Tactical commit before experimental redesign of knuckle.

This commit is contained in:
Simon Brooke 2025-09-24 10:25:49 +01:00
parent 72797decb0
commit 0a3c553512
3 changed files with 61 additions and 62 deletions

View file

@ -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")
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])
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, 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])
@ -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])
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));
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 fourbar_axle_half( length, chord, long_skew) {
shoulder=650;
lat_skew=30;
module fourbar_axle_half( length=1000, chord=100, lat_skew=35, long_skew=30, shoulder=650) {
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([0, 0, 0 - v_offset])
translate([-15, 0, 0 - v_offset])
rotate([90-rise, 0, 180])
color("black")
airfoil(h=l_hlb, L=chord);
// lower knuckle
translate([(0 - (chord*1.25)), l_hlb * cos(rise), 30])
rotate([0, long_skew, 0])
color("black")
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
translate([(0 - (chord*1.25)), (l_hlb * cos(rise) + 72), -62])
lower_bar_end_knuckle(chord, 12, rise, lat_skew);
}
module fourbar(length=1000, chord=100, long_skew=30, lat_skew=30, shoulder=650) {
w = (length * sin( lat_skew)) + ( shoulder / 2);
module fourbar(length=1000, chord=100, lat_skew=30, long_skew=30, shoulder=650) {
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();
translate([0, 77, 0])
lower_bar_end_knuckle();
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);

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

View file

@ -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])