What it is
Four parametric fixtures that hold the 223 × 65 × 50 mm model block by its 6 mm tether groove — printed, machined, zero-hardware, and a rotary carrier that flips it 180° without unloading it. A 21-section guide whose tables are generated from the CAD reports.
Version history
Straight from the project’s own card data — what each version added.
SLOTRAIL-223 — 5 printed parts, 298 g, 94 mm² support. The block hangs on the rail; flip = lift off and roll.
SLOTRAIL-223-M — machined: base, 2 saddles, 2 caps, collar, bought bar. 2.0 kg, ≤2 setups, 0 sloped faces.
SLOTRAIL-223-ZH — zero hardware: integral dovetail + 10° self-locking wedge. 439 g, 49 mm² support.
SLOTRAIL-223-X — rail-as-axle rotary carrier, lever-throw 180° indexed by a 5 mm pin; jaw travels 20 mm.
The guide: 21 sections, 478,737 B, seven cross-variant sections generated from the reports; verify_guide.py clean, 8/8 builds, 3/3 print audits.
Files on the site
What broke, and what I’d change
Not written yet. This is the part only I can write — what actually went wrong, and what I’d do differently. It lives in builds/reflections/f1-jig.md (see _TEMPLATE.md); as soon as that file has words in it, this section fills in on the next build.
Everything else on this page — the spec, the version history, the file counts — is generated from the project’s own build notes and files, so nothing here is guesswork.
Build spec
The project’s own build notes, rendered. Open the raw .md ↗
Show the spec
F1 Model Block Jig — four fixtures, one datum
Category: Parametric CAD (build123d) · Status: Done, unprinted
Four fixtures that hold the official 223 × 65 × 50 mm F1 in Schools model block while it is machined: a printed pair of beds, a machined aluminium version, a zero-hardware version with no screws at all, and a rotary carrier that flips the block through 180° without unloading it. One self-contained guide.html — 21 sections, every table generated from the CAD report files.
Stack / Tools: F1 in Schools (Development Class, 2024-25), build123d 0.13, numpy-stl, Playwright, FDM printing, 3-axis CNC.
Build path:
- V1 — SLOTRAIL-223. Two printed beds + rail + collar. 5 parts, 298 g. The block hangs on a 6 mm rail
- V2 — SLOTRAIL-223-M. Same datum, machined: base plate, two saddles, two clamp caps, collar. 2.0 kg of
- V3 — SLOTRAIL-223-ZH. Zero hardware: integral sliding dovetail joins the halves, a sliding wedge on a
- V4 — SLOTRAIL-223-X. The rail becomes an axle. Lever-throw 180° flip with a 5 mm detent pin in a
- V5 — the guide. Seven cross-variant sections (choose / BOM / every part / assembly / the numbers /
in its own tether groove; flip = lift off, roll, put back.
6061, ≤2 setups, 0 sloped faces, bought 6 × 6 mm ground bar.
10° self-locking incline replaces every screw. 5 parts, 439 g.
5.05 mm hole, jaw travels 20 mm so 203–223 mm blocks fit, 10 parts / 448 g.
evidence / files) generated from the four report files, plus per-fixture build sequences with the measurement that catches each step going wrong.
Why the groove. Every commercial jig clamps the outer faces, which are the two surfaces the rules do not control — a 65.4 mm block is legal and sits crooked in a 65.0 mm vice. The 6 × 6 mm tether groove is moulded, full length, and 6.00 mm on every block, so it is the datum. Seat 74.000, rail top 80.000, mirror plane 77.000, X stop 223.000 — identical in all four reports, so one CAM formula covers every fixture.
The numbers that matter. Block solid 703,489.6 mm³, 9/9 official dimensions exact. Fixture ∩ block 0.000 mm³ in both operations. Rotary sweep of 37 poses 0°→180°: worst case 0.000 mm³ at 0°. Detent slop 0.169° = 0.191 mm across the face, against a 1.0 mm rule. Printed rail sags 0.61 mm over 291 mm versus 0.01 mm for bought ground bar — which is why the BOM says buy the bar.
Not proven. None of the four has been printed or cut. The 5.9 mm rail in a 6.0 mm groove leaves 0.1 mm to a ±0.2 mm printer. The rotary version indexes at 0° and 180° only — at 90° the block droops 0.96°, which is 0.83 mm across the face. Every one of these is written into the guide, with the test that would settle it.