Updated documentation for racks.

README.md

@@ -32,6 +32,28 @@ The rack module matches the gear module directly, without additional helix-based
 * `helix_angle` = bevel angle perpendicular to the rack's length; 0° = straight teeth
 
 
+## Parametric Herringbone Gear Rack
+
+<img src="examples/herringbone_rack.png" alt="Herringbone Rack" width="300" />
+
+Creates a herringbone gear rack by mirroring two helical racks.
+
+This script adjusts the pressure angle in the transverse section to the helix angle: e.g. with a 20° helix angle, a pressure angle of 20° becomes a pressure angle of 21.17° in the transverse section.
+The rack module matches the gear module directly, without additional helix-based scaling.
+
+### Format
+
+`herringbone_rack(modul, length, height, width, pressure_angle=20, helix_angle=45)`
+
+#### Parameters
+* `modul` = height of the tooth above the pitch line
+* `length` = length of the rack
+* `height` = height from bottom to the pitch line
+* `width` = face width
+* `pressure_angle` = pressure angle, standard value = 20° according to DIN 867. Should not be greater than 45°.
+* `helix_angle` = bevel angle perpendicular to the rack's length; 0° = straight teeth
+
+
 ## Parametric Involute Spur Gear
 
 <img src="examples/spur_gear.png" alt="Spur Gear" width="300" />

examples/herringbone_rack.scad

@@ -1,3 +1,4 @@
 include <../gears.scad>
 
+rotate([90,0,0])
 herringbone_rack(modul=1, length=60, height=5, width=20, pressure_angle=20, helix_angle=45);

examples/mountable_herringbone_rack.scad

@@ -1,3 +1,4 @@
 include <../gears.scad>
 
+rotate([90,0,0])
 mountable_herringbone_rack(modul=1, length=60, height=5, width=20, pressure_angle=20, helix_angle=45, profile=3, head="PH", fastners=3);

examples/mountable_rack.scad

@@ -1,3 +1,4 @@
 include <../gears.scad>
 
+rotate([90,0,0])
 mountable_rack(modul=1, length=60, height=5, width=20, pressure_angle=20, helix_angle=0, profile=3, head="PH", fastners=3);

examples/rack.scad

@@ -1,4 +1,4 @@
 include <../gears.scad>
 
-rotate([0,0,180])
+rotate([90,0,0])
 rack(modul=1, length=60, height=5, width=20, pressure_angle=20, helix_angle=0);

examples/render_examples.sh

@@ -12,12 +12,34 @@ else
   exit 1
 fi
 
-for scad in "${SCRIPT_DIR}"/*.scad; do
+render_one() {
+  local scad="$1"
+  local base
   base="$(basename "${scad}" .scad)"
   if [[ "${base}" == "demo" ]]; then
-    continue
+    return 0
   fi
-  out="${SCRIPT_DIR}/${base}.png"
+  local out="${SCRIPT_DIR}/${base}.png"
   "${OPENSCAD_BIN}" -o "${out}" --imgsize 800,800 "${scad}"
   echo "Rendered ${out}"
-done
+}
+
+if [[ "${1:-}" != "" ]]; then
+  target="${1}"
+  if [[ "${target}" != /* ]]; then
+    if [[ "${target}" != *.scad ]]; then
+      target="${SCRIPT_DIR}/${target}.scad"
+    else
+      target="${SCRIPT_DIR}/${target}"
+    fi
+  fi
+  if [[ ! -f "${target}" ]]; then
+    echo "Error: SCAD file not found: ${target}" >&2
+    exit 1
+  fi
+  render_one "${target}"
+else
+  for scad in "${SCRIPT_DIR}"/*.scad; do
+    render_one "${scad}"
+  done
+fi

gears.scad

@@ -199,21 +199,29 @@ module involute_rack(modul, length, height, width, pressure_angle = 20, helix_an
     );
 
     translate([-pitch*(nz-1)/2,0,0]){
-        intersection(){
-            copier([1,0,0], nz, pitch, 0){
-                multmatrix(m = [
-                    [1,0,x_slope,0],
-                    [0,1,0,0],
-                    [0,0,1,0],
-                    [0,0,0,1]
-                ])
-                    linear_extrude(height = width, convexity = 10)
-                        polygon(points_2d);
+        union(){
+            intersection(){
+                copier([1,0,0], nz, pitch, 0){
+                    multmatrix(m = [
+                        [1,0,x_slope,0],
+                        [0,1,0,0],
+                        [0,0,1,0],
+                        [0,0,0,1]
+                    ])
+                        linear_extrude(height = width, convexity = 10)
+                            polygon(points_2d);
+                };
+                translate([abs(x_shift),-height-0.5,-0.5]){
+                    cube([length,height+mx+1,width+1]);         // Cuboid which includes the Volume of the Rack
+                }
             };
-            translate([abs(x_shift),-height-0.5,-0.5]){
-                cube([length,height+mx+1,width+1]);             // Cuboid which includes the Volume of the Rack
+            body_height = height - (mx + c);
+            if (body_height > 0) {
+                translate([abs(x_shift),-height,0]){
+                    cube([length,body_height,width]);           // Rectangular rack body
+                }
             }
-        };
+        }
     };
 }