The nurse trailer in 3D
A 600-gallon trailer that takes clean water from the farm's fill station to the edge of the field. The sprayer fills itself from it through a chemical inductor on the trailer, so the trailer carries no pump, no engine and no battery — only surge brakes and lamps. It hitches to the Drumlin truck's ball or to the farm tractor's drawbar. Run each tyre over a bump, flip the slow-moving-vehicle sign up for the tractor, or put the jack down. A design in progress — nothing is built.
Why no pump. The straddler already carries a spray pump of about 50 gallons a minute. At the field edge it draws water from the trailer through the inductor, where the chemical is poured in, and fills its own 300-gallon tank in six to eight minutes. Mixing happens there, at least 100 feet from any well, and the trailer needs no power at all.
Surge brakes. When the trailer pushes on its coupler, a master cylinder in the coupler applies all four brakes — behind the truck or the tractor, with no brake controller and no wiring. The drums free themselves when backing, so it reverses without a solenoid. Loaded it weighs about 3,070 kg (6,770 lb) on two 3,500 lb axles joined by an equalizer, so one tyre can ride over a bump while the other carries on.
One trailer, two hitches. The coupler head bolts on: a 2-5/16 inch ball head for the truck and a drop clevis for the tractor's drawbar. The spare head rides bolted to the front of the frame. The clevis is drawn for a 16 inch drawbar — an assumed height, to be measured before the part is cut. Full, about 12 % of the load rests on the hitch.
Water only. The big tank carries clean water. Concentrate rides in its own labelled containers and goes into the inductor at the field. The slow-moving-vehicle sign flips up behind the tractor and hangs out of sight behind the truck. Both are readings of the Wisconsin rules, not legal advice.
The clearance check ran with each tyre over a 100 mm bump, the sign flipping and the jack swinging down, with both hitch heads. No part passes through another. What it does not show: the leaf springs (only their pads are drawn), the brake lines, the wiring, and how it stops — the brakes are sized by arithmetic, not a test. The figures are estimates from the design, not a weighing.