The raspberry sprayer in 3D
Tractor 2 is one small articulated machine, 40 inches wide, for the red raspberry alleys — four feet between the canes in spring. It is copied from the narrow vineyard tractors: four equal tall tyres, all of them driven, and a hinge in the middle that steers it and lets the two halves roll against each other on rough ground. The operator rides the front half; the low tank, the sprayer and the vertical booms ride the rear, and a battery box hangs low at each end. Steer it to either lock, roll the halves, or slide the booms out for the wider black raspberry rows. A design in progress — nothing is built.
Copied from the vineyard tractor. The layout is the BCS Valiant's: four equal 7.50-16 tyres on a 794 mm track. Tall narrow tyres roll easier on soft ground than wide flotation tyres, which would not fit the alley anyway. The machine is hinged in the middle: two steering cylinders swing it, and an oscillating joint lets the halves roll up to 10° apart, so all four wheels stay down in a rutted alley.
Two motors, no driveshaft across the hinge. One 51.2-volt motor drives each axle through a reduction and a differential, so four-wheel drive needs nothing to bend through the joint. Spraying at five miles an hour takes about 3 kW at the wheels on grass and about 7 kW on soft ground — estimates, not a test.
Low where it counts. The 100-gallon tank is a custom low shape between the hinge and the rear axle, and the two battery boxes hang at the ends, only 155 mm off the ground, where the low lift trolley reaches each one from its own end. A pinned guard with a plastic-faced skid bar stands ahead of each box, 5 mm lower than its steel case, so a ditch edge or the farm's irrigation pipe meets the guard, not the battery. The price is a shallow 9° approach at each end: loading ramps no steeper than 8°.
On a slope. The joint in the middle lets the two halves roll up to 10° against each other, so each half can tip on its own. Driving straight, a front wheel lifts at about 34° of side slope. Fully turned, the roll axis runs across the front half and a front wheel lifts at 23–27°, depending on the tank; the roll stop then holds it to 27–29°. The rule on the machine: turn on the level, cross slopes straight. These are static estimates — the finished machine goes on a tilt table before it goes on a hill.
Turning. At full lock the outside of the machine turns in about 3.4 metres, a loop turn inside a 16-foot headland. In the alley the rear half swings toward the canes the moment it steers, so it drives straight out of the row and turns in the headland.
The clearance check swung the hinge to both locks, rolled the halves and slid the booms out. No part passes through another. What it does not show: the motors and axles by part number, the roll bar's strength and the spray coverage. The masses are estimates.