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 + 0.8; // add some tolerance
   6 motor_len  = 69.5 + 0.5;
   7
   8 segment_overlap = 15;
   9
  10 loose_fit_diam_diff = 0.5; // cylinder with outer diameter d1
  11         // will fit loosely into the hole with inner diameter
  12         // d1 + loose_fit_diam_diff
  13 tight_fit_diam_diff = 0.25; // cylinder with outer diameter d1
  14         // will fit tightly into the hole with inner diameter
  15         // d1 + tight_fit_diam_diff
  16
  17 thin_wall = 1.0; // depends on the print width
  18 thick_wall = 2*thin_wall + loose_fit_diam_diff/2;
  19         // motor_diam + 2*thick_wall is the outer diameter of the rocket
  20 motor_wall = thick_wall; // above the motor
  21
  22 clip_height = 3.5;
  23 clip_width = 1.2;
  24 clip_clearance = 1.0;
  25 clip_inner_space = motor_diam/2 - 1.0;
  26
  27 rod_diam = 3.4 + 1;
  28 rubber_beam_height = 3;
  29 rubber_beam_width = 1.5;
  30
  31 fin_thickness = 1.5;
  32
  33 eps = 0.01;
  34 infty = 250;
  35
  36 //----------------- MOTOR MODULE -----------------------------
  37
  38 module fin() {
  39         assign(h1 = 2*motor_len/3, // near end height
  40                 h2 = 20,        // far end height
  41                 h_off = motor_len, // height offset of the far height
  42                 w = 30, // distance of the far height
  43                 fin_w = fin_thickness)
  44         translate([0, -fin_w/2, -h1])
  45         hull() {
  46                 cube([eps, fin_w, h1]); // near end
  47                 translate([w, 0, h_off]) // far end
  48                         cube([eps, fin_w, h2]);
  49         };
  50 };
  51
  52 // alternative fin layout
  53 module fin2() {
  54         assign(h1 = motor_len/2, // near end height
  55                 w2 = 23,        // bottom/far end width
  56                 h_off = 60, // height offset of the far height
  57                 w = 30, // distance of the far height
  58                 fin_w = fin_thickness)
  59         translate([0, -fin_w/2, -h1])
  60         hull() {
  61                 cube([eps, fin_w, h1]); // near end
  62                 translate([w-w2, 0, h_off]) // far end
  63                         cube([w2, fin_w, eps]);
  64         };
  65 };
  66
  67 rod_hole_height = 20;
  68 rod_hole_side = 1.5*(rod_diam + thin_wall);
  69
  70 module motor_module_solid()
  71 {
  72         // cone from loose_fit to tight fit, 1/3 of segment overlap
  73         cylinder(r1 = motor_diam/2 + thin_wall,
  74                 r2 = motor_diam/2 + thick_wall - thin_wall - tight_fit_diam_diff/2,
  75                 h = segment_overlap/3 + eps);
  76
  77         // tight fit cylinder, 2/3 of segment overlap
  78         translate([0, 0, segment_overlap/3])
  79                 cylinder(r = motor_diam/2 + thick_wall - thin_wall - tight_fit_diam_diff/2,
  80                 h = 2*segment_overlap/3 + eps);
  81
  82         // conical joint between the two cylinders
  83         translate([0, 0, segment_overlap - thick_wall + thin_wall])
  84                 cylinder(r1 = motor_diam/2 + thick_wall - thin_wall - tight_fit_diam_diff/2,
  85                         r2 = motor_diam/2 + thick_wall,
  86                         h = thick_wall - thin_wall + eps);
  87
  88         // the thick cylinder above it
  89         translate([0, 0, segment_overlap])
  90                 cylinder(r = motor_diam/2 + thick_wall,
  91                 h = motor_len + motor_wall - segment_overlap);
  92
  93         // fins
  94         for (a = [60, 180, 300]) {
  95                 rotate([0, 0, a])
  96                 translate([motor_diam/2 + thick_wall-thin_wall, 0, motor_wall + motor_len])
  97                         // fin();
  98                         fin2();
  99         };
 100
 101         // rod hole holder
 102         hull() {
 103                 translate([motor_diam/2 + thick_wall - rod_diam/2 - thin_wall,
 104                         0, segment_overlap])
 105                         scale([1, 1.4, 1])
 106                         cylinder(r = rod_diam/2 + thin_wall, h = eps);
 107                 translate([motor_diam/2 + thick_wall + thin_wall + rod_diam/2, 0, segment_overlap + rod_hole_side])
 108                         scale([1, 1.1, 1])
 109                         cylinder(r = rod_diam/2 + thin_wall, h = rod_hole_height);
 110                 translate([motor_diam/2 + thick_wall - rod_diam/2 - thin_wall,
 111                         0, segment_overlap + 2*rod_hole_side + rod_hole_height])
 112                         scale([1, 1.4, 1])
 113                         cylinder(r = rod_diam/2 + thin_wall, h = eps);
 114         };
 115
 116         // motor clip
 117         for (angle = [120, -120]) rotate([0, 0, angle]) intersection() {
 118                 translate([clip_inner_space, -infty/2,
 119                         motor_len + motor_wall + clip_clearance])
 120                         cube([clip_width, infty, clip_height]);
 121                 rotate([0, 0, -60])
 122                         translate([-infty/2, 0, 0]) cube(infty);
 123                 rotate([0, 0, -120])
 124                         translate([-infty/2, 0, 0]) cube(infty);
 125         };
 126 };
 127
 128 module motor_module() {
 129         difference() {
 130                 motor_module_solid();
 131
 132                 // top ring to hold the motor inside
 133                 translate([0, 0, -eps])
 134                         cylinder(r = motor_diam/2 - motor_wall,
 135                                 h = motor_wall + 2*eps);
 136
 137                 // motor hole
 138                 translate([0, 0, motor_wall - eps])
 139                         cylinder(r = motor_diam/2, h = motor_len + 2*eps);
 140
 141                 // three rails inside the motor hole
 142                 translate([0, 0, segment_overlap + thick_wall]) difference() {
 143                         union() {
 144                                 cylinder(r = motor_diam/2 + thin_wall,
 145                                         h = motor_len - segment_overlap - 2*thick_wall + eps);
 146                                 translate([0, 0, motor_len - segment_overlap - 2*thick_wall])
 147                                         cylinder(r1 = motor_diam/2 + thin_wall, r2 = motor_diam/2, h = thick_wall + eps);
 148                         };
 149                         for (a = [0, 120, 240]) rotate([0, 0, a])
 150                                 translate([motor_diam/2 + 2.5, 0, -eps])
 151                                         cylinder(r = 3, h = infty);
 152                 };
 153
 154                 // rod hole
 155                 translate([motor_diam/2 + thick_wall + thin_wall + eps + rod_diam/2, 0, 0])
 156                         cylinder(r = rod_diam/2, h = infty);
 157         };
 158 };
 159
 160 // -------------------- CENTRAL TUBE ---------------------
 161
 162 central_tube_h = 97;
 163
 164 central_clip_r = 12;
 165 central_clip_w = 4;
 166 central_clip_wall = 1.5;
 167 central_clip_clearance = 2.5;
 168
 169 module central_tube_solid() {
 170         cylinder(r = motor_diam/2 + thick_wall, h = central_tube_h);
 171 };
 172
 173 module central_tube() {
 174         difference() {
 175                 central_tube_solid();
 176                 translate([0, 0, -eps])
 177                         cylinder(r = motor_diam/2 + thick_wall - thin_wall,
 178                                 h = infty);
 179         };
 180         // rubber band holder
 181         intersection() {
 182                 cylinder(r = motor_diam/2 + thick_wall - eps, h = central_tube_h);
 183 /*
 184                 translate([motor_diam/2 - thick_wall, -infty/2,
 185                         segment_overlap + thick_wall])
 186                         cube([thin_wall, infty, rubber_beam_height]);
 187 */
 188                 translate([-central_clip_w/2,
 189                         central_clip_r + motor_diam/2 + thick_wall - 2*thin_wall - central_clip_clearance,
 190                         central_tube_h/3]) rotate([0, 90, 0]) difference() {
 191                         cylinder(r = central_clip_r, h = central_clip_w);
 192                         translate([0, 0, -eps])
 193                                 cylinder(r = central_clip_r - central_clip_wall, h = central_clip_w + 2*eps);
 194                 }
 195         };
 196 };
 197
 198 //------------------------- FRONT CONE -----------------------
 199 cone_h = 45;
 200 cone_resolution = 40;
 201 cone_solid_h = 10;
 202
 203 function bez_i4(t, ctls) =
 204         (pow(1-t, 3) * ctls[0])
 205         + (3 * t * pow(1-t, 2) * ctls[1])
 206         + (3 * pow(t, 2) * (1-t) * ctls[2])
 207         + (pow(t, 3) * ctls[3]);
 208
 209 module bezier_cone(cps, res)
 210 {
 211         for (t = [0:1:res])
 212                 translate([0, 0, (bez_i4(t/res, cps))[0]])
 213                         cylinder(r1 = (bez_i4(t/res, cps))[1],
 214                                 r2 = (bez_i4((t + 1)/res, cps))[1],
 215                                 h = (bez_i4((t + 1)/res, cps))[0]
 216                                     - (bez_i4(t/res, cps))[0] + eps);
 217 };
 218
 219 module front_cone_body() {
 220         translate([0, 0, segment_overlap])
 221                 bezier_cone([
 222                         [ 0, motor_diam/2 + thick_wall ], // start
 223                         [ cone_h/4, motor_diam/2 + thick_wall ], // cp 1
 224                         [ cone_h - motor_diam/2 - thick_wall, motor_diam/2 + thick_wall ], // cp 2
 225                         [ cone_h, 0 ],
 226                 ], 40);
 227
 228         translate([0, 0, segment_overlap-thick_wall+thin_wall])
 229                 cylinder(r1 = motor_diam/2+thin_wall,
 230                         r2 = motor_diam/2 + thick_wall,
 231                         h = thick_wall - thin_wall + eps);
 232
 233         cylinder(r = motor_diam/2+thin_wall, h = segment_overlap + eps);
 234 };
 235
 236 module front_cone() {
 237         difference() {
 238                 front_cone_body();
 239                 intersection() {
 240                         translate([0, 0, segment_overlap])
 241                                 bezier_cone([
 242                                         [ 0.7*thin_wall, motor_diam/2 + thick_wall - thin_wall ], // start
 243                                 [ cone_h/4-0.7*thin_wall, motor_diam/2 + thick_wall - thin_wall], // cp 1
 244                                 [ cone_h - motor_diam/2 - thick_wall + thin_wall - 1.4*thin_wall, motor_diam/2 + thick_wall - thin_wall ], // cp 2
 245                                 [ cone_h - 1.4*thin_wall, 0 ],
 246                         ], 40);
 247                         cylinder(r = motor_diam/2 + thick_wall + eps,
 248                                 h = cone_h + segment_overlap - cone_solid_h);
 249                 };
 250
 251                 translate([0, 0, segment_overlap-thick_wall+1.7*thin_wall])
 252                         cylinder(r1 = motor_diam/2,
 253                                 r2 = motor_diam/2 + thick_wall-thin_wall,
 254                                 h = thick_wall-thin_wall + eps);
 255
 256                 translate([0, 0, -eps])
 257                         cylinder(r = motor_diam/2, h = segment_overlap + 2*eps);
 258         };
 259         // rubber band holder
 260         intersection() {
 261                 cylinder(r = motor_diam/2 + thin_wall/2, h = segment_overlap);
 262                 translate([motor_diam/3-thin_wall/2, -infty/2,
 263                         segment_overlap - thick_wall - rubber_beam_height - eps])
 264                         cube([rubber_beam_width, infty, rubber_beam_height]);
 265         };
 266 };
 267
 268 debug = 0;
 269
 270 if (debug == 1) {
 271 // debug
 272 difference($fn = 16) {
 273         front_cone();
 274         // central_tube();
 275         // motor_module();
 276
 277         translate([0, 0, -infty/2]) cube(infty);
 278 };
 279
 280 } else {
 281
 282 // production
 283 assign($fn = 128) {
 284
 285 translate([motor_diam + thick_wall, 0, 0])
 286         motor_module();
 287
 288 rotate([0, 0, 120])
 289 translate([motor_diam + thick_wall, 0, 0])
 290         central_tube();
 291
 292 rotate([0, 0, 240])
 293 translate([motor_diam + thick_wall, 0, 0])
 294         front_cone();
 295
 296 }
 297 }