the different rakes was very similar.
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`Savoie and Beauregard (1988) studied four windrow inverters that significantly increased the drying rate
`compared to a control with no manipulation of the forage in a windrow. In addition they indicated that an inverter could
`advantageously replace a hay tedder.
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`Although no research has been reported on windrow mergers, their losses would be expected to be similar to the
`windrow inverters because they both pickup the windrow and do not move it across the ground. The drying rate of
`forage gathered with a windrow merger is generally not an issue because merging usually takes place right before the
`forage harvester.
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`Windrow Shape and Condition
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`To produce a consistent, high quality forage the raked or merged windrow must be uniform to ensure the
`moisture is the same throughout the windrow. Based on field experience and observations, the rotary rakes produce a
`more uniform and less roped windrow than wheel or parallel-bar rakes. Windrow inverters and mergers will not
`produce a roped windrow, but can often produce a non-uniform windrow if the belt does not properly take the crop off
`the pick-up. In all cases the equipment must be properly adjusted operated to obtain the most uniform windrows.
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`It is important to produce windrows free of rocks, soil and other debris to avoid problems with forage harvester
`knife wear, knife damage, clostridia fermentation (especially in high moisture silages) and excess ash content in the
`feed. Equipment that rolls or slides the windrow across the ground will have a greater risk of having rocks and soil
`contaminate the windrow. This becomes more important with high capacity forage harvesters requiring a greater
`distance for swaths to be moved. Machines that pickup the swath, displace it with a cross-conveyor and then lay it
`down on the ground at another location will have less risk of contaminating the windrow. In a study of rock movement
`caused by rakes and a windrow inverter, Hoover (1996) found that the inverter and wheel rake moved significantly
`fewer rocks than the other rake equipment. The rotary rake moved significantly more rocks than the other rakes.
`Although no studies have been done with windrow mergers and since they are handle the windrow similar to an
`inverter, it is safe to imply that the merger would move fewer rocks.
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`With increased forage yields, raking and merging equipment must be sufficiently aggressive to move the large
`quantity of forage. Equipment that is ground driven will have greater difficulty picking these swaths. These would
`include the wheel rakes and ground driven parallel-bar rakes. PTO and hydraulic driven rakes and mergers can become
`more aggressive by maintaining a higher operating speed relative to the forward travel speed.
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`Today, forage producers have many options in equipment for moving swaths and creating windrows. Careful
`selection of this equipment should be made to choose a system the machine that best meets the needs with respect to
`crop yield and cutting and harvesting machine size. Also it is extremely important to properly adjust and operate these
`machines to insure minimum losses and rapid drying.
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`Buckmaster, D.R. 1993. Alfalfa raking losses as measured on artificial stubble. Transactions of the ASAE. 36(3):645-
`651.
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`Garthe, J. W., P. M. Anderson, R. J. Hoover and S. L. Fales. 1988. Field test of a swath/windrow hay inverter. ASAE
`Paper 88-1549. ASAE, St. Joseph, MI. 15 pp.
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`Hoover, L.L. 1996. A comparative rake study of dry matter loss, drying rate, and rock movement in alfalfa fields.
`B.S. Honors Thesis. The Pennsylvania State University. 33 pp.
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`Rotz, C. A. and P. Savoie. 1991. Economics of swath manipulation during fie] d curing of alfalfa. Applied Engineering
`in Agriculture. 7(3)316-323
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`Savoie, P. C. and S. Beauregard. 1988. Hay windrow inversion. ASAE Paper 88-1548. ASAE, St. Joseph, MI. 13 pp.
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`Savoie, P., C. A. Rotz, H.F. Bucholtz and R. C. Brook. 1982. Hay harvesting system losses and drying rates.
`Transaction of the ASAE. 25(3) 581-585, 589.
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`Shearer, S. A., G. M. Turner, M. Collins and W. 0. Peterson. 1992. Effect of swath and windrow manipulation on
`alfalfa drying and quality. Applied Engineering in Agriculture. 8(30) 303-307.
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