Define hardpoints. Inspect the mechanism.

Geometry and transient dynamics

VehicleLab 1.10.0 supports Double-Wishbone geometry and kinematics. Hardpoint geometry does not yet alter Full-Car transient forces. Existing equivalent vertical stiffness and damping remain the authoritative inputs to the 7-DOF model. Geometry does not change completed simulation channels, metrics, CSV, reports or deterministic videos.

Canonical architecture

A vehicle has independent front and rear suspension definitions. Each stores mechanism type, geometry metadata, explicit hardpoints and an orientation constraint under vehiclelab.suspension.v1. Only double-wishbone is implemented. The solver is an engineering service in simulation-core, separate from the transient force kernel. Visualization consumes its solved state directly.

Coordinates and mirroring

Define the left corner. The local origin is its wheel centre at design ride height: (0, 0, 0). +X is vehicle forward, +Y vehicle left, +Z up. The editor displays millimetres; canonical data and the solver use metres. Wheel centre is derived from this origin rather than duplicating track or wheelbase. Right geometry mirrors Y, including spindle reference; X and Z stay unchanged.

Vehicle placement adds the existing axle longitudinal position and ±half of the axle track. Front and rear geometry therefore do not store a second set of vehicle dimensions. The inspection viewport defaults to the left corner for hardpoint clarity; choose Whole axle to inspect mirroring at the current track. Geometry uses a uniform physical scale.

Hardpoints and attachments

A hardpoint is a mounting or joint position in the design pose. The two upper inboard pivots define the upper-arm hinge; the two lower pivots define the lower hinge. Each ball joint moves with its rigid arm. Their separation defines the rigid upright.

Spring/damper upper mounts are chassis-fixed. Both lower mounts are attached rigidly to the lower wishbone, including any bracket offset from the arm plane. The wheel centre and spindle reference belong to the upright. The spindle reference is an endpoint measured from the wheel-centre origin, defining the wheel axle direction.

Locked heading assumption

Two ball joints alone leave a free rotation of the upright about their connecting axis. VehicleLab explicitly constrains its longitudinal basis to chassis +X projected perpendicular to that axis. The lateral basis is the cross product of the ball-joint axis and that projected direction. Wheel centre and spindle reference retain their design coordinates in this orthonormal upright frame.

This is an ideal locked-heading constraint, not a tie-rod or steering-system model. There is no steering input or steering dynamics. No toe or camber curve is reported in this release. An upright nearly parallel to chassis +X is rejected because this frame becomes singular.

VehicleLab Generic geometry

Front and Rear are independently authored educational geometries, not any named production vehicle. Both are validated over −50 to +50 mm wheel travel. Coordinates below are the left design pose in mm.

VehicleLab Generic Front Double Wishbone

VehicleLab Generic Rear Double Wishbone

Customize geometry

1. At Full-Car Vehicle, choose Customize Geometry for the axle. Editing starts from its current valid geometry.
2. Enter grouped X/Y/Z coordinates, then Apply Geometry. Schema, geometric and design-Jacobian checks run before acceptance. Invalid edits leave the last valid definition and solved display intact.
3. Reset to VehicleLab Generic restores that axle and the default travel study.

Geometry remains session-local to the active Full-Car workspace. Changing model or reloading can reset it. It is excluded from project.v1; there is no geometry project migration in 1.10.0. This avoids confusing an inspection definition with currently uncoupled dynamics, and respects the existing unsupported spatial-project boundary.

Jounce, rebound and motion ratio

Jounce > 0 means the wheel centre moves up relative to the chassis; rebound < 0 means down. Wheel-centre Z is the travel constraint, rather than ball-joint Z. Spring/damper compression is design length minus current geometric length. Positive compression means the element is shorter.

Motion ratio = d(element compression) / d(wheel-centre jounce). It is signed and dimensionless. A negative value means that element extends during increasing jounce; values are neither clamped nor smoothed. A deterministic centred derivative uses a 10 µm wheel-travel step; verification compares 1, 10 and 100 µm steps and an independent closed-form parallel-arm derivative.

Solver and feasible travel

Each wishbone uses an exact rotation about its inboard hinge. Two arm angles satisfy rigid ball-joint separation and prescribed wheel-centre Z. Damped Newton iteration with centred angular Jacobian follows the design branch in steps of at most 1 mm. Large angle steps, poor residual descent, loss of Jacobian independence or unreachable travel fail explicitly. Link and wheel travel residuals must converge below 10⁻¹¹ m. Zero travel reproduces all entered design points exactly.

The default study requests ±50 mm. Advanced requested bounds may bracket zero within ±150 mm. Each direction is checked in ≤1 mm increments and stops at its first infeasible sample; the scrub range retains only that contiguous feasible interval. Derivative neighbours must also solve. Each scrub position is solved again, so sampled feasibility never licenses interpolation across an unsolved configuration. The service rejects nonfinite requests and has a ±500 mm request limit.

Validation rejects nonfinite coordinates, coincident pivots, ball joints on hinge axes, insufficient upright separation, degenerate spindle references, zero-length spring/damper elements and lower mounts on the lower-arm hinge. Thresholds represent explicit v1 geometry admission limits, not a collision or strength analysis. Design singularities are rejected before applying custom geometry.

Visualization and boundaries

Visualize Suspension uses the Engineering Viewport: orbit, pan, zoom, Fit scene, Reset view, Expand/Restore and Engineering 3/4, Front, Side and Top cameras. Labelled markers and links follow exactly the same solved state as the length and motion-ratio readouts. Cyan points are chassis-fixed; orange points move; green is the spring and violet is the damper. Wheels are schematic. A localized WebGL failure retains editing and numerical inspection.

This is rigid mechanism kinematics, not a full multibody or K&C solver. Collision, compliance, steering linkage, roll centres, anti-dive/squat, tyre-force kinematics, static ride-height solve and geometry-coupled transient forces are deferred. The next fidelity layer can use the solved displacement and local motion ratio without changing this canonical geometry contract.

Visualize Road follows the same define → visualize workflow. Quarter-Car and prescribed corner inputs use temporal profiles; Half-Car shows its actual front/rear timing relationship; procedural spatial and OpenCRG roads use canonical road geometry in 3D. All road previews remain presentation-only.