topeak-mtx-tortec-expeditionrack-adapter: correct for bolt offset

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 4f2170391de834803ab56c9614750d230cb6a3be..fc10f61913e473a15752533da1c4aacdca988f3f 100644 (file)
--- a/topeak-mtx-tortec-expeditionrack-adapter.scad
+++ b/topeak-mtx-tortec-expeditionrack-adapter.scad
@@ -85,7 +85,8 @@ brk_bolt_nut_top_y = -brk_nearbolt_recess_depth
                       
 brk_bolt_nut_r = brk_bolt_nut_across_flats/2 / cos(360/12);
 
-function elevation_of(z) = rear_elevation_nominal - z * rack_shear_ratio;
+function elevation_of_bolt_for(z) = rear_elevation_nominal
+  - (z - brk_block_z/2) * rack_shear_ratio;
 
 echo(rack_shear_ratio);
 
@@ -320,13 +321,13 @@ module Principal(){
 module Front(){ ////toplevel
   // xxx elevation is wrong
   Principal($elevation_nominal=
-           elevation_of(rear_to_cross_rail + rear_bolt_to_front_bolt),
+      elevation_of_bolt_for(rear_to_cross_rail + rear_bolt_to_front_bolt),
            $foreaftmaint_dz= 0);
 }
 
 module Rear(){ ////toplevel
   Principal($elevation_nominal=
-           elevation_of(rear_to_cross_rail),
+      elevation_of_bolt_for(rear_to_cross_rail),
            $foreaftmaint_dz= rear_to_cross_rail);
 }