Research fastening alternatives to the hex-screw + captive-nut scheme#41
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Research fastening alternatives to the hex-screw + captive-nut scheme#41MJohnson459 wants to merge 5 commits into
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Surveys heat-set inserts, thread-forming screws, printed threads, nyloc/ threadlocker, and standoffs for the M3 joints in the PLA printed parts. Recommends blind heat-set insert bores in the mounts (plates and their 3.5 mm ORP grid unchanged), Loctite 243 on drive-train joints, nyloc on the servo lugs, and optional M2.5 standoffs for the Pi board. Includes per-joint table, BOM delta (~£34), and the implied CAD changes for the follow-up implementation task. Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01MhciiHzvW1Q2aWzjq3qC9n
Review feedback on the first draft: the captive-slot joints do not loosen (only bare-nut joints do), the M3+nut scheme was convention- matching rather than a hard constraint, and the survey read as fastener selection when the open question is joint architecture. Rewritten to audit the inherited constraints, separate location (printed pins in the existing ORP grid holes) from clamping (minimum screw count), retain boards with clips, strap the battery, and reserve nyloc for the joints that actually loosen. BOM delta drops from ~£34 to ~£7 with the plates still untouched. Co-Authored-By: Claude Fable 5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01UuQ3gEFZvHCN53EL2HdmpV
…slots Second review round reframed the problems: nested sensor stacks make the sensor a structural nut-retainer with an exactly-M3x12 screw, and the top plate fastens from inside the chassis sandwich. Bottom-plate joints and slotted nuts were never failing, and the build is now static apart from the SO-101 arm. Recommendation is now three geometry changes reusing existing hardware: hex nut pockets under every Chassis Top hole (all top-deck parts, including the arm, fasten from above; screw length non-critical; Pi hazard deleted), roofed nut slots in the mounts (mount+sensor becomes a bench unit), and nyloc on the servo lugs. BOM delta ~GBP 4. Prior options (inserts, pins, quick-release tiers) move to a considered/ not-adopted playbook. Co-Authored-By: Claude Fable 5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01UuQ3gEFZvHCN53EL2HdmpV
Three observations from operating Mote that bound how much the ORP standard should be deferred to: 20 mm pitch is too coarse for dense fitting on a 235 mm plate; the standard fixes a hole pattern but no functional datums, so grid compatibility gives fastener interchange rather than part interchange (the servo mounts had to be fitted to the plate by hand to place the wheels); and fastening is unspecified, so every ORP design re-solves nut retention ad hoc. Notes TurtleBot 3's tileable waffle plates as prior art for granularity and extensibility. Co-Authored-By: Claude Fable 5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01UuQ3gEFZvHCN53EL2HdmpV
Review of the fastening research kept producing workable whole-robot schemes that all felt off, because they were uniform systems preserving generality the prototype has outgrown. design/REDESIGN.md records the diagnosis, drafts the v2 requirements (built by others, swappable camera/battery behind fixed interfaces, serviceability by declared class, ORP as an expansion zone), and lays out the phased path: audit (joint schedule + SO-101/TB3 teardowns), design rules, iterative per-subsystem redesign, and a clean-build validation. Fastening decisions move into Phase 3 per joint; the trapped-nut scheme stays as the default candidate and interim fix. Co-Authored-By: Claude Fable 5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01UuQ3gEFZvHCN53EL2HdmpV
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…icts Review of the parallel fastening research (task #144 / PR #41) settled the direction differently from this branch's insert recommendation, and both surveys now feed the v2 redesign process (design/REDESIGN.md, on that branch), which decides fastening per joint. Rename fastening.md to mounting_survey.md and cut it to what is durable here: the measured state of the STLs, the half-pitch grid rule, and hole_survey.py. Drop the heat-set inserts BOM line and the front-runner claim in ASSEMBLY.md; keep the constraint warnings, the nyloc line, and the README grid rule. Co-Authored-By: Claude Fable 5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01UuQ3gEFZvHCN53EL2HdmpV
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Adds design/research/fastening.md and design/REDESIGN.md on branch worktree-fastening-research — the fastening research (reworked through three review rounds: fastener survey → joint geometry → corrected problem statement) and the v2 redesign process that review converged on.
fastening.md
REDESIGN.md — the process the review kept circling toward:
Companion: PR #38 (task #141) is rescoped to the measured STL survey (research/mounting_survey.md + hole_survey.py) and doc fixes — no file collision remains. Follow-up chain proposed as Voro tasks #147–#151; proposed task #146 is superseded.
Verified: pixi run lint passes; no CAD/STL/3MF files touched. Standing flag: the 50mm chassis standoffs are absent from BOM.md.
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https://claude.ai/code/session_01UuQ3gEFZvHCN53EL2HdmpV