feat: Right-handed spring

nhf/parts/joints.py

@@ -314,12 +314,12 @@ class TorsionJoint:
         l = self.spring_tail_length
         if self.right_handed:
             r2 = -r2
-        # This is (0, r2) and (l, r2) transformed by rotation matrix
-        # [[c, s], [-s, c]]
         return [
             (0, 0, height),
             (c, s, height)
         ]
+        # This is (0, r2) and (l, r2) transformed by rotation matrix
+        # [[c, s], [-s, c]]
         return [
             (s * r2,         -s * l + c * r2, height),
             (c * l + s * r2, -s * l + c * r2, height),
@@ -332,6 +332,7 @@ class TorsionJoint:
             height=self.spring_height,
             thickness=self.spring_thickness,
             tail_length=self.spring_tail_length,
+            right_handed=self.right_handed,
         )
 
     def track(self):

nhf/parts/springs.py

@@ -5,11 +5,14 @@ def torsion_spring(radius=12,
                    height=20,
                    thickness=2,
                    omega=90,
-                   tail_length=25):
+                   tail_length=25,
+                   right_handed: bool = False):
     """
     Produces a torsion spring with abridged geometry since sweep is very slow in
     cq-editor.
     """
+    if right_handed:
+        omega = -omega
     base = (
         Cq.Workplane('XY')
         .cylinder(height=height, radius=radius,
@@ -17,12 +20,14 @@ def torsion_spring(radius=12,
     )
     base.faces(">Z").tag("top")
     base.faces("<Z").tag("bot")
+
+    box_shift = -radius if right_handed else radius-thickness
     result = (
         base
         .cylinder(height=height, radius=radius - thickness, combine='s',
                   centered=(True, True, True))
         .transformed(
-            offset=(0, radius-thickness),
+            offset=(0, box_shift),
             rotate=(0, 0, 0))
         .box(
             length=tail_length,
@@ -33,18 +38,19 @@ def torsion_spring(radius=12,
         .transformed(
             offset=(0, 0, height - thickness),
             rotate=(0, 0, omega))
-        .center(-tail_length, radius-thickness)
+        .center(-tail_length, box_shift)
         .box(
             length=tail_length,
             width=thickness,
             height=thickness,
             centered=False)
     )
-    result.polyline([(0, radius, 0), (tail_length, radius, 0)],
+    r = -radius if right_handed else radius
+    result.polyline([(0, r, 0), (tail_length, r, 0)],
                     forConstruction=True).tag("directrix_bot")
     c, s = math.cos(omega * math.pi / 180), math.sin(omega * math.pi / 180)
     result.polyline([
-        (s * tail_length, c * radius - s * tail_length, height),
-        (c * tail_length + s * radius, c * radius - s * tail_length, height)],
+        (s * tail_length, c * r - s * tail_length, height),
+        (c * tail_length + s * r, c * r - s * tail_length, height)],
         forConstruction=True).tag("directrix_top")
     return result

nhf/parts/test.py

@@ -40,6 +40,9 @@ class TestJoints(unittest.TestCase):
         for slot in range(j.rider_n_slots):
             with self.subTest(slot=slot):
                 self.torsion_joint_collision_case(j, slot)
+    def test_torsion_joint_collision_right_handed(self):
+        j = joints.TorsionJoint(right_handed=True)
+        self.torsion_joint_collision_case(j, 1)
 
 
 class TestHandle(unittest.TestCase):