wheel.scad

R1 = 17;
R2 = 12;
R3 = 2.5;
// Minimal thickness in hole
H0 = 1;
// Height of bars
H1 = 4;
// Height of circle
H2 = 6;
// Extra hole padding
E = 0.5;
// L is the distance between wheels,
// Full width will be L + 2 * H2
L = 45;
// Number of bars
N = 4;
// Width of bar
A = 3.5;

$fa=1;
$fs = 0.01;

// Radius of intersection of bars.
rr = A/(2*sin(90/N));
module wheel() {
intersection(){
    cylinder(h=3*L, r=R1, center=true);
    union() {
        translate([0,0,H1])
            cylinder(h=H2-H1, r1=rr, r2=R3);
        
        difference(){
            cylinder(h=H2, r=2*R1);
            cylinder(h=3*L, r=R2, center=true);
        }
        for(n=[0:N]){
            translate([0,0,H1/2])
            rotate([0, 0, 180*n/N])
            cube([A, 2*R1, H1], center=true);
        }
    }
}

}
module wheel_axle(with_axle) {
if (with_axle) {
    union() {
        wheel();
        cylinder(h=L+2*H2, r=R3);
    }
} else {
    difference() {
        wheel();
        translate([0,0,H0])
            cylinder(h=2*H2-H0,r=R3+E);
    }
}
}

union(){
    wheel_axle(true);
    translate([0, 2*R1+2, 0])
        wheel_axle(false);
}

wheel.stl