[family-assembly] swivel_ball_joint_mount: JW Winco GN 784 mounting clamp

designs/swivel_ball_joint_mount/NOTES.md

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+# GN 784 modeling notes
+
+## Evidence boundary
+
+- Anchor: JW Winco GN 784 official product page and US catalog PDF
+  (`https://www.jwwinco.com/en-us/products/3.6-Moving-Transferring-Connecting-with-Joints-Couplings-and-Gears/ball-joints/GN-784-Aluminum-Mounting-Clamps-with-Swivel-Ball-Joint`
+  and `https://live-catalog.jwwinco.com/pdf/winco/us/784.pdf`).
+- The eight entries in `_CATALOG_ROWS` reproduce the eight printed table rows.
+  Each row carries `d1`, the nonblank `d2`/`d3`/`d4` alternatives, applicable
+  `r1` or `r2`, `l1`, and the complete common row (`d5` through torque).
+- Type A maps only to a published `d2` or `d3` field. Type B maps only to a
+  published `d4` field. A blank field returns no catalog combination.
+- Internal usable thread depth follows the catalog footnote: `1.5D` for metric
+  `d2`/`d3` and `1.2D` for inch `d3`. Type B uses the printed external-stud
+  length `l1`.
+- Finish is fixed to ELS metadata and is not sampled. Clamp and stop torques
+  remain source metadata; they are not converted into performance claims.
+
+## Difficulty and coupling
+
+- `catalog_row` selects a complete printed row; dimensions never interpolate.
+- `refine()` jointly chooses `ball_type` and `thread_code` from that row's
+  nonblank alternatives.
+- Easy: rows `31-M5/M6` and `39-M5/M6`, metric Type A, identification 2.
+- Medium: metric alternatives from all eight rows, Type A/B, identification
+  1/2, with 0 or 30 degree ball poses.
+- Hard: every published metric or inch alternative from all eight rows,
+  Type A/B, identification 1/2, with 0, 30, or 90 degree ball poses.
+
+## Explicit proportion rules
+
+The drawing does not dimension the hidden socket seat, base-seat fit, split,
+clamp screw body, lever body, socket recess, small steps, fillets, chamfers,
+thread helices, casting draft, or surface texture. They are deliberately
+simplified and sourced as `proportion`:
+
+- spherical seat radial clearance:
+  `max(0.20 mm, 0.012*d6)`;
+- base seat diametral member: `base_d = 0.80*d1`;
+- base seat radial clearance:
+  `max(0.15 mm, 0.008*d1)`;
+- base thickness: `0.28*h3`;
+- top opening radius:
+  `max(0.44*d6, d7/2 + spherical_seat_clearance)`;
+- clamp screw diameter: `0.18*d1`;
+- clamp screw radial clearance:
+  `max(0.20 mm, 0.012*d1)`;
+- 90 degree stem-sweep slot: lower thin-neck diameter plus radial running
+  clearance `max(0.25 mm, 0.010*d1)`; the resulting slot remains narrower
+  than the `d7` middle collar;
+- lower thin ball-neck diameter: `0.55*d7`;
+- lower thin ball-neck length: from its `0.58*(d6/2)` sphere overlap to beyond
+  the housing outside radius by `max(0.60 mm, 0.030*d1)`; this is also longer
+  than the housing radial wall thickness;
+- lever handle width: `0.20*l2`;
+- lever handle thickness: `0.17*d1`;
+- identification 2 head length: `0.16*d1`.
+
+Threads are represented by nominal cylindrical holes/studs, not helices.
+Small edge treatments and casting draft are omitted for deterministic,
+reviewable geometry.
+
+## Static assembly and deliberate deviations
+
+- The result is a four-solid `cq.Assembly` named `housing`, `ball`, `base`, and
+  `clamp_actuator`. It encodes no mates or joints; `swivel_angle` selects a
+  deterministic static pose from vertical (0 degrees) to horizontal
+  (90 degrees).
+- The housing slot clears the complete 0-90 degree sweep of only the lower
+  thin neck toward the side opposite the clamp actuator. The neck reaches
+  beyond the housing outside surface before the `d7` middle collar begins, so
+  the middle collar stays outside and the slot can remain narrower than it.
+  The drawing's separate 360-degree annotation is not exposed as an
+  unsupported second motion axis.
+- The ball stem is modeled as a lower thin neck, a thick `d7` middle collar,
+  and a thin upper threaded member. Type A cuts the sourced internal usable
+  thread depth down the upper member; Type B keeps the upper stud solid.
+- The ball is separated from its spherical seat by the documented proportion
+  clearance while the opening remains smaller than `d6`, preserving capture.
+- The base plate sits in a clearance pocket. The `d5` thread and offset `d8`
+  anti-rotation hole are plain cylindrical cuts.
+- Hidden clamping wedges, pins, retainers, screw tips, lever reindexing
+  mechanism, hand-knob option, GN 784.1 flange, payload hardware, and surface
+  texture are excluded as required by Issue #60.

designs/swivel_ball_joint_mount/family.json

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+{
+  "family": "swivel_ball_joint_mount",
+  "standard": "JW Winco GN 784",
+  "base_plane": "XY",
+  "description": "A four-component aluminum GN 784 mounting clamp with a captured 0-90 degree swivel ball, Type A or B thread, and adjustable-lever or hex-socket clamp actuator.",
+  "source": "JW Winco GN 784 official product page and catalog PDF; documented proportion rules for unmarked construction details",
+  "contributor": "sunzhenchuan007",
+  "solids": 4,
+  "components": [
+    {
+      "name": "housing",
+      "quantity": 1,
+      "description": "Black-anodized cylindrical socket housing"
+    },
+    {
+      "name": "ball",
+      "quantity": 1,
+      "description": "Plain-aluminum captured ball with the selected Type A or B boss"
+    },
+    {
+      "name": "base",
+      "quantity": 1,
+      "description": "Plain-aluminum bottom base plate with d5 and d8 holes"
+    },
+    {
+      "name": "clamp_actuator",
+      "quantity": 1,
+      "description": "Selected identification 1 adjustable lever or identification 2 set screw"
+    }
+  ]
+}