[family] guitar_tuning_machine_head: sealed geared tuning machine

[BenchCAD]

Family

• Family: guitar_tuning_machine_head — cat:music-hardware
• Closes [family] guitar_tuning_machine_head #9

Reference (issue #9 — Grover Rotomatic 102 / Gotoh SG381)

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 sealed geared tuning machine: baseplate + sealed gear housing + string post with
a press-in bushing collar + worm/key shaft + a locating-screw hole. 11 params, one
feature (worm_both_sides = key shaft exits one side or both). The 14:1–18:1 gear
ratio is internal and not a CAD dimension here.

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

difficulty	baseplate_l	baseplate_w	plate_t	housing_w	housing_h	post_d	solids	valid	bbox (mm)
easy s0	28.18	12.81	1.23	18.1	16.88	6.26	1	yes	28×14×45
medium s0	31.29	12.49	2.01	17.19	19.42	5.87	1	yes	31×14×41
hard s0	32.5	13.4	2.24	27.93	23.29	5.96	1	yes	32×16×53
hard s1	32.8	17.6	1.29	27.28	14.37	5.92	1	yes	33×21×45
hard s2	32.78	17.13	2.55	18.45	22.94	5.97	1	yes	33×19×52

bench2 validate guitar_tuning_machine_head --seeds 5 → PASS (11 params, difficulties distinct, 15/15 unique shapes).

Checklist

• bench2 validate passes locally (CI re-runs it)
• all four renders committed; the part matches the Grover/Gotoh drawings across tiers + extremes
• one family, only designs/guitar_tuning_machine_head/, body has Closes #9
• DCO-signed; sources cited, nothing fabricated

Sources used

• Grover Rotomatic 102 dimensioned drawing (WD Music): post Ø6, bushing Ø7.8–9.9, housing ~27×24 mm, post height ~27 mm, mount screw Ø2.6.
• Gotoh SG381 drawing: post Ø6, hex bushing OD 14 mm, housing ~27×22 mm.

Note: housing/post/bushing/key-shaft modelled as primitives at catalog sizes;
the internal worm-and-wheel and the tuning button are not modelled.

[github-actions]

bench2 validate

guitar_tuning_machine_head

  ✓ family.json: keys + base_plane valid
  ✓ pieces: build(11 params) + PARAM_SPEC + check present
  ✓ PARAM_SPEC: 11 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/guitar_tuning_machine_head

Previews: see the previews artifact on this run.

[HaozheZhang6]

Validate passes. Dims match the Grover Rotomatic drawing (post Ø6, bushing ~Ø9.9, housing ~27×24, mount Ø2.6), and sealing the gear housing as a solid box is fine — the gears are internal and hidden, so there's nothing to reconstruct there.

Two features from the reference are dropped, both external and visible in every view:

• Tuning button / key. The worm shaft is only a ~2 mm stub poking out the housing side with nothing on the end. The button is the single most recognizable feature of a tuner; without it the part reads as "a post on a box." Stand the key shaft off the housing and put a button/knob on its end.
• String hole through the post. The post is a plain cylinder — add the transverse string hole near its top.

Everything else (baseplate, bushing collar, mount hole, one/both-sides shaft toggle) is a reasonable representation.