pawelw fc22645d7c fix(physics): articulated couplers stall freight trains (eu07/maszyna#553) (#255) ...

* fix(physics): articulated couplers stall freight trains (eu07/maszyna#553)

Articulated wagons (T3000e, N-230, N-234) set up with CType=Articulated
barely moved in a freight train and jerked.

- The articulated joint took the spring force up to DmaxC = 0.05 m only,
  225 kN, well short of its FmaxC of 850 kN and of what a loaded section
  in a freight train takes. It overstretched and the sections collided at
  every physics step. Dmax is now sized so the spring carries FmaxC
  (0.19 m stretched, 0.09 m pressed in), never below the old 0.05 m.
- ComputeCollision() scaled the velocities of both vehicles by
  sqrt(1 - beta), so each collision braked the pair as a whole: two
  coupled vehicles in a sustained "collision" lost a third of their speed
  per step. The restitution now applies to the velocities relative to the
  centre of mass only, and the pair keeps its momentum.

Tests: the articulated joint carries FmaxC within its travel; a jerked
articulated set and a jerked screw-coupled pair keep their momentum. On
the code before the fix both pairs stop dead within 3 s.

* style(physics): English-only comment in ComputeCollision()

The comment above the collision velocities started in Polish and went on in English.

* style(physics): SonarQube findings in the #553 fix

std::lerp for the collision velocities (cpp:S6179) and test locals renamed so they no longer shadow the end and coupling enumerators (cpp:S1117).

2026-11-05 10:25:26 +01:00

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