rocket.scad

   1
   2 // The Estes A8-3 and C6-7 motors have diameter of 17.7 mm,
   3 // length 69.5 mm. The Estes Alpha launch pad has rod diameter 3.4 mm.
   4
   5 motor_diam = 17.7 + 0.5; // add some tolerance
   6 motor_len  = 69.5 + 0.5;
   7 motor_wall = 2;
   8
   9 segment_overlap = 15;
  10
  11 thin_wall = 1.0; // depends on the print width
  12 thick_wall = 2.5*thin_wall;
  13
  14 clip_spring_angle = 45;
  15 clip_spring_depth = 20;
  16
  17 rod_diam = 4;
  18
  19 eps = 0.01;
  20 infty = 1000;
  21
  22 //----------------- MOTOR MODULE -----------------------------
  23
  24 module fin() {
  25         assign(h1 = 2*motor_len/3, // near end height
  26                 h2 = 20,        // far end height
  27                 h_off = motor_len, // height offset of the far height
  28                 w = 30, // distance of the far height
  29                 fin_w = thin_wall)
  30         translate([0, -fin_w/2, -h1])
  31         hull() {
  32                 cube([eps, fin_w, h1]); // near end
  33                 translate([w, 0, h_off]) // far end
  34                         cube([eps, fin_w, h2]);
  35         };
  36 };
  37
  38 // alternative fin layout
  39 module fin2() {
  40         assign(h1 = motor_len/2, // near end height
  41                 w2 = 18,        // bottom/far end width
  42                 h_off = 50, // height offset of the far height
  43                 w = 30, // distance of the far height
  44                 fin_w = thin_wall)
  45         translate([0, -fin_w/2, -h1])
  46         hull() {
  47                 cube([eps, fin_w, h1]); // near end
  48                 translate([w-w2, 0, h_off]) // far end
  49                         cube([w2, fin_w, eps]);
  50         };
  51 };
  52
  53 rod_hole_height = 15;
  54 rod_hole_side = 1.5*(rod_diam + thin_wall);
  55
  56 module motor_module_solid()
  57 {
  58         // the lowest part is for joining the segments
  59         cylinder(r = motor_diam/2 + thin_wall, h = segment_overlap + eps);
  60
  61         // conical joint between the two cylinders
  62         translate([0, 0, segment_overlap - thick_wall + thin_wall])
  63                 cylinder(r1 = motor_diam/2 + thin_wall,
  64                         r2 = motor_diam/2 + thick_wall,
  65                         h = thick_wall - thin_wall + eps);
  66
  67         // protrusions to hold the main tube in place
  68         for (a = [60, 180, 300]) {
  69                 rotate([0, 0, a]) {
  70                         translate([motor_diam/2 - thin_wall, 0, 0])
  71                                 cylinder(r1 = thick_wall-thin_wall/2, r2 = thick_wall, h = segment_overlap/3 + eps);
  72                         translate([motor_diam/2 - thin_wall, 0, segment_overlap/3])
  73                                 cylinder(r = thick_wall, h = 2*segment_overlap/3 + eps);
  74                 };
  75         };
  76
  77         // the thick cylinder above it
  78         translate([0, 0, segment_overlap])
  79                 cylinder(r = motor_diam/2 + thick_wall,
  80                 h = motor_len + motor_wall - segment_overlap);
  81
  82         // clip spring
  83         translate([0, 0, motor_len + motor_wall])
  84                 intersection() {
  85                         translate([motor_diam/2+6, infty/2, 4])
  86                         rotate([90, 0, 0])
  87                                 cylinder(r = 8, h = infty);
  88                         cylinder(r = motor_diam/2 + thick_wall, h = infty);
  89                         rotate([0, 0, -clip_spring_angle/2+eps])
  90                                 cube(infty);
  91                         rotate([0, 0, clip_spring_angle/2-eps])
  92                                 scale([1, -1, 1])
  93                                 cube([infty, infty, 8]);
  94                 };
  95
  96         // fins
  97         for (a = [60, 180, 300]) {
  98                 rotate([0, 0, a])
  99                 translate([motor_diam/2 + thick_wall-thin_wall, 0, motor_wall + motor_len])
 100                         // fin();
 101                         fin2();
 102         };
 103
 104         // rod hole holder
 105         hull() {
 106                 translate([motor_diam/2 + thick_wall - rod_diam/2 - thin_wall,
 107                         0, segment_overlap])
 108                         scale([1, 1.4, 1])
 109                         cylinder(r = rod_diam/2 + thin_wall, h = eps);
 110                 translate([motor_diam/2 + thick_wall + rod_diam/2, 0, segment_overlap + rod_hole_side])
 111                         scale([1, 1.1, 1])
 112                         cylinder(r = rod_diam/2 + thin_wall, h = rod_hole_height);
 113                 translate([motor_diam/2 + thick_wall - rod_diam/2 - thin_wall,
 114                         0, segment_overlap + 2*rod_hole_side + rod_hole_height])
 115                         scale([1, 1.4, 1])
 116                         cylinder(r = rod_diam/2 + thin_wall, h = eps);
 117         };
 118
 119 };
 120
 121 module motor_module() {
 122         difference() {
 123                 motor_module_solid();
 124
 125                 // top ring to hold the motor inside
 126                 translate([0, 0, -eps])
 127                         cylinder(r = motor_diam/2 - motor_wall,
 128                                 h = motor_wall + 2*eps);
 129
 130                 // motor hole
 131                 translate([0, 0, motor_wall - eps])
 132                         cylinder(r = motor_diam/2, h = motor_len + 2*eps);
 133
 134                 // three rails inside the motor hole
 135                 translate([0, 0, segment_overlap + thick_wall]) difference() {
 136                         union() {
 137                                 cylinder(r = motor_diam/2 + thin_wall,
 138                                         h = motor_len - segment_overlap - 2*thick_wall + eps);
 139                                 translate([0, 0, motor_len - segment_overlap - 2*thick_wall])
 140                                         cylinder(r1 = motor_diam/2 + thin_wall, r2 = motor_diam/2, h = thick_wall + eps);
 141                         };
 142                         for (a = [60, 180, 300]) rotate([0, 0, a])
 143                                 translate([motor_diam/2 + 2.5, 0, -eps])
 144                                         cylinder(r = 3, h = infty);
 145                 };
 146
 147                 // clip spring
 148                 for (r = [-clip_spring_angle/2, clip_spring_angle/2]) {
 149                         rotate([0, 0, r])
 150                         translate([-thin_wall/2, 0, motor_len + motor_wall - clip_spring_depth])
 151                                 cube([infty, thin_wall, infty]);
 152                 };
 153                 translate([0, 0, motor_len - eps])
 154                 intersection() {
 155                         cylinder(r = motor_diam/2 + thin_wall,
 156                                 h = thick_wall + 2*eps);
 157                         rotate([0, 0, -clip_spring_angle/2+eps])
 158                                 cube(infty);
 159                         rotate([0, 0, clip_spring_angle/2-eps])
 160                                 scale([1, -1, 1])
 161                                 cube([infty, infty, 8]);
 162                 };
 163
 164
 165                 // rod hole
 166                 translate([motor_diam/2 + thick_wall + eps + rod_diam/2, 0, 0])
 167                         cylinder(r = rod_diam/2, h = infty);
 168         };
 169 };
 170
 171 // -------------------- CENTRAL TUBE ---------------------
 172
 173 central_tube_h = 80;
 174
 175 module central_tube_solid() {
 176         cylinder(r = motor_diam/2 + thick_wall, h = central_tube_h);
 177 };
 178
 179 module central_tube() {
 180         difference() {
 181                 central_tube_solid();
 182                 translate([0, 0, -eps])
 183                         cylinder(r = motor_diam/2 + thick_wall - thin_wall,
 184                                 h = infty);
 185         };
 186 };
 187
 188 //------------------------- FRONT CONE -----------------------
 189 cone_h = 45;
 190 cone_resolution = 40;
 191
 192 function bez_i4(t, ctls) =
 193         (pow(1-t, 3) * ctls[0])
 194         + (3 * t * pow(1-t, 2) * ctls[1])
 195         + (3 * pow(t, 2) * (1-t) * ctls[2])
 196         + (pow(t, 3) * ctls[3]);
 197
 198 module bezier_cone(cps, res)
 199 {
 200         for (t = [0:1:res])
 201                 translate([0, 0, (bez_i4(t/res, cps))[0]])
 202                         cylinder(r1 = (bez_i4(t/res, cps))[1],
 203                                 r2 = (bez_i4((t + 1)/res, cps))[1],
 204                                 h = (bez_i4((t + 1)/res, cps))[0]
 205                                     - (bez_i4(t/res, cps))[0] + eps);
 206 };
 207
 208 module front_cone_body() {
 209         translate([0, 0, segment_overlap])
 210                 bezier_cone([
 211                         [ 0, motor_diam/2 + thick_wall ], // start
 212                         [ cone_h/2, motor_diam/2 + thick_wall ], // cp 1
 213                         [ cone_h - motor_diam/2 - thick_wall, motor_diam/2 + thick_wall ], // cp 2
 214                         [ cone_h, 0 ],
 215                 ], 40);
 216
 217         translate([0, 0, segment_overlap-thick_wall+thin_wall])
 218                 cylinder(r1 = motor_diam/2+thin_wall,
 219                         r2 = motor_diam/2 + thick_wall,
 220                         h = thick_wall - thin_wall + eps);
 221
 222         cylinder(r = motor_diam/2+thin_wall, h = segment_overlap + eps);
 223 };
 224
 225 module front_cone() {
 226         difference() {
 227                 front_cone_body();
 228                 translate([0, 0, segment_overlap])
 229                         bezier_cone([
 230                                 [ 0.7*thin_wall, motor_diam/2 + thick_wall - thin_wall ], // start
 231                         [ cone_h/2-0.7*thin_wall, motor_diam/2 + thick_wall - thin_wall], // cp 1
 232                         [ cone_h - motor_diam/2 - thick_wall + thin_wall - 1.4*thin_wall, motor_diam/2 + thick_wall - thin_wall ], // cp 2
 233                         [ cone_h - 1.4*thin_wall, 0 ],
 234                 ], 40);
 235
 236                 translate([0, 0, segment_overlap-thick_wall+1.7*thin_wall])
 237                         cylinder(r1 = motor_diam/2,
 238                                 r2 = motor_diam/2 + thick_wall-thin_wall,
 239                                 h = thick_wall-thin_wall + eps);
 240
 241                 translate([0, 0, -eps])
 242                         cylinder(r = motor_diam/2, h = segment_overlap + 2*eps);
 243
 244                 // debug
 245                 // translate([0, 0, -eps]) cube(infty);
 246         };
 247 };
 248
 249 module thread_holder() {
 250         rotate([0, 90, 0]) {
 251                 translate([0, 0, -1.5]) difference() {
 252                         cylinder(r = 10, h = 3);
 253                         translate([0, 0, -eps])
 254                                 cylinder(r = 8, h = 3 + 2*eps);
 255                 };
 256         };
 257 }
 258
 259 // thread_holder();
 260
 261 $fn = 128;
 262
 263 translate([motor_diam + thick_wall, 0, 0])
 264         motor_module();
 265
 266 rotate([0, 0, 120])
 267 translate([motor_diam + thick_wall, 0, 0])
 268         central_tube();
 269
 270 rotate([0, 0, 240])
 271 translate([motor_diam + thick_wall, 0, 0])
 272         front_cone();
 273