difference() {
rim(radius, wall_width * 2, width);
translate([0, 0, width / 2]) {
tread(radius, tread_radius); } }
linear_extrude(height = wheel_square_spoke_thickness) {
difference() {
difference() {
rim(radius, wall_width * 2, width);
translate([0, 0, width / 2]) {
tread(radius, tread_radius); } }
linear_extrude(height = wheel_square_spoke_thickness) {
difference() {