Added SBR rails

This change adds
- SBR rails. For now only SBR16
- The bearing block that goes with it (SBR16UU)
- An 'open' linear bearing (LM16UUOP) that is used by the bearing block
- A 28mm circlip that has a wider opening than then normal circlip.
(circlip_28iw)

vitamins/sbr_rails.scad

@@ -0,0 +1,31 @@
+//
+// NopSCADlib Copyright Chris Palmer 2020
+// nop.head@gmail.com
+// hydraraptor.blogspot.com
+//
+// This file is part of NopSCADlib.
+//
+// NopSCADlib is free software: you can redistribute it and/or modify it under the terms of the
+// GNU General Public License as published by the Free Software Foundation, either version 3 of
+// the License, or (at your option) any later version.
+//
+// NopSCADlib is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY;
+// without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
+// See the GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License along with NopSCADlib.
+// If not, see <https://www.gnu.org/licenses/>.
+//
+include <../core.scad>
+include <../vitamins/bearing_blocks.scad>
+
+//
+// SBR Rails
+//
+
+//                        d  h   B   T  carriage P    S2            C   S3            S3L
+SBR16S     = ["SBR16S",  16, 25, 40, 5, SBR16UU, 150, M5_cap_screw, 30, M5_cap_screw, 18  ];
+
+sbr_rails = [SBR16S];
+
+use <sbr_rail.scad>