topeak-mtx-tortec-expeditionrack-adapter: adjust for shear not rotate

Signed-off-by: Ian Jackson <ijackson@chiark.greenend.org.uk>

diff --git a/topeak-mtx-tortec-expeditionrack-adapter.scad b/topeak-mtx-tortec-expeditionrack-adapter.scad
index 49441beaa1add203df6e31652fe5cda2eabd4bd0..f2bdf45f9f379954da73d79e6219fee5981fe581 100644 (file)
--- a/topeak-mtx-tortec-expeditionrack-adapter.scad
+++ b/topeak-mtx-tortec-expeditionrack-adapter.scad
@@ -103,7 +103,10 @@ rack_shear_ratio = - front_to_rear_elevation_change / rear_to_front_distance;
 front_to_cross_rail =
   cross_rail_distance * sqrt(1 - rack_shear_ratio * rack_shear_ratio)
   - rear_bolt_to_front_bolt
-  - rear_to_cross_rail;
+  - rear_to_cross_rail
+  - sqrt( pow( cross_rail_distance * rack_shear_ratio, 2 )
+         - pow(  front_to_rear_elevation_change, 2 ) )
+  ;
 
 brk_bolt_nut_top_y = -brk_nearbolt_recess_depth
   - brk_bolt_eff_len + brk_bolt_nut_th + brk_bolt_len_slop;
@@ -420,7 +423,7 @@ module RackForDemoCrosses(){
              ]) {
       translate([0,0,z])
        linextr_x_yz(rack_rail_x, -rack_rail_x)
-       circle(r= rack_rail_dia/2, $fn=6);
+       circle(r= rack_rail_dia/2, $fn=8);
     }
   }
 }