cosplay: Touhou/Houjuu Nue #4
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@ -3,6 +3,9 @@ import math
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import cadquery as Cq
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import nhf.parts.springs as springs
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from nhf import Role
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import nhf.utils
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TOL = 1e-6
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@dataclass
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class HirthJoint:
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@ -232,17 +235,31 @@ class TorsionJoint:
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"""
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This jonit consists of a rider puck on a track puck. IT is best suited if
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the radius has to be small and vertical space is abundant.
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The rider part consists of:
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1. A cylinderical base
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2. A annular extrusion with the same radius as the base, but with slots
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carved in
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3. An annular rider
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The track part consists of:
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1. A cylindrical base
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2. A slotted annular extrusion where the slot allows the spring to rest
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3. An outer and an inner annuli which forms a track the rider can move on
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"""
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# Radius limit for rotating components
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radius: float = 40
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disk_height: float = 10
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track_disk_height: float = 10
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rider_disk_height: float = 8
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radius_spring: float = 15
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radius_axle: float = 6
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# Offset of the spring hole w.r.t. surface
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spring_hole_depth: float = 4
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# If true, cover the spring hole. May make it difficult to insert the spring
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# considering the stiffness of torsion spring steel.
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spring_hole_cover_track: bool = False
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spring_hole_cover_rider: bool = False
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# Also used for the height of the hole for the spring
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spring_thickness: float = 2
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@ -253,13 +270,17 @@ class TorsionJoint:
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groove_radius_outer: float = 35
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groove_radius_inner: float = 20
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groove_depth: float = 5
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rider_gap: float = 2
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n_slots: float = 8
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rider_gap: float = 1
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rider_n_slots: float = 4
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# Degrees of the first and last rider slots
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rider_slot_begin: float = 0
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rider_slot_span: float = 90
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right_handed: bool = False
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def __post_init__(self):
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assert self.disk_height > self.spring_hole_depth
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assert self.radius > self.groove_radius_outer
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assert self.groove_radius_outer > self.groove_radius_inner
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assert self.groove_radius_inner > self.radius_spring
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@ -268,7 +289,7 @@ class TorsionJoint:
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@property
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def total_height(self):
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return 2 * self.disk_height + self.spring_height
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return self.track_disk_height + self.rider_disk_height + self.spring_height
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@property
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def _radius_spring_internal(self):
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@ -295,6 +316,10 @@ class TorsionJoint:
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r2 = -r2
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# This is (0, r2) and (l, r2) transformed by rotation matrix
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# [[c, s], [-s, c]]
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return [
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(0, 0, height),
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(c, s, height)
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]
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return [
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(s * r2, -s * l + c * r2, height),
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(c * l + s * r2, -s * l + c * r2, height),
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@ -320,14 +345,24 @@ class TorsionJoint:
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spring_hole_profile = (
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Cq.Sketch()
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.circle(self.radius)
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.polygon(self._slot_polygon(flip=False), mode='s')
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.circle(self.radius_spring, mode='s')
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)
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slot_height = self.spring_thickness
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if not self.spring_hole_cover_track:
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slot_height += self.groove_depth
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slot = (
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Cq.Workplane('XY')
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.sketch()
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.polygon(self._slot_polygon(flip=False))
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.finalize()
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.extrude(slot_height)
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.val()
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)
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result = (
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Cq.Workplane('XY')
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.cylinder(
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radius=self.radius,
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height=self.disk_height,
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height=self.track_disk_height,
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centered=(True, True, False))
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.faces('>Z')
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.tag("spring")
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@ -340,9 +375,10 @@ class TorsionJoint:
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.extrude(self.groove_depth)
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.faces('>Z')
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.hole(self.radius_axle * 2)
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.cut(slot.moved(Cq.Location((0, 0, self.track_disk_height))))
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)
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# Insert directrix`
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result.polyline(self._directrix(self.disk_height),
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result.polyline(self._directrix(self.track_disk_height),
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forConstruction=True).tag("directrix")
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return result
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@ -357,9 +393,9 @@ class TorsionJoint:
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.circle(self.radius_spring, mode='s')
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.parray(
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r=0,
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a1=0,
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da=360,
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n=self.n_slots)
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a1=self.rider_slot_begin,
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da=self.rider_slot_span,
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n=self.rider_n_slots)
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.each(slot, mode='s')
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#.circle(self._radius_wall, mode='a')
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)
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@ -367,43 +403,58 @@ class TorsionJoint:
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Cq.Sketch()
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.circle(self.groove_radius_outer, mode='a')
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.circle(self.groove_radius_inner, mode='s')
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#.circle(self._radius_wall, mode='a')
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)
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if not self.spring_hole_cover_rider:
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contact_profile = (
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contact_profile
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.parray(
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r=0,
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a1=0,
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da=360,
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n=self.n_slots)
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a1=self.rider_slot_begin,
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da=self.rider_slot_span,
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n=self.rider_n_slots)
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.each(slot, mode='s')
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.reset()
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)
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middle_height = self.spring_height - self.groove_depth - self.rider_gap
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#.circle(self._radius_wall, mode='a')
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middle_height = self.spring_height - self.groove_depth - self.rider_gap - self.spring_thickness
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result = (
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Cq.Workplane('XY')
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.cylinder(
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radius=self.radius,
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height=self.disk_height,
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height=self.rider_disk_height,
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centered=(True, True, False))
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.faces('>Z')
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.tag("spring")
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.workplane()
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.placeSketch(wall_profile)
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.extrude(middle_height)
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.faces(tag="spring")
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.workplane()
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# The top face might not be in one piece.
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#.faces('>Z')
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.workplane(offset=middle_height)
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.placeSketch(contact_profile)
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.extrude(self.groove_depth + self.rider_gap)
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.faces(tag="spring")
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.workplane()
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.circle(self._radius_spring_internal)
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.extrude(self.spring_height)
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.faces('>Z')
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#.faces(tag="spring")
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#.workplane()
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.hole(self.radius_axle * 2)
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)
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for i in range(self.n_slots):
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theta = 2 * math.pi * i / self.n_slots
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result.polyline(self._directrix(self.disk_height, theta),
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theta_begin = math.radians(self.rider_slot_begin) + math.pi
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theta_span = math.radians(self.rider_slot_span)
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if abs(math.remainder(self.rider_slot_span, 360)) < TOL:
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theta_step = theta_span / self.rider_n_slots
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else:
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theta_step = theta_span / (self.rider_n_slots - 1)
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for i in range(self.rider_n_slots):
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theta = theta_begin - i * theta_step
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result.polyline(self._directrix(self.rider_disk_height, theta),
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forConstruction=True).tag(f"directrix{i}")
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return result
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def rider_track_assembly(self):
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def rider_track_assembly(self, directrix=0):
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rider = self.rider()
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track = self.track()
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spring = self.spring()
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@ -412,10 +463,10 @@ class TorsionJoint:
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.add(spring, name="spring", color=Role.DAMPING.color)
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.add(track, name="track", color=Role.PARENT.color)
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.constrain("track?spring", "spring?top", "Plane")
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.constrain("track?directrix", "spring?directrix_bot", "Axis")
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.add(rider, name="rider", color=Role.CHILD.color)
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.constrain("rider?spring", "spring?bot", "Plane")
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.constrain("track?directrix", "spring?directrix_bot", "Axis")
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.constrain("rider?directrix0", "spring?directrix_top", "Axis")
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.constrain(f"rider?directrix{directrix}", "spring?directrix_top", "Axis")
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.solve()
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)
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return result
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@ -1,6 +1,6 @@
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import unittest
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import cadquery as Cq
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from nhf.checks import binary_intersection
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from nhf.checks import binary_intersection, pairwise_intersection
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from nhf.parts import joints, handle, metric_threads
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class TestJoints(unittest.TestCase):
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@ -22,12 +22,25 @@ class TestJoints(unittest.TestCase):
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"Hirth joint assembly must not have intersection")
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def test_joints_comma_assembly(self):
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joints.comma_assembly()
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def test_torsion_joint(self):
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j = joints.TorsionJoint()
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assembly = j.rider_track_assembly()
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bbox = assembly.toCompound().BoundingBox()
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self.assertAlmostEqual(bbox.zlen, j.total_height)
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def torsion_joint_collision_case(self, joint: joints.TorsionJoint, slot: int):
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assembly = joint.rider_track_assembly(slot)
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bbox = assembly.toCompound().BoundingBox()
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self.assertAlmostEqual(bbox.zlen, joint.total_height)
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self.assertEqual(pairwise_intersection(assembly), [])
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def test_torsion_joint_collision(self):
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j = joints.TorsionJoint()
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for slot in range(j.rider_n_slots):
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with self.subTest(slot=slot):
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self.torsion_joint_collision_case(j, slot)
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class TestHandle(unittest.TestCase):
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