infty = 100;
eps = 0.01;

wall = 0.6;		// minimum wall
d_x = 25;		// inner diameter in the X axis
y_scale = 0.5;		// scale y/x
height = 2.5;           // height of the rim

module half(d_x, y_scale, height) {
	hull($fn = 128) {
		scale([1, (d_x*y_scale+height)/(d_x+height), 1])
			cylinder(r = d_x/2 + height/2, h = eps);
		translate([0, 0, height/2])
			scale([1, y_scale, 1])
			cylinder(r = d_x/2, h = eps);
	}
}

module pulley(d_x, y_scale, height, center_hole_d) {
	difference() {
		union() {
			half(d_x, y_scale, height);
			translate([0, 0, height]) scale([1, 1, -1])
				half(d_x, y_scale, height);
		}
		translate([0, 0, -eps])
			cylinder(r = center_hole_d/2, h = height + 2*eps);
	}
}

pulley(d_x = 15, y_scale = 0.5, height=2.5, center_hole_d = 3);

translate([0, 20, 0])
pulley(d_x = 30, y_scale = 0.5, height=2.5, center_hole_d = 5);