Much work on the lower knuckle, and I've learned a lot. However, because

I forgot to allow for all the weird skews, this is wrong. It's remediable,
but not now!

model/fourbar.scad

@@ -2,7 +2,7 @@
 
 // (c) Simon Brooke 2025; CC-BY-SA
 
-
+include <BOSL2/std.scad>
 include <NACAAirfoils/files/Naca4.scad>
 include <library/skew.scad>
 include <wheel.scad>
@@ -34,31 +34,58 @@ module fourbar_leg(length=1000, chord=100, long_skew=30, lat_skew=30) {
 }
 
 
-module lower_knuckle(chord=100, pivot_radius=12) {
+module loawer_bar_end_knuckle(chord=100, pivot_radius=12, rise=8) {
     l_body=chord * 1.5;
     w_body=pivot_radius * 2.5;
-    h_axis=pivot_radius * 3;
+    h_axis=pivot_radius * 2.75;
         
     difference() {
         union () {
-            translate([0, w_body/2, h_axis])
+            translate([l_body/2, w_body/2, h_axis])
                 rotate([0, 90, 0])
-                    cylinder(h=l_body, r=w_body/2);
+                    cyl(h=l_body, r=w_body/2, rounding=5);
-            cube([l_body, w_body, h_axis]);
+            translate([l_body/2, w_body/2, h_axis/2])
-            translate([chord * 1.25, w_body, 0])
+            cuboid([l_body, w_body, h_axis], rounding=5, except=TOP);
+            // bulge for wheel axle; the fork insertion end of
+            // a lefty axle is 25mm diameter
+            translate([chord * 1.25, w_body/2, 0])
                 rotate([90, 0, 0])
-                    cylinder(h=w_body, r=pivot_radius * 2);
+                    cyl(h=w_body, r=25, rounding=5);
+            // fairing for this
+            translate([chord * 1.25, w_body/2, -7.5])
+                rotate([80, 0, 270])
+                    prismoid([w_body, 35], [w_body, 10], rounding=5, h=l_body/2);
+
         }
         translate([ chord*0.25, -1, pivot_radius * 3])
             cube([chord, pivot_radius * 4, pivot_radius * 4]);
+        // scoop for leg-bottom knuckle to rotate within
         translate([ chord*0.25, w_body/2, h_axis])
             rotate([0, 90, 0])
-                cylinder(h=chord, r=pivot_radius * 1.5);
+                cylinder(h=chord, r=pivot_radius * 1.3);
-        // throough hole for pivot axle
+        // through hole for pivot axle
         translate([-1, w_body/2, h_axis])
             rotate([0, 90, 0])
-            cylinder(h=l_body+2, r=pivot_radius/3);   
+                cylinder(h=l_body+2, r=pivot_radius/3); 
+        // through hole for wheel axle  
+        translate([chord * 1.25, w_body +1, 0])
+            rotate([90, 0, 0])
+                cylinder(h=w_body-5, r=12.5); 
     } 
+    
+    // airfoil stub to be epoxied into the lower bar of 
+    // the linkage
+    translate([(chord * 1.25) - 1, 5 - chord, 0])
+        rotate([90-rise, 0, 180])
+            airfoil(h=chord, L=chord-2);
+    // root reinforcement for the above
+    translate([chord * 1.25, 5 - chord/3, 9])
+        rotate([90, 0, 180])
+            airfoil(h=chord/3, L=chord);
+    translate([(chord * .75), 0, 10])
+    rotate([90, 0, 0])
+        prismoid([chord -1, 6], [chord -2, 0], h=(chord/3));
+
 }
 
 module fourbar_axle_half( length, chord, long_skew) {
@@ -85,7 +112,7 @@ module fourbar_axle_half( length, chord, long_skew) {
     translate([(0 - (chord*1.25)), l_hlb * cos(rise), 30])
         rotate([0, long_skew, 0])
         color("black")
-        lower_knuckle(chord, 12);
+        loawer_bar_end_knuckle(chord, 12, rise);
        
     // wheel
     translate([-50, l_hlb + 72, -40])
@@ -121,10 +148,9 @@ module fourbar(length=1000, chord=100, long_skew=30, lat_skew=30, shoulder=650)
 
 translate([-125, 0, 0])
     color("blue")
-    lower_knuckle();
+    loawer_bar_end_knuckle();
-/* translate([0, 77, 0])
+translate([0, 77, 0])
-    rotate([270, 0, 0]) 
+    wheel(); 
-    wheel();*/
 translate([0, 40, 0])
     color("silver")
     rotate([90, 0, 0])

model/wheel.scad

@@ -20,42 +20,43 @@
 module wheel (iso=451) {
     radius=(iso/2)+7;
     
-    // rim
+    rotate([270, 0, 0]) {
-    color("grey")
+        // rim
-    difference() {
+        color("grey")
-        cylinder(h=22, r=radius, center=true);
+        difference() {
-        translate([0,0, -11])
+            cylinder(h=22, r=radius, center=true);
-            cylinder(h=26, r=(radius-10));
+            translate([0,0, -11])
+                cylinder(h=26, r=(radius-10));
+        }
+        
+        // carbon cones covering the spokes
+        color("black")
+            translate([0,0, 4])
+            cylinder(h=26.6, r1=radius, r2=22.5);
+        color("black")
+                mirror([0, 0, -1])
+            translate([0,0, 4])
+                    cylinder(h=14.4, r1=radius, r2=29);   
+        
+        // tyre
+        color("black")
+        rotate_extrude(convexity = 10)
+        translate([radius +10, 0, 0])
+            circle(r = 12, $fn = 100);
+        
+        // hub
+        color("grey")
+        translate([0, 0, -40])
+        cylinder(h=65, r=22.5);
+        
+        // axle 
+        color("silver") {
+            translate([0, 0, -45])
+                cylinder(h=70, r1=12.5, r2=7.5);
+            translate([0, 0, -60])
+                cylinder(h=25, r=12.5);
+        }
     }
-    
-    // carbon cones covering the spokes
-    color("black")
-        translate([0,0, 4])
-        cylinder(h=26.6, r1=radius, r2=22.5);
-    color("black")
-            mirror([0, 0, -1])
-        translate([0,0, 4])
-                cylinder(h=14.4, r1=radius, r2=29);   
-    
-    // tyre
-    color("black")
-    rotate_extrude(convexity = 10)
-    translate([radius +10, 0, 0])
-        circle(r = 12, $fn = 100);
-    
-    // hub
-    color("grey")
-    translate([0, 0, -40])
-    cylinder(h=65, r=22.5);
-    
-    // axle 
-    color("silver") {
-        translate([0, 0, -45])
-            cylinder(h=70, r1=12.5, r2=7.5);
-        translate([0, 0, -85])
-            cylinder(h=40, r=12.5);
-    }
-    
 }
 
 // wheel();