Articulated Steam Locomotive

An articulated (e.g. Mallet) steam locomotive with multiple engine sets.

• Kind: ArticulatedSteamLocomotive
• Extends: SteamLocomotive

Fields

All SteamLocomotive fields are inherited. Additional fields:

articulationType

ArticulationType = Simple

Steam flow arrangement.

bodyTransform

TransformReference

Direct child of the model root holding the main body — boiler, cab, and the rear engine. Required; each engine set’s own bodyTransform names a sibling of it. See Model structure below.

engineSets

EngineSet[] = []

Additional engine sections.

Model structure

An articulated locomotive is modeled as a single asset. The model root carries no geometry of its own — each section that pivots independently, the main body and every engine set, is a direct child of it:

my-mallet            (model root)
├── body             (main body: boiler, cab, rear engine)
└── front            (front engine set)

bodyTransform and each engine set’s own bodyTransform point at those children, one level deep:

"modelIdentifier": "./my-mallet",
"bodyTransform": { "path": ["body"] },
"engineSets": [
  { "identifier": "front", "bodyTransform": { "path": ["front"] } }
]

bodyTransform is required. Without it, the model root would double as the body, nesting every engine set inside it instead of beside it.

Each section has its own AnimationMap and Animator — animations and wheelset transforms are looked up within the section that uses them. That includes components: parent one to @engineSet:front and its animations come from the front section. To pose linkage that follows the reverser on an engine set, such as a front power reverser, use a PropertyAnimation on the reverser key. The model root must carry no Rigidbody, and section transforms must stay unrotated and unscaled; the game normalizes them at load, so bake scale and orientation into the model itself.

EngineSet

Each engine set defines an independently-pivoting engine section.

bodyTransform

TransformReference

The direct child of the model root holding this engine set.

brakeAnimations

AnimationReference[] = []

Brake rig animations.

driverWheelsetIndex

int

Index of main driver in this set’s wheelsets.

identifier

string

Engine set ID (e.g. "front-engine").

maximumBoilerPressure

float

Steam pressure (PSI).

phaseOffset

float

Wheel rotation phase offset (0—1).

pistonDiameterInches

float

Cylinder bore (inches).

pistonStrokeInches

float

Piston stroke (inches).

pivotOffset

float

Offset from main pivot (meters). See Car Geometry.

weightOnDrivers

float

Weight on drivers (pounds).

wheelsets

Wheelset[] = []

Wheelsets for this engine section. Each wheelset’s own transform names its wheels and rods within this section — never the section’s bodyTransform itself. See Car Geometry for how pivotOffset places them.

Enums

ArticulationType

Simple — Both engines receive high-pressure steam.

Compound — Mallet arrangement: high-pressure rear, exhaust-fed front.