-module spin_2d(weight_radius,
- arms,
- wall_thickness,
- bearing_radius) {
- bearing_holder_radius = bearing_radius + wall_thickness;
- weight_holder_radius = weight_radius + wall_thickness;
-
- ring(bearing_holder_radius, bearing_radius);
-
- /*
- * imagine a triangle with one point at the origin, at the
- * center of the spinning bearing holder, one point in the middle of
- * the weight holder, and one point at the center of a circle tangent
- * to the first two, called the joiner circle.
- * the radius of the joiner circle is the arithmetic average of the
- * weight holder and bearing holder.
- */
- joiner_radius = (bearing_holder_radius + weight_holder_radius) / 2;
- /* a: goes between the center of the weight holder and the center of
- the joiner circle. */
- a = joiner_radius + weight_holder_radius;
- /* b: length of the base, which goes along the x-axis between
- the origin and the center of the weight holder. */
- b = weight_holder_radius + bearing_holder_radius;
- /* c: goes between origin and joiner circle. */
- c = bearing_holder_radius + joiner_radius;
-
- /* A: angle at the origin, between the base and segment from origin
- to center of joiner circle.
- it is calculated using law of cosines, given the lengths of
- all 3 sides of the triangle. */
- A = acos((pow(b, 2) + pow(c, 2) - pow(a, 2)) / (2 * b * c));
- /* find the center of the joiner circle */
- joiner_x = cos(A) * c;
- joiner_y = sin(A) * c;
-
- /* find the points where the circles meet */
- bearing_joiner_point = [cos(A) * bearing_holder_radius,
- sin(A) * bearing_holder_radius];
- bearing_weight_point = [bearing_holder_radius, 0];
- /* C: angle between x-axis and line-segment between center of weight
- holder and center of joiner.
- it is calculated using law of cosines, given the lengths of
- all 3 sides of the triangle. */
- C = acos((pow(a, 2) + pow(b, 2) - pow(c, 2)) / (2 * a * b));
- weight_joiner_point = [b - cos(C) * weight_holder_radius,
- sin(C) * weight_holder_radius];
- for(arm = [0 : arms - 1]) {
- rotate(arm * 360.0 / arms) {
- difference() {
- polygon([bearing_weight_point,
- bearing_joiner_point,
- weight_joiner_point]);
- translate([joiner_x, joiner_y]) {
- circle(joiner_radius); }
- translate([weight_holder_radius + bearing_holder_radius, 0]) {
- circle(weight_holder_radius); } }
- mirror(v = [0, 1, 0]) {
- difference() {
- polygon([bearing_weight_point,
- bearing_joiner_point,
- weight_joiner_point]);
- translate([joiner_x, joiner_y]) {
- circle(joiner_radius); }
- translate([weight_holder_radius + bearing_holder_radius, 0]) {
- circle(weight_holder_radius); } } }
- translate([weight_holder_radius + bearing_holder_radius, 0]) {
- ring(weight_holder_radius, weight_radius); } } } }
+module fillet(r) {
+ offset(r = -r) { offset(delta = r) { children(); } } }
+
+module spin_footprint(weight_radius,
+ bearing_radius,
+ round_extra,
+ wall,
+ arms) {
+ thinner_radius = (bearing_radius < weight_radius)?
+ bearing_radius : weight_radius;
+ fillet(thinner_radius) {
+ for(arm = [0 : arms - 1]) {
+ hull() {
+ circle(bearing_radius + round_extra);
+ rotate( (arm / arms) * 360 ) {
+ translate([bearing_radius + wall + weight_radius, 0]) {
+ circle(weight_radius + round_extra); } } } } } }
+
+module mirrored(axis) {
+ children();
+ mirror(axis) children(); }