# Agent Record — Modular Pedestal Drum Stack - **Runtime:** Claude Opus 4.7 (1M context), Claude Code CLI, sonnet-round-5 lane - **Skills loaded:** sheet-metal, instrument-maker (per dispatch contract) - **Sprint:** 2026-05-20 sheet-metal-instruments Round 5 (percussion), Lane 08 - **Date:** 2026-05-21 ## qmd queries run + key citations ```bash qmd search "drum stack pedestal" -c instrument-builds # no direct hits — fully greenfield qmd search "snare drum sheet metal" -c instrument-builds qmd vector-search "drum membrane vibration mode" qmd vector-search "drum kit shell sheet metal" ``` Top citations consulted: - `qmd://instrument-builds/docs/textbook/chapters/01-acoustics-foundations.md:348` — "Drumheads obey a 2D wave equation; their normal modes are Bessel functions, not sines. The fundamental of an ideal circular membrane of radius `a`, areal density `σ`, and tension `T` per unit ..." — used as the basis for the Bessel-function membrane model in `modular-pedestal-drum-stack-starter.wl`. - `qmd://instrument-builds/docs/textbook/chapters/03-instrument-families.md:304` — drum-family catalogue (djembe, ashiko, conga, dundun, bodhran, frame drums, snare/tom) and 12" djembe head sample geometry — used to anchor the diameter steps and target tension range. - `qmd://instrument-wiki/synthesis/wolfram-model-patterns.md:131` — repo-wide list of existing Wolfram starters for vessel-flute Helmholtz, ceramic vessel-lab, duntong/instrument-m... — modeled the layout of this repo's modular-pedestal-drum-stack-starter.wl after these patterns (header, ClearAll, dataset output). - `qmd://instrument-wiki/index.md:27` — wiki pointers to ceramic-hang, ceramic-tongue-drum, wood-shell-tongue-drum entries for adjacent percussion designs. - `qmd://instrument-builds/skills/v3/instrument-maker-v3/build-packets/2026-05-02-tng-001-tongue-drum/assembly-manual.md` — reference for assembly-manual format and step granularity. - `/mnt/c/Users/Tony/Documents/GitHub/handpan/explorer.html` — explorer template for Heifer Zephyr design tokens, sidebar TOC, CSV/MD fetch viewers. - `~/.claude/skills/sheet-metal/SKILL.md` (referenced by SHARED.md) — authority chain for cylinder rolling, K-factor, bend allowance, seam strategy. - `~/.claude/skills/instrument-maker/SKILL.md` (referenced by SHARED.md) — authority chain for family/tuning, bore-vs-membrane geometry, validation gates. No existing Heifer Zephyr build covers a 5-drum pedestal stack — this is a fully greenfield contribution to the portfolio. ## Major assumptions - **Pentatonic A-minor as default scale.** A2-C3-E3-G3-A3 chosen over a chromatic array to favour fast melodic phrases and reduce per-stroke aim. Tuning can be changed at fabricator level with no shell-dimension changes. - **1.2 mm cold-rolled steel for shells.** Within slip-roll capability for all 5 diameters (50 mm minimum radius on drum-5 is at the practical floor; a coupon test is called out in `risks.md`). - **Bessel-membrane ideal model with 3% air-load correction.** Predicted frequencies do not include shell-membrane coupling beyond a Love thin-cylinder ring-mode sanity check. Future agents with FEM access should refine. - **Standard snare-style lug hardware.** Bought lugs, claws, rods — non-novel, reduces fabrication scope to shells + pole + base. - **Single-head open-shell construction.** Open bottom radiates downward; if v0.2 wants more bass on drum-1, consider double-headed conversion. ## Unknowns I'd punt to next round - DXF flat-pattern files — placeholder `drawings/README.md` only. Needs a SolidWorks pass. - SLDPRT/STEP files in `cad/` — placeholder only. - Actual photographs — `images/` is empty; `photo-shotlist.md` lists intended shots. - Full FEM coupling between shell and membrane — current model assumes shell is acoustically inert below the head's third partial. May not hold for drum-1. - Pole bending under lateral mallet impact at the top drum — quoted at 5 mm max in `validation.csv` based on cantilever beam estimate; needs measurement. - The 100 mm drum (drum-5) has loose tension and may favor a 7-mil head; `modular-pedestal-drum-stack-starter.wl` sensitivity check shows this drops tension below 110 N/m which is at the low end of useful — alternative tuning to B3 or C4 is a possible v0.2 fork. ## Files produced 23 files across the repo root and `drawings/`, `cad/`, `cnc/`, `wolfram/`, `learn-to-play/{,fingerings/,scales/,tunes/}`, `images/`: ``` LICENSE LICENSE-HARDWARE.md LICENSE-DOCS.md .gitignore README.md design.md parameters.csv modular-pedestal-drum-stack-starter.wl validation.csv tuning-notes.md bom.csv sourcing.csv cut-list.csv bend-table.csv hardware.csv risks.md solidworks-plan.md flat-pattern-checklist.md fabrication-plan.md assembly-manual.md photo-shotlist.md supplier-rfq.md visual-bom-brief.md explorer.html agent-record.md card-for-showcase.html cnc/cnc-plan.json cnc/operations.csv cnc/setup-sheet.md drawings/README.md cad/README.md wolfram/README.md learn-to-play/README.md learn-to-play/fingerings/strike-zones.md learn-to-play/scales/pentatonic-warmups.md learn-to-play/tunes/first-melody.md ``` ## Coupon tests recommended - **Slip-roll minimum radius** — bend a 1.2 mm × 320 mm × 100 mm CRS strip to 50 mm radius before committing the drum-5 shell blank. If spring-back > 5°, drop drum-5 to 1.0 mm stock. - **Bend allowance verification** — bend one bracket blank (60 × 60 × 1.2 mm) with two 90° folds at 20 mm and 40 mm; verify final dimensions match the bend-table.csv prediction within 0.3 mm. - **TIG seam on a shell offcut** — practice the butt-weld seam on a 100 mm rolled section of scrap before committing to a shell. - **Bearing-edge chamfer on lathe** — set up the 4-jaw chuck on one offcut and cut a 45° chamfer; verify finish quality and contact-patch width. ## Confidence - Acoustic targets: **medium** — Bessel model is sound; air-load and stiffness corrections roughly cancel; expect ±20 cents from prediction to first tuning. - Flat patterns: **medium-high** — circumference math is exact; bend allowance matches a competent shop's expectations. DXF files are not produced. - Fabrication plan: **medium-high** — sequence is conventional sheet-metal + TIG work; the slip-roll min-radius on drum-5 is the only soft spot. - BOM: **medium** — sources verified by name; SKU details and pricing are ballpark. ## Suggested next-round task A natural follow-up is **CAD authority**: drive the SolidWorks model with the design table here, export DXF flat patterns for all 5 shells + brackets + base, and generate the STEP kit. Also: a `sheet-music` skill pass to extend the `learn-to-play/tunes/` content with proper notation and audio renderings. A v0.2-physical round would be the build itself — order materials per `supplier-rfq.md`, fabricate per `fabrication-plan.md`, fill the `measured` column of `validation.csv`, and capture photos from `photo-shotlist.md`.