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Bolt Jr+ — Shake Appears Only While Traveling on Track

Summary

On a Bolt Jr+, arm and camera shake appeared specifically while the robot travels along the track, and disappeared when the same move was run with the track axis disabled (arm-only). Hand-pushing the track with the robot powered off, pinch wheel removed, showed no play or looseness in the rail system itself, so a purely mechanical rail fault was ruled out as the sole cause. This is a distinct symptom family from lens/probe-induced shake — see Macro / Probe Shake Rigging for that.

Symptoms

  • Arm and camera shake while Bolt Jr+ travels on track.
  • Disabling the track axis and running the same move with the arm alone produces no shake.
  • Hand-pushing the track (robot off, pinch wheel removed) shows no looseness in the rail system.
  • All track and mounting screws confirmed tightened.
  • Shake is speed-dependent: worse at medium-low velocity, better at both high speed and very low speed.

Community Guidance

[FIELD WORKAROUND] Checklist — Rail Joints, Racking, and Pinchwheel Condition

Community — Timothy Heys Cerchio, Peter Constan-Tatos — 26 July 2026

Timothy Heys Cerchio: "Most likely mechanical. And usually that comes from a bad joint between precision rails or, more often, from a misaligned racking joint. Or sometimes from dirt or debris on the Pinion, or a 'dented' pinchwheel... Or tight/loose pinchwheel. So, quite a few things to check."

Checklist, in order:

  1. Check for a bad joint between precision rail sections, or a misaligned racking joint at a rail-to-rail transition.
  2. Check the pinion for dirt or debris.
  3. Check the pinchwheel for denting.
  4. Check pinchwheel tightness — both too tight and too loose can cause the same symptom. Peter Constan-Tatos noted he never leaves the pinchwheel tight overnight, as a preventative habit.
  5. Note whether the shake happens regularly on every pinion/pinchwheel rotation (points to the pinion/pinchwheel itself) or at one specific point along the rails (points to a joint).
  6. Note whether it appears specifically on a change of track direction (points to backlash).
  7. Try offsetting the move along the rails, or running a track-only move (no arm), to see whether the shake persists independent of rail position — this helps separate a localized rail-joint fault from a pinchwheel/pinion-wide issue.

confidence_score: 0.72