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 = 0.9; // depends on the print width
  12 thick_wall = 2.2*thin_wall;
  13
  14 clip_spring_angle = 45;
  15 clip_spring_depth = 20;
  16
  17 rod_diam = 4;
  18 rubber_beam_height = 3;
  19
  20 eps = 0.01;
  21 infty = 1000;
  22
  23 //----------------- MOTOR MODULE -----------------------------
  24
  25 module fin() {
  26         assign(h1 = 2*motor_len/3, // near end height
  27                 h2 = 20,        // far end height
  28                 h_off = motor_len, // height offset of the far height
  29                 w = 30, // distance of the far height
  30                 fin_w = thin_wall)
  31         translate([0, -fin_w/2, -h1])
  32         hull() {
  33                 cube([eps, fin_w, h1]); // near end
  34                 translate([w, 0, h_off]) // far end
  35                         cube([eps, fin_w, h2]);
  36         };
  37 };
  38
  39 // alternative fin layout
  40 module fin2() {
  41         assign(h1 = motor_len/2, // near end height
  42                 w2 = 23,        // bottom/far end width
  43                 h_off = 60, // height offset of the far height
  44                 w = 30, // distance of the far height
  45                 fin_w = thin_wall)
  46         translate([0, -fin_w/2, -h1])
  47         hull() {
  48                 cube([eps, fin_w, h1]); // near end
  49                 translate([w-w2, 0, h_off]) // far end
  50                         cube([w2, fin_w, eps]);
  51         };
  52 };
  53
  54 rod_hole_height = 15;
  55 rod_hole_side = 1.5*(rod_diam + thin_wall);
  56
  57 module motor_module_solid()
  58 {
  59         // the lowest part is for joining the segments
  60         cylinder(r = motor_diam/2 + thin_wall, h = segment_overlap + eps);
  61
  62         // conical joint between the two cylinders
  63         translate([0, 0, segment_overlap - thick_wall + thin_wall])
  64                 cylinder(r1 = motor_diam/2 + thin_wall,
  65                         r2 = motor_diam/2 + thick_wall,
  66                         h = thick_wall - thin_wall + eps);
  67
  68         // protrusions to hold the main tube in place
  69         for (a = [60, 180, 300]) {
  70                 rotate([0, 0, a]) {
  71                         translate([motor_diam/2 + thick_wall - thin_wall/2 - thick_wall, 0, 0])
  72                                 cylinder(r1 = thick_wall-thin_wall/2, r2 = thick_wall, h = segment_overlap/3 + eps);
  73                         translate([motor_diam/2 + thick_wall - thin_wall/2 - thick_wall, 0, segment_overlap/3])
  74                                 cylinder(r = thick_wall, h = 2*segment_overlap/3 + eps);
  75                 };
  76         };
  77
  78         // the thick cylinder above it
  79         translate([0, 0, segment_overlap])
  80                 cylinder(r = motor_diam/2 + thick_wall,
  81                 h = motor_len + motor_wall - segment_overlap);
  82
  83         // clip spring
  84         translate([0, 0, motor_len + motor_wall])
  85                 intersection() {
  86                         translate([motor_diam/2+6, infty/2, 4])
  87                         rotate([90, 0, 0])
  88                                 cylinder(r = 8, h = infty);
  89                         cylinder(r = motor_diam/2 + thick_wall, h = infty);
  90                         rotate([0, 0, -clip_spring_angle/2+eps])
  91                                 cube(infty);
  92                         rotate([0, 0, clip_spring_angle/2-eps])
  93                                 scale([1, -1, 1])
  94                                 cube([infty, infty, 8]);
  95                 };
  96
  97         // fins
  98         for (a = [60, 180, 300]) {
  99                 rotate([0, 0, a])
 100                 translate([motor_diam/2 + thick_wall-thin_wall, 0, motor_wall + motor_len])
 101                         // fin();
 102                         fin2();
 103         };
 104
 105         // rod hole holder
 106         hull() {
 107                 translate([motor_diam/2 + thick_wall - rod_diam/2 - thin_wall,
 108                         0, segment_overlap])
 109                         scale([1, 1.4, 1])
 110                         cylinder(r = rod_diam/2 + thin_wall, h = eps);
 111                 translate([motor_diam/2 + thick_wall + rod_diam/2, 0, segment_overlap + rod_hole_side])
 112                         scale([1, 1.1, 1])
 113                         cylinder(r = rod_diam/2 + thin_wall, h = rod_hole_height);
 114                 translate([motor_diam/2 + thick_wall - rod_diam/2 - thin_wall,
 115                         0, segment_overlap + 2*rod_hole_side + rod_hole_height])
 116                         scale([1, 1.4, 1])
 117                         cylinder(r = rod_diam/2 + thin_wall, h = eps);
 118         };
 119
 120 };
 121
 122 module motor_module() {
 123         difference() {
 124                 motor_module_solid();
 125
 126                 // top ring to hold the motor inside
 127                 translate([0, 0, -eps])
 128                         cylinder(r = motor_diam/2 - motor_wall,
 129                                 h = motor_wall + 2*eps);
 130
 131                 // motor hole
 132                 translate([0, 0, motor_wall - eps])
 133                         cylinder(r = motor_diam/2, h = motor_len + 2*eps);
 134
 135                 // three rails inside the motor hole
 136                 translate([0, 0, segment_overlap + thick_wall]) difference() {
 137                         union() {
 138                                 cylinder(r = motor_diam/2 + thin_wall,
 139                                         h = motor_len - segment_overlap - 2*thick_wall + eps);
 140                                 translate([0, 0, motor_len - segment_overlap - 2*thick_wall])
 141                                         cylinder(r1 = motor_diam/2 + thin_wall, r2 = motor_diam/2, h = thick_wall + eps);
 142                         };
 143                         for (a = [0, 120, 240]) rotate([0, 0, a])
 144                                 translate([motor_diam/2 + 2.5, 0, -eps])
 145                                         cylinder(r = 3, h = infty);
 146                 };
 147
 148                 // clip spring
 149                 for (r = [-clip_spring_angle/2, clip_spring_angle/2]) {
 150                         rotate([0, 0, r])
 151                         translate([-thin_wall/2, 0, motor_len + motor_wall - clip_spring_depth])
 152                                 cube([infty, thin_wall, infty]);
 153                 };
 154                 translate([0, 0, motor_len - eps])
 155                 intersection() {
 156                         cylinder(r = motor_diam/2,
 157                                 h = thick_wall + 2*eps);
 158                         rotate([0, 0, -clip_spring_angle/2+eps])
 159                                 cube(infty);
 160                         rotate([0, 0, clip_spring_angle/2-eps])
 161                                 scale([1, -1, 1])
 162                                 cube([infty, infty, 8]);
 163                 };
 164
 165
 166                 // rod hole
 167                 translate([motor_diam/2 + thick_wall + eps + rod_diam/2, 0, 0])
 168                         cylinder(r = rod_diam/2, h = infty);
 169         };
 170 };
 171
 172 // -------------------- CENTRAL TUBE ---------------------
 173
 174 central_tube_h = 85;
 175
 176 module central_tube_solid() {
 177         cylinder(r = motor_diam/2 + thick_wall, h = central_tube_h);
 178 };
 179
 180 module central_tube() {
 181         difference() {
 182                 central_tube_solid();
 183                 translate([0, 0, -eps])
 184                         cylinder(r = motor_diam/2 + thick_wall - thin_wall,
 185                                 h = infty);
 186         };
 187         // rubber band holder
 188         intersection() {
 189                 cylinder(r = motor_diam/2 + thick_wall - eps, h = central_tube_h);
 190                 translate([motor_diam/2-thin_wall, -infty/2,
 191                         segment_overlap + thick_wall])
 192                         cube([thin_wall, infty, rubber_beam_height]);
 193         };
 194 };
 195
 196 //------------------------- FRONT CONE -----------------------
 197 cone_h = 45;
 198 cone_resolution = 40;
 199 cone_solid_h = 10;
 200
 201 function bez_i4(t, ctls) =
 202         (pow(1-t, 3) * ctls[0])
 203         + (3 * t * pow(1-t, 2) * ctls[1])
 204         + (3 * pow(t, 2) * (1-t) * ctls[2])
 205         + (pow(t, 3) * ctls[3]);
 206
 207 module bezier_cone(cps, res)
 208 {
 209         for (t = [0:1:res])
 210                 translate([0, 0, (bez_i4(t/res, cps))[0]])
 211                         cylinder(r1 = (bez_i4(t/res, cps))[1],
 212                                 r2 = (bez_i4((t + 1)/res, cps))[1],
 213                                 h = (bez_i4((t + 1)/res, cps))[0]
 214                                     - (bez_i4(t/res, cps))[0] + eps);
 215 };
 216
 217 module front_cone_body() {
 218         translate([0, 0, segment_overlap])
 219                 bezier_cone([
 220                         [ 0, motor_diam/2 + thick_wall ], // start
 221                         [ cone_h/2, motor_diam/2 + thick_wall ], // cp 1
 222                         [ cone_h - motor_diam/2 - thick_wall, motor_diam/2 + thick_wall ], // cp 2
 223                         [ cone_h, 0 ],
 224                 ], 40);
 225
 226         translate([0, 0, segment_overlap-thick_wall+thin_wall])
 227                 cylinder(r1 = motor_diam/2+thin_wall,
 228                         r2 = motor_diam/2 + thick_wall,
 229                         h = thick_wall - thin_wall + eps);
 230
 231         cylinder(r = motor_diam/2+thin_wall, h = segment_overlap + eps);
 232 };
 233
 234 module front_cone() {
 235         difference() {
 236                 front_cone_body();
 237                 intersection() {
 238                         translate([0, 0, segment_overlap])
 239                                 bezier_cone([
 240                                         [ 0.7*thin_wall, motor_diam/2 + thick_wall - thin_wall ], // start
 241                                 [ cone_h/2-0.7*thin_wall, motor_diam/2 + thick_wall - thin_wall], // cp 1
 242                                 [ cone_h - motor_diam/2 - thick_wall + thin_wall - 1.4*thin_wall, motor_diam/2 + thick_wall - thin_wall ], // cp 2
 243                                 [ cone_h - 1.4*thin_wall, 0 ],
 244                         ], 40);
 245                         cylinder(r = motor_diam/2 + thick_wall + eps,
 246                                 h = cone_h + segment_overlap - cone_solid_h);
 247                 };
 248
 249                 translate([0, 0, segment_overlap-thick_wall+1.7*thin_wall])
 250                         cylinder(r1 = motor_diam/2,
 251                                 r2 = motor_diam/2 + thick_wall-thin_wall,
 252                                 h = thick_wall-thin_wall + eps);
 253
 254                 translate([0, 0, -eps])
 255                         cylinder(r = motor_diam/2, h = segment_overlap + 2*eps);
 256         };
 257         // rubber band holder
 258         intersection() {
 259                 cylinder(r = motor_diam/2 + thin_wall/2, h = segment_overlap);
 260                 translate([motor_diam/3-thin_wall/2, -infty/2,
 261                         segment_overlap/2 - rubber_beam_height/2])
 262                         cube([thin_wall, infty, rubber_beam_height]);
 263         };
 264 };
 265
 266 module thread_holder() {
 267         rotate([0, 90, 0]) {
 268                 translate([0, 0, -1.5]) difference() {
 269                         cylinder(r = 10, h = 3);
 270                         translate([0, 0, -eps])
 271                                 cylinder(r = 8, h = 3 + 2*eps);
 272                 };
 273         };
 274 }
 275
 276 // thread_holder();
 277
 278 /*
 279 // debug
 280 difference() {
 281         // front_cone();
 282         // central_tube();
 283         motor_module();
 284
 285         translate([0, 0, -eps]) cube(infty);
 286 };
 287 */
 288
 289 // production
 290 $fn = 128;
 291
 292 translate([motor_diam + thick_wall, 0, 0])
 293         motor_module();
 294
 295 rotate([0, 0, 120])
 296 translate([motor_diam + thick_wall, 0, 0])
 297         central_tube();
 298
 299 rotate([0, 0, 240])
 300 translate([motor_diam + thick_wall, 0, 0])
 301         front_cone();