sl-mechanical
2fa72e169e
New chassis design files for the SaltyRover rough-terrain variant: • saltyrover_chassis_r2.scad — Deck plate (500×480×6mm Al, laser-cut DXF), 4× M3-adjustable pivot brackets, 4× CSI corner camera mounts (45° outward, 20° down), D435i front bracket (8° tilt), stem collar. All RENDER modes for STL and DXF export included. • rover_spring_arm.scad — Trailing-arm spring suspension (×4). Pivot on M8 bolt; captured 14mm OD compression spring (50mm free, ~5 N/mm); open-end axle dropout slot with retainer cap. Provides 25mm bump + 15mm droop travel. Bearing-seat recess for caliper-verified 37.8mm collar OD. • rover_electronics_bay.scad — PETG electronics bay (240×200×80mm internal). FC standoffs 30.5×30.5mm M3 and Jetson Orin 58×49mm M3 — shared SaltyLab swappable pattern. Ventilation slots all 4 walls + lid. Lid integrates 100mm RPLIDAR A1M8 tower (58mm BC, matched to rplidar_mount.scad). Split-print halves for 220mm beds included. • rover_chassis_r2_BOM.md — Full BOM, mass estimate (frame ~2.15kg; reduce to <2kg by setting DECK_T=5), assembly sequence, critical dimensions. Sensor positions: RPLIDAR top-centre on bay lid, D435i front, 4× IMX219 at deck corners. Shares 30.5mm FC + 58mm Jetson + Ø25mm stem patterns with SaltyLab for swappable electronics. Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
273 lines
12 KiB
OpenSCAD
273 lines
12 KiB
OpenSCAD
// ============================================================
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// rover_spring_arm.scad — SaltyRover Spring Suspension Arm
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// Issue: #109 Agent: sl-mechanical Date: 2026-03-01
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// ============================================================
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//
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// Trailing-arm spring suspension for rough terrain.
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// One arm per wheel (print 4×).
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//
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// Mechanical principle:
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// The arm pivots on an M8 bolt through the pivot bracket
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// (saltyrover_chassis_r2.scad → pivot_bracket).
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// A captured compression spring between the pivot bracket's
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// spring boss and the arm's spring pocket provides restoring
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// force. When a wheel strikes a bump, the arm swings upward
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// (rotating around the pivot) and compresses the spring.
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//
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// Pivot bracket (chassis-fixed)
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// │
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// [M8 pivot]──────────────────[Motor axle dropout]
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// │ [Trailing arm] │
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// └──[Spring upper seat] │
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// │ │
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// [Spring] │
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// │ │
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// [Spring pocket in arm] │
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//
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// Spring spec (wire form compression, standard size):
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// OD : 14 mm (slides over bracket's 14 mm guide boss)
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// ID : ~10 mm
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// Free length : 50 mm
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// Solid height: ~20 mm
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// Travel (max): 25 mm → spring compressed to 25 mm
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// Spring rate : ~5 N/mm (soft — adjust to robot mass)
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// Part no. : e.g. Lee Spring LCI 014M 05 S (or equivalent)
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//
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// Wheel travel:
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// Bump (compression): 25 mm (spring coils bind before hard stop)
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// Droop (extension) : 15 mm (limited by pivot bracket flange)
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// Total travel : 40 mm
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//
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// Axle-to-ground height at full compression (worst case bump):
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// AXLE_H − TRAVEL_BUMP = 127 − 25 = 102 mm above ground ✓
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//
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// Print:
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// Material : PETG or PC (PC recommended for structural rigidity)
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// Settings : 5 perimeters, 60 % gyroid infill
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// Orientation: pivot boss flat face on build plate; no supports needed
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// Qty: 4×
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//
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// Export commands:
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// STL (main arm × 4):
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// openscad rover_spring_arm.scad -D 'RENDER="arm_stl"' -o rover_spring_arm.stl
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// STL (spring retainer cap × 4):
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// openscad rover_spring_arm.scad -D 'RENDER="retainer_stl"' -o rover_spring_retainer.stl
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// Assembly preview:
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// openscad rover_spring_arm.scad -D 'RENDER="assembly"'
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// ============================================================
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$fn = 64;
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e = 0.01;
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// ── Motor axle (BOM.md caliper-verified) ────────────────────────────────────
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AXLE_D = 16.11; // axle base section OD (caliper)
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AXLE_FLAT = 13.00; // D-cut chord width (caliper)
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AXLE_D_DCUT = 15.95; // D-cut section OD (caliper)
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BEARING_OD = 37.80; // bearing seat collar OD (caliper)
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BEARING_RECESS_H = 8.0; // recess depth for bearing seat on inboard face
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// ── Arm geometry ─────────────────────────────────────────────────────────────
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// Pivot end is at X=0, Y=0, Z=0 (pivot CL)
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// Motor axle end is at X = +ARM_REACH (outboard, positive X = outboard)
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ARM_REACH = 75.0; // pivot CL to motor axle CL (outboard reach)
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ARM_W = 38.0; // arm width (fore-aft / Y direction)
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ARM_T = 14.0; // arm thickness (vertical / Z direction)
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ARM_TAPER = 4.0; // taper at motor end (arm narrows by this amount)
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// Pivot boss
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PIV_BOSS_OD = ARM_W; // boss is as wide as arm for structural continuity
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PIV_BOSS_L = ARM_T; // boss length = arm thickness
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PIV_D = 8.5; // M8 clearance bore through pivot
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// ── Suspension spring parameters ────────────────────────────────────────────
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SPG_OD = 14.0; // spring OD (matches bracket guide boss OD)
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SPG_FREE_L = 50.0; // spring free length (see spec above)
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SPG_TRAVEL = 25.0; // max bump travel / spring compression
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SPG_POCKET_D = SPG_OD + 1.5; // pocket bore (spring slides in with clearance)
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SPG_POCKET_H = SPG_TRAVEL + 5; // pocket depth (captures spring bottom)
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// Spring pocket CL from pivot (along arm)
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SPG_POS_X = ARM_REACH * 0.45; // ~45% along arm from pivot
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// ── Motor axle dropout slot ──────────────────────────────────────────────────
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// Open-end slot at motor end of arm. Retained by spring_retainer_cap.
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DROP_W = AXLE_D + 1.0; // slot width (snug but not interference)
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DROP_DEPTH = AXLE_D + 4.0; // slot depth from arm end inward
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// ── Spring retainer cap ──────────────────────────────────────────────────────
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// Small cap that closes the open axle slot from below, screwing onto the arm.
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// Prevents axle from dropping out; provides second bearing recess face.
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RET_T = 6.0; // cap thickness
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RET_W = ARM_W + 4.0; // cap wider than arm for alignment lip
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RET_BOLT_D = M3_D; // 2× M3 bolts retain the cap
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M2_D = 2.3;
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M3_D = 3.3;
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M4_D = 4.3;
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M5_D = 5.3;
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M8_D = 8.5;
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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 == "assembly") {
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assembly();
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} else if (RENDER == "arm_stl") {
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spring_arm();
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} else if (RENDER == "retainer_stl") {
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spring_retainer_cap();
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}
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// ============================================================
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// FULL ASSEMBLY PREVIEW
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// ============================================================
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module assembly() {
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color("SteelBlue", 0.85) spring_arm();
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color("CornflowerBlue", 0.80)
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translate([ARM_REACH, 0, -(ARM_T/2 + RET_T)])
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spring_retainer_cap();
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// Phantom spring (compressed)
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%color("LimeGreen", 0.5)
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translate([SPG_POS_X, 0, ARM_T/2])
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cylinder(d = SPG_OD, h = SPG_FREE_L - SPG_TRAVEL);
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// Phantom motor axle
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%color("Tomato", 0.3)
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translate([ARM_REACH, 0, 0])
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rotate([0, 90, 0])
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cylinder(d = AXLE_D, h = 120, center = true);
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// Phantom pivot bolt (M8)
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%color("Gray", 0.5)
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rotate([0, 90, 0])
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cylinder(d = 8, h = ARM_T + 20, center = true);
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// Phantom bracket guide boss (from pivot_bracket)
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%color("DarkGray", 0.4)
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translate([SPG_POS_X, 0, ARM_T/2])
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cylinder(d = SPG_OD, h = 20);
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}
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// ============================================================
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// SPRING ARM
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// ============================================================
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// Pivot CL at (0, 0, 0). Arm extends toward +X.
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// Pivots around Y-axis (M8 bolt runs in Y direction).
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// Spring acts in Z (vertical) at SPG_POS_X along arm.
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// Motor axle runs in Y direction at (ARM_REACH, 0, 0).
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// ============================================================
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module spring_arm() {
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w_motor = ARM_W - ARM_TAPER; // narrower at motor end
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difference() {
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union() {
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// ── Main arm body (tapered hull) ──────────────────────────
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hull() {
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// Pivot end — full-width rectangular section
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translate([0, -ARM_W/2, -ARM_T/2])
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cube([e, ARM_W, ARM_T]);
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// Motor end — slightly narrower
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translate([ARM_REACH - DROP_DEPTH, -w_motor/2, -ARM_T/2])
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cube([e, w_motor, ARM_T]);
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}
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// ── Pivot boss (cylindrical for hinge strength) ───────────
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// Cylindrical boss sits at pivot CL; flange provides washer seat.
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rotate([90, 0, 0]) {
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difference() {
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cylinder(d = PIV_BOSS_OD, h = PIV_BOSS_L, center = true);
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}
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}
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// ── Spring pocket boss (raised above arm top face) ─────────
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// Boss rises to meet the bracket's spring guide boss.
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// The compression spring is captured between the two bosses.
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translate([SPG_POS_X, 0, ARM_T/2])
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cylinder(d = SPG_OD + 8, h = 8);
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// ── Axle retention lug at motor end (prevents side loading) ─
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translate([ARM_REACH - ARM_T, -w_motor/2, -ARM_T/2])
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cube([ARM_T, w_motor, ARM_T - BEARING_RECESS_H]);
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}
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// ── M8 pivot bore (through pivot boss in Y direction) ─────────
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rotate([90, 0, 0])
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cylinder(d = PIV_D, h = PIV_BOSS_L + 2*e, center = true);
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// ── Spring pocket bore (from top, captures spring bottom) ─────
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// Bore is slightly larger than spring OD for easy insertion.
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translate([SPG_POS_X, 0, ARM_T/2 - e])
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cylinder(d = SPG_POCKET_D, h = SPG_POCKET_H + e);
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// ── Spring pocket access slot (allows spring preload assembly) ─
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// Lateral slot lets spring be pressed in from side during assembly.
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translate([SPG_POS_X - SPG_OD/2, -SPG_OD/2 - 0.5, ARM_T/2 - e])
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cube([SPG_OD, SPG_OD + 1, SPG_POCKET_H + e]);
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// ── Motor axle dropout slot (open at arm tip end, +X) ─────────
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// Slot width = axle OD + 1 mm; depth = DROP_DEPTH inward.
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// Motor axle slides in from the open end.
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translate([ARM_REACH - DROP_DEPTH, -DROP_W/2, -ARM_T/2 - e])
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cube([DROP_DEPTH + e, DROP_W, ARM_T + 2*e]);
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// Rounded bore at inner end of dropout slot (distributes load)
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translate([ARM_REACH - DROP_DEPTH, 0, -ARM_T/2 - e])
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cylinder(d = DROP_W, h = ARM_T + 2*e);
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// ── Bearing seat recess (inboard face of axle slot) ──────────
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// Prevents bearing collar (Ø37.8) from clashing with arm face.
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translate([ARM_REACH - DROP_DEPTH - BEARING_RECESS_H, 0, -ARM_T/2 - e])
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cylinder(d = BEARING_OD + 1.5, h = BEARING_RECESS_H + e);
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// ── Retainer cap M3 bolt holes (2×, for spring_retainer_cap) ──
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for (dy = [-ARM_W/4, ARM_W/4])
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translate([ARM_REACH - DROP_DEPTH/2, dy, -ARM_T/2 - e])
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cylinder(d = M3_D - 0.3, h = ARM_T/2 + e);
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// Slightly tight bore — M3 self-taps into PETG at 3.0 mm
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// ── Lightening slot (mid-arm, between pivot boss and spring) ──
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lx1 = PIV_BOSS_OD/2 + 5;
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lx2 = SPG_POS_X - SPG_OD/2 - 5;
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translate([lx1, -(ARM_W/4), -ARM_T/2 - e])
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cube([max(lx2 - lx1, 1), ARM_W/2, ARM_T + 2*e]);
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}
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}
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// ============================================================
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// SPRING RETAINER CAP
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// ============================================================
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// Clips onto the open axle slot at the arm tip.
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// Prevents motor axle from falling out of the dropout slot.
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// 2× M3 bolts thread into the arm's self-tap holes.
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// Also provides the outboard bearing-seat face.
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// ============================================================
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module spring_retainer_cap() {
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w_cap = ARM_W - ARM_TAPER + 2;
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difference() {
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union() {
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cube([DROP_DEPTH, w_cap, RET_T], center = true);
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// Alignment lips (engage the arm slot edges)
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for (dy = [-1, 1])
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translate([0, dy * (w_cap/2 + 1), 0])
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cube([DROP_DEPTH - 2, 2, RET_T + 4], center = true);
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}
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// Axle bore (clearance) — round section
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cylinder(d = AXLE_D + 0.8, h = RET_T + 2*e, center = true);
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// Bearing seat recess (outboard face)
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translate([0, 0, RET_T/2 - BEARING_RECESS_H/2])
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cylinder(d = BEARING_OD + 1.5, h = BEARING_RECESS_H + e, center = true);
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// 2× M3 bolt clearance holes
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for (dy = [-ARM_W/4, ARM_W/4])
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translate([0, dy, 0])
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cylinder(d = M3_D, h = RET_T + 2*e, center = true);
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}
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}
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