Parametric tractor wheel

// A tractor wheel: the parametric car wheel retuned with tall-sidewall, deep-lug
// defaults. Remix of mick/parametric-wheel; geometry unchanged, numbers retuned.
// Uses threads.scad by Ryan A. Colyer, released with CC0 into the public domain.
// Published on RemixCAD as remixcad/threads.
use <remixcad/threads/threads.scad>

/* [Size] */
// Diameter measured over the tread, the outside of the wheel.
outer_diameter = 84; // [20:1:200]
// Diameter where tyre meets rim. Small against the outer diameter for the tall sidewall.
rim_diameter = 30; // [10:1:160]
// Width across the wheel, bead to bead.
width = 26; // [4:1:80]

/* [Tread] */
// Lugs around the tyre. Few and coarse is the tractor look.
tread_blocks = 12; // [0:1:80]
// How deep each groove is cut into the crown.
tread_depth = 6; // [0:0.1:6]
// How far the lugs rake across the tread, in degrees.
tread_angle = 40; // [0:1:60]
// Groove width as a share of the space between lugs.
tread_gap = 0.55; // [0.1:0.01:0.7]
// How round the tyre shoulders are. Square lets the lugs bite over the edge.
shoulder = 0.3; // [0:0.05:1]

/* [Face] */
// Thickness of the closed face disc.
face_thickness = 4; // [2:0.5:10]
// Centre bore for the axle.
bore_diameter = 8; // [2:1:40]
// Lug bolts around the bore.
lug_count = 5; // [0:1:10]
// Bolt circle diameter the lugs sit on.
lug_circle = 16; // [6:1:120]
// Round vents in the face. Zero closes the face.
vent_count = 6; // [0:1:16]
// Diameter of each vent.
vent_diameter = 3.5; // [0:0.5:30]

/* [Bolts] */
// Nominal metric size of the lug bolts, so 4 is an M4.
bolt_size = 4; // [3:1:8]
// Bolt length under the head.
bolt_length = 14; // [6:1:30]
// Show the bolts, or leave the holes open for real fasteners.
show_bolts = true;

/* [Shape] */
// Wall thickness of the rim barrel.
wall = 2.4; // [1:0.1:6]
// How far the rim flanges stand proud of the barrel.
flange = 1.2; // [0:0.1:4]
// Facets around the wheel. More is smoother and slower.
smoothness = 96; // [24:8:192]

/* [Hidden] */
outer_radius = outer_diameter / 2;
rim_radius = rim_diameter / 2;
half_width = width / 2;
shoulder_radius = shoulder * min(half_width, outer_radius - rim_radius) * 0.9;
pitch = tread_blocks > 0 ? 360 / tread_blocks : 360;
groove_width = 2 * PI * outer_radius * (pitch / 360) * tread_gap;
flange_height = 1.4;
// The lug hole clears the bolt, and both hole circles stay inside the barrel wall.
lug_hole = bolt_size + 0.6;
lug_radius = min(lug_circle / 2, rim_radius - wall - lug_hole / 2 - 1);
vent_radius_pos = min(rim_radius - wall - vent_diameter / 2 - 0.5,
                      lug_radius + lug_hole / 2 + vent_diameter / 2 + 0.8);
bolt_head_height = 0.7 * bolt_size;

// ---- Tyre, from mick/parametric-wheel ----

module section() {
  hull() {
    translate([rim_radius, -half_width]) square([0.01, width]);
    translate([outer_radius - shoulder_radius, -half_width + shoulder_radius])
      circle(r = shoulder_radius, $fn = 32);
    translate([outer_radius - shoulder_radius, half_width - shoulder_radius])
      circle(r = shoulder_radius, $fn = 32);
  }
}

module carcass() {
  rotate_extrude($fn = smoothness) section();
}

module grooves() {
  for (index = [0 : max(tread_blocks - 1, 0)]) {
    rotate([0, 0, index * pitch])
      translate([outer_radius, 0, 0])
        rotate([tread_angle, 0, 0])
          cube([tread_depth * 2, groove_width, width * 3], center = true);
  }
}

module tyre() {
  if (tread_blocks > 0 && tread_depth > 0) {
    difference() {
      carcass();
      grooves();
    }
  } else {
    carcass();
  }
}

// ---- Rim, from mick/parametric-wheel ----

module barrel() {
  difference() {
    cylinder(h = width, r = rim_radius, center = true, $fn = smoothness);
    cylinder(h = width + 1, r = rim_radius - wall, center = true, $fn = smoothness);
  }
}

module flanges() {
  for (z = [-half_width, half_width - flange_height])
    translate([0, 0, z])
      difference() {
        cylinder(h = flange_height, r = rim_radius + flange, $fn = smoothness);
        translate([0, 0, -0.5])
          cylinder(h = flange_height + 1, r = rim_radius - wall, $fn = smoothness);
      }
}

module face() {
  translate([0, 0, half_width - face_thickness])
    difference() {
      cylinder(h = face_thickness, r = rim_radius - wall / 2, $fn = smoothness);
      translate([0, 0, -0.5])
        cylinder(h = face_thickness + 1, d = bore_diameter, $fn = smoothness);
      if (lug_count > 0)
        for (i = [0 : lug_count - 1])
          rotate([0, 0, i * 360 / lug_count])
            translate([lug_radius, 0, -0.5])
              cylinder(h = face_thickness + 1, d = lug_hole, $fn = 32);
      if (vent_count > 0 && vent_diameter > 0)
        for (i = [0 : vent_count - 1])
          rotate([0, 0, (i + 0.5) * 360 / vent_count])
            translate([vent_radius_pos, 0, -0.5])
              cylinder(h = face_thickness + 1, d = vent_diameter, $fn = 32);
    }
}

module rim() {
  union() {
    barrel();
    flanges();
    face();
  }
}

// ---- Bolts, from remixcad/metric-bolt via the parent ----

// Head out, seated just proud of the face, the way a wheel is bolted up.
module bolts() {
  if (lug_count > 0)
    for (i = [0 : lug_count - 1])
      rotate([0, 0, i * 360 / lug_count])
        translate([lug_radius, 0, half_width + bolt_head_height + 0.5])
          rotate([180, 0, 0])
            MetricBolt(bolt_size, bolt_length, 0.4);
}

module wheel() {
  tyre();
  rim();
  if (show_bolts) bolts();
}

wheel();