sl-mechanical
d93919e26f
Three new chassis design files for the SaltyTank continuous-track variant: • saltytank_chassis.scad — Deck plate (500×360×8mm Al, DXF export), 2× side track frames (6mm Al, CNC/laser), idler tensioner sliding block, 4× CSI corner camera mounts (45°/20°), D435i front bracket (8° tilt), stem collar (Ø25mm shared). Drive sprocket mounts accept hoverboard hub motors with caliper-verified D-cut bore (16.11mm/13mm flat) + 52mm BC hub flange bolt pattern. M6 tensioner bolt adjusts idler ±15mm for track tension. Shared FC 30.5×30.5mm + Jetson 58×49mm M3 patterns. Electronics bay footprint matches rover_electronics_bay.scad exactly. • saltytank_skid_plate.scad — Sacrificial underside skid panel (360×500mm). 4mm HDPE (DXF) or PETG print; countersunk M4 FHCS bolt-on. 4× drain/ inspection slots; optional printed ribs (RIB_PRINT=true). Ground clearance of hull between tracks: 90mm (exceeds 50mm requirement). • saltytank_BOM.md — Full BOM: deck plate, side frames, drive sprockets, idler wheels + tensioners, road wheels (2/side), track belts (1109mm circumference calc), skid plate, sensor brackets, electronics bay (rover_electronics_bay.scad reused unchanged). Frame mass ≈ 2.98 kg (just under 3 kg target). Assembly sequence and track tensioning procedure included. Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
215 lines
9.2 KiB
OpenSCAD
215 lines
9.2 KiB
OpenSCAD
// ============================================================
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// saltytank_skid_plate.scad — SaltyTank Underside Skid Plate
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// Issue: #121 Agent: sl-mechanical Date: 2026-03-01
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// ============================================================
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//
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// Bolt-on underside protection panel for rough terrain.
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// Mounts to the underside of the deck plate, covering the hull
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// floor between the two track frames.
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//
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// Purpose:
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// • Protects electronics bay wiring + deck underside from rock strikes
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// • Sacrificial layer — replace without reworking deck plate
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// • Provides a smooth low-drag hull bottom for terrain sliding
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// • Four drain / inspection slots (water / mud egress)
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//
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// Material options:
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// Primary : 4 mm HDPE (high-density polyethylene)
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// — lightweight, impact resistant, low friction surface
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// Alternative: 2 mm 304 stainless steel
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// — heavier (+0.5 kg), extremely wear resistant
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// Prototype : 6 mm plywood (quick, cheap; not weatherproof)
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//
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// Dimensions: BODY_W × BODY_L × SKID_T
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// = 360 × 500 × 4 mm (fits between track inner faces)
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//
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// Mounting:
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// 8× M4 SHCS from below; nuts captured in deck plate M4 rivet-nuts
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// (see saltytank_chassis.scad skid plate attachment holes)
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// Countersunk (FHCS) variant available — set COUNTERSINK = true
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//
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// Coordinate: Z=0 at skid top face (= deck plate underside)
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// Ground contact surface at Z = -(FRAME_H) = -90 mm (in deck coords)
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// Skid sits immediately below deck: deck_bottom → skid_top
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//
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// RENDER options:
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// "skid_stl" STL for 3D printing (4 mm PETG, prototype)
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// "skid_2d" DXF for waterjet / CNC (HDPE or steel plate)
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// "assembly" preview with deck ghost
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//
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// Export commands:
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// DXF (HDPE / steel — recommended):
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// openscad saltytank_skid_plate.scad -D 'RENDER="skid_2d"' -o saltytank_skid.dxf
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// STL (3D print prototype):
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// openscad saltytank_skid_plate.scad -D 'RENDER="skid_stl"' -o saltytank_skid.stl
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// ============================================================
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$fn = 64;
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e = 0.01;
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// ── Skid plate dimensions ────────────────────────────────────────────────────
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// Must match saltytank_chassis.scad BODY_W and BODY_L exactly.
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BODY_L = 500.0; // fore-aft — copy from saltytank_chassis.scad
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BODY_W = 360.0; // left-right
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SKID_T = 4.0; // skid plate thickness (4 mm HDPE)
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SKID_R = 12.0; // corner radius (matches deck corners, ease of cleaning)
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FRAME_H = 90.0; // side frame height (from saltytank_chassis.scad)
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// ── Skid reinforcement ribs (under-surface, printed variant only) ─────────────
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// Ribs add stiffness to the printed skid without adding flat-surface area.
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// Ribs are omitted on the CNC/laser version (material stiffness is sufficient).
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RIB_H = 8.0; // rib height below skid top face
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RIB_T = 3.0; // rib wall thickness
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RIB_PRINT = false; // set true to add ribs (print only; skip for DXF)
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// ── Attachment bolt holes (M4) ───────────────────────────────────────────────
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// Pattern must match saltytank_chassis.scad skid plate holes exactly.
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// 2 rows × 3 columns = 6 holes + 2 corners = 8 total
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BOLT_D = 4.3; // M4 clearance
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BOLT_INSET_X = 20.0; // CL inset from left/right edge
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BOLT_INSET_Y = 25.0; // CL inset from front/rear edge
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// Countersinking (flat-head bolts flush with skid surface — preferred for terrain)
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COUNTERSINK = true;
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CSINK_ANGLE = 82; // M4 FHCS countersink angle (82° for DIN 7991)
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CSINK_OD = 8.0; // M4 FHCS head diameter
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// ── Drain / inspection slots ─────────────────────────────────────────────────
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DRAIN_W = 20.0; // slot width
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DRAIN_L = 60.0; // slot length
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DRAIN_R = 10.0; // slot corner radius
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// ── Road-wheel axle pass-through slots ───────────────────────────────────────
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// The road wheel axles sit OUTSIDE the skid plate (they're in the side frames),
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// so no axle holes are needed in the skid plate.
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// The skid plate is a solid panel between the track frames.
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// ── Fasteners ─────────────────────────────────────────────────────────────────
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M4_D = 4.3;
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// ============================================================
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// RENDER DISPATCH
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// ============================================================
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RENDER = "assembly";
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if (RENDER == "skid_stl") {
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skid_plate();
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} else if (RENDER == "skid_2d") {
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projection(cut = true)
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translate([0, 0, -SKID_T / 2])
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skid_plate_flat_only();
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} else if (RENDER == "assembly") {
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assembly();
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}
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// ============================================================
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// ASSEMBLY PREVIEW
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// ============================================================
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module assembly() {
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color("Sienna", 0.85) skid_plate();
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// Ghost deck plate above
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%color("Silver", 0.25)
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translate([0, 0, SKID_T])
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linear_extrude(8)
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minkowski() {
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square([BODY_L - 24, BODY_W - 24], center = true);
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circle(r = 12);
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}
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// Ghost side frames (simplified)
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for (sx = [-1, 1])
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%color("SteelBlue", 0.20)
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translate([sx * (BODY_W/2 + 3), 0, SKID_T])
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cube([6, BODY_L, FRAME_H + 8], center = true);
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}
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// ============================================================
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// SKID PLATE (3D print — includes optional ribs)
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// ============================================================
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module skid_plate() {
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difference() {
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union() {
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// ── Base plate ─────────────────────────────────────────────
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linear_extrude(SKID_T)
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skid_profile_2d();
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// ── Reinforcement ribs (printed version only) ──────────────
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if (RIB_PRINT) {
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// Longitudinal centre rib
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translate([0, 0, SKID_T])
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cube([RIB_T, BODY_L - 40, RIB_H], center = true);
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// Lateral ribs (3× fore-aft)
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for (ry = [-BODY_L/4, 0, BODY_L/4])
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translate([0, ry, SKID_T])
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cube([BODY_W - 40, RIB_T, RIB_H], center = true);
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}
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}
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// ── Attachment bolt holes ──────────────────────────────────────
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for (bpos = bolt_positions())
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translate([bpos[0], bpos[1], -e]) {
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cylinder(d = BOLT_D, h = SKID_T + 2*e);
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if (COUNTERSINK)
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// Countersink cone from top face
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translate([0, 0, SKID_T + e])
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cylinder(d1 = CSINK_OD, d2 = BOLT_D,
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h = (CSINK_OD - BOLT_D) / (2 * tan(CSINK_ANGLE/2)));
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}
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// ── Drain / inspection slots (4×, one per quadrant) ───────────
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for (sx = [-1, 1])
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for (sy = [-1, 1]) {
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dx = sx * (BODY_W/4 + 15);
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dy = sy * (BODY_L/4 + 20);
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translate([dx - DRAIN_W/2 + DRAIN_R, dy - DRAIN_L/2 + DRAIN_R, -e])
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linear_extrude(SKID_T + 2*e)
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minkowski() {
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square([DRAIN_W - 2*DRAIN_R, DRAIN_L - 2*DRAIN_R]);
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circle(r = DRAIN_R);
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}
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}
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}
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}
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// 2D profile of skid plate (shared by skid_plate and DXF export)
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module skid_profile_2d() {
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minkowski() {
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square([BODY_L - 2*SKID_R, BODY_W - 2*SKID_R], center = true);
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circle(r = SKID_R);
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}
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}
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// Flat-only version for DXF projection (no ribs)
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module skid_plate_flat_only() {
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difference() {
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linear_extrude(SKID_T) skid_profile_2d();
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for (bpos = bolt_positions())
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translate([bpos[0], bpos[1], -e])
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cylinder(d = BOLT_D, h = SKID_T + 2*e);
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for (sx = [-1, 1])
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for (sy = [-1, 1]) {
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dx = sx * (BODY_W/4 + 15);
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dy = sy * (BODY_L/4 + 20);
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translate([dx - DRAIN_W/2 + DRAIN_R, dy - DRAIN_L/2 + DRAIN_R, -e])
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linear_extrude(SKID_T + 2*e)
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minkowski() {
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square([DRAIN_W - 2*DRAIN_R, DRAIN_L - 2*DRAIN_R]);
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circle(r = DRAIN_R);
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}
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}
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}
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}
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// ── Bolt position list (8 positions matching saltytank_chassis.scad) ──────────
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function bolt_positions() = [
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// From saltytank_chassis.scad skid plate holes (sx × (BODY_W/2 - 20), sy × BODY_L/3)
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[-BODY_W/2 + BOLT_INSET_X, -BODY_L/3],
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[-BODY_W/2 + BOLT_INSET_X, 0],
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[-BODY_W/2 + BOLT_INSET_X, +BODY_L/3],
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[+BODY_W/2 - BOLT_INSET_X, -BODY_L/3],
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[+BODY_W/2 - BOLT_INSET_X, 0],
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[+BODY_W/2 - BOLT_INSET_X, +BODY_L/3]
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];
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