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96
model/fourbar.scad
View file

@ -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();
// lower_knuckle();
// fourbar();
// fourbar_axle_half(1000,100, 30);

144
model/lowerknuckle.scad
View file

@ -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();

2
model/subframe.scad
View file

@ -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])

4
model/tricycle.scad
View file

@ -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])

71
model/wheel.scad
View file

@ -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();