Hux
Side and top views of the working model, and the stair climb. Drag the joints, request a wheel position, or press Play. The 9.5 by 9.5 inch stair is a design target, not a validated capability; the V1 finish line is one step, 9 of 10 (R37). The layout the model is drawn to is Sheet 1
Sheet 2; its roll axes (3.0"), leg plane and body-CoM offset (+1") come from spec.js.
Positive hip angle puts the knee to the rear. Knee bend brings the lower tube forward under the hip. Balance is the 92% crouch, hip over the axle, knee behind. Request a wheel position and the hip and knee follow. The red dot is the center of mass, and the dashed line is gravity down to the tread under it. Motor boxes are rough envelopes, not parts.
Neutral overall width is 14 inches; hip roll changes the swept envelope. The head is the center box. Wheels and legs sit outside it. Track is 12.75 inches with a 1.25 inch tire. The knee folds rearward.
Inspect a candidate stair motion. Side and front views share one spatial chain with joint limits. Red crosses are requested wheel positions; dashed red lines show targets the mechanism cannot reach. CoM includes both legs. The verdict below rejects invalid geometry, forces and actuator demands. Playback does not establish a working gait.
The actual spatial links and whole-robot CoM are projected here. Hip axes are 5.4″ from the body center. Hip holding torque is calculated separately from the gravity moment about the tire. Requested sway is not automatically achievable.
Each of these rebuilds the climb. Defaults are the working assumptions in docs/research/leg-geometry.md, not decisions. The verdict below is for one step at these settings.