Shaft sections and carriers

The generator supports an ordered shaft_chains declaration in a vehicle_template version 1 definition. Each section has its own CAD owner, endpoint pair, axis, mass contribution and mesh binding. Existing single-section shafts definitions continue to work unchanged. The new chain implementation has offline regression coverage; it has not yet passed native BeamNG acceptance.

Prepare a two-section shaft

For a two-section front propshaft:

1. In the separate real-physics project, assign two groups with the Front driveshaft section role. Select only the bodies belonging to each section. Give them distinguishable names. Selection/list order does not define their physical order.
2. Assign the stationary bearing housing/bracket to Propshaft carrier bearing / bracket. It is a separate mass-owning group with reviewed frame mounts.
3. In the reviewed definition, list three ordered joint centres and two sections. Each joint names its mounted housing/carrier by component ID, not display name. segments[i] joins joints[i] to joints[i+1]. Every joint needs an explicit support; an unsupported intermediate joint is currently rejected.
4. Set each section’s plunge_m explicitly: zero gives a fixed-length compliant rod; a positive value allows that much axial travel in each direction. No slip joint or extra gear reduction is inferred from the mesh.
5. Include carrier fixed_mounts before preparing/calibrating the frame, then regenerate the full vehicle and run settle/supported/articulation pilots. Adding or moving a carrier mount requires fresh frame calibration.

examples/shaft-chain-fragment.json shows two non-collinear synthetic sections. Merge it into a reviewed definition with actual component IDs and measured coordinates; it is not a complete vehicle definition and its example points must not be applied to real CAD. Remove the replaced legacy shafts entry. All section owners must appear exactly once.

How the support is represented

At the intermediate support, both sections contribute half their CAD mass to a shared positional node. Three support beams and an angular point constraint locate it on the separately mounted carrier. Each section binds only to its own endpoints and their local supports. Native motion recording includes these nodes, checks support drift, and checks length against each section’s declared plunge. The chain and its mass allocations are sealed into package provenance and remain unchanged during appearance replacement or namespace forks.

Limits of the model

This is an equivalent supported positional linkage, not a rotating universal-joint simulation. It retains the existing ideal frontPropshaft powertrain device (or the existing CVT-to-rear reduction for an output-shaft chain). Shaft spin animation, Cardan phasing/angular-speed variation, shaft bending/spin inertia and torsional fracture are not modeled. Endpoint mass lumping preserves each section’s total mass, but does not fit its full CAD inertia. The supported joint centre is an explicit constraint, not an inferred carrier-bearing location. BeamNG’s bounded-beam documentation describes the axial limits; its props documentation describes the separate local-axis animation system.