158 lines
7.2 KiB
OpenSCAD
158 lines
7.2 KiB
OpenSCAD
// LEGO-compatible self-locking Torsen-like differential housing
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// With either double-bevel or single-bevel 36t gear
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// (c) Vitaliy Filippov 2015
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// License: GNU GPL 3.0 or later
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// How to use it - see http://www.thingiverse.com/thing:1236953
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$fn = 100;
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torsen_diff_36t();
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module torsen_diff_36t() {
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rotate([90, 0, 0])
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union() {
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difference() {
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// double bevel:
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rotate([90, 0, 0]) double_bevel_36t();
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translate([0, 4, 0]) rotate([90, 0, 0]) cylinder(r=3.8, h=8, center=true);
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//// single bevel:
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// rotate([-90, 0, 0]) single_bevel(36);
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rotate([90, 0, 0]) cylinder(r=2.6, h=10, center=true);
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}
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translate([0, 0, 8]) difference() {
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union() {
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translate([0, 8, 0]) rotate([90, 0, 90]) cylinder(r=2.8, h=7.2, center=true);
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translate([0, 8-2.8, 0]) cube([7.2, 2.8*2, 2.8*2], center=true);
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translate([-3.2, 8, 0]) rotate([90, 0, 90]) cylinder(r=3.6, h=0.8, center=true);
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translate([-3.2, 8-3.2, 0]) cube([0.8, 3.6*2, 3.6*2], center=true);
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translate([3.2, 8, 0]) rotate([90, 0, 90]) cylinder(r=3.6, h=0.8, center=true);
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translate([3.2, 8-3.2, 0]) cube([0.8, 3.6*2, 3.6*2], center=true);
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translate([0, 8, 0]) rotate([90, 0, 90]) axleround(h=16);
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}
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}
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translate([0, 0, -8]) difference() {
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union() {
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translate([0, 8, 0]) rotate([90, 0, 90]) cylinder(r=2.8, h=7.2, center=true);
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translate([0, 8-2.8, 0]) cube([7.2, 2.8*2, 2.8*2], center=true);
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translate([-3.2, 8, 0]) rotate([90, 0, 90]) cylinder(r=3.6, h=0.8, center=true);
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translate([-3.2, 8-3.2, 0]) cube([0.8, 3.6*2, 3.6*2], center=true);
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translate([3.2, 8, 0]) rotate([90, 0, 90]) cylinder(r=3.6, h=0.8, center=true);
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translate([3.2, 8-3.2, 0]) cube([0.8, 3.6*2, 3.6*2], center=true);
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translate([0, 8, 0]) rotate([90, 0, 90]) axleround(h=16);
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}
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}
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}
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}
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module axleround(h = 24, axleradius = 2.3, axlemesh = 1.7) {
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translate([0, 0, -h/2]) difference() {
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cylinder($fn=16, r=axleradius, h=h);
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translate([axlemesh/2, axlemesh/2, -1]) cube([axleradius, axleradius, h+2]);
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translate([axlemesh/2, -axlemesh/2-axleradius, -1]) cube([axleradius, axleradius, h+2]);
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translate([-axlemesh/2-axleradius, axlemesh/2, -1]) cube([axleradius, axleradius, h+2]);
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translate([-axlemesh/2-axleradius, -axlemesh/2-axleradius, -1]) cube([axleradius, axleradius, h+2]);
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}
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}
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module single_bevel(nteeth = 28) {
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union() {
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intersection() {
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translate([0, 0, 1.5])
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linear_extrude(slices=5, height=2.5, scale=(nteeth/2+1-2.5*tan(45))/(nteeth/2+1))
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gear_concat_flat(mm_per_tooth=3.4, number_of_teeth=nteeth, backlash=2, clearance=0.8, trim_factor=0.7);
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cylinder($fn=nteeth*2, h=4, r=2.98*(nteeth/2+1)/3.1415926+0.5);
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}
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cylinder($fn=nteeth*2, h=4, r=2.98*(nteeth/2-1)/3.1415926);
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cylinder($fn=nteeth*2, h=1.5, r=2.98*(nteeth/2+1)/3.1415926+0.5);
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}
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}
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// An attempt to make something like standard 36t double bevel gear...
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// std lego 36t gear outer radius = ~36.5
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// std lego 36t gear root radius = ~32.2
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module double_bevel_36t() {
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intersection() {
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union() {
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translate([0, 0, 1.1])
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linear_extrude(slices=5, height=2.5, scale=(36/2+1-2.5*tan(45))/(36/2+1))
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gear_concat_flat(mm_per_tooth=3.4, number_of_teeth=36, backlash=2, clearance=0.8, trim_factor=0.7);
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translate([0, 0, -1.1])
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rotate([180, 0, 0])
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linear_extrude(slices=5, height=2.5, scale=(36/2+1-2.5*tan(45))/(36/2+1))
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gear_concat_flat(mm_per_tooth=3.4, number_of_teeth=36, backlash=2, clearance=0.8, trim_factor=0.7);
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translate([0, 0, -3.6])
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cylinder($fn=36*2, h=7.2, r=2.98*(36/2-1)/3.1415926);
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translate([0, 0, -1.1])
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cylinder($fn=36*2, h=2.2, r=2.98*(36/2+1)/3.1415926+0.5);
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}
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translate([0, 0, -8]) linear_extrude(slices=5, height=16)
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gear_concat_flat(mm_per_tooth=2.98, number_of_teeth=36, pressure_angle=15, backlash=-0.5, clearance=-0.3);
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}
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}
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// Same in 2D (non-extruded)
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module gear_concat_flat(
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mm_per_tooth = 3, //this is the "circular pitch", the circumference of the pitch circle divided by the number of teeth
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number_of_teeth = 11, //total number of teeth around the entire perimeter
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pressure_angle = 28, //Controls how straight or bulged the tooth sides are. In degrees.
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clearance = 0.0, //gap between top of a tooth on one gear and bottom of valley on a meshing gear (in millimeters)
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backlash = 0.0, //gap between two meshing teeth, in the direction along the circumference of the pitch circle
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trim_factor = 1
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) {
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pi = 3.1415926;
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p = mm_per_tooth * number_of_teeth / pi / 2; //radius of pitch circle
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c = p + mm_per_tooth / pi - clearance; //radius of outer circle
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b = p*cos(pressure_angle); //radius of base circle
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r = p - mm_per_tooth / pi; //radius of root circle
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t = mm_per_tooth/2-backlash/2; //tooth thickness at pitch circle
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k = -iang(b, p) - t/2/p/pi*180; //angle to where involute meets base circle on each side of tooth
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polygon(
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points = gear_points_trimmed(r, b, c, k, number_of_teeth, number_of_teeth, trim_factor),
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paths = [ range(15*(number_of_teeth)) ]
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);
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};
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function gear_points_trimmed(r, b, c, k, number_of_teeth, i, f) =
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(i <= 0 ? [] : concat(
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gear_points_trimmed(r, b, c, k, number_of_teeth, i-1, f),
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tooth_base_points_trimmed(r, b, c, k, number_of_teeth, i, f)
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));
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function tooth_base_points_trimmed(r, b, c, k, number_of_teeth, i, f) =
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(r < b ? concat(
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[ polar(r*f, i*360/number_of_teeth + k) ],
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tooth_points(r, b, c, k, number_of_teeth, i),
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[ polar(r*f, i*360/number_of_teeth - k),
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polar(r*f, i*360/number_of_teeth + 180/number_of_teeth) ]
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) : concat(
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tooth_points(r, b, c, k, number_of_teeth, i),
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[ polar(r*f, i*360/number_of_teeth + 180/number_of_teeth) ]
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));
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function tooth_points(r, b, c, k, number_of_teeth, i) = [
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q7r(0/5,r,b,c,k,1,i*360/number_of_teeth),
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q7r(1/5,r,b,c,k,1,i*360/number_of_teeth),
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q7r(2/5,r,b,c,k,1,i*360/number_of_teeth),
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q7r(3/5,r,b,c,k,1,i*360/number_of_teeth),
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q7r(4/5,r,b,c,k,1,i*360/number_of_teeth),
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q7r(5/5,r,b,c,k,1,i*360/number_of_teeth),
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q7r(5/5,r,b,c,k,-1,i*360/number_of_teeth),
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q7r(4/5,r,b,c,k,-1,i*360/number_of_teeth),
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q7r(3/5,r,b,c,k,-1,i*360/number_of_teeth),
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q7r(2/5,r,b,c,k,-1,i*360/number_of_teeth),
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q7r(1/5,r,b,c,k,-1,i*360/number_of_teeth),
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q7r(0/5,r,b,c,k,-1,i*360/number_of_teeth),
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];
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function range(n) = (n >= 0 ? concat(range(n-1), [n]) : []);
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// radius a fraction f up the curved side of the tooth, rotated at 'rot' angle
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function q7r(f,r,b,r2,t,s,rot) = q6r(b,s,t,(1-f)*max(b,r)+f*r2,rot);
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// point at radius d on the involute curve, rotated at 'rot' angle
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function q6r(b,s,t,d,rot) = polar(d,rot+s*(iang(b,d)+t));
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// convert polar to cartesian coordinates
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function polar(r,theta) = r*[sin(theta), cos(theta)];
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//unwind a string this many degrees to go from radius r1 to radius r2
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function iang(r1,r2) = sqrt((r2/r1)*(r2/r1) - 1)/3.1415926*180 - acos(r1/r2);
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