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A good enough for now, working, parameterised, four bar linkage. Pleased!

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Simon Brooke 2025-09-04 22:09:22 +01:00
parent 57f1021400
commit 4cdce5dc0a
1 changed files with 52 additions and 17 deletions
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69
model/fourbar.scad
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@ -5,31 +5,66 @@ include <Library/NACAAirfoils/files/Naca4.scad>
include <Library/skew.scad>
module fourbar_leg(length=1000, chord=100, long_skew=30, lat_skew=30) {
// upper pivot needs a complex trig transformation!
translate([(length * cos(long_skew) * cos(lat_skew)) - (2 * chord),
length * cos(long_skew) * sin(lat_skew), 0])
rotate([0, 90+long_skew, 0])
cylinder(h=chord, r=12);
h = length * cos(lat_skew) * cos( long_skew);
w = length * sin( lat_skew);
d = length * sin( long_skew);
// lower pivot:
translate([0-chord, -12, (chord/2) * sin(long_skew) * sin(lat_skew)])
rotate([0, 90+long_skew, 0])
cylinder(h=chord, r=12);
// aerofoil section
skew([0, long_skew, 0, 0, 0, 0])
rotate([lat_skew, 0, 180])
airfoil(h=length, L=chord);
translate([0, 0-w, 0]) {
// upper pivot needs a complex trig transformation!
translate([d - (chord/2), w, h + chord])
rotate([0, 90+long_skew, 0])
color("black")
cylinder(h=chord, r=12);
// lower pivot:
translate([0 - chord, 0, (chord/2 * sin(long_skew))])
rotate([0, 90+long_skew, 0])
color("black")
cylinder(h=chord, r=12);
// aerofoil section
skew([0, long_skew, 0, 0, 0, 0])
rotate([lat_skew, 0, 180])
color("black")
airfoil(h=length, L=chord);
}
}
module fourbar_axle_half( length, chord) {
translate([0, 0, -120])
rotate([82, 0, 180])
color("black")
airfoil(h=length, L=chord);
// lower knuckle
translate([-chord, length, -60])
color("black")
cube([chord, chord/4, chord/2]);
// wheel
translate([0, length + 50, -50])
// Pierre Rouzeau's wheel is beautifully modelled and parameterised, but it doesn't seem to be scaled as I'd expect...
wheel(rim=451, spoke_nbr=32);
}
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, long_skew, lat_skew);
translate([0, shoulder/2, 0])
translate([0, (shoulder/2), 0])
mirror([0, 1, 0])
fourbar_leg(length, chord, long_skew, lat_skew);
}
fourbar_axle_half(w, chord);
mirror([0, 1, 0])
fourbar_axle_half(w, chord);
}
fourbar(600, 100, 30, 30, 650);
fourbar(700, 100, 30, 35, 650);