INPUTS
Wheel profile
Steeper (larger) = more climb-resistant
Rise/run across the tread (~0.05 = 1:20)
Track
HO NMRA standard is 0.649"
Lateral displacement
Compare a second standard (overlay)
Drawn as a dashed green outline for side-by-side flange comparison.
RESULTS
Flange clearance
—
gap before flange bears on rail
Free lateral play
—
total side-to-side wander
Rolling-radius difference
—
the self-steering signal at this shift
Flange-climb (Nadal)
—
L/V limit before climb
Wheelset
Rail heads
Comparison profile
Flange contact
Simplified 2D geometry for insight, not contact mechanics. Flange clearance = (gauge − back-to-back − flange thickness) / 2 each side. Rolling-radius difference ≈ 2 × conicity × lateral shift — this is what steers a wheelset through curves with no steering mechanism. The Nadal ratio (≈ tan of the flange face angle) is the classic single-wheel flange-climb limit; higher tolerates more lateral (L) vs. vertical (V) force. Confirm anything critical against the actual NMRA/NEM/Proto standards and physical testing.