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 + 1.2; // add some tolerance
   6 motor_len  = 69.5 + 0.5;
   7
   8 segment_overlap = 15;
   9
  10 loose_fit_diam_diff = 1.1; // 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 = 0.4; // 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 - 1.5;
  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 // rod holder
  37
  38 module rod_holder() {
  39         // rod hole holder
  40         hull() {
  41                 translate([motor_diam/2 + thick_wall + thin_wall + rod_diam/2, 0, 0])
  42                         cylinder(r = rod_diam/2 + thin_wall, h = thick_wall);
  43                 translate([motor_diam/2 + thick_wall - thin_wall - rod_diam/2, 0, 0])
  44
  45                         cylinder(r = rod_diam/2 + thin_wall, h = 3*thick_wall);
  46         }
  47 }
  48
  49 module rod_hole() {
  50         // rod hole
  51         translate([motor_diam/2 + thick_wall + thin_wall + eps + rod_diam/2, 0, 0])
  52                 cylinder(r = rod_diam/2, h = infty);
  53 }
  54
  55 //----------------- MOTOR MODULE -----------------------------
  56
  57 module fin() {
  58         assign(h1 = 2*motor_len/3, // near end height
  59                 h2 = 20,        // far end height
  60                 h_off = motor_len, // height offset of the far height
  61                 w = 30, // distance of the far height
  62                 fin_w = fin_thickness)
  63         translate([0, -fin_w/2, -h1])
  64         hull() {
  65                 cube([eps, fin_w, h1]); // near end
  66                 translate([w, 0, h_off]) // far end
  67                         cube([eps, fin_w, h2]);
  68         };
  69 };
  70
  71 // alternative fin layout
  72 module fin2() {
  73         assign(h1 = motor_len/2, // near end height
  74                 w2 = 23,        // bottom/far end width
  75                 h_off = 60, // height offset of the far height
  76                 w = 30, // distance of the far height
  77                 fin_w = fin_thickness)
  78         translate([0, -fin_w/2, -h1])
  79         hull() {
  80                 cube([eps, fin_w, h1]); // near end
  81                 translate([w-w2, 0, h_off]) // far end
  82                         cube([w2, fin_w, eps]);
  83         };
  84 };
  85
  86 rod_hole_height = 20;
  87 rod_hole_side = 1.5*(rod_diam + thin_wall);
  88
  89 module motor_module_solid()
  90 {
  91         // cone from loose_fit to tight fit, 1/3 of segment overlap
  92         cylinder(r1 = motor_diam/2 + thin_wall,
  93                 r2 = motor_diam/2 + thick_wall - thin_wall - tight_fit_diam_diff/2,
  94                 h = segment_overlap/3 + eps);
  95
  96         // tight fit cylinder, 2/3 of segment overlap
  97         translate([0, 0, segment_overlap/3])
  98                 cylinder(r = motor_diam/2 + thick_wall - thin_wall - tight_fit_diam_diff/2,
  99                 h = 2*segment_overlap/3 + eps);
 100
 101         // conical joint between the two cylinders
 102         translate([0, 0, segment_overlap - thick_wall + thin_wall])
 103                 cylinder(r1 = motor_diam/2 + thick_wall - thin_wall - tight_fit_diam_diff/2,
 104                         r2 = motor_diam/2 + thick_wall,
 105                         h = thick_wall - thin_wall + eps);
 106
 107         // the thick cylinder above it
 108         translate([0, 0, segment_overlap])
 109                 cylinder(r = motor_diam/2 + thick_wall,
 110                 h = motor_len + motor_wall - segment_overlap);
 111
 112         // fins
 113         for (a = [60, 180, 300]) {
 114                 rotate([0, 0, a])
 115                 translate([motor_diam/2 + thick_wall-thin_wall, 0, motor_wall + motor_len])
 116                         // fin();
 117                         fin2();
 118         };
 119
 120         // motor clip
 121         for (angle = [120, -120]) rotate([0, 0, angle]) intersection() {
 122                 translate([clip_inner_space, -infty/2,
 123                         motor_len + motor_wall + clip_clearance])
 124                         cube([clip_width, infty, clip_height]);
 125                 rotate([0, 0, -60])
 126                         translate([-infty/2, 0, 0]) cube(infty);
 127                 rotate([0, 0, -120])
 128                         translate([-infty/2, 0, 0]) cube(infty);
 129         };
 130
 131         translate([0, 0, motor_len + motor_wall])
 132                 scale([1, 1, -1])
 133                 rod_holder();
 134 };
 135
 136 module motor_module() {
 137         difference() {
 138                 motor_module_solid();
 139
 140                 // top ring to hold the motor inside
 141                 translate([0, 0, -eps])
 142                         cylinder(r = motor_diam/2 - motor_wall,
 143                                 h = motor_wall + 2*eps);
 144
 145                 // motor hole
 146                 translate([0, 0, motor_wall - eps])
 147                         cylinder(r = motor_diam/2, h = motor_len + 2*eps);
 148
 149                 // three rails inside the motor hole
 150                 translate([0, 0, segment_overlap + thick_wall]) difference() {
 151                         union() {
 152                                 cylinder(r = motor_diam/2 + thin_wall,
 153                                         h = motor_len - segment_overlap - 2*thick_wall + eps);
 154                                 translate([0, 0, motor_len - segment_overlap - 2*thick_wall])
 155                                         cylinder(r1 = motor_diam/2 + thin_wall, r2 = motor_diam/2, h = thick_wall + eps);
 156                         };
 157                         for (a = [0, 120, 240]) rotate([0, 0, a])
 158                                 translate([motor_diam/2 + 2.5, 0, -eps])
 159                                         cylinder(r = 3, h = infty);
 160                 };
 161
 162                 rod_hole();
 163         };
 164 };
 165
 166 // -------------------- CENTRAL TUBE ---------------------
 167
 168 central_tube_h = 97;
 169
 170 central_clip_r = 12;
 171 central_clip_w = 4;
 172 central_clip_wall = 1.5;
 173 central_clip_clearance = 2.5;
 174
 175 module central_tube_solid() {
 176         cylinder(r = motor_diam/2 + thick_wall, h = central_tube_h);
 177         rod_holder();
 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                 rod_hole();
 187         };
 188 };
 189
 190 //------------------------- FRONT CONE -----------------------
 191 cone_h = 45;
 192 cone_resolution = 40;
 193 cone_solid_h = 10;
 194
 195 function bez_i4(t, ctls) =
 196         (pow(1-t, 3) * ctls[0])
 197         + (3 * t * pow(1-t, 2) * ctls[1])
 198         + (3 * pow(t, 2) * (1-t) * ctls[2])
 199         + (pow(t, 3) * ctls[3]);
 200
 201 module bezier_cone(cps, res)
 202 {
 203         for (t = [0:1:res])
 204                 translate([0, 0, (bez_i4(t/res, cps))[0]])
 205                         cylinder(r1 = (bez_i4(t/res, cps))[1],
 206                                 r2 = (bez_i4((t + 1)/res, cps))[1],
 207                                 h = (bez_i4((t + 1)/res, cps))[0]
 208                                     - (bez_i4(t/res, cps))[0] + eps);
 209 };
 210
 211 module front_cone_body() {
 212         translate([0, 0, segment_overlap])
 213                 bezier_cone([
 214                         [ 0, motor_diam/2 + thick_wall ], // start
 215                         [ cone_h/4, motor_diam/2 + thick_wall ], // cp 1
 216                         [ cone_h - motor_diam/2 - thick_wall, motor_diam/2 + thick_wall ], // cp 2
 217                         [ cone_h, 0 ],
 218                 ], 40);
 219
 220         translate([0, 0, segment_overlap-thick_wall+thin_wall])
 221                 cylinder(r1 = motor_diam/2+thin_wall,
 222                         r2 = motor_diam/2 + thick_wall,
 223                         h = thick_wall - thin_wall + eps);
 224
 225         cylinder(r = motor_diam/2+thin_wall, h = segment_overlap + eps);
 226 };
 227
 228 module front_cone() {
 229         difference() {
 230                 front_cone_body();
 231                 intersection() {
 232                         translate([0, 0, segment_overlap])
 233                                 bezier_cone([
 234                                         [ 0.7*thin_wall, motor_diam/2 + thick_wall - thin_wall ], // start
 235                                 [ cone_h/4-0.7*thin_wall, motor_diam/2 + thick_wall - thin_wall], // cp 1
 236                                 [ cone_h - motor_diam/2 - thick_wall + thin_wall - 1.4*thin_wall, motor_diam/2 + thick_wall - thin_wall ], // cp 2
 237                                 [ cone_h - 1.4*thin_wall, 0 ],
 238                         ], 40);
 239                         cylinder(r = motor_diam/2 + thick_wall + eps,
 240                                 h = cone_h + segment_overlap - cone_solid_h);
 241                 };
 242
 243                 translate([0, 0, segment_overlap-thick_wall+1.7*thin_wall])
 244                         cylinder(r1 = motor_diam/2,
 245                                 r2 = motor_diam/2 + thick_wall-thin_wall,
 246                                 h = thick_wall-thin_wall + eps);
 247
 248                 translate([0, 0, -eps])
 249                         cylinder(r = motor_diam/2, h = segment_overlap + 2*eps);
 250         };
 251 };
 252
 253 debug = 0;
 254
 255 if (debug == 1) {
 256 // debug
 257 difference($fn = 16) {
 258         front_cone();
 259         central_tube();
 260         motor_module();
 261
 262         translate([0, 0, -infty/2]) cube(infty);
 263 };
 264
 265 } else {
 266
 267 // production
 268 $fn = 128;
 269
 270 translate([motor_diam + thick_wall, 0, 0])
 271         motor_module();
 272
 273 rotate([0, 0, 120])
 274 translate([motor_diam + thick_wall, 0, 0])
 275         central_tube();
 276
 277 rotate([0, 0, 240])
 278 translate([motor_diam + thick_wall, 0, 0])
 279         front_cone();
 280
 281 }