design(mechanical): rigorous observatory mechanical-design proof-out - #105
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… torque proof First slice of the mechanical-design proof-out. Establishes the single-source-of- truth parameter set (params.py) with sourced/derived/assumed provenance tags, the SI units layer, the common BudgetResult type, and the exemplar axis-torque budget. The torque proof already lands the boldest result: MN78 counterweight-FREE needs 49.9 Nm at RA vs the CSF-32 127 Nm rating (SF 2.5) and 26.5 Nm at DEC vs 70 Nm (SF 2.6) — deleting the ~9 kg of counterweights is quantitatively feasible, the same principle the ZWO AM5 / RST-135 exploit. 5/5 tests green. Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01SKZMQ755R7q38SKqJsCQsg
…nerated report Completes the rigorous mechanical-design proof-out. Turns the repo's asserted-but- uncomputed design into 11 first-principles budgets (torque, stiffness, dynamics, encoder tracking, balance, bearings, wind, pier, thermal, enclosure, power), each a calc module + pytest asserting its margin. A weighted-Pugh trade study runs the selection permutations with a sensitivity pass, parametric OpenSCAD + an SVG preview fill the empty CAD appendix, and report.py generates MECHANICAL_DESIGN.md from the calculator (a diff-test forbids drift). 121/121 tests green. Honest tally: 6 PASS / 5 FAIL — the FAILs are real findings the repo's prose hid: - stiffness 43.5" vs 5": the deep-groove 6008/6006 bearings (not the walls) are 98% of the error -> angular-contact 7008/7006 pairs required. - tracking: baseline dual-encoder chain 5.02" RMS vs 1" -> on-axis high-res absolute encoder REQUIRED (proposed ring reaches 0.54"). - survival wind: 9.2 kN roof uplift, SF 0.19 -> hold-down anchors mandatory (unspecced). - thermal: 22 K diurnal swing walks focus ~10x depth-of-focus -> temp-comp focuser. - off-grid power: 12 V pack 3.3 h vs 10 h night -> 48 V pack (13.4 h) or DGX duty-cycle. Selected build banks two won bold picks (counterweight-FREE GEM, active-thermal roof) plus the mandatory on-axis encoder; keeps baselines where they already pass. Every input tagged sourced/derived/assumed; the three governing voids the repo omits (survival wind, snow, seismic) are filled as labelled assumptions. Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01SKZMQ755R7q38SKqJsCQsg
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Summary
Turns the repo's documented-but-unproven mechanical design (
NIGHTWATCH_Build_Package.md+ thepos/expert-persona reviews) into a rigorous, reproducible, self-consistent engineering proof-out under a newdesign/mechanical/tree. It runs the selection permutations as a weighted trade study, proves out every choice with first-principles calculations carrying stated assumptions and margins, makes and defends the bold choices the numbers justify, and fills the CAD and environmental-load voids. 121/121 tests green.Type of Change
Changes Made
design/mechanical/calc/params.py— single source of truth for every mechanical parameter,sourced/derived/assumedtagged; resolves 7 cross-file contradictions (MN76 vs MN78 mass, 2048 vs 8192 PPR, temp units, site coords, deep-groove-vs-angular-contact bearings) in one place.evaluate() -> BudgetResult+ a pytest asserting its margin: torque, stiffness, dynamics, encoder tracking, balance, bearings, wind, pier, thermal, enclosure, power.design/mechanical/tradestudy/— morphological (Zwicky) + weighted-Pugh matrices with a precision/cost sensitivity pass; a pass/fail gate on the 1″ tracking target disqualifies the baseline encoder a naive weighted sum would have kept.design/mechanical/cad/— parametric OpenSCAD (RA/DEC housings, pier adapter, counterweight shaft, assembly) + a zero-dependency SVG elevation previewer, filling the empty "all.stepPending" appendix.design/mechanical/MECHANICAL_DESIGN.md— generated byreport.pyfrom the calculator;test_report.pybyte-compares so it can never drift from the code.Results — 6 PASS / 5 FAIL (the FAILs are the value)
Safety Checklist
Testing
python3 -m pytest design/mechanical/tests/ -q→ 121 passed.scadcarries its render commandDocumentation
design/mechanical/MECHANICAL_DESIGN.md(generated, 780 lines) — resolved-contradiction & filled-void tables, 11 proofs, provenance ledger, trade study, CAD, selected-config + cost-delta + roadmap, risk register.Additional Notes
Every input is labelled
Sourced /Derived /Assumed — nothing is measured field data; the observatory has never been built. The three governing structural loads the repo omits (survival wind, snow, seismic) are added as clearly-labelled assumptions. Left as a draft for your review; thedesign/tree is isolated from the runtime code and from CI'sservices/ voice/ nightwatch/lint/type scope.🤖 Generated with Claude Code