Tactical commit before experimental redesign of knuckle.

model/fourbar.scad

@@ -7,10 +7,19 @@ include <NACAAirfoils/files/Naca4.scad>
 include <library/skew.scad>
 include <wheel.scad>
 
-module fourbar_leg(length=1000, chord=100, long_skew=30, lat_skew=30) {
+$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) {
     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!
@@ -23,7 +32,12 @@ module fourbar_leg(length=1000, chord=100, long_skew=30, lat_skew=30) {
         translate([0 - chord, 0, (chord/2 * sin(long_skew))])
             rotate([0, 90+long_skew, 0])
             color("black")
-            cylinder(h=chord, r=12);
+            difference() {
+                cylinder(h=chord, r=12);
+                        // through hole for pivot axle
+                translate([0, -1, 0])
+                    cylinder(h=chord+2, r=pivot_radius/3); 
+            }
         
         // aerofoil section
         sskew([0, long_skew, 0, 0, 0, 0])
@@ -34,7 +48,7 @@ module fourbar_leg(length=1000, chord=100, long_skew=30, lat_skew=30) {
 }
 
 
-module loawer_bar_end_knuckle(chord=100, pivot_radius=12, rise=8) {
+module lower_bar_end_knuckle(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;
@@ -44,17 +58,19 @@ module loawer_bar_end_knuckle(chord=100, pivot_radius=12, rise=8) {
             translate([l_body/2, w_body/2, h_axis])
                 rotate([0, 90, 0])
                     cyl(h=l_body, r=w_body/2, rounding=5);
-            translate([l_body/2, w_body/2, h_axis/2])
+            
-            cuboid([l_body, w_body, h_axis], rounding=5, except=TOP);
+            // '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 * 1.25, w_body/2, 0])
+            translate([chord * 0.25, w_body/2, 0])
-                rotate([90, 0, 0])
+               rotate([90, 0, 0])
                     cyl(h=w_body, r=25, rounding=5);
             // fairing for this
-            translate([chord * 1.25, w_body/2, -7.5])
+            translate([chord * 0.25, w_body/2, -3])
-                rotate([80, 0, 270])
+                rotate([80, 0, 90])
-                    prismoid([w_body, 35], [w_body, 10], rounding=5, h=l_body/2);
+                    prismoid([w_body, 45], [w_body, 10], rounding=5, h=l_body * .75);
 
         }
         translate([ chord*0.25, -1, pivot_radius * 3])
@@ -68,93 +84,76 @@ module loawer_bar_end_knuckle(chord=100, pivot_radius=12, rise=8) {
             rotate([0, 90, 0])
                 cylinder(h=l_body+2, r=pivot_radius/3); 
         // through hole for wheel axle  
-        translate([chord * 1.25, w_body +1, 0])
+        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, 5 - chord, 0])
+    translate([chord*1.25, 1, 30])
-        rotate([90-rise, 0, 180])
+        rotate([90 + rise, 360 - lat_skew, 0])
-            airfoil(h=chord, L=chord-2);
+            airfoil(h=chord, L=2 - chord);
-    // root reinforcement for the above
+    
-    translate([chord * 1.25, 5 - chord/3, 9])
+//    // brake disk
-        rotate([90, 0, 180])
+//    translate([(0 - (chord*1.25)), (l_hlb * cos(rise)), 1])
-            airfoil(h=chord/3, L=chord);
+//        rotate([90, 0, 0])
-    translate([(chord * .75), 0, 10])
+//            color("silver")
-    rotate([90, 0, 0])
+//                cylinder( h=1.5, r=75);
-        prismoid([chord -1, 6], [chord -2, 0], h=(chord/3));
+//    // wheel (obviously)            
+//    translate([(0 - (chord*1.25)), (l_hlb * cos(rise)), -10])
+//        wheel();
 
 }
 
-module fourbar_axle_half( length, chord, long_skew) {
+module fourbar_axle_half( length=1000, chord=100, lat_skew=35, long_skew=30, shoulder=650) {
-    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.
+    // 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
     fudge=0;
     
-    w = ((length * sin(lat_skew) ) + ( shoulder / 2));
+    w = ((length * cos(lat_skew) ));
     l_hlb= w * (1/cos(rise)) + fudge;
-    v_offset=l_hlb * sin(rise);
+    v_offset=(l_hlb * sin(rise)) + 38;
     
-    echo("long_skew", long_skew);
+    translate([-15, 0, 0 - v_offset])
-    
-    translate([0, 0, 0 - v_offset])
         rotate([90-rise, 0, 180])
-        color("black")
+            color("black")
-        airfoil(h=l_hlb, L=chord);
+                airfoil(h=l_hlb, L=chord);
     
     // lower knuckle
-    translate([(0 - (chord*1.25)), l_hlb * cos(rise), 30])
+    rotate([0, long_skew, 0])
-        rotate([0, long_skew, 0])
+        translate([(0 - (chord*1.25)), (l_hlb * cos(rise) + 72), -62])
-        color("black")
+            lower_bar_end_knuckle(chord, 12, rise, lat_skew);
-        loawer_bar_end_knuckle(chord, 12, rise);
-       
-    // 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, long_skew=30, lat_skew=30, shoulder=650) {
+module fourbar(length=1000, chord=100, lat_skew=30, long_skew=30, shoulder=650) {
-    w = (length * sin( lat_skew)) + ( shoulder / 2);
-
-    
     translate([0, 0-(shoulder/2), 0])
-        fourbar_leg( length, chord, long_skew, lat_skew);
+        fourbar_leg( length, chord, lat_skew, long_skew);
     
     translate([0, (shoulder/2), 0])
         mirror([0, 1, 0])
-        fourbar_leg(length, chord, long_skew, lat_skew);
+            fourbar_leg(length, chord, lat_skew, long_skew);
     
-    fourbar_axle_half(w, chord, long_skew);
+    fourbar_axle_half(length, chord, lat_skew, long_skew, shoulder);
     
     mirror([0, 1, 0])
-        fourbar_axle_half(w, chord, long_skew);
+        fourbar_axle_half(length, chord, lat_skew, long_skew, shoulder);
 }
 
 translate([-125, 0, 0])
     color("blue")
-    loawer_bar_end_knuckle();
+    lower_bar_end_knuckle();
-translate([0, 77, 0])
+translate([-100, 74, 0])
     wheel(); 
-translate([0, 40, 0])
+translate([-100, 34, 0])
     color("silver")
     rotate([90, 0, 0])
     cylinder(h=1.5, r=75);
 
-// fourbar();
+// fourbar(length=1000, chord=100, long_skew=30, lat_skew=35, shoulder=650);
 // fourbar_axle_half(1000,100, 30);

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, 90, 0])
+        rotate([0, 0, 90])
         wheel(iso=rim);
         
     translate([-42, 382, 93])

model/tricycle.scad

@@ -12,7 +12,7 @@ rotate([0, 0, 270])
 translate([0, 1300, 180])
 subframe(structure="carbon");
 translate([0, 0, 320])
-fourbar(700, 100, 30, 35, 650);
+fourbar(length=1000, chord=100, long_skew=30, lat_skew=35, shoulder=650);
 
 translate([800, 0, 120])
 rotate([0, 4, 0])