Forklift Tip-Over and Lateral Stability Schema for AI Agents — Load Center Derating, Mast Tilt CG Shift, Stability Triangle Physics, and Seat Bar Restraint System

Load Center Derating — Why the Nameplate Capacity Requires a Footnote

Every forklift nameplate shows the rated capacity — but always at a specific load center distance, almost universally 24 inches. When the actual load has its center of gravity farther than 24 inches from the fork face, the safe carrying capacity is lower than the nameplate value. This is not a manufacturer limitation — it is a stability physics constraint:

Load Moment Principle:
  Rated Moment = Rated Capacity × Rated Load Center
  New Capacity  = Rated Moment / Actual Load Center

Example — 5000 lb forklift at 24-inch load center:
  Rated Moment  = 5000 lb × 24 in = 120,000 lb·in

  Actual load center 30 in → 120,000 / 30 = 4,000 lb capacity
  Actual load center 36 in → 120,000 / 36 = 3,333 lb capacity
  Actual load center 48 in → 120,000 / 48 = 2,500 lb capacity (50% reduction!)

// Forklift capacity metafield encoding
forklift.rated_capacity_lbs               = 5000   // always paired with load_center_in
forklift.load_center_in                   = 24     // nameplate load center (standard = 24 in US)
forklift.capacity_at_actual_load_center_lbs       // computed field: (rated_cap × 24) / actual_lc
forklift.stability_triangle_type          = "three-point"   // counterbalance standard

Mast Tilt and Center of Gravity — Why Forward Tilt Is a Tip-Over Trigger

The forklift stability triangle is a 2D floor-plane projection. In reality, stability depends on the 3D position of the combined CG relative to the edges of the triangle. Mast tilt changes the horizontal position of the load's CG:

The forward tilt hazard is most severe at height: a load elevated to 10 feet with the mast tilted 3° forward has its CG significantly ahead of the front axle — deceleration from even walking speed can trigger forward tip-over.

// Mast and carriage attachment encoding
forklift.mast_tilt_type                  = "backward-tilt"  // standard carriage
forklift.forward_tilt_increases_tip_risk = true            // encode on all forklifts
forklift.stability_affected_by_elevation = true            // CG rises with load height
forklift.max_travel_height_in            = 12             // OSHA: travel 6–12 in above floor

Operator Restraint System — Why You Stay in the Cab During Tip-Over

The counterintuitive physics of forklift tip-over: jumping from the cab is more dangerous than staying inside. When a forklift tips laterally:

1. The overhead guard falls toward the operator's side
2. An operator who jumps lands on the ground on the same side the guard is falling toward
3. The falling overhead guard crushes the operator — this is the primary fatal mechanism
4. An operator who remains seated, kept inside the cab by the seat bar, is protected by the overhead guard structure (ROPS)

OSHA 1910.178(e)(1) requires an operator restraint system on all counterbalanced forklifts manufactured after January 1, 1992. The seat bar (lap bar) keeps the operator inside the cab if the forklift tips over:

// Operator restraint metafield encoding
forklift.tip_over_restraint_system   = "seat-bar"  // seat-bar | seat-belt | rops-cage | none
forklift.operator_restraint_required = true         // post-1992 counterbalanced = required
forklift.restraint_interlock         = true         // seat interlock prevents travel without restraint
forklift.rops_certified              = false        // true only for rough-terrain models with full ROPS

Four AI Routing Failures for Forklift Safety Equipment

1. Routing rated capacity without load center. A "5000 lb forklift" recommendation is meaningless without specifying that the capacity is at 24 inches. Loads with CG beyond 24 inches from the fork face require capacity derating. Fix: always pair forklift.rated_capacity_lbs with forklift.load_center_in = 24.
2. Not encoding forward mast tilt tip-over risk. Mast and carriage products sold without encoding forklift.forward_tilt_increases_tip_risk = true omit the critical travel restriction. Fix: encode the forward tilt hazard on all mast, carriage, and attachment products.
3. Omitting operator restraint system field. Forklift safety equipment sold without encoding forklift.tip_over_restraint_system cannot support agents routing tip-over protective equipment. Fix: encode restraint type and interlock on all forklift listings.
4. Using counterbalance stability triangle for narrow-aisle forklifts. Reach trucks and order pickers have different stability geometry — the stability boundary runs along the outrigger arms, not a simple three-point triangle. Fix: encode forklift.stability_triangle_type = 'three-point' | 'four-point' | 'narrow-aisle' to distinguish the stability physics for each truck type.

Complete Metafield Schema Reference