Controls

On a phone, tap the steering-wheel button to show the two joysticks: left drives and steers, right works the boom and bucket like a loader's single lever. Drag the view to orbit, pinch to zoom.

To load: lower the boom, level the bucket (Return to dig), drive into the pile, then curl while lifting slightly. The pile pushes back: drive too deep and the tyres spin or the hydraulics stall (you hear the relief valve), so lift and curl to break out. Carry with the bucket racked back; brake hard and the heap sloshes over the lip. Dump anywhere: the sand pours off the edge and builds a pile at its angle of repose.

Loading the truck: the tipper waits in the bay north of the pile. Lift to full height while you drive up to its side, stop with the bucket over the body and dump. Spread the passes along the body. Once it holds about 18 t it drives the haul loop, tips at the west spot and comes back. Everything is solid: bucket, boom, frames, wheels and cab collide with the truck's cab, chassis, body walls and wheels. A hit stops the machine, rocks the truck on its springs and you hear it. In the cab view, drag to look around: the joystick, steering wheel, pedals and gauges move with what you do.

More: reverse with the bucket flat on the ground to back-drag and level loose sand. Push the boom down against the floor to lift the front wheels. Loose sand gives less grip than the hard floor, and the tyres leave ruts and push up small berms.

About this twin

A real-time model of a 23-tonne-class articulated wheel loader, built in three.js r187 and running entirely offline from this single file.

What is measured or published. Main dimensions follow public spec sheets for machines of this class: 3.55 m wheelbase, 2.23 m tread, 26.5R25 L3 tyres, 4.2 m³ general-purpose bucket with bolt-on cutting edge, 4.25 m hinge-pin height at full lift, ±37° articulation, 23.2 t operating weight, gear speeds 6.7 / 13.5 / 24.2 / 39.5 km/h, 373 L/min implement pump.

What is reconstructed. Manufacturer pin coordinates are not public, so the Z-bar linkage pin positions were solved numerically to hit 0.44 m / 4.25 m hinge-pin height and the class rack-back and dump angles. The result racks back about 37° at the ground, 57° at carry and up to 90° at full lift (published for the class: 39° / 50° / 62°), and dumps about 45° at full lift. The cylinder strokes, bucket angle and hinge-pin height shown in the twin panel are computed from that geometry every frame. Bucket: 3.16 m³ struck plus a 2:1 heap, 4.2 m³ heaped. The body shape, panels, cab, grilles and details are a generic, unbranded design in the style of this machine class, not a copy of any manufacturer's machine.

Soil and material. The ground is a deformable sand heightfield (12.5 cm cells) that slumps at its angle of repose (31–37°, varying cell to cell). The load in the bucket is a second sand heightfield laid on the bucket's inner surface. It slides at its repose angle under the real gravity direction, which includes bucket tilt, machine pitch and roll, and the bucket's own acceleration, so it sloshes when you brake. It heaps above the strike-off line and pours off the cutting edge, the side plates or the spill guard. Sand only enters through the mouth. Steel pressing into sand, or a full bucket pushing on, bulldozes it aside. Every cubic metre is conserved between pile, bucket, falling stream and ground, apart from the settling of loose sand under the tyres.

Forces. Digging resistance follows the Reece / McKyes earth-moving equation for dry sand: cutting depth, surcharge and bucket width. Bulldozing resistance comes from the volume being pushed. Tyre grip is limited by traction (about 0.62 on the compacted floor, 0.38 on loose sand), and the excess turns the wheels as slip. The wheels follow the terrain, with the front axle rigid and the rear axle oscillating ±12°, and gravity acts on slopes. Boom and bucket forces are capped by relief pressure, so they slow and stall under load. A 62° rack-back stop stands in for the class linkage limit.

The truck. A three-axle (6×4) tipper of the 26-tonne class: 4.2 m wheelbase, twin 315/80R22.5 tyres on the bogie, a 5.2 × 2.3 × 1.3 m steel body (about 15 m³ struck) on a rear hinge, a telescopic front-mounted ram and a top-hinged tailgate that hangs open as the body rises. Its payload is a third sand heightfield inside the body: sand from the bucket is caught where it actually lands, slides at its angle of repose as the truck brakes, corners and tips, and rolls over a side wall if heaped too high. The sprung chassis sits lower and squats at the rear as it fills (about 8 cm when full) and rocks on its springs when something hits it. A simple driver model drives the haul loop with pure-pursuit steering and Ackermann front wheels, plans its speed to stop at marks, waits if the loader is in the way, reverses on full lock until the tailgate meets the toe of the stockpile, tips, lowers and comes back.

The cab. The operator's station is modelled part by part: air-suspension seat with bellows, slide rails and belt; seat-mounted console with the two-axis implement joystick, F-N-R rocker and backlit keys; tilting steering column with a three-spoke wheel and spinner knob; brake and accelerator pedals; analogue tachometer, speedometer, fuel and coolant gauges with a warning-lamp strip; a colour display on the front post; side console with rocker switches, HVAC panel and key switch; headliner with vents, dome light and radio; and a dusty, tinted inner glass layer. Everything moves with the machine: the wheel turns with the articulation, the joystick tilts with boom and bucket commands, the pedals press, the needles and the display follow the engine, speed, gear, payload, fuel and temperatures. From the seat the eye rides the rear frame, lags behind braking and cornering, picks up engine and ground vibration, and follows the bucket up as it rises. The cab muffles the high frequencies of the machine sound.

Contact. The bucket, boom, frames, cab and tyres of the loader and the cab, chassis, body walls, tailgate and tyres of the truck are solid oriented boxes (tyres as many-sided rounds), tested with the separating-axis method every frame. A move that would push steel into steel is undone: travel stops with a small rebound, and a cylinder pushing against the truck stalls on its relief valve. Moves that back out of contact are always allowed. A hit is heard as a steel clang or a tyre thump, shakes the view and rocks the truck.

Simplified. The drivetrain (converter rimpull per gear with auto-shift), the articulated steering kinematics, hydraulic flow sharing and all soil parameters are approximations for training and demonstration. It is not a certified simulator and does not use OEM control data.

Lighting. The sky and distant quarry are the CC0 HDRI Quarry 01 by Greg Zaal (Poly Haven). Its sun was measured (azimuth, 10° elevation, irradiance) and replaced by a shadow-casting light of the same power so shadows and reflections stay consistent. Near-field sand: CC0 Aerial Sand by Rob Tuytel (Poly Haven), colour-matched to the HDRI ground. Everything else is generated in code. three.js is MIT-licensed.