[family] round_duct_butterfly_damper: round HVAC balancing damper

[BenchCAD]

Family

• Family: round_duct_butterfly_damper — cat:hvac-ductwork
• Closes [family] round_duct_butterfly_damper #6

Reference (issue #6 — Ruskin MDRS25 / CDR94)

Datasheet drawing	Part photo

Generated — benchmark views (what the model sees)

Three-view + iso — hard example

Extremes — smallest & largest sampled instances

How it's parameterized

A round manual balancing / butterfly damper in the closed position (frame spool + blade disc on a diametral shaft + hand-quadrant shaft extension). 8 params, one feature (square_shaft = MDRS25 square axle vs CDR94 round axle). Frame depth / blade / shaft ranges come from the Ruskin size tables.

Verification (every sampled instance — one non-degenerate solid)

difficulty	duct_d	wall	frame_depth	blade_t	shaft_d	handle_ext	solids	valid	bbox (mm)
easy s0	266.5	1.09	151.02	1.52	20.13	63.26	1	yes	341×267×151
medium s0	453.96	1.25	153.69	1.57	38.46	85.64	1	yes	555×454×154
hard s0	676.9	1.47	156.97	1.64	63.68	113.02	1	yes	811×677×157
hard s1	565.52	2.9	174.51	9.56	30.58	73.87	1	yes	667×566×175
hard s2	342.83	1.53	288.42	2.28	49.61	98.28	1	yes	451×343×288

bench2 validate round_duct_butterfly_damper --seeds 4 → PASS (8 params complete, difficulties distinct, 12/12 unique shapes).

Checklist

• bench2 validate passes locally (CI re-runs it)
• all three renders committed and match the reference across easy/medium/hard + extremes
• one family, only designs/round_duct_butterfly_damper/, body has Closes #6
• DCO-signed; every source/check() cites a real rule or honest proportion — nothing fabricated

Sources used

• Ruskin MDRS25 (light manual quadrant) + CDR94 (heavy control) round-damper datasheets — frame depth 152/229/305 mm, blade 1.5–10 mm, axle 10–76 mm, Ø 102–1829 mm.
• wall, handle_ext, stub — sheet gauge / quadrant standoff (proportion).

[github-actions]

bench2 validate

round_duct_butterfly_damper

  ✓ family.json: keys + base_plane valid
  ✓ pieces: build(8 params) + PARAM_SPEC + check present
  ✓ PARAM_SPEC: 8 params, all entries complete
  ✓ easy: 4/4 seeds sample+check+build+execute clean
  ✓ medium: 4/4 seeds sample+check+build+execute clean
  ✓ hard: 4/4 seeds sample+check+build+execute clean
  ✓ difficulty separation: difficulties produce distinct programs
  ✓ geometry novelty: 12/12 unique shapes (0% duplicate)
  ✓ solids: every instance non-degenerate, 1 solid(s) each
PASS — designs/round_duct_butterfly_damper

Previews: see the previews artifact on this run.

[HaozheZhang6]

Checked against the Ruskin MDRS25/CDR94 tables in #6: the size ranges, wall<=D/40 (rolled sheet), shaft_d<=0.20*D axle ratio, and blade/bore/handle constraints all read as engineering-true. Ran bench2 validate in a clone — passes, 12/12 unique. Renders show the frame spool, the closed blade disc across the bore, the diametral shaft with bearing stub + handle extension, and the round-vs-square axle toggle; the blade is visible down the bore so it reconstructs from the views. Extremes sane.

Didn't check: whether the blade should carry any offset/seal detail in the closed position — modelled here as a plain disc coincident with the bore wall.