| 1 | /* GNU AGPLv3 (or later at your option) |
| 2 | see bottom for more license info */ |
| 3 | |
| 4 | /* spin thing that erin likes */ |
| 5 | $fn = 500; |
| 6 | |
| 7 | weight = "penny"; |
| 8 | // weight = "608zz"; |
| 9 | bearing = "608zz"; |
| 10 | wall_thickness = 2; |
| 11 | _608zz_radius = 22; |
| 12 | penny_radius = 19.05 / 2; |
| 13 | penny_thickness = 1.52; |
| 14 | weight_radius = (weight == "penny") ? penny_radius : _608zz_radius; |
| 15 | bearing_radius = (bearing == "608zz") ? _608zz_radius : 1/0; |
| 16 | arms = 3; |
| 17 | |
| 18 | module spin(weight_radius, |
| 19 | arms, |
| 20 | wall_thickness, |
| 21 | bearing_radius) { |
| 22 | bearing_holder_radius = bearing_radius + wall_thickness; |
| 23 | weight_holder_radius = weight_radius + wall_thickness; |
| 24 | |
| 25 | circle(bearing_holder_radius); |
| 26 | |
| 27 | /* |
| 28 | * imagine a right triangle with one point at the origin, at the |
| 29 | * center of the spinning bearing holder, one point in the middle of |
| 30 | * the weight holder, and one point at the center of a circle tangent |
| 31 | * to the first two, called the joiner circle. |
| 32 | * the radius of the joiner circle is the arithmetic average of the |
| 33 | * weight holder and bearing holder. |
| 34 | */ |
| 35 | joiner_radius = (bearing_holder_radius + weight_holder_radius) / 2; |
| 36 | /* a: goes between the center of the weight holder and the center of |
| 37 | the joiner circle. */ |
| 38 | a = joiner_radius + weight_holder_radius; |
| 39 | /* b: length of the base, which goes along the x-axis between |
| 40 | the origin and the center of the weight holder. */ |
| 41 | b = weight_holder_radius + bearing_holder_radius; |
| 42 | /* c: goes between origin and joiner circle. */ |
| 43 | c = bearing_holder_radius + joiner_radius; |
| 44 | |
| 45 | /* A: angle at the origin, between the base and hypotenuse. |
| 46 | it is calculated using law of cosines, given the lengths of |
| 47 | all 3 sides of the triangle. */ |
| 48 | A = acos((pow(b, 2) + pow(c, 2) - pow(a, 2)) / (2 * b * c)); |
| 49 | /* find the center of the joiner circle */ |
| 50 | joiner_x = cos(A) * c; |
| 51 | joiner_y = sin(A) * c; |
| 52 | |
| 53 | /* find the points where the circles meet */ |
| 54 | bearing_joiner_point = [cos(A) * bearing_holder_radius, |
| 55 | sin(A) * bearing_holder_radius]; |
| 56 | bearing_weight_point = [bearing_holder_radius, 0]; |
| 57 | /* C: angle between x-axis and line-segment between center of weight |
| 58 | holder and center of joiner. |
| 59 | it is calculated using law of cosines, given the lengths of |
| 60 | all 3 sides of the triangle. */ |
| 61 | C = acos((pow(a, 2) + pow(b, 2) - pow(c, 2)) / (2 * a * b)); |
| 62 | weight_joiner_point = [b - cos(C) * weight_holder_radius, |
| 63 | sin(C) * weight_holder_radius]; |
| 64 | for(arm = [0 : arms - 1]) { |
| 65 | rotate(arm * 360.0 / arms) { |
| 66 | difference() { |
| 67 | polygon([bearing_weight_point, |
| 68 | bearing_joiner_point, |
| 69 | weight_joiner_point]); |
| 70 | translate([joiner_x, joiner_y]) { |
| 71 | circle(joiner_radius); } } |
| 72 | mirror(v = [0, 1, 0]) { |
| 73 | difference() { |
| 74 | polygon([bearing_weight_point, |
| 75 | bearing_joiner_point, |
| 76 | weight_joiner_point]); |
| 77 | translate([joiner_x, joiner_y]) { |
| 78 | circle(joiner_radius); } } } |
| 79 | translate([weight_holder_radius + bearing_holder_radius, 0]) { |
| 80 | circle(weight_holder_radius); } } } } |
| 81 | |
| 82 | /* |
| 83 | This file is part of 3d-printables. |
| 84 | |
| 85 | 3d-printables is free software: you can redistribute it and/or modify |
| 86 | it under the terms of the GNU Affero General Public License as published by |
| 87 | the Free Software Foundation, either version 3 of the License, or |
| 88 | (at your option) any later version. |
| 89 | |
| 90 | 3d-printables is distributed in the hope that it will be useful, |
| 91 | but WITHOUT ANY WARRANTY; without even the implied warranty of |
| 92 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
| 93 | GNU Affero General Public License for more details. |
| 94 | |
| 95 | You should have received a copy of the GNU Affero General Public License |
| 96 | along with challenge-bot. If not, see <http://www.gnu.org/licenses/>. |
| 97 | */ |