2005 - Volume #29, Issue #2, Page #10

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Big Sprayer Built For Muddy Fields

Big Sprayer Built For Muddy Fields SPRAYING Miscellaneous 29-2-10 Getting a spray rig into and out of a muddy field can be a real challenge, whether after a rain or following an irrigation rig. That's why Mark Ellsworth built his own self-propelled, 4-WD spray boom. "It has tremendous pull in the mud," he says. "We had a spot where water flowed through a plowed area after a heavy rain. I drove it in, and it sank to the axle hubs. It groaned a little, but it climbed right back out." To get that kind of pull, Ellsworth built his rig lightweight and put big tractor tires on it with articulated steering. The self-leveling boom hangs from a pivot point like a pendulum. The 4-cyl. motor and transmission came out of a Toyota Corona car. The operator seat and controls are mounted on the front end. The 325-gal. tank and 100-ft. boom mount at the rear. Axles and differentials were reclaimed from two cars with the same gear ratio, while four 38-in. high Farmall M wheels were adapted to fit the car axles. Ellsworth used old chains and sprockets to build an 8-to-1 gear reduction unit to slow the drive shaft. A chain transfers power to a sprocket welded to the front differential, and a telescoping driveline transfers power from the front to the rear end differential. "The telescoping drive line minimizes the effect of articulation by splitting the angle at each differential," explains Ellsworth. The two yokes flex at the hinge point, a unique joint Ellsworth designed that allows front and rear yokes to pivot independently of each other. A framework is built around it for the two hydraulic cylinders that turn the power unit. "The key to articulation working is for the hinge point to be exactly half way between the two axles," says Ellsworth. "If it is, you can take two axles off the same model car and turn one around and you get 4-WD." The hinge bracket is similar to a clevis-type tool bar hitch. A center beam welded from two channel irons extends from the rear frame forward to fit between the jaws of the clevis-type bracket. Two bushing supports in the beam hold a bushing bracket. A bolt extending through the jaws of the bracket and the bushing bracket forms the pivot or articulation point of the rig. An 18-in. long by 1-in. thick by 2-in. wide steering bar is welded to the back of the hinge bracket and forward of the articulation point. The ends of the bar extend about 7 in. out to either side of the bracket. Hydraulic cylinders mounted to the axle of the rear unit and about a foot to either side of the bracket extend out to connect to the ends of the steering bar. A steel tube machined down from the arm of a heavy-duty hydraulic cylinder is welded to the front of the bracket and extends forward and through a sleeve machined out of the same cylinder. It is this sleeve that is welded to the frame of the front end of the power unit. An end cap bolted to the inner tube extends over the edges of the sleeve and holds the front and rear structures together. When a hydraulic cylinder is extended, the bracket is forced to pivot, causing the unit to turn left or right. When a wheel on one side of the power unit climbs over a bump or an obstacle, the inner tube rotates within the sleeve, allowing the other three wheels to remain in contact with the ground. This flexibility of the frames and an equally unique pendulum mount help the boom self level regardless of the field conditions. This was essential for the rig's original, very narrow wheelbase and a desired 100-ft. boom width. "At first, if the boom started to rock, the entire machine would tip over," explains Ellsworth. "To counteract that, we decided to have the boom pivot independent of machine motion." He also substituted 2 1/2-ton truck axles for the car axles for a wider base, more weight and pulling power. The old M wheels were again adapted with new bolt patterns to match the truck axles. "We welded the bolt patterns offset," says Ellsworth. "If the wheels are mounted one way, the tractor has a 76-in. wheel base to straddle two 38-in. rows. If we turn t