SaltyBot Chassis — Bill of Materials
Task: bd-1iy5 / prototype-baseplate
Rev: C — 2026-02-28 (vertical stem architecture; batteries on mast carousel)
Agent: sl-mechanical
⚠ Axle Measurement Update (Rev B)
PR #7 (chassis_frame.scad) used placeholder values. The table below records the
caliper-verified hub motor axle dimensions. All new designs must use these.
| Feature |
Measured |
PR #7 placeholder |
Delta |
| Axle base diameter (round, near hub) |
16.11 mm |
14 mm |
+2.11 mm |
| D-cut shaft OD |
15.95 mm |
— (not modelled) |
new |
| D-cut flat chord |
13.00 mm |
— |
new |
| Total axle protrusion |
65.5 mm |
~60 mm est. |
+5.5 mm |
| Base section length |
15.0 mm |
— |
new |
| D-cut section length |
43.35 mm |
— |
new |
| Tip / shoulder |
3.0 mm |
— |
new |
| Bearing seat collar OD |
37.8 mm |
— |
new |
| Tire OD |
254 mm (10×2.125") |
170 mm motor OD only |
— |
| Axle CL height above ground |
127 mm |
310 mm (wrong) |
−183 mm |
chassis_frame.scad should be updated in a follow-on task to match Rev B values.
Structural / Fabricated Parts
Prototype Base Plate (prototype_baseplate.scad) — Rev C
Batteries are removed from the base plate. Plate is now compact (680×130mm).
Stem socket replaces battery tray. See Part B (stem clamp) below.
| # |
Part |
Qty |
Material |
Cut size |
Notes |
| 1 |
Base plate |
1 |
6mm 5052-H32 Al or 8mm acrylic |
680×130mm blank |
RENDER="plate_2d" → DXF |
| 2 |
Dropout clamp — lower |
2 |
8mm 6061-T6 Al |
90×70mm blank |
Round bore Ø16.51mm; RENDER="clamp_lower_2d" |
| 3 |
Dropout clamp — upper |
2 |
8mm 6061-T6 Al |
90×70mm blank |
D-cut bore; RENDER="clamp_upper_2d" |
| 4 |
Stem flange ring |
2 |
6mm Al or acrylic |
Ø82mm disc |
One above + one below plate; RENDER="stem_flange_2d" |
| 5 |
Vertical stem tube |
1 |
38.1mm OD × 1.5mm wall 6061-T6 Al |
1050mm length |
1.5" EMT conduit is a drop-in alternative |
| 6 |
MCU standoff M3×6mm nylon |
4 |
Nylon |
— |
ESP32 BALANCE / IO board isolation (dimensions TBD) |
| 7 |
Ø4mm × 16mm alignment pin |
8 |
Steel dowel |
— |
Dropout clamp-to-plate alignment |
Battery Stem Clamp (stem_battery_clamp.scad) — Part B
| # |
Part |
Qty |
Material |
Notes |
| 8 |
Collar half |
2 |
PETG FDM (5 perimeters, 40% infill) |
Print flat-side-down; mirror 2nd in slicer. Bore Ø38.6mm |
| 9 |
Radial arm |
4 |
4mm 5052-H32 Al (laser-cut) or PETG FDM |
RENDER="arm_2d" for DXF with ARM_THICK=4; or print at 8mm |
| 10 |
Battery cradle |
4 |
PETG FDM (4 perimeters, 30% infill) |
U-channel, open top; holds 1 pack per cradle |
| 11 |
M6×60 SHCS |
4 |
SS |
2 collar clamping bolts × 2 sides |
| 12 |
M6 hex nut |
4 |
SS |
Captured in collar nut pockets |
| 13 |
M6×12 set screw |
2 |
SS, cup-point |
1 per collar half for height lock |
| 14 |
M4×20 SHCS |
8 (16 for 4) |
SS |
Arm-to-collar bolts (2 per arm) |
| 15 |
M4×16 SHCS |
8 (16 for 4) |
SS |
Cradle-to-arm bolts (2 per cradle) |
| 16 |
M4 hex nut |
16 (32 for 4) |
SS |
Nuts for items 14 + 15 |
| 17 |
Velcro strap 25mm × 600mm |
4–8 |
— |
1–2 per battery pack through cradle slots |
Full Chassis (chassis_frame.scad) — Rev A (placeholder values — pending Rev B update)
| # |
Part |
Qty |
Material |
Notes |
| 6 |
Main deck plate |
1 |
6mm 5052 aluminium plate, 640×220mm |
CNC router or waterjet; all holes per chassis_frame.scad |
| 7 |
Longitudinal rib (front) |
1 |
4mm 5052 aluminium, 600×40mm |
Laser-cut; press-fit into deck slots |
| 8 |
Longitudinal rib (rear) |
1 |
4mm 5052 aluminium, 600×40mm |
Same file, symmetric |
| 9 |
Motor fork bracket (L) |
1 |
8mm 6061 aluminium |
Update fork slot to Ø16.51mm before cutting |
| 10 |
Motor fork bracket (R) |
1 |
8mm 6061 aluminium |
Mirror of item 9 |
| 11 |
Battery tray |
1 |
3mm PETG FDM or 3mm aluminium fold |
chassis_frame.scad — battery_tray() module |
| 12 |
FC mount plate / standoffs |
1 set |
PETG or nylon FDM |
Includes 4× M3 nylon standoffs, 6mm height |
| 13 |
Jetson Nano mount plate |
1 |
4mm 5052 aluminium or 4mm PETG FDM |
B01 58×58mm hole pattern |
| 14 |
Front bumper bracket |
1 |
5mm PETG FDM |
Saddle clamps for 22mm EMT conduit |
| 15 |
Rear bumper bracket |
1 |
5mm PETG FDM |
Mirror of item 14 |
Motors
| # |
Part |
Qty |
Source / Spec |
Notes |
| 16 |
Hoverboard hub motor |
2 |
10×2.125" pneumatic tire, 36V nominal, ~350W |
Axle: Ø16.11mm base / Ø15.95mm D-cut / 13mm flat; bearing seat Ø37.8mm — all caliper-verified |
| 17 |
Motor hall-sensor cable extension |
2 |
6-pin JST-PH 300mm |
Route through deck cable slot |
| 18 |
Axle lock nut |
4 |
M16×1.5 or thread-matched to actual axle tip |
Confirm thread at tip before ordering; calipers show Ø≈10mm at tip |
Electronics Mounts
⚠️ ARCHITECTURE CHANGE (2026-04-03): Mamba F722S (STM32F722) is retired.
Replaced by ESP32 BALANCE + ESP32 IO. Board dimensions and hole patterns TBD — await spec from max.
| # |
Part |
Qty |
Spec |
Notes |
| 13 |
ESP32 BALANCE board |
1 |
TBD — mount pattern TBD |
PID balance loop; replaces Mamba F722S |
| 13b |
ESP32 IO board |
1 |
TBD — mount pattern TBD |
Motor/sensor/comms I/O |
| 14 |
Nylon M3 standoff 6mm |
4 |
F/F nylon |
ESP32 board isolation |
| 15 |
Anti-vibration grommet M3 |
4 |
Ø6mm silicone |
Under ESP32 mount pads |
| 16 |
Jetson Orin module |
1 |
69.6×45mm module + carrier |
58×58mm M3 carrier hole pattern |
| 17 |
Nylon M3 standoff 8mm |
4 |
F/F nylon |
Jetson board standoffs |
Battery (Vertical Stem Mount — Rev C)
Batteries mount VERTICALLY on the stem carousel, not on the base plate.
Each pack stands upright (420mm tall) in a cradle at the end of a radial arm.
| # |
Part |
Qty |
Spec |
Notes |
| 18 |
Battery pack |
2–4 |
24V, 420×88×56 mm each (caliper-verified) |
Snap into battery cradle from above |
| 19 |
BMS board |
1 |
Matched to cell chemistry |
Mount to stem or base plate underside; run wiring down stem |
Battery stem clamp — configuration guide
| Config |
Arm count |
Carousel weight |
Balance |
Notes |
| 2-pack |
2 arms, 180° apart |
~1.4 kg |
✅ Symmetric |
Minimum configuration |
| 4-pack |
4 arms, 90° apart |
~2.8 kg |
✅ Symmetric |
Maximum practical config |
| 3-pack |
3 arms, 120° apart |
~2.1 kg |
⚠ Asymmetric mass |
Needs counter-balance or avoid |
CG height tuning
Slide entire carousel up/down the stem with M6 collar bolts loosened. Tighten at desired height. Typical balance point (initial estimate): batteries centred at 450–600 mm above base plate. Adjust in ≈50 mm increments during commissioning.
Bumper Rail
| # |
Part |
Qty |
Spec |
Notes |
| 21 |
3/4" EMT conduit |
2 |
22mm OD, 660mm length |
Front and rear bumper rail; bent or straight |
| 22 |
Conduit saddle clamp M4 |
6 |
3D-printed integral to bracket (items 9/10) |
Back-up: standard pipe clamp 22mm |
Fasteners
| # |
Part |
Qty |
Spec |
Use |
| 20 |
M5×16 SHCS |
16 |
ISO 4762, SS |
Dropout clamp bolts (4 per clamp × 4) |
| 21 |
M5×20 SHCS |
8 |
ISO 4762, SS |
Stem flange bolts (4 per flange × 2) |
| 22 |
M5 hex nut |
24 |
ISO 4032, SS |
|
| 23 |
M4×20 SHCS |
16 |
ISO 4762, SS |
Arm-to-collar (2 per arm × 4 arms × 2) |
| 24 |
M4×16 SHCS |
16 |
ISO 4762, SS |
Cradle-to-arm (2 per cradle × 4 arms × 2) |
| 25 |
M4 hex nut |
32 |
ISO 4032, SS |
|
| 26 |
M6×60 SHCS |
4 |
ISO 4762, SS |
Collar clamping bolts |
| 27 |
M6 hex nut |
4 |
ISO 4032, SS |
Captured in collar pockets |
| 28 |
M6×12 set screw |
2 |
ISO 4026, SS cup-point |
Stem height lock (1 per collar half) |
| 29 |
M3×10 SHCS |
12 |
ISO 4762, SS |
ESP32 mount + miscellaneous |
| 30 |
M3×6 BHCS |
4 |
ISO 4762, SS |
ESP32 board bolts (qty TBD pending board spec) |
| 31 |
Axle lock nut (match axle tip thread) |
4 |
Flanged, confirm thread |
2 per motor |
| 32 |
Flat washer M5 |
32 |
SS |
|
| 33 |
Flat washer M4 |
32 |
SS |
|
| 34 |
Ø4×16 dowel pin |
8 |
Steel |
Dropout clamp alignment |
Tools Required for Assembly
- Torque wrench (M14 axle nuts: 35–40 N·m; M5: 4 N·m)
- M2.5 / M3 / M4 / M5 hex drivers
- Thread locker (Loctite 243 blue for all structural fasteners)
- Dial caliper — verify motor OD, axle flat before machining fork slot
Estimated Masses
| Assembly |
Est. mass |
| Aluminium deck + ribs |
~1.1 kg |
| Motor forks (×2 Al) |
~0.4 kg |
| Motors (×2) |
~3.6 kg |
| Battery (6S 4Ah LiPo) |
~0.7 kg |
| Electronics (FC + Jetson + wiring) |
~0.5 kg |
| Bumpers + brackets |
~0.3 kg |
| Fasteners |
~0.2 kg |
| Total estimate |
~6.8 kg |
sl-mechanical
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