The truck in 3D
The same flat-panelled farm truck on a used diesel, now drawn as parts: a 1996–97 Cummins 5.9 12-valve with its mechanical injection pump, an NV4500 five-speed and an NP241 transfer case, full-float Dana 60 and Dana 70 axles on 35 inch tyres, leaf springs under the axles, heavy-duty pickup brakes, its own welded frame and the same cab, hood and oak deck as the electric truck. Steer it with the slider, twist the axles, or lift the body off to see the engine and both driveshafts. A design in progress — nothing is built.
Why a used engine. A new crate diesel has no road certificate for a homemade truck; an engine pulled from a titled truck, kept the way it was certified, is the legal path — and the 12-valve is the last big Cummins with a mechanical injection pump: no computer on the fuel, no particulate filter, no exhaust fluid. The paperwork comes first: a letter to the EPA and to the state's Vehicle Research Unit before a donor is bought.
What the diesel changes. The oil pan has to clear the front axle at full bump, so the hood stands taller and the frame sits 115 mm higher, on its own weldment. To keep the headroom, the seats stand in wells pressed into the cab floor: 1,009 mm from the cushion to the roof, and the roof still fits under a seven-foot door. It is rated for 4,500 kg (9,900 lb), still a light truck, which leaves about 960 kg of payload on a curb weight of about 3,540 kg.
Brakes and springs. The axles take heavy-duty pickup brakes by pattern: the 2009–18 Ram 2500/3500 rotors and twin-piston calipers, with the parking brake in the rear hats and a hydraulic booster run from the power-steering pump, since a diesel has no manifold vacuum. The leaf springs hang under the axles, the common pickup arrangement, with a limit strap at each wheel. Big rear brakes on a light rear end lock the rear wheels first, so an adjustable proportioning valve (the electric truck's Wilwood 260-8419) trims the rear line. It sits on the firewall above the booster, reached over the driver's wing with the hood up, out of the road spray, and it is set on the empty truck.
Fuel on the outside. A 56 gallon side-saddle tank hangs outside the left frame rail behind the cab, with a steel toolbox outside the right one — parts picked from an image model's idea of this truck, then checked into the design. About 750 miles a tank at an assumed 15 mpg.
The steering. A box on the left rail, a 270 mm pitman arm, a drag link to the left knuckle and a tie rod behind the axle — the slider moves them the way the checked model does. The limit straps hold the front axle to 100 mm of droop, which keeps the front driveshaft's worst joint at about 9°, and the rear to 130 mm.
The axles twist as far as they really can: one wheel hanging on its strap, the other on its bump stop, about 12° each way. Reaching there showed the U-bolts would meet the bump rubbers first, so the pads they strike stand taller (the price is 16 mm less bump travel), and the front wings sit 73 mm higher with an arch over each wheel so the tyre clears them even at full lock. The clearance check ran through the whole steering sweep and both of those twists; no part passes through another. The pedals are drawn now — a hanging box with brake, clutch and a cable throttle, the clutch's master and slave cylinders — and the Ram's three-cable parking brake from a foot pedal to both rear hubs, with the brake lines along the outside of the rails kept clear of everything that moves. What it does not show: strength and the valve's final setting — Wilwood does not publish its full curve, so the setting is a calculation until it is made on a road. The figures are estimates from the design, not a weighing.