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While the researchers have pronounced the Darwin string thinner “good to go,” it’s not considered perfect—not by the Canadian company that’s selling it, nor by Pennsylvania State University agricultural engineer Dr. Paul Heinemann. They’re still tweaking it.

“We would like to automate the positioning of the rotating spindle so the operator doesn’t have so much work to do with the steering,” Heinemann told growers at the Mid-Atlantic Fruit and Vegetable ­Convention in Hershey, Pennsylvania.

The Darwin is now mounted on the front of a tractor, and the driver steers it to follow the tree canopy. Heinemann thinks it would be better rear-mounted and equipped with hydraulics and joystick controls the operator would use to move the unit while the tractor is steered straight.

“The tractor can’t steer fast enough to keep the rotating spindle next to the canopy,” he said. ­Operator fatigue is also a problem.

He thinks a manual joystick would be easier to use than hydraulic levers. The joystick could move the spindle in and out and also tilt the angle of the spindle to fit the shape of the tree.

With that, the manufacturer, N.M. Bartlett of Beamsville, Ontario, agrees. Manufacturers’ representative Matt Peters said the joystick is in the works and will be available this year.

“We will be working in cooperation with Penn State and Fruit-Tec to make the machine even more user-friendly with the addition of the joy-stick control,” Peters told Good Fruit Grower. “I’ve told growers that it will be available for next year, so we better be able to deliver.”

It would be available as a retrofit kit for units already in the field.

Heinemann also plans to test, this spring, sonar and laser sensors that would move the spindle automatically, so the tractor driver would be just that—only a driver. The positioning would be fully automated.

Penn State horticulturist Dr. Jim Schupp estimates that improvements would increase orchard thinning speed from about 2.5 miles per hour currently to 6 miles per hour, with less operator fatigue.