Onbashira rotor-stator mechanism

nhf/materials.py

@@ -25,6 +25,9 @@ class Role(Flag):
     PARENT = auto()
     CHILD = auto()
     CASING = auto()
+    STATOR = auto()
+    ROTOR = auto()
+    BEARING = auto()
     # Springs, cushions
     DAMPING = auto()
     # Main structural support
@@ -59,6 +62,9 @@ ROLE_COLOR_MAP = {
     Role.PARENT:     _color('blue4', 0.6),
     Role.CASING:     _color('dodgerblue3', 0.6),
     Role.CHILD:      _color('darkorange2', 0.6),
+    Role.STATOR:     _color('gray', 0.5),
+    Role.ROTOR:      _color('blue3', 0.5),
+    Role.BEARING:    _color('green3', 0.8),
     Role.DAMPING:    _color('springgreen', 1.0),
     Role.STRUCTURE:  _color('gray', 0.4),
     Role.DECORATION: _color('lightseagreen', 0.4),

nhf/touhou/yasaka_kanako/onbashira.py

@@ -16,11 +16,27 @@ class Onbashira(Model):
 
     side_thickness: float = 25.4 / 8
 
+    # Dimensions of gun barrels
+    barrel_diam: float = 45.0
+    barrel_length: float = 300.0
+    # Radius from barrel centre to axis
+    rotation_radius: float = 75.0
+    # Radius of ball bearings
+    bearing_ball_diam: float = 30.0
+    bearing_ball_gap: float = 1.0
+    bearing_height: float = 40.0
+    bearing_thickness: float = 20.0
+
     material_side: Material = Material.WOOD_BIRCH
+    material_bearing: Material = Material.PLASTIC_PLA
+    material_bearing_ball: Material = Material.ACRYLIC_TRANSPARENT
     material_brace: Material = Material.ALUMINUM
 
     def __post_init__(self):
         assert self.n_side >= 3
+        # Bulk must be large enough for the barrel + bearing to rotate
+        assert self.bulk_radius - self.side_thickness - self.bearing_thickness - self.bearing_diam > self.rotation_radius + self.barrel_diam / 2
+        assert self.bearing_height > self.bearing_diam
 
     @property
     def angle_side(self) -> float:
@@ -29,11 +45,17 @@ class Onbashira(Model):
     def angle_dihedral(self) -> float:
         return 180 - self.angle_side
     @property
-    def barrel_radius(self) -> float:
+    def bulk_radius(self) -> float:
         """
-        Calculate radius of the barrel to the centre
+        Calculate radius of the bulk to the centre
         """
         return self.side_width / 2 / math.tan(math.radians(self.angle_side / 2))
+    @property
+    def bearing_diam(self) -> float:
+        return self.bearing_ball_diam + self.bearing_ball_gap
+    @property
+    def bearing_radius(self) -> float:
+        return self.bulk_radius - self.side_thickness - self.bearing_thickness - self.bearing_diam / 2
 
     @target(name="side-panel", kind=TargetKind.DXF)
     def profile_side_panel(self) -> Cq.Sketch:
@@ -55,7 +77,7 @@ class Onbashira(Model):
             .polyline([
                 (-w/2, 0),
                 (w/2, 0),
-                (0, self.barrel_radius),
+                (0, self.bulk_radius),
             ])
             .close()
             .extrude(l)
@@ -64,10 +86,100 @@ class Onbashira(Model):
         # Intersect the side panel
         return result * intersector
 
+    def bearing_channel(self) -> Cq.Solid:
+        """
+        Generates a toroidal channel for the ball bearings
+        """
+        return Cq.Solid.makeTorus(
+            radius1=self.bearing_radius,
+            radius2=self.bearing_diam/2,
+        )
+    @target(name="inner-rotor")
+    def inner_rotor(self) -> Cq.Workplane:
+        r_outer = self.bearing_radius
+        base = Cq.Solid.makeCylinder(
+            radius=r_outer,
+            height=self.bearing_height
+        ).translate(Cq.Vector(0,0,-self.bearing_height/2))
+        r_rot = self.rotation_radius
+        channel = self.bearing_channel()
+        return (
+            Cq.Workplane()
+            .add(base - channel)
+            .faces(">Z")
+            .workplane()
+            .polygon(
+                nSides=self.n_side,
+                diameter=2 * r_rot,
+                forConstruction=True
+            )
+            .vertices()
+            .hole(self.barrel_diam)
+        )
+        return base - channel
+    @target(name="outer-rotor")
+    def outer_rotor(self) -> Cq.Workplane:
+        polygon_radius = (self.bulk_radius - self.side_thickness) / math.cos(math.radians(self.angle_side / 2))
+        profile = (
+            Cq.Sketch()
+            .regularPolygon(
+                r=polygon_radius,
+                n=self.n_side,
+            )
+        )
+        inner = Cq.Solid.makeCylinder(
+            radius=self.bearing_radius,
+            height=self.bearing_height,
+        )
+        base = (
+            Cq.Workplane()
+            .placeSketch(profile)
+            .extrude(self.bearing_height)
+            .cut(inner)
+            .translate(Cq.Vector(0,0,-self.bearing_height/2))
+            .cut(self.bearing_channel())
+        )
+        r = self.bearing_radius * 2
+        subtractor = Cq.Solid.makeBox(
+            length=r * 2,
+            width=r * 2,
+            height=self.bearing_height,
+        ).translate(Cq.Vector(-r, -r, -self.bearing_height))
+        return base - subtractor
+    def bearing_ball(self) -> Cq.Solid:
+        return Cq.Solid.makeSphere(radius=self.bearing_ball_diam/2, angleDegrees1=-90)
+
+    def assembly_bearing(self) -> Cq.Assembly:
+        a = (
+            Cq.Assembly()
+            .addS(
+                self.inner_rotor(),
+                name="inner",
+                material=self.material_bearing,
+                role=Role.ROTOR,
+            )
+            .addS(
+                self.outer_rotor(),
+                name="outer",
+                material=self.material_bearing,
+                role=Role.STATOR,
+            )
+        )
+        for i in range(self.n_side):
+            ball = self.bearing_ball()
+            a = a.addS(
+                ball,
+                name=f"bearing_ball{i}",
+                material=self.material_bearing_ball,
+                role=Role.BEARING,
+                loc=Cq.Location.rot2d(i * 360/self.n_side) * Cq.Location(self.bearing_radius, 0, 0),
+            )
+        return a
+
     def assembly(self) -> Cq.Assembly:
         a = Cq.Assembly()
         side = self.side_panel()
-        r = self.barrel_radius
+        r = self.bulk_radius
         for i in range(6):
             a = a.addS(
                 side,