3xD 1.7-rc2 release notes
10 November 2026 · Release candidate · Pending owner approval
Compared with the previous complete 1.6-rc1 kit, 1.7-rc2 raises both front hub spring seats by 1 mm to compensate for the selected 5 mm front springs. Both complete chassis packs now include the raised hubs and updated spring hardware records. Only the two hub STL files change; the other 41 selections are identical.
Raised front spring seats
The upper annular seat extends from local 11 mm to 12 mm along the kingpin. The lower hub, axle centre, steering tab and selected 4.75 mm kingpin bore are preserved, as are the H0 steering-link, axle and hex interfaces. This is a local addition, not an overall hub stretch.
Replace both handed hubs for this setup. Reuse the arms, camber-only upper brace, lower root tie and existing top shims. No additional spacer or kingpin-length change is specified. Do not mix old and raised hub heights or assume a 6 mm spring has clearance in the raised setup.
Stored front-spring hardware
| Item | Current specification |
|---|---|
| Quantity | Two front springs per car |
| Free length | 5 mm |
| Outside diameter | 6 mm |
| Intended wire grades | Soft 0.40 / medium 0.42 / hard 0.44 mm |
| Hub pairing | Both revised 12 mm-seat hubs, +1 mm upper seat |
| Solid height, rate and installed preload | Unmeasured for the new springs |
The intended kit default remains medium 0.42 mm wire, but matching 0.42/0.44 stock has not been verified. The found 0.40 × 6 × 5 mm Amazon listing is a soft trial, not a tested medium substitute. No alternative wire range is selected. Both hardware lists and the included front_spring_current.json now record the 5 mm spring and raised-hub pairing explicitly.
The 5 mm free-length selection was already included in 1.6-rc1; the new change is the hub-seat compensation and its build guidance. Do not reuse the old 6 mm spring’s reported 1.4 mm solid height for the new springs.
Complete downloads
- Download 1.7-rc2 — complete 3 mm GRP chassis kit
- Download 1.7-rc2 — complete 4 mm printed chassis kit
Each kit retains 43 distinct STL selections and 46 required part instances, including fit-pending rear bearing inserts. Both setup-specific chassis, bumper and rear ride-height selections remain intact; both use a 3 mm pod plate. Default 4-1 arms use the 1° camber brace. Hardware lists, structured spring information, cutting DXFs, manifests, hashes, CAD pictures and validation are included. No G-code is supplied.
Validation and remaining checks
The hub geometry is unchanged from the partial 1.7-rc1 candidate, now superseded by these complete packs. Prior CAD checks verified closed single solids, a flat +1 mm seat, preserved lower interfaces and exact mirroring. Complete inventory and frozen artifact hashes were checked: two hubs changed from 1.6-rc1, 41 STL files unchanged.
At an unchanged axle and upper-seat position, the 1 mm smaller gap restores the geometric compression lost by shortening a spring from 6 to 5 mm. This does not establish spring force or usable travel. If solid height is unchanged, coil-bind margin is 1 mm smaller. Check full bump, droop retention, kingpin sliding and steering with the actual springs. Existing bearing-fit, strength and endurance checks remain pending. No print job was sent; publication is not release approval.