Add (empty) x carriage.

lib/linear_bearing.scad

 x_rail_hole_off = 5;
 x_rail_block_len = (y_carriage_length - x_rail_cutout_y) / 2;
 
+draw_x_carriage = false;
 draw_y_carriage = false;
-draw_rail_len = 100;
+draw_y_carriage_idlers = true;
+draw_rail_len = 200;
 
+// y-carriage belt idlers
 idler_a_blue = [  19,               15,  5.5];
 idler_a_red  = [  19, x_rail_dist + 15, 12.5];
 idler_b_blue = [30.3, x_rail_dist + 15, 12.5];
     
     // idlers for the corexy belts
     translate([0, 0, y_carriage_wall]) {
-        if (!draw_y_carriage) {
+        if (draw_y_carriage_idlers) {
             translate(idler_a)
                 bearing_idler();
             
     }
 }
 
+x_carriage_width = 60;
+x_carriage_len_add = 10;
+x_carriage_wall = 10;
+x_carriage_bearing_off = 3;
+
+module x_carriage() {
+    //color("green")
+    difference() {
+        color("green")
+        cube([x_carriage_width, x_rail_dist + (2 * x_carriage_len_add), x_carriage_wall]);
+        
+        for (i = [0 : 1 : 1]) {
+            translate([lm8uu_height + x_carriage_bearing_off + (i * (x_carriage_width - (2 * x_carriage_bearing_off) - lm8uu_height)), 0, ])
+            rotate([0, -90, 0]) {
+                // x-bearings
+                color("magenta")
+                %translate([0, x_carriage_len_add, 0])
+                    lm8uu();
+                
+                color("magenta")
+                %translate([0, x_rail_dist + x_carriage_len_add, 0])
+                    lm8uu();
+                
+                color("green")
+                translate([0, x_carriage_len_add, 0])
+                    cylinder(d = lm8uu_outer + lm8uu_dia_add, h = lm8uu_height + lm8uu_len_add);
+                
+                color("green")
+                translate([0, x_rail_dist + x_carriage_len_add, 0])
+                    cylinder(d = lm8uu_outer + lm8uu_dia_add, h = lm8uu_height + lm8uu_len_add);
+                
+                color("green")
+                translate([0, x_carriage_len_add, -x_carriage_width])
+                    cylinder(d = lm8uu_inner + rail_dia_add, h = x_carriage_width * 2);
+                
+                color("green")
+                translate([0, x_rail_dist + x_carriage_len_add, -x_carriage_width])
+                    cylinder(d = lm8uu_inner + rail_dia_add, h = x_carriage_width * 2);
+            }
+        }
+    }
+}
+
 if (draw_y_carriage) {
     translate([(lm8uu_outer + lm8uu_dia_add) / 2 + y_carriage_rail_support, 0, 0])
     rotate([-90, 0, 0]) {
     translate([(2 * y_carriage_width + y_carriage_block_width) + draw_rail_len -5, y_carriage_length, 0])
         rotate([0, 0, 180])
         y_carriage(idler_a_red, idler_b_red);
+    
+    if (draw_x_carriage) {
+        translate([y_carriage_width + y_carriage_block_width + ((draw_rail_len - x_carriage_width) / 2), y_carriage_len_add - x_carriage_len_add, 0])
+            x_carriage();
+    }
+} else if (draw_x_carriage) {
+    x_carriage();
 }

xyRepRap.scad

 
 rail_mount_dist = 12;
 y_carriage_pos = 175;
+x_carriage_pos = 180;
 
 module rail(length) {
     cylinder(d = rail_dia, h = length);
 
 module x_rails() {
     // TODO length calculate properly!
+    
+    color("cyan")
     translate([30, y_carriage_pos, 15])
         rotate([0, 90, 0])
         rail(outer_length - (4 * slot));
+    
+    color("cyan")
     translate([30, y_carriage_pos + x_rail_dist, 15])
         rotate([0, 90, 0])
         rail(outer_length - (4 * slot));
+    
+    translate([x_carriage_pos, y_carriage_pos - x_carriage_len_add, slot / 2])
+        x_carriage();
 }
 
 module motion_xy() {
     translate([slot, slot, outer_height])
         y_rails();
     
-    color("cyan")
     translate([slot, slot + y_carriage_len_add, outer_height - (1.5 * slot)])
         x_rails();
 
             gt2_belt(outer_length - (5 * slot) - y_carriage_pos);
     }
     
+    // x carriage belts on blue side
+    color("blue")
+    translate([slot + 29, slot + 32 + 25 + y_carriage_pos, outer_height - 1])
+        rotate([180, 0, 0])
+        gt2_belt(x_carriage_pos - 20);
+    color("red")
+    translate([slot + 15, slot + 23 + y_carriage_pos, outer_height - 8])
+        rotate([180, 0, 0])
+        gt2_belt(x_carriage_pos - 6);
+    
+    // x carriage belts on red side
+    color("red")
+    translate([slot + 50 + x_carriage_pos, slot + 32 + 25 + y_carriage_pos, outer_height - 8])
+        rotate([180, 0, 0])
+        gt2_belt(outer_width - x_carriage_pos - (2 * slot) - 80);
+    color("blue")
+    translate([slot + 50 + x_carriage_pos, slot + 23 + y_carriage_pos, outer_height - 1])
+        rotate([180, 0, 0])
+        gt2_belt(outer_width - x_carriage_pos - (2 * slot) - 70);
+    
     // long back belts
     color("blue")
     translate([slot + 15, slot + 10, outer_height - 7])