[family] drum_tension_lug

[BenchCAD]

Family: drum_tension_lug
Category: Musical Instrument Hardware — cat:music-hardware (#4)
Anchor: SD Sparedrum L-series — https://sparedrum.com/drum-parts-lugs (cross-checked: Pearl 2016 spare-parts catalog, vintagedrumreference tension-rod guide)

A drum shell tension lug: a cast/chromed body screwed to the outside of the shell that houses a threaded insert; the tension rod passes through the counterhoop and threads into the lug to tension the drumhead.

Claim it: self-assign, then re-verify the evidence below before coding.
Done = one scoped PR (designs/drum_tension_lug/ only) that closes this issue.
Start here: AGENTS.md + docs/DESIGN_SPEC.md.

Reference images

Datasheet drawing	Part photo

Dimension table

Model	Type	Body L×H×W mm	Hole spacing mm	Mount hole Ø mm	Rod thread
L20BD	bass, single	42×27×23	25	6	#12-24 (7/32")
L20SDTT	snare/tom	42×23×23	25	6	#12-24
L16SDTT	snare/tom	—	38	6	#12-24
L16BD	bass	—	57	6	#12-24
L13BD	bass, single-point	—	(single)	8	#12-24
min		42×23×23	25	6	—
max		42×27×23	70+	8	—

Within one supplier, mount-hole Ø and rod thread are ~constant (6 mm / #12-24); body H/W/L and hole spacing (25-70 mm, 44 discrete c-c values) vary. Rod thread varies across makers: #12-24 / 7-32 (US standard), #10-32 & M5 (DW/PDP), 1/4-20 (Sonor), M6 (bass claws) — Pearl catalog + vintagedrumreference.

Parameters to verify at claim

• body_length: 42 mm (compact) up to 150-300 mm (full-length tube lugs) — Sparedrum / Pearl
• body_height: 23-27 mm — Sparedrum L20 pair (same length & spacing, different height ⇒ independent)
• body_width: ~20-23 mm — Sparedrum / US8759653B2 cross-check (~20.6 mm)
• mount_hole_spacing: 25-70 mm (44 discrete c-c values) — Sparedrum facet
• mount_hole_diameter: 6 or 8 mm — Sparedrum SKUs
• rod_thread: [family] round_duct_butterfly_damper: round HVAC balancing damper #12-24 / 7-32 baseline; M5 / 1/4-20 / M6 exceptions — Pearl cross-check

Engineering constraints

• the threaded insert receives the rod perpendicular to the drumhead plane — sets the rod entry axis
• two mount screws straddle the shell centerline at the hole spacing — symmetric load into the shell
• lug length < drum depth − 2× bearing-edge margin — else the lug overhangs the shell

[github-actions]

✅ Registry check: drum_tension_lug collides with none of the 0 known names.

Thanks for the proposal! Whoever claims this verifies it first — the
5-minute evidence check in CONTRIBUTING.md ("Claiming an issue = you verify it"):
standard link real · dimensioned drawing · table with min/max rows · two numbers spot-checked.

Gaps? Fill them yourself (credited) or label needs-evidence with one comment naming what's missing.

新人中文指南: GETTING_STARTED.zh.md · Questions → Discord

[BenchCAD]

Superseded by #78 (stop_bar_tailpiece) per maintainer review: this example is too obscure, and its "drawing" is dimension arrows overlaid on a product render — not a true 2D orthographic sheet, which is now the reference standard (#76). The replacement is a common part with Gotoh's official parametric 2D multi-view drawing. Closing; the name stays in the registry as proposed history.