topeak-mtx-tortec-expeditionrack-adapter.scad

   1 // -*- C -*-
   2
   3 // brk_*: "bracket", the Topeak MTX bracket
   4 // rack_*: the Tortec rack
   5 // adapt_*: the adapter, ie this file
   6
   7 include <utils.scad>
   8
   9 // strength factor, set to 1 for real prints
  10 //$strf = 0.25;
  11 $strf = 1;
  12
  13 brk_recess_actual = 5.20;
  14
  15 rack_rail_dia = 10.40 + 0.30;
  16 rack_width_inner = 115.86 - 1.0; // between insides of rails
  17
  18 rear_elevation_nominal = 10.04;
  19 // ^ top of rack to bottom of bracket, at rack cross rail (fam)
  20 rear_to_front_distance = 230; // rack cross rail (fam) to very front end
  21 rear_to_cross_rail = 35.05; // bolt centre to rail centre, rail to rear
  22 rear_bolt_to_front_bolt = 155.4;
  23
  24 general_gap_y = 1.0;
  25
  26 strap_w = 8.0 + 1.0;
  27 strap_th = 2.5;
  28 strap_barrel_dia = 14;
  29 strap_guide_sz = 1;
  30
  31 brk_block_xw = 68.5;
  32 brk_block_z = 14.55 - 0.75;
  33
  34 brk_bolt_dia = 4.0 + 0.5;
  35 brk_nearbolt_recess_dia = 8.86 + 1.5;
  36 brk_nearbolt_recess_depth = 1.09 + 0.25;
  37
  38 brk_bolt_eff_len = 11.78 - 1.0; // inside of recess, to end of bolt
  39 brk_bolt_len_slop = 2.0;;
  40 brk_bolt_nut_th = 3.89;
  41 brk_bolt_nut_across_flats = 7.86 + 0.50;
  42
  43 brk_overall_w = 90.07;
  44
  45 fit_slope_len = 5;
  46
  47 // "foreaftmaint" aka "fam" is the hook-like part that stops
  48 // the adapter sliding forwards/backwards along the rails
  49 foreaftmaint_r_slop = 0.75;
  50
  51 main_sz_y = $strf * 18;
  52 grasp_sz = $strf * 6;
  53 grasp_thin_sz = $strf * 0.5;
  54 beside_strap_sz = $strf * 8;
  55 main_sz_core_z = $strf * 18;
  56
  57 // "length" in for-aft direction of interaction with rack rail
  58 min_on_rail_sz_z = $strf * 25;
  59
  60 $fa=10;
  61 $fs=1;
  62
  63 // calculated
  64
  65 main_sz_rhs_z = max(min_on_rail_sz_z, beside_strap_sz*2 + strap_w);
  66 main_sz_lhs_z = min_on_rail_sz_z;
  67
  68 main_sz_x_fam = main_sz_y;
  69
  70 brk_bottom_y = -brk_recess_actual;
  71 adapt_main_top_y = brk_bottom_y - general_gap_y;
  72
  73 // on LHS, so -ve
  74 rack_rail_x = -(rack_width_inner/2 + rack_rail_dia/2);
  75 rack_rail_outer_x = -(rack_width_inner/2 + rack_rail_dia);
  76
  77 grasp_large_r = (rack_rail_dia + grasp_sz)/2;
  78 grasp_small_r = (rack_rail_dia + grasp_thin_sz)/2;
  79 grasp_large_x = rack_rail_outer_x + grasp_large_r;
  80 grasp_small_x = rack_rail_outer_x + grasp_small_r;
  81
  82 block_x = grasp_large_x + grasp_large_r;
  83 block_y_min = adapt_main_top_y - main_sz_y;
  84
  85 strap_barrel_x = rack_width_inner/2 + strap_barrel_dia/2;
  86
  87 rack_shear_ratio = -rear_elevation_nominal / rear_to_front_distance;
  88
  89 brk_bolt_nut_top_y = -brk_nearbolt_recess_depth
  90   - brk_bolt_eff_len + brk_bolt_nut_th + brk_bolt_len_slop;
  91
  92 brk_bolt_nut_r = brk_bolt_nut_across_flats/2 / cos(360/12);
  93
  94 function elevation_of_bolt_for(z) = rear_elevation_nominal
  95   - (z - brk_block_z/2) * rack_shear_ratio;
  96
  97 function rack_rail_y_of_elevation(elevation_nominal) =
  98   brk_bottom_y - elevation_nominal - general_gap_y  - rack_rail_dia/2;
  99
 100 echo(rack_shear_ratio);
 101
 102 module GraspElevation(){
 103   hull(){
 104     translate([ grasp_large_x, adapt_main_top_y - grasp_large_r ])
 105       circle(grasp_large_r);
 106
 107     translate([ grasp_small_x, $rack_rail_y - rack_rail_dia/2 ])
 108       circle(grasp_small_r);
 109
 110     translate([ rack_rail_x + grasp_large_r/2,
 111                 $rack_rail_y - rack_rail_dia/2 ])
 112       circle(grasp_small_r);
 113
 114     translate([ grasp_large_x, $rack_rail_y + rack_rail_dia/2 ])
 115       circle(grasp_large_r);
 116
 117     translate([ grasp_large_x + grasp_large_r/2,
 118                 $rack_rail_y + rack_rail_dia/2 ])
 119       circle(grasp_large_r);
 120   }
 121 }
 122
 123 module BlockElevation(){
 124   hull(){
 125     rectfromto([ +block_x, adapt_main_top_y ],
 126                [ -block_x, block_y_min ]);
 127     rectfromto([ -grasp_large_x, adapt_main_top_y ],
 128                [ +grasp_large_x, adapt_main_top_y - 0.1 ]);
 129   }
 130   hull(){
 131     rectfromto([ +block_x, adapt_main_top_y ],
 132                [ -block_x, block_y_min ]);
 133     rectfromto([ grasp_large_x, block_y_min ],
 134                [ 0, block_y_min + 0.1 ]);
 135   }
 136 }
 137
 138 module MainExtrude(z){
 139   linextr(0, z)
 140     children();
 141 }
 142 module RackShear(){
 143   s = rack_shear_ratio;
 144   multmatrix([ [ 1, 0,  0, 0 ],
 145                [ 0, 1, s , 0 ],
 146                [ 0, 0,  1, 0 ],
 147                [ 0, 0,  0, 1 ] ])
 148     children();
 149 }
 150
 151 module GraspFixingElevation(){
 152   intersection(){
 153     union(){
 154       hull(){
 155         mirror([1,0]) {
 156           GraspElevation();
 157         }
 158         translate([ -block_x, block_y_min ] + [0,0.1]*1 )
 159           circle(0.1);
 160       }
 161       translate([ strap_barrel_x, $strap_barrel_y ])
 162         circle(strap_barrel_dia/2 + strap_guide_sz);
 163     }
 164     union(){
 165       rectfromto([0, $rack_rail_y],
 166                  [rack_width_inner, 50]);
 167       intersection(){
 168         translate([ rack_rail_x, $rack_rail_y ])
 169           circle(r = rack_width_inner/2 - rack_rail_x);
 170         polygon([ [ -block_x-0.1, 0 ],
 171                   [ rack_width_inner/2, 0 ],
 172                   $rail_fixing_fit_corner,
 173                   $rail_fixing_fit_corner + [-1,-1] * fit_slope_len,
 174                   [ -grasp_large_x - grasp_large_r*2, block_y_min ],
 175                   [ -block_x-0.1 -2, block_y_min +2 ]]);
 176       }
 177     }
 178   }
 179 }
 180
 181 module StrapBarrelElevation(){
 182   translate([ strap_barrel_x, $strap_barrel_y ])
 183     circle(strap_barrel_dia/2);
 184 }
 185
 186 // Bracket support block, goes up inside bracket
 187 // Z origin is bolt hole
 188 module BrkBlock(){
 189   linextr( -brk_block_z/2,
 190            +brk_block_z/2 ) {
 191     rectfromto([ -brk_block_xw/2, adapt_main_top_y - 0.1 ],
 192                [ +brk_block_xw/2, 0 ]);
 193   }
 194 }
 195
 196 // Z origin is bolt hole
 197 module BoltHole(){
 198   linextr_y_xz( -100, 10 )
 199     circle(brk_bolt_dia/2);
 200
 201   linextr_y_xz( -brk_nearbolt_recess_depth, 10)
 202     circle(brk_nearbolt_recess_dia/2);
 203
 204   linextr_y_xz( -100, brk_bolt_nut_top_y ) {
 205     circle( r= brk_bolt_nut_r, $fn = 6 );
 206     translate([ 0, brk_bolt_nut_across_flats/2 ])
 207       circle( r=brk_bolt_nut_r/2, $fn = 4);
 208   }
 209 }
 210
 211 module IfFam(){
 212   if ($foreaftmaint_dz) {
 213     children();
 214   }
 215 }
 216
 217 module FamLinextr(){
 218   IfFam()
 219     linextr_x_yz(-main_sz_x_fam/2, +main_sz_x_fam/2)
 220     rotate(-90)
 221     children();
 222 }
 223
 224 module FamGraspElevation(){
 225   difference(){
 226     hull(){
 227       ybot = $rack_rail_y - rack_rail_dia/2 + grasp_large_r
 228         - fit_slope_len * 0.5;
 229       for (y = [
 230                 ybot,
 231                 adapt_main_top_y - grasp_large_r
 232                 ])
 233         for (dx= [-1,+1] * rack_rail_dia/2)
 234           translate([ -$foreaftmaint_rail_z + dx, y ])
 235             circle(r= grasp_large_r);
 236     }
 237     translate([0, adapt_main_top_y])
 238       rectfromto([-500, 0], [500, 500]);
 239   }
 240 }
 241
 242 module Principal(){
 243   // calculated
 244   $rack_rail_y = rack_rail_y_of_elevation($elevation_nominal);
 245
 246   $strap_barrel_y = $rack_rail_y + rack_rail_dia/2 + strap_barrel_dia/2;
 247
 248   $rail_fixing_fit_corner = [
 249     rack_width_inner/2,
 250     $rack_rail_y - rack_rail_dia/2
 251   ];
 252
 253   $foreaftmaint_rail_z = brk_block_z/2 + $foreaftmaint_dz;
 254
 255   difference(){
 256     union(){
 257       MainExtrude(main_sz_lhs_z){
 258         GraspElevation();
 259       }
 260       RackShear() MainExtrude(main_sz_rhs_z){
 261         StrapBarrelElevation();
 262       }
 263       translate([ 0,0, brk_block_z/2]) {
 264         BrkBlock();
 265       }
 266
 267       difference(){
 268         union(){
 269           MainExtrude(main_sz_core_z){
 270             BlockElevation();
 271           }
 272           if ($strf<1) {
 273             MainExtrude(max(brk_block_z, main_sz_rhs_z)){
 274               rectfromto([-8, 0],
 275                          [+8, block_y_min]);
 276               rectfromto([-block_x -5,  adapt_main_top_y],
 277                          [-grasp_large_x, block_y_min]);
 278             }
 279           }
 280           RackShear() MainExtrude(main_sz_rhs_z){
 281             GraspFixingElevation();
 282           }
 283         }
 284
 285         translate([0,0, main_sz_rhs_z/2]) linextr(-strap_w/2, +strap_w/2) {
 286           translate([ rack_width_inner/2 - strap_th, 0 ])
 287             rectfromto([ 0, -50 ], [ 50, 50 ]);
 288         }
 289       }
 290
 291         FamLinextr(){
 292           rectfromto([ -$foreaftmaint_rail_z, adapt_main_top_y ],
 293                      [ 0, block_y_min]);
 294           FamGraspElevation();
 295         }
 296
 297       RackShear()
 298         FamLinextr()
 299         FamGraspElevation();
 300     }
 301
 302     RackShear() linextr(-10, main_sz_lhs_z+main_sz_rhs_z) {
 303       for (mx=[0,1]) {
 304         mirror([mx,0]) {
 305           translate([ rack_rail_x, $rack_rail_y ]){
 306             hull(){
 307               for (dx = [-rack_rail_dia, 0])
 308                 translate([dx, 0])
 309                   circle(r= rack_rail_dia/2);
 310             }
 311           }
 312         }
 313       }
 314     }
 315
 316     RackShear() IfFam(){
 317       // Distance from bolt hole, in backwards direction
 318       cr = rack_rail_dia/2 + foreaftmaint_r_slop;
 319       translate([ 0, $rack_rail_y, $foreaftmaint_rail_z ])
 320         linextr_x_yz(+rack_rail_x,
 321                      -rack_rail_x) {
 322         hull(){
 323           for (dy=[0,50]) {
 324             translate([-dy,0])
 325               circle(r= cr);
 326           }
 327         }
 328         hull(){
 329           for (dd=[[0,0], [-1,-1], [-1,+1]]) {
 330             translate(
 331                       [-1, 0] * (rack_rail_dia - fit_slope_len)
 332                       + 20 * dd
 333                       )
 334               circle(r= cr);
 335           }
 336         }
 337       }
 338     }
 339
 340     translate([ 0,0, brk_block_z/2]) BoltHole();
 341   }
 342 }
 343
 344 module RackForDemo(){ ////toplevel
 345   elevation = elevation_of_bolt_for(rear_to_cross_rail);
 346   rack_rail_y = rack_rail_y_of_elevation(elevation);
 347
 348   rotate([-atan(rack_shear_ratio), 0,0])
 349     translate([0, rack_rail_y, brk_block_z/2 + rack_rail_y*rack_shear_ratio]) {
 350       for (m=[0]) mirror([m,0,0]) {
 351         linextr(-50, 50 + rear_to_cross_rail)
 352           translate([rack_rail_x, 0])
 353           circle(r= rack_rail_dia/2);
 354         }
 355       translate([0,0, rear_to_cross_rail])
 356         linextr_x_yz(rack_rail_x, -rack_rail_x)
 357         circle(r= rack_rail_dia/2);
 358     }
 359 }
 360
 361 module Front(){ ////toplevel
 362   // xxx elevation is wrong
 363   Principal($elevation_nominal=
 364       elevation_of_bolt_for(rear_to_cross_rail + rear_bolt_to_front_bolt),
 365             $foreaftmaint_dz= 0);
 366 }
 367
 368 module Rear(){ ////toplevel
 369   Principal($elevation_nominal=
 370       elevation_of_bolt_for(rear_to_cross_rail),
 371             $foreaftmaint_dz= rear_to_cross_rail);
 372 }
 373
 374 module SomeDemo(){
 375   rotate([90, 0, 0]){
 376     children();
 377
 378     color("blue")
 379       translate([ 0, -2, -4 ])
 380       square(center=true, [ brk_overall_w, 1 ]);
 381
 382   }
 383 }
 384
 385 module FrontDemo(){ ////toplevel
 386   SomeDemo() Front();
 387 }
 388 module RearDemo(){ ////toplevel
 389   SomeDemo() Rear();
 390 }
 391 module RearRackDemo(){ ////toplevel
 392   rotate([atan(rack_shear_ratio),0,0]) SomeDemo() {
 393     Rear();
 394     %RackForDemo();
 395   }
 396 }