Forgot the 'skew' library!

README.md

@@ -8,11 +8,9 @@ Design of a highly experimental recumbent tricycle, not software at all.
 
 Still at a very preliminary, pre-prototype stage. Work is documented [here](https://www.journeyman.cc/blog/tags-output/Tricycle/).
 
-## Copyright
+## Dependencies
 
-Copyright © Simon Brooke, 2024-2025; may be used and modified under [Creative Commons Attribution-Share Alike](https://creativecommons.org/licenses/by-sa/4.0/deed.en) licence.
-
-#### Parts of the following libraries are incorporated into this model
+The following libraries are used into this model. They should be downloaded and installed into your [OpenSCAD library directory](https://en.wikibooks.org/wiki/OpenSCAD_User_Manual/Libraries), which on Linux systems is usually `$HOME/.local/share/OpenSCAD/libraries`.
 
 | Library                                                      | Referenced as      | Author                                                       | Licence                                                      |
 | ------------------------------------------------------------ | ------------------ | ------------------------------------------------------------ | ------------------------------------------------------------ |
@@ -24,4 +22,6 @@ Copyright © Simon Brooke, 2024-2025; may be used and modified under [Creat
 
 
 
- but (currently) uses elements from's [BentSim](https://github.com/PRouzeau/BentSim) project, which is [GPL](https://github.com/PRouzeau/BentSim/blob/master/LICENSE) licensed, and sprockets from s, which is licensed under .
+## Copyright
+
+Copyright © Simon Brooke, 2024-2025; may be used and modified under [Creative Commons Attribution-Share Alike](https://creativecommons.org/licenses/by-sa/4.0/deed.en) licence.

model/chainset.scad

@@ -3,17 +3,16 @@
 // (c) Simon Brooke 2025; CC-BY-SA
 // Derived from Hampus Andersson's Sprocket Generator
 
-
 include <SprocketGenerator2/files/Sprocket_Generator_v2_example_10.scad>
 include <BOSL2/std.scad>
 
 include <pedal.scad>
 
-function sprocket_radius(teeth=52, roller=7.9, pitch=12.7) = let(roller_radius = roller/2,
-                radius = pitch/(2*sin(180/teeth)))
-                sqrt((radius*radius) - (pitch*(roller_radius+tolerance))+((roller_radius+tolerance)*(roller_radius+tolerance)));
+function sprocket_radius(teeth=52, roller=7.9, pitch=12.7) = 
+    let(roller_radius = roller/2,
+        radius = pitch/(2*sin(180/teeth)))
+        sqrt((radius*radius) - (pitch*(roller_radius+tolerance))+((roller_radius+tolerance)*(roller_radius+tolerance)));
 	
-
 module chainring( teeth=52, roller=7.9, pitch=12.7) {
     radius = sprocket_radius(teeth=teeth, roller=roller, pitch=pitch);
     
@@ -36,6 +35,14 @@ module spider(radius, arms) {
 }
 
 
+/**
+ * parameterised chainset with, currently, only one chainring; and, 
+ * currently, derailleur-sized chain. Parameters are:
+ * `teeth`: the number of teeth, obviously;
+ * `arms`: the number of arms on the spider;
+ * `crank`: the length of the crank, in millimetres;
+ * `bbshell`: the width of the bottom bracket shell, in millimetres.
+ */
 module chainset(teeth=53, arms=5, crank=172, bbshell=68) {
     radius = sprocket_radius(teeth=teeth);
     
@@ -54,9 +61,9 @@ module chainset(teeth=53, arms=5, crank=172, bbshell=68) {
     prismoid(size1=[10, 25], size2=[7, 18], h=crank +20);
     
     // pedals
-    translate([0-crank, 0, 20 + bbshell])
+    translate([0-crank, 0, 8+bbshell])
         pedal();
-    translate([crank, 0, 0-4])
+    translate([crank, 0, 0-2])
         mirror([0, 0, 1])
         pedal();
     
@@ -73,4 +80,4 @@ module chainset(teeth=53, arms=5, crank=172, bbshell=68) {
 // chainring();
 // spider(90, 1);
 
-chainset(teeth=82, crank=140);
+// chainset(teeth=82, crank=140);

model/fourbar.scad

@@ -3,7 +3,7 @@
 // (c) Simon Brooke 2025; CC-BY-SA
 
 
-include <BentSim/Bike_accessories.scad>
+include <BentSim/Library/Bike_accessories.scad>
 include <NACAAirfoils/files/Naca4.scad>
 include <library/skew.scad>
 

model/library/skew.scad

@@ -0,0 +1,43 @@
+/* Taken from https://gist.github.com/boredzo/fde487c724a40a26fa9c?permalink_comment_id=4258747 */
+
+/* skew takes an array of six angles:
+ * x along y
+ * x along z
+ * y along x
+ * y along z
+ * z along x
+ * z along y
+ */
+module skew(dims) {
+matrix = [
+	[ 1, dims[0]/45, dims[1]/45, 0 ],
+	[ dims[2]/45, 1, dims[4]/45, 0 ],
+	[ dims[5]/45, dims[3]/45, 1, 0 ],
+	[ 0, 0, 0, 1 ]
+];
+multmatrix(matrix)
+children();
+}
+
+/* example:
+ * skew([45, 0, 0, 0, 0, 0])
+ * cube([10,10,10]);
+ */
+
+// Skews the child geometry.
+// xy: Angle towards X along Y axis.
+// xz: Angle towards X along Z axis.
+// yx: Angle towards Y along X axis.
+// yz: Angle towards Y along Z axis.
+// zx: Angle towards Z along X axis.
+// zy: Angle towards Z along Y axis.
+module skew2(xy = 0, xz = 0, yx = 0, yz = 0, zx = 0, zy = 0) {
+	matrix = [
+		[ 1, tan(xy), tan(xz), 0 ],
+		[ tan(yx), 1, tan(yz), 0 ],
+		[ tan(zx), tan(zy), 1, 0 ],
+		[ 0, 0, 0, 1 ]
+	];
+	multmatrix(matrix)
+	children();
+}

model/pedal.scad

@@ -2,15 +2,31 @@
 
 // (c) Simon Brooke 2025; CC-BY-SA
 
+include <BOSL2/std.scad>
 
 module pedal(){
-    rotate([0, 270, 0])
-    scale([.6, .6, .6])
-    translate([-50, -160, 0])
-    linear_extrude(height = 10, center = true)
-        // color("black")
-        import("library/look-keo.svg");
-    cylinder(h=80, r=6);
+    color("black")
+    intersection() {
+        rotate([0, 270, 0])
+            scale([.45, .45, .45])
+            translate([-20, -160, 0])
+            linear_extrude(height = 40, center = true)
+            import("library/look-keo.svg");
+        
+        rotate([0, 90, 90])
+            translate([-50, 0, -43])
+            prismoid(size1=[60, 25], size2=[60, 5], height=90);
+    }
+    
+    // axle
+    color("black")
+        cylinder(h=80, r=7.1);
+    translate([0, 0, 8])
+        color("black")
+        cylinder(h=3, r=9);
+    translate([0, 0, 12])
+        color("black")
+        cylinder(h=12, r1=10, r2=9);
     }
     
 // pedal();

model/subframe.scad

@@ -12,31 +12,31 @@ include <epicyclic.scad>
 module subframe () {
     // front leg (supports cross-shaft, epicyclic, motor
     translate([-25, 1820, -550])
-        color("grey")
+        color("silver")
         cube([50, 25, 230]);
     // bottom bracket leg
     translate([-25, 1690, -578])
-        color("grey")
+        color("silver")
         cube([50, 25, 310]);
     // wheel leg
     translate([-70, 1430, -593])
         rotate([0, 5, 0])
-        color("grey")
+        color("silver")
         cube([25, 75, 363]);
     // front upper
     translate([-25, 2000, -385])
         rotate([70, 0, 0])
-        color("grey")
+        color("silver")
         cube([50, 25, 330]);
     // central upper
     translate([-25, 1700, -275])
         rotate([82, 0, 0])
-        color("grey")
+        color("silver")
         cube([50, 25, 370]);
     // rear leg
     translate([-25, 1200, -515])
         rotate([-23, 0, 0])
-        color("grey")
+        color("silver")
         cube([50, 25, 344]);
     
     // wheel
@@ -46,6 +46,12 @@ module subframe () {
         scale([0.70, 0.70, 0.70])
         wheel(rim=451, spoke_nbr=0);
         
+    translate([-30, 1467.5, -450])
+        rotate([0, 90, 0])
+        color("grey")
+        sprocket(teeth=30, roller=7.9, pitch=12.7);
+
+        
     rotate([90, 0, 90])
         translate([1680, -410, -40])
         chainset( teeth=82, crank=140);