# Risk Register — Bass Surface Drum ## Safety | Risk | Likelihood | Severity | Mitigation | |---|---|---|---| | TIG arc burn / UV exposure during 2513 mm seam weld | medium | medium | Full PPE, rest hands every 30 mm, attempt back-purge to reduce sugaring | | Slip-roll pinch on 2600 mm blank | medium | high | Two-person operation, roller stand for trailing edge | | Bead-roller hand pinch on final pass | low | medium | Push sticks for last 100 mm | | Clamp ring drop (14 kg 4 mm plate) | medium | medium | Two-person lift, gloves, protect bearing flange | | Sharp edges on un-deburred frame blank | high | low | Deburr after every cut before forming | | Paint VOC exposure during cure | medium | medium | Ventilated cure space, 24 h before any contact | | M10 bolt under tension snapping during tuning | low | high | Grade 8.8 minimum; replace any bolt that has been over-torqued past 25 Nm | ## Ergonomic | Risk | Likelihood | Severity | Mitigation | |---|---|---|---| | Drum too heavy to carry one-handed | high | low | This is a stage/floor instrument; document carrying with a strap or two-person carry | | Mallet causes hand fatigue | low | low | Bought mallets have well-known handles; not a fabrication concern | | Player strikes the bearing flange and dents head | medium | low | Strike zone is at least 100 mm inside the flange; document in `assembly-manual.md` | ## Manufacturability | Risk | Likelihood | Severity | Mitigation | |---|---|---|---| | 4 mm bearing-flange radius cracks CRS at the bend | medium | medium | Coupon test before production; fallback to 6 mm radius or local anneal | | Cylinder rolls oval instead of round | medium | high | Multi-pass rolling, measure at 6 points every pass, jig if needed | | Seam weld craters at start/stop | medium | medium | Use TIG runoff tabs (extra material before and after the seam) | | Stiffening bead doesn't reach 3 mm depth | medium | high | Add 4th pass if needed; if still shallow, add a separate welded-in ring | | Doubler doesn't lay flat against inside of curved frame | medium | low | Pre-roll the doubler to roughly match frame ID before spot-welding | | Lug-bracket PCD drifts off true | medium | medium | Use a jig — wood disk with 6 wedges glued at 60° spacing | ## Acoustic-failure modes | Risk | Likelihood | Severity | Mitigation | |---|---|---|---| | Fundamental lands above 60 Hz (too tight) | medium | low | Loosen in star pattern; if still high, swap to heavier σ head | | Fundamental lands below 42 Hz (too loose) | medium | low | Tighten in star pattern; if still low, swap to lighter σ head or smaller diameter | | Off-center strike does not excite (1,1) cleanly | low | medium | Re-tension head evenly; check for one-lug-overtightened condition | | Azimuthal pitch varies > 1 Hz around rim | medium | medium | This means head tension is uneven — full re-tension start over from finger-tight | | Bearing flange contact is uneven | medium | high | Frame is out of round; this requires re-rolling or a new frame | | Head develops dead spot over time | low | medium | Hide may be drying unevenly; condition flesh side only, not strike face | | Hide cracks at first full-tension state | low | high | Hide was over-tensioned while wet; release immediately, dry slowly, retry with new hide | | Cinematic mallet too hard, produces high-frequency artifact | low | low | Choose softer mallet (felt vs. wool); the bought mallet matters | ## Supply | Risk | Likelihood | Severity | Mitigation | |---|---|---|---| | Hide supplier out of stock for thick steerhide | medium | medium | Document synthetic Remo bass head as fallback; will shift acceptance band slightly | | CRS sheet from service center delivered out of spec | low | medium | Measure incoming and reject if outside +/- 5% on thickness | | Laser-cut clamp ring delivered with rough kerf | medium | low | Specify "deburred" in RFQ; if not deburred, hand-deburr before paint | ## IP / Release | Risk | Likelihood | Severity | Mitigation | |---|---|---|---| | Dual license confusion downstream | low | low | LICENSE pointer file + per-file SPDX headers (this packet follows that) | | Hide sourcing flagged as ethical concern | medium | low | Document supplier provenance; offer synthetic-head alternative as default for ethically-concerned makers | ## Release Gates The packet remains **private** until each of these is cleared: - [ ] Human frame-drum player review (someone who has played 800 mm-class frame drums) - [ ] Metal-forming safety/process review by shop lead - [ ] Supplier/IP/public-release review - [ ] Measured V0 prototype validation data exists in `validation.csv` - [ ] At least one capstone photo set has been shot per `photo-shotlist.md` ## Sandbox / Manager notes This packet was authored in a Claude sprint pane. The repo was successfully `gh repo create`d as `tonykoop/bass-surface-drum` and pushed; subsequent commits go through gh PR + squash-merge cycles. No sandbox-DNS blockage was hit for this lane.