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 brk_recess_actual = 5.20;
  10
  11 rack_rail_dia = 10.40 + 0.50;
  12 rack_width_inner = 115.86 + 1.0; // between insides of rails
  13
  14 rear_elevation_nominal = 10.04; // top of rack to bottom of bracket
  15 rear_to_front_distance = 230;
  16
  17 general_gap_y = 1.0;
  18
  19 strap_w = 8.0;
  20 strap_th = 2.5;
  21 strap_barrel_dia = 12;
  22 strap_guide_sz = 2;
  23
  24 main_sz_y = 20;
  25 grasp_sz = 12;
  26 beside_strap_sz = 8;
  27
  28 // calculated
  29
  30 main_sz_z = beside_strap_sz*2 + strap_w;
  31
  32 brk_bottom_y = -brk_recess_actual;
  33 adapt_main_top_y = brk_bottom_y + general_gap_y;
  34
  35 // on LHS, so -ve
  36 rack_rail_x = -(rack_width_inner/2 + rack_rail_dia/2);
  37 rack_rail_outer_x = -(rack_width_inner/2 + rack_rail_dia);
  38
  39 grasp_large_r = (rack_rail_dia + grasp_sz)/2;
  40 grasp_large_x = rack_rail_outer_x + grasp_large_r;
  41
  42 block_x = grasp_large_x + grasp_large_r/2;
  43 block_y_min = adapt_main_top_y - main_sz_y;
  44
  45 strap_barrel_x = rack_width_inner/2 + strap_barrel_dia/2;
  46
  47 module GraspElevation(){
  48   hull(){
  49     translate([ grasp_large_x, adapt_main_top_y - grasp_large_r ])
  50       circle(grasp_large_r);
  51
  52     translate([ grasp_large_x, $rack_rail_y - rack_rail_dia/2 ])
  53       circle(grasp_large_r);
  54
  55     translate([ grasp_large_x, $rack_rail_y + rack_rail_dia/2 ])
  56       circle(grasp_large_r);
  57   }
  58 }
  59
  60 module BlockElevation(){
  61   rectfromto([ +block_x, adapt_main_top_y ],
  62              [ -block_x, block_y_min ]);
  63 }
  64
  65 module MainExtrude(){
  66   linextr(0, main_sz_z)
  67     children();
  68 }
  69 module RackShear(){
  70   multmatrix([ [ 1, 0,   0, 0 ],
  71                [ 0, 1, 0.1, 0 ],
  72                [ 0, 0,   1, 0 ],
  73                [ 0, 0,   0, 1 ] ])
  74     children();
  75 }
  76
  77 module GraspFixingElevation(){
  78   intersection(){
  79     union(){
  80       mirror([1,0]) GraspElevation();
  81       translate([ strap_barrel_x, $strap_barrel_y ])
  82         circle(strap_barrel_dia/2 + strap_guide_sz);
  83     }
  84     union(){
  85       rectfromto([0, $rack_rail_y],
  86                  [rack_width_inner, 50]);
  87       intersection(){
  88         translate([ rack_rail_x, $rack_rail_y ])
  89           circle(r = rack_width_inner/2 - rack_rail_x, $fa=1);
  90         polygon([ [ 0, 0 ],
  91                   [ rack_width_inner/2, 0 ],
  92                   [ rack_width_inner/2, $rack_rail_y - rack_rail_dia/2 ],
  93                   [ -block_x, block_y_min ],
  94                   [ 0, block_y_min ]]);
  95       }
  96     }
  97   }
  98 }
  99
 100 module StrapBarrelElevation(){
 101   translate([ strap_barrel_x, $strap_barrel_y ])
 102     circle(strap_barrel_dia/2);
 103 }
 104
 105 module Principal(){
 106   // calculated
 107   $rack_rail_y = brk_bottom_y - $elevation_nominal
 108     - general_gap_y  - rack_rail_dia/2;
 109
 110   $strap_barrel_y = $rack_rail_y + rack_rail_dia/2 + strap_barrel_dia/2;
 111
 112   difference(){
 113     union(){
 114       MainExtrude(){
 115         GraspElevation();
 116         BlockElevation();
 117       }
 118       RackShear() MainExtrude(){
 119         StrapBarrelElevation();
 120       }
 121
 122       difference(){
 123         RackShear() MainExtrude(){
 124           GraspFixingElevation();
 125         }
 126
 127         translate([0,0, main_sz_z/2]) linextr(-strap_w/2, +strap_w/2) {
 128           translate([ rack_width_inner/2 - strap_th, 0 ])
 129             rectfromto([ 0, -50 ], [ 50, 50 ]);
 130         }
 131       }
 132     }
 133
 134     RackShear() linextr(-10, main_sz_z+10) {
 135       for (mx=[0,1]) {
 136         mirror([mx,0]) {
 137           translate([ rack_rail_x, $rack_rail_y ]){
 138             hull(){
 139               for (dx = [-rack_rail_dia, 0])
 140                 translate([dx, 0])
 141                   circle(r= rack_rail_dia/2);
 142             }
 143           }
 144         }
 145       }
 146     }
 147   }
 148 }
 149
 150 Principal($elevation_nominal=0);