diff --git a/model/fourbar.scad b/model/fourbar.scad
index 3f07b39..aa8e814 100644
--- a/model/fourbar.scad
+++ b/model/fourbar.scad
@@ -2,25 +2,15 @@
 
 // (c) Simon Brooke 2025; CC-BY-SA
 
-include <BOSL2/std.scad>
+
 include <NACAAirfoils/files/Naca4.scad>
 include <library/skew.scad>
-include <lowerknuckle.scad>
 include <wheel.scad>
 
-$fn=64;
-
-// Wherever you see unexplained numbers in this file, they are
-// fudge because I don't yet properly understand the coordinate
-// transforms and can't remember enough of the trigonometry I
-// learned 60 years ago. There REALLY should not be any unexplained
-// numbers.
-
-module fourbar_leg(length=1000, chord=100, lat_skew=35, long_skew=30) {
+module fourbar_leg(length=1000, chord=100, long_skew=30, lat_skew=30) {
     h = length * cos(lat_skew) * cos( long_skew);
     w = length * sin( lat_skew);
     d = length * sin( long_skew);
-    pivot_radius = 12;
     
     translate([0, 0-w, 0]) {
         // upper pivot needs a complex trig transformation!
@@ -33,12 +23,7 @@ module fourbar_leg(length=1000, chord=100, lat_skew=35, long_skew=30) {
         translate([0 - chord, 0, (chord/2 * sin(long_skew))])
             rotate([0, 90+long_skew, 0])
             color("black")
-            difference() {
-                cylinder(h=chord, r=12);
-                        // through hole for pivot axle
-                translate([0, -1, 0])
-                    cylinder(h=chord+2, r=pivot_radius/3); 
-            }
+            cylinder(h=chord, r=12);
         
         // aerofoil section
         sskew([0, long_skew, 0, 0, 0, 0])
@@ -49,55 +34,72 @@ module fourbar_leg(length=1000, chord=100, lat_skew=35, long_skew=30) {
 }
 
 
-module fourbar_axle_half( length=1000, chord=100, lat_skew=35, long_skew=30, shoulder=650) {
+module lower_knuckle(chord=100, pivot_radius=12) {
+    difference() {
+        cube([chord * 1.5, pivot_radius * 3, chord*.66]);
+        translate([ chord*0.25, -1, pivot_radius * 2])
+            cube([chord, pivot_radius * 4, pivot_radius * 4]);
+    }
+}
+
+module fourbar_axle_half( length, chord, long_skew) {
+    shoulder=650;
+    lat_skew=30;
     rise=8;
     
     // I've got something wrong in computing the half-lower-bar
-    // length, and I don't know what. It scales with lat_skew, but
-    // (unsurprisingly) not liniarly. Fudge of 23 works for lat_skew of 30; 34 works for lat_skew of 35
+    // length, and I don't know what.
     fudge=0;
     
-    w = ((length * cos(lat_skew) ));
+    w = ((length * sin(lat_skew) ) + ( shoulder / 2));
     l_hlb= w * (1/cos(rise)) + fudge;
-    v_offset=(l_hlb * sin(rise)) + 38;
+    v_offset=l_hlb * sin(rise);
+
+    echo("long_skew", long_skew);
     
-    translate([-15, 0, 0 - v_offset])
+    translate([0, 0, 0 - v_offset])
         rotate([90-rise, 0, 180])
-            color("black")
-                airfoil(h=l_hlb, L=chord);
+        color("black")
+        airfoil(h=l_hlb, L=chord);
     
     // lower knuckle
-    rotate([0, long_skew, 0])
-        translate([(0 - (chord*1.25)), (l_hlb * cos(rise) + 72), -62])
-            lower_bar_end_knuckle(chord, 12, rise, lat_skew);
-    
-    rotate([0, long_skew, 0])
-        translate([(0 - (chord*1.25)), (l_hlb * cos(rise) + 155), -62])
-        wheel();
-    rotate([0, long_skew, 0])
-        translate([(0 - (chord*1.25)), (l_hlb * cos(rise) + 115), -62])
-            rotate([90, 0, 0])
-                color("silver")
-                    cylinder( h=1.5, r=75);
-
+    translate([(0 - (chord*1.25)), l_hlb * cos(rise), 30])
+        rotate([0, long_skew, 0])
+        color("black")
+        lower_knuckle(chord, 12);
+       
+    // wheel
+    translate([-50, l_hlb + 72, -40])
+        rotate([270, 0, 0])
+        wheel(iso=451); 
+        
+    // brake disk
+    translate([-50, l_hlb + 35, -40])
+        color("silver")
+        rotate([90, 0, 0])
+        cylinder(h=1.5, r=75);
+    // brake caliper
 }
 
 
 
-module fourbar(length=1000, chord=100, lat_skew=30, long_skew=30, shoulder=650) {
+module fourbar(length=1000, chord=100, long_skew=30, lat_skew=30, shoulder=650) {
+    w = (length * sin( lat_skew)) + ( shoulder / 2);
+
+    
     translate([0, 0-(shoulder/2), 0])
-        fourbar_leg( length, chord, lat_skew, long_skew);
+        fourbar_leg( length, chord, long_skew, lat_skew);
     
     translate([0, (shoulder/2), 0])
         mirror([0, 1, 0])
-            fourbar_leg(length, chord, lat_skew, long_skew);
+        fourbar_leg(length, chord, long_skew, lat_skew);
     
-    fourbar_axle_half(length, chord, lat_skew, long_skew, shoulder);
+    fourbar_axle_half(w, chord, long_skew);
     
     mirror([0, 1, 0])
-        fourbar_axle_half(length, chord, lat_skew, long_skew, shoulder);
+        fourbar_axle_half(w, chord, long_skew);
 }
 
-
-// fourbar(length=1000, chord=100, long_skew=30, lat_skew=35, shoulder=650);
-// fourbar_axle_half();
\ No newline at end of file
+// lower_knuckle();
+// fourbar();
+// fourbar_axle_half(1000,100, 30);
\ No newline at end of file
diff --git a/model/lowerknuckle.scad b/model/lowerknuckle.scad
deleted file mode 100644
index 4377230..0000000
--- a/model/lowerknuckle.scad
+++ /dev/null
@@ -1,144 +0,0 @@
-// lowerknuckle.scad
-
-// (c) Simon Brooke 2025; CC-BY-SA
-
-include <BOSL2/std.scad>
-include <NACAAirfoils/files/Naca4.scad>
-include <library/skew.scad>
-include <wheel.scad>
-
-$fn=64;
-
-
-module lower_bar_end_knuckle_old(chord=100, pivot_radius=12, rise=8,lat_skew=30) {
-    l_body=chord * 1.5;
-    w_body=pivot_radius * 2.5;
-    h_axis=pivot_radius * 2.75;
-    
-    difference() {
-        union () {
-            translate([l_body/2, w_body/2, h_axis])
-                rotate([0, 90, 0])
-                    cyl(h=l_body, r=w_body/2, rounding=5);
-            
-            // 'except=TOP' in phrase introduces the spurious hulls
-            translate([l_body/2, w_body/2, h_axis*.75])
-                cuboid([l_body, w_body, h_axis * .75], rounding=5);
-            // bulge for wheel axle; the fork insertion end of
-            // a lefty axle is 25mm diameter
-            translate([chord * 0.25, w_body/2, 0])
-               rotate([90, 0, 0])
-                    cyl(h=w_body, r=25, rounding=5);
-            // fairing for this
-            translate([chord * 0.25, w_body/2, -3])
-                rotate([80, 0, 90])
-                    prismoid([w_body, 45], [w_body, 10], rounding=5, h=l_body * .75);
-
-        }
-        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 * 1.3);
-        // 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); 
-        // through hole for wheel axle  
-        translate([ chord * 0.25, 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, 30])
-        rotate([90 + rise, 360 - lat_skew, 0])
-            airfoil(h=chord, L=2 - chord);
-    
-//    // brake disk
-//    translate([(0 - (chord*1.25)), (l_hlb * cos(rise)), 1])
-//        rotate([90, 0, 0])
-//            color("silver")
-//                cylinder( h=1.5, r=75);
-//    // wheel (obviously)            
-//    translate([(0 - (chord*1.25)), (l_hlb * cos(rise)), -10])
-//        wheel();
-
-}
-
-module lower_bar_end_knuckle(chord=100, pivot_radius=12, rise=8,lat_skew=30, colour="blue") {
-    l_body=chord * 2;
-    w_body=pivot_radius * 2.5;
-    h_axis=pivot_radius * 2.75;
-    
-    difference() {
-        union () {
-            // (more streamlined) body
-            translate([160, w_body/2, -22])
-                rotate([0,0,180])
-                    scale([1, 2, 1])
-                        color( colour)
-                            airfoil(h=70, L=l_body);
-            // boss for wheel axle
-            translate([ chord * 0.25, w_body * 0.9, 0])
-                rotate([90, 0, 0])
-                    color( colour)
-                    cyl(h=w_body * 1.25, r=20, rounding=5); 
-
-        }
-        // 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 * 1.3);
-        // space for the airfoil leg to emerge
-        translate([ chord*0.25, w_body*.75, pivot_radius * 2.25])
-            rotate([lat_skew + 45, 0, 0])
-                cube([chord, pivot_radius * 4, pivot_radius * 4]);
-        // through hole for pivot axle
-        translate([-1, w_body/2, h_axis])
-            rotate([0, 90, 0])
-                cylinder(h=250, r=pivot_radius/3); 
-        // through hole for wheel axle  
-        translate([ chord * 0.25, w_body *1.5, 0])
-            rotate([90, 0, 0])
-                cylinder(h=w_body * 1.4, r=12.5); 
-        // slice off the front bottom
-        translate([chord * 1.25, w_body/2, 0 - w_body])
-            rotate([270-lat_skew, 0, 90])
-                color( colour)
-                    cuboid([2* w_body, 2*w_body, l_body *.75]);
-        // slice off the upper back
-        translate([0, w_body/2, w_body * 2.5])
-            rotate([270-lat_skew, 0, 90])
-                color( colour)
-                    cuboid([2* w_body, 2*w_body, l_body *.75]);
-    } 
-
-    // airfoil stub to be epoxied into the lower bar of 
-    // the linkage
-    translate([chord*1.25, 1, 30])
-        rotate([90 + rise, 360 - lat_skew, 0])
-            color( colour)
-                airfoil(h=chord, L=2 - chord);
-    
-//    // brake disk
-//    translate([(0 - (chord*1.25)), (l_hlb * cos(rise)), 1])
-//        rotate([90, 0, 0])
-//            color("silver")
-//                cylinder( h=1.5, r=75);
-//    // wheel (obviously)            
-//    translate([(0 - (chord*1.25)), (l_hlb * cos(rise)), -10])
-//        wheel();
-
-}
-
-//translate([-125, 0, 0])
-//    lower_bar_end_knuckle();
-//translate([-125, 0, 125])
-//    color("blue")
-//    lower_bar_end_knuckle();
-//translate([-100, 74, 0])
-//    wheel(); 
-
diff --git a/model/subframe.scad b/model/subframe.scad
index a61f099..705c543 100644
--- a/model/subframe.scad
+++ b/model/subframe.scad
@@ -11,7 +11,7 @@ include <epicyclic.scad>
 module subframe_cycleparts(rim=451, chainring_teeth=82, crank=140) {
         // wheel
     translate([0, 382, 93])
-        rotate([0, 0, 90])
+        rotate([0, 90, 0])
         wheel(iso=rim);
         
     translate([-42, 382, 93])
diff --git a/model/tricycle.scad b/model/tricycle.scad
index 3874f72..b05b4f7 100644
--- a/model/tricycle.scad
+++ b/model/tricycle.scad
@@ -11,8 +11,8 @@ include <hull.scad>
 rotate([0, 0, 270])
 translate([0, 1300, 180])
 subframe(structure="carbon");
-translate([0, 0, 250])
-fourbar(length=1000, chord=100, long_skew=30, lat_skew=35, shoulder=650);
+translate([0, 0, 320])
+fourbar(700, 100, 30, 35, 650);
 
 translate([800, 0, 120])
 rotate([0, 4, 0])
diff --git a/model/wheel.scad b/model/wheel.scad
index dfb7f72..eb9dcce 100644
--- a/model/wheel.scad
+++ b/model/wheel.scad
@@ -20,43 +20,42 @@
 module wheel (iso=451) {
     radius=(iso/2)+7;
     
-    rotate([270, 0, 0]) {
-        // rim
-        color("grey")
-        difference() {
-            cylinder(h=22, r=radius, center=true);
-            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);
-        }
+    // rim
+    color("grey")
+    difference() {
+        cylinder(h=22, r=radius, center=true);
+        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, -85])
+            cylinder(h=40, r=12.5);
+    }
+    
 }
 
 // wheel();
\ No newline at end of file