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Dep. of Soil & Crop Sciences, Colorado State Univ., Agric. Exp. Stn., Western Colorado Research Center, 1910 L Road, Fruita, CO 81521
* Corresponding author (calvin.pearson{at}colostate.edu)
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ABSTRACT |
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 TOP ABSTRACT INTRODUCTIONDESIGN AND DESCRIPTIONNOTESPERFORMANCE AND EVALUATIONAPPENDIXREFERENCES |
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40 s and can handle plot samples weighing as much as 54 kg (120 lb). The forage plot harvester can be switched from harvesting research plots and made ready to harvest commercial fields or vice versa in approximately 30 min. Our automated forage harvester performed exceptionally well during its first year of operation in 2006. The cost of the materials for the automated weighing system was slightly less than $6000.
Abbreviations: UHMW, ultra high molecular weight
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NOTES |
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TOPABSTRACTINTRODUCTIONDESIGN AND DESCRIPTIONNOTESPERFORMANCE AND EVALUATIONAPPENDIXREFERENCES |
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Received for publication February 19, 2007.
Dep. of Soil & Crop Sciences, Colorado State Univ., Agric. Exp. Stn., Western Colorado Research Center, 1910 L Road, Fruita, CO 81521
* Corresponding author (calvin.pearson{at}colostate.edu)
Received for publication February 19, 2007.
Harvesting forage plots can be tedious, time consuming, and labor intensive without the proper plot equipment. Various forage plot harvesters have been developed over the years and were designed primarily to decrease the amount of hand labor needed for plot harvest, increase the ease of plot harvest, and do it at an affordable cost while maintaining or improving data integrity. Automated, commercially built, forage plot harvesters cost $50,000 to $80,000 USD or more. This article describes an automated forage plot harvesting system that has an electronic data collection system, harvests plots quickly and efficiently, and can be used for both plot harvest and commercial-scale fields. The automated harvesting system consists of three major components—a weighing platform, a discharge platform, and an electronic data collection system. Only one person is needed to operate the automated forage harvester and collect yield data. The average time required for harvesting a 3.0 by 4.6 m (10 by 15 ft) alfalfa (Medicago sativa subsp. sativa) plot is 40 s and can handle plot samples weighing as much as 54 kg (120 lb). The forage plot harvester can be switched from harvesting research plots and made ready to harvest commercial fields or vice versa in approximately 30 min. Our automated forage harvester performed exceptionally well during its first year of operation in 2006. The cost of the materials for the automated weighing system was slightly less than $6000.
Abbreviations: UHMW, ultra high molecular weight
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INTRODUCTION |
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TOPABSTRACTINTRODUCTIONDESIGN AND DESCRIPTIONNOTESPERFORMANCE AND EVALUATIONAPPENDIXREFERENCES |
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Equipment that is well suited to the task is important when harvesting forage plots for several reasons. Expeditious and timely harvest of field plots of forages can minimize variability in the data that can occur when inclement weather interrupts plot harvest. Research capacity can be increased with the proper research equipment. Some forage field research may require a large number of treatments and, hence, a large number of field plots. A plot harvester that has the capability to harvest plots quickly and efficiently will allow researchers to manage a large number of field research plots. Additionally, the proper research plot equipment can permit the harvest of forage plots under a variety of conditions and situations, and will also permit harvesting a broad range of grass and legume species.
Various forage plot harvesters have been developed over the years (Buker, 1967; Paterson and Browning, 1962; Swallow, 1967; McCormick and Hoveland, 1971; Marsh, 1992; Stewart and Welty, 1987; Barnes et al., 1984; Wiersma et al., 1990). These forage plot harvesters were designed primarily to decrease the amount of hand labor needed for plot harvest, increase the ease of plot harvest, and do it at an affordable cost while maintaining or improving data integrity. Commercially built forage plot harvesters that are highly automated have been available for many years. Automated forage plot harvesters are expensive, currently costing $50,000 to $80,000 or more, depending on the manufacturer and features of the machine.
Because of their size, some plot harvesters are not well suited for operating in fields with rough terrain, particularly fields with furrows. Commercially available forage plot harvesters are dedicated machines that are used for research applications only. Equipment that can be used for both research and general farm use increases their versatility and hence the cost effectiveness of the machinery. Pedersen and Moore (1995) developed such a harvester for silage corn and other similar forage crops.
An automated forage plot harvester was developed at Colorado State University using a field-scale commercial swather in 1993 (Pearson and Robinson, 1994). This forage plot harvesting system had a weigh bin that attached underneath the swather directly behind the hay conditioner. The forage plot harvester could be converted to harvest both research plots and commercial-scale fields. The harvester had an electronic weighing system and a belt conveyor in the bottom of the weigh bin for discharging weighed samples. This forage plot harvesting system was used successfully for many years; however, an improvement in the basic design was envisioned that would reduce the amount of labor required for harvesting plots while still maintaining or improving performance. A new design was also an opportunity to upgrade the data collection system and make it completely electronic. This article describes an automated forage plot harvesting system that has an electronic data collection system, harvests plots quickly and efficiently, and can be used for both plot harvest and commercial-scale fields.
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DESIGN AND DESCRIPTION |
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TOPABSTRACTINTRODUCTIONDESIGN AND DESCRIPTIONNOTESPERFORMANCE AND EVALUATIONAPPENDIXREFERENCES |
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Hood
The hood on the weighing platform was constructed of 16-gauge sheet metal by bending a single piece of sheet metal. The dimensions of the hood are 152.7 cm wide by 152.4 cm long by 45.7 cm high (60 1/4 by 60 by 18 in). To add rigidity, 3.2 mm thick by 2.5 cm high by 2.5 cm wide (1/8 by 1 by 1 in) square tubing was affixed across the front edge on the underside of the top of the hood using 6.4 by 19.0 mm long (1/4 by 3/4 in) self-drilling, threaded fasteners with hex heads. To add strength to the sides of the hood, two pieces of angle iron (2.5 by 2.5 cm by 3.2 mm thick by 45.7 cm long) (1 by 1 by 1 1/8 by 18 in) were welded vertically on both sides of the hood. One piece was welded 24.1 cm (9.5 in) from the front of the hood and the other piece was welded 32.4 cm (12 3/4 in) from the back of the hood.
The hood fits on top of the weighing platform. A 3.2 cm (1 1/8 in) ledge on the bottom of the hood fits along the support rails of the conveyor assembly and 6.4 by 19.0 mm long (1/4 by 3/4 in long) self-drilling, threaded fasteners with hex heads were used to attach the hood to the support rails.
Two backstop flaps were hung inside the hood crosswise to form a barrier for forage moving from the front to the back of the platform. One flap was positioned at 30.5 cm (12 in) from the exit end of the hood and a shorter flap was attached at 66.0 cm (26 in) from the exit end of the hood (Fig. 1C). The flaps were fastened to rectangular tubing (2.5 by 5.1 cm by 3.18 mm thick) (1 by 2 by 1/8 in) on the 5.1 cm (2 in) side and the tubing was fastened to the underside of the top of the hood on the 2.5 cm (1 in) side of the tubing using 6.4 by 19.0 mm long (1/4 by 3/4 in) self-drilling, threaded fasteners with hex heads. A screw with a flat washer went through the grommet and was screwed to the support tube.
Backstop flaps keep the cut forage within the confines of the weighing platform during the harvesting step. Once the forage is weighed, the conveyor belt is activated and the weight of the forage moves the forage sample past the flaps and onto the discharge platform. The longer backstop flap is 132.1 wide by 38.1 cm high (52 by 15 in) (finished measurements), which leaves a 5.1 cm (2 in) gap between the flap and the conveyor belting. The shorter flap is also 132.1 cm wide but only 29.2 cm high (52 by 11 1/2 in), creating a 14.0 cm (5 1/2 in) gap between the flap and the conveyor belt. Both flaps are made of vinyl-coated polyester material with a density of 5.5 kg m–2 (18 oz ft–2) (Seattle Textile Co., Seattle, WA). The top 5.1 cm (2 in) section of the flap is four layers thick and five no. 2 size grommets are evenly spaced along the length of the flap and centered vertically within the top 5.1 cm (2 in).
At the bottom of the flaps, the vinyl-coated polyester material was folded over and stitched lengthwise to form a 2.5 cm (1 in) opening (pocket) along the length of the flaps. This allows a rod or dowel to be inserted along the bottom of the flap to provide weight to the flap. The material, such as rod or dowel, can be changed as needed to obtain the proper weight so the forage will fill to the back of the weighing platform without spilling out and onto the discharge platform.
The longer flap that is closest to the exit end of the weighing platform can be extended horizontally to the back of the weighing platform. In this position, the end of the flap extends beyond the weighing platform, allowing the rod or dowel to be easily inserted in or taken out. The shorter flap was installed farther inside the hood, so we drilled a 2.7 cm (1 1/8 in) hole on one side of the hood for easy access to insert or take out a rod or dowel.
Weighing Platform Assembly
The weighing platform is constructed of two support rails, two rollers, three cross members, and a metal floor pan. The support rails were made by bending plate metal that was 12.7 cm (5 in) wide and 4.8 mm (3/16 in) thick so that it formed a channel that was 7.6 cm (3 in) wide with 2.5 cm (1 in) sides. The length of the two support rails for the weighing platform is 152.4 cm (60 in) (Fig. 1D). Cross member supports were constructed of 11-gauge rectangular tubing that was 2.5 by 7.6 cm (1 by 3 in) and 151.4 cm (59 5/8 in) long. End plates that were 7.6 cm (3 in) square were welded to the ends of the tubing. Two 15.9 mm diam. (5/8 in) holes were drilled into the end plates and the cross members were bolted to the support rails using 9.5 mm (3/8 in) bolts that were 2.5 cm (1 in) long. The three cross members on the weighing platform were spaced 38 cm (15 in) apart along the support rails (Fig. 2A).
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The two cross members on the discharge platform were constructed similarly to those on the weighing platform, but those on the discharge platform were centered 25.4 cm (10 in) apart along the support rails and bolted in place using 9.5 mm (3/8 in) hex bolts that were 2.5 cm (1 in) long.
Floor Pans
The conveyor belt tracks in the bottom of the metal floor pan. This helps to keep the belting properly aligned and also prevents plant material from getting underneath the belting and around the rollers. The floor pan for the weighing platform was constructed of 14-gauge sheet metal. The sheet metal was bent from a single piece to form dimensions that are 152.4 wide by 148.6 long by 6.4 cm tall sides (60 by 58 1/2 by 2 1/2 in). The floor pan was welded to the top of the cross member supports. The floor pan for the discharge platform was constructed of 16-gauge sheet metal. The sheet metal was bent from a single piece to form dimensions that are 152.4 wide by 64.8 long by 10.2 cm tall sides (60 by 25 1/2 by 4 in). The floor pan for the discharge platform was also welded to the top of the cross member supports. The top 2.5 cm (1 in) of the side of the floor pan was bent outwards at approximately a 30° angle from vertical. This prevents plant material from catching on the sides of the discharge platform.
Black ultra high molecular weight (UHMW) polyethylene material was bolted at a 20 to 25 cm (8–10 in) spacing using carriage bolts (6.4 by 19.0 mm long; 1/4 by 3/4 in) along the sides of the floor pan and along the bottom of the inside of the hood of the weighing platform to form a wear plate for the conveyor belt and to prevent plant material from getting underneath the belting. Similarly, UHMW was bolted along both sides of the floor pan on the discharge platform at a 15 to 20 cm (6–8 in) spacing using carriage bolts (6.4 by 19.0 mm long; 1/4 by 3/4 in). The dimensions of UHMW for the weighing platform were 6.4 wide by 157.5 cm long by 6.4 mm thick (2.5 by 62 by 1/4 in), and the dimensions of UHMW on the discharge platform were 7.6 wide by 76.2 cm long by 6.4 mm thick (3 by 30 by 1/4 in). The lengths of UHMW were longer than the floor pans on both platforms and were positioned so they extended slightly beyond the pans on both the front and the back. This was done to channel plant material along the conveyor and also to prevent plant material from getting underneath the belting.
Conveyor Rollers and Belts
The conveyor belt on each platform can be adjusted to obtain the proper tension. One of the rollers on each platform was fitted with a tightener on each end (Fig. 2C). The set of tighteners on the weighing platform is at the front of the platform and the set of tighteners on the discharge platform is at the back of the platform.
Belting on the conveyor platform is two-ply polyester, 3.2 mm thick (1/8 in) (Beltservice Corporation, Portland, OR), and is 150.5 wide by 336.2 cm long (59 1/4 by 132 3/8 in). Belting on the discharge platform is polyvinylchloride with a crescent top cleat, 6.4 mm thick (1/4 in) (Beltservice Corporation, Portland, OR) and is 151.8 wide by 163.2 cm long (59 3/4 by 64 1/4 in). Conveyor belts are coupled with clipper lacings.
Two rollers, 152.4 cm (60 in) long with a 7.6 cm (3 in) diam. were mounted at each end on both the weighing platform and the discharge platform. A 25.4 mm (1 in) shaft goes through the entire roller and extends 63.5 mm (2 1/2 in) beyond each end of the rollers, except for the end that attaches to the hydraulic motor. This end is 88.9 mm (3 1/2 in) long and has a 6.4 mm (1/4 in) slotted keyway that is 4.4 cm (1 3/4 in) long. Flange bearings (unit no. UCFB205–16, IPTCI Bearings, St. Paul, MN) with a 25.4 mm (1 in) bore were bolted to the ends of the support rails with three, 9.5 mm (3/8 in) bolts that were 38.1 mm (1 1/2 in) long on each bearing (Fig. 2C). Each of the four tightener assemblies was made by making slots at the end of the support rails (Fig. 1D; Fig. 2B). The cut end of a 7.6 cm (3 in) long, 9.5 mm (3/8 in) diam. piece of all thread was welded to a 6.4 cm (2 1/2 in) section of 5.1 by 7.6 cm (2 by 3 in) angle iron. Another piece of angle iron with the same dimensions was welded to the support rail to form the anchored side of the tightener as shown in Fig. 2C.
Hydraulics
Two hydraulic motors were required for the automated weighing system, one motor for the weighing platform and another one for the discharge platform. The hydraulic motor for the weighing platform is a Model 20 W4F (Orbmark Durst, Regal-Beloit Corp., Beloit, WI) and was mounted on the right side at the back of the weighing platform (Fig. 2D). The hydraulic motor for the discharge platform is a Model 101-1004-009 Char-Lynn (Eaton Corp., Eden Prairie, MN) and is mounted on the left side at the front of the discharge platform. It was necessary to mount the hydraulic motor at the front of the discharge platform to maintain sufficient clearance so the swivel wheels at the back of the swather could rotate fully without hitting any part of the discharge platform.
Each motor is bolted to a mounting plate with four bolts 9.5 mm diam. (3/8 in) by 2.5 cm (1 in) long that go through a mounting plate and into threaded holes in the hydraulic motor. The mounting plate is constructed of 4.8 mm (3/16 in) thick metal plate measuring 10.5 by 21.6 mm (4 1/8 by 8 1/4 in). The end of a 6.4 mm thick (1/4 in), 5.1 cm by 5.1 cm (2 by 2 in) piece of angle iron 12.7 cm (5 in) in length was welded into the channel of the support rail and a piece of plate metal measuring 5.1 by 10.2 cm (2 by 4 in) was welded to the end of the angle iron. The mounting plate for each hydraulic motor was bolted to the respective platform as shown in Fig. 2D using three hex bolts 9.5 mm diam. (3/8 in) by 2.5 cm (1 in).
Each hydraulic motor and drive shaft on the roller is coupled with a black spider coupler element sandwiched between two, three-jaw metal couplers. The metal coupler is held on the shaft of the hydraulic motor using a 6.4 mm (1/4 in) thick Woodruff key and a set screw and the metal coupler on the conveyor roller is fastened to the shaft with a 6.4 mm (1/4 in) thick slotted key and set screw.
Hydraulic hose is connected from the swather platform (head) lift control valve at the power-beyond port to the hydraulic motors. Hydraulic lines interconnect to a hydraulic control valve with variable flow (Model C-503, Prince Manufacturing Corp., Sioux City, IA) that is mounted in the cab of the swather. This valve is used to operate the conveyor on the weighing platform. The swather operator can activate the conveyor from the cab to empty the weighing platform once the forage plot weight is recorded. The hydraulic motor on the discharge platform also has a hydraulic control valve with variable flow control (Model FC51–1/2 Brand Hydraulics, Omaha, NE) and is mounted to the frame on the left side of the swather. This hydraulic assembly is used to operate the discharge platform. The variable flow valves allow the speed of each conveyor to be adjusted separately. For example, the conveyor on the discharge platform is set to operate continuously during plot harvest.
Hangers
Near the corners, the weighing platform is suspended from four weigh bars by hangers. The hangers on the front of the weighing platform are 57.8 cm (22 3/4 in) long and the hangers at the back of the weighing platform are 65.0 cm (25 5/8 in) long. Hangers are constructed of angle iron 3.8 by 3.8 cm by 6.35 mm thick (1 1/2 by 1 1/2 by 1/4 in). At the top of the hanger, two holes were drilled at the same distance from the top, one hole has a 15.9 mm (5/8 in) diam. and fits snugly onto the weigh bar, and the other hole has a 19.0 mm (3/4 in) diam. and is used for access to attach a clip pin through the hole of the weigh bar.
The hangers are attached to a hanger bracket on the weighing platform by bolts 15.9 mm (5/8 in) diam. by 3.8 cm (1 1/2 in) long. Hanger brackets at the front of the weighing platform were welded to the top of the support rail while the hanger brackets at the back of the weighing platform were welded inside the channel of the support rail. Hanger brackets are constructed of 6.4 mm thick (1/4 in), 5.1 by 5.1 cm (2 by 2 in) angle iron that is 6.4 cm (2 1/2 in) long. The 12.7 cm long (5 in) angle iron support for the hydraulic motor is also used as a hanger bracket. A 19.0 mm (5/8 in) hole was drilled in the vertical side of the angle iron hanger brackets. To prevent the weighing platform from shifting during operation, bolts connecting the hangers to the tabs on the weighing platform are tightened snugly.
Weighing Electronics
Two of the four 341-kg (750-lb) capacity weigh bars (Avery Weigh-Tronix, Fairmont, MN) are mounted to the swather frame using channel iron 4.8 mm thick by 12.7 wide with 4.4 wings and 12.1 cm long (1/4 by 5 by 1 3/4 by 4 3/4 in). Sections of 2.5 cm (i.d.) (1 in) pipe, 12.7 cm (5 in) long, were welded along the wing and back of the channel iron pieces. One end of the piece of channel iron was welded to the swather frame at the back on both sides of the swather, so that the mounting brackets (channel iron and pipe section) were perpendicular to the frame. The other two weigh bars are mounted at the front of the swather using angle iron. Angle iron sections, 5.1 by 7.6 by 12.7 cm long and 6.4 mm thick (2 by 3 by 5 by 1/4 in) were welded to the frame at the front of the swather. The weigh bars fit snug inside the 2.5 cm (i.d.) (1 in) pipe and are held in place by a hex bolt 6.4 mm (1/4 in) diam. by 5.1 cm (2 in) long that goes through the mounting bracket and weigh bar.
Four weigh bars are connected by cables to an electronic weighing indicator (Model 615, Avery Weigh-Tronix, Fairmont, MN). A transfer data module (TDM-40, Avery Weigh-Tronix, Fairmont, MN) connects to the weighing indicator along with a WP-233 (Avery Weigh-Tronix, Fairmont, MN) register tape printer. The printer and the transfer data module are cabled to the weighing indicator with a "Y" pigtail cable. Data from the transfer data module are saved as a text file and are easily downloaded using Transfer Data Software (TDS-40, Avery Weigh-Tronix, Fairmont, MN). Data can then be copied into other software programs. The pigtail, downloading cable for a personal computer, and the software were included in the hardware purchased from Avery Weigh-Tronix. The printer is used as a paper backup for data.
Power to the weighing system is routed from the battery on the swather using an adaptor supplied with the electronic weighing system. With the weighing platform mounted on the swather and with the header table resting in the down position, the weigh bin is positioned 6.4 cm (2 1/2 in) from the back of the hay conditioner. The clearance between the top of the hood on the weighing platform and the underside of the swather is 5.1 cm (2 in). Clearance from the bottom of the weighing platform to a flat surface is 21.6 cm (8 1/2 in). In western Colorado, the clearance from alfalfa stubble in a typical furrow-irrigated field to the bottom of the weighing platform is 7.0 cm (3 in).
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We expect the forage plot harvester would also work well for many other forage grasses and legume species. We have harvested alfalfa plots as large as 14.0 m2 (150 ft2) and weighing as much as 54 kg (120 lb). Another advantage of this harvester is that only one person is needed to operate the harvester and collect data. This eliminates workers from being around the machine when it is operating and reduces safety issues and health concerns associated with noise, dust, and other particulate matter produced while the swather is operating in the field.
The average time required for harvesting a 3.0 by 4.6 m (10 by 15 ft) alfalfa plot is approximately 40 s. As with the first version, this second generation, automated forage harvester can be switched from harvesting research plots and made ready to harvest commercial fields or vice versa in 30 min. This second-generation, automated forage harvester has performed exceptionally well. Because of its excellent performance, we have been able to conduct our forage research with less labor than the previous version.
We constructed a custom pallet, measuring 132.1 wide by 182.9 long by 20.3 cm high (52 by 72 by 8 in), to move and store both the weighing platform and discharge platform (Fig. 1C). A piece of 19.1 mm (3/4 in) thick plywood, measuring 121.9 by 157.5 cm (48 by 62 in) and covered with carpeting, lays on top of the hood of the weighing platform and the discharge platform rests on top of the carpeted plywood. This prevents the discharge platform from marring the top of the hood during storage.
All metal parts of the weighing system except the rollers were sandblasted before painting. Primer paint was applied to the sandblasted, bare metal. Several coats of acrylic enamel paint were applied to the primed metal using a gravity feed pneumatic air sprayer.
One challenge we encountered with the forage weighing system was the large conveyor belt on the weighing platform. We experienced difficulty with the conveyor belt staying centered on the rollers. With careful adjustment of the tighteners on the rollers we were able to overcome this problem. Nevertheless, based on our discussions with the supplier of the conveyor belting, we possibly would have minimized or possibly avoided this problem if we had purchased different belting. Given our experience and information obtained from other people, thicker, more rigid conveyor belting that was suitable to operate on a 7.62 cm (3 in) roller would have been preferable. On the other hand, the problem may have been related to the exactness that was ultimately needed to adjust the tightener on the weighing platform.
The cost of the materials for the automated weighing system was slightly less than $6000. This amount did not include the electronics for the weighing system. The labor required to fabricate the automated weighing system was provided by the author and Ag Experiment Station employees and was not included in the cost of the forage weighing system. The Appendix contains a parts list for the weighing system.
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APPENDIX |
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ACKNOWLEDGMENTS |
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1 Mention of a trade name or proprietary product does not imply endorsement by the author, the Agricultural Experiment Station, or Colorado State University.
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