cosplay: Touhou/Houjuu Nue #4
132
nhf/joints.py
132
nhf/joints.py
|
|
@ -4,126 +4,86 @@ import cadquery as Cq
|
|||
import nhf.springs as NS
|
||||
from nhf import Role
|
||||
|
||||
def hirth_tooth_angle(n_tooth):
|
||||
"""
|
||||
Angle of one whole tooth
|
||||
"""
|
||||
return 360 / n_tooth
|
||||
|
||||
@dataclass(frozen=True)
|
||||
class HirthJoint:
|
||||
"""
|
||||
A Hirth joint attached to a cylindrical base
|
||||
"""
|
||||
|
||||
# r
|
||||
radius: float = 60
|
||||
# r_i
|
||||
radius_inner: float = 40
|
||||
base_height: float = 20
|
||||
n_tooth: float = 16
|
||||
# h_o
|
||||
tooth_height: float = 16
|
||||
tooth_height_inner: float = 2
|
||||
|
||||
def __post_init__(self):
|
||||
# Ensures tangent doesn't blow up
|
||||
assert self.n_tooth >= 5
|
||||
assert self.radius > self.radius_inner
|
||||
assert self.tooth_height >= self.tooth_height_inner
|
||||
|
||||
@property
|
||||
def _theta(self):
|
||||
return math.pi / self.n_tooth
|
||||
|
||||
@property
|
||||
def tooth_angle(self):
|
||||
return hirth_tooth_angle(self.n_tooth)
|
||||
return 360 / self.n_tooth
|
||||
|
||||
|
||||
def generate(self, tag_prefix="", is_mated=False, tol=0.01):
|
||||
"""
|
||||
is_mated: If set to true, rotate the teeth so they line up at 0 degrees.
|
||||
|
||||
FIXME: The curves don't mate perfectly. See if non-planar lofts can solve
|
||||
this issue.
|
||||
FIXME: Mate is not exact when number of tooth is low
|
||||
"""
|
||||
c, s, t = math.cos(self._theta), math.sin(self._theta), math.tan(self._theta)
|
||||
span = self.radius * t
|
||||
radius_proj = self.radius / c
|
||||
span_inner = self.radius_inner * s
|
||||
# 2 * raise + (inner tooth height) = (tooth height)
|
||||
inner_raise = (self.tooth_height - self.tooth_height_inner) / 2
|
||||
# Outer tooth triangle spans 2*theta radians. This profile is the radial
|
||||
# profile projected onto a plane `radius` away from the centre of the
|
||||
# cylinder. The y coordinates on the edge must drop to compensate.
|
||||
|
||||
# The drop is equal to, via similar triangles
|
||||
drop = inner_raise * (radius_proj - self.radius) / (self.radius - self.radius_inner)
|
||||
outer = [
|
||||
(span, -tol - drop),
|
||||
(span, -drop),
|
||||
(0, self.tooth_height),
|
||||
(-span, -drop),
|
||||
(-span, -tol - drop),
|
||||
]
|
||||
adj = self.radius_inner * c
|
||||
# In the case of the inner triangle, it is projected onto a plane `adj` away
|
||||
# from the centre. The apex must extrapolate
|
||||
|
||||
# Via similar triangles
|
||||
#
|
||||
# (inner_raise + tooth_height_inner) -
|
||||
# (tooth_height - inner_raise - tooth_height_inner) * ((radius_inner - adj) / (radius - radius_inner))
|
||||
apex = (inner_raise + self.tooth_height_inner) - \
|
||||
inner_raise * (self.radius_inner - adj) / (self.radius - self.radius_inner)
|
||||
inner = [
|
||||
(span_inner, -tol),
|
||||
(span_inner, inner_raise),
|
||||
(0, apex),
|
||||
(-span_inner, inner_raise),
|
||||
(-span_inner, -tol),
|
||||
]
|
||||
tooth = (
|
||||
phi = math.radians(self.tooth_angle)
|
||||
alpha = 2 * math.atan(self.radius / self.tooth_height * math.tan(phi/2))
|
||||
#alpha = math.atan(self.radius * math.radians(180 / self.n_tooth) / self.tooth_height)
|
||||
gamma = math.radians(90 / self.n_tooth)
|
||||
# Tooth half height
|
||||
l = self.radius * math.cos(gamma)
|
||||
a = self.radius * math.sin(gamma)
|
||||
t = a / math.tan(alpha / 2)
|
||||
beta = math.asin(t / l)
|
||||
dx = self.tooth_height * math.tan(alpha / 2)
|
||||
profile = (
|
||||
Cq.Workplane('YZ')
|
||||
.polyline(inner)
|
||||
.polyline([
|
||||
(0, 0),
|
||||
(dx, self.tooth_height),
|
||||
(-dx, self.tooth_height),
|
||||
])
|
||||
.close()
|
||||
.workplane(offset=self.radius - adj)
|
||||
.polyline(outer)
|
||||
.close()
|
||||
.loft(ruled=False, combine=True)
|
||||
.extrude(-self.radius)
|
||||
.val()
|
||||
.rotate((0, 0, 0), (0, 1, 0), math.degrees(beta))
|
||||
.moved(Cq.Location((0, 0, self.base_height)))
|
||||
)
|
||||
angle_offset = hirth_tooth_angle(self.n_tooth) / 2 if is_mated else 0
|
||||
h = self.base_height + self.tooth_height
|
||||
teeth = (
|
||||
core = Cq.Solid.makeCylinder(
|
||||
radius=self.radius_inner,
|
||||
height=self.tooth_height,
|
||||
pnt=(0, 0, self.base_height),
|
||||
)
|
||||
angle_offset = self.tooth_angle / 2 if is_mated else 0
|
||||
result = (
|
||||
Cq.Workplane('XY')
|
||||
.cylinder(
|
||||
radius=self.radius,
|
||||
height=self.base_height + self.tooth_height,
|
||||
centered=(True, True, False))
|
||||
.faces(">Z")
|
||||
.tag(f"{tag_prefix}bore")
|
||||
.cut(core)
|
||||
.polarArray(
|
||||
radius=adj,
|
||||
radius=self.radius,
|
||||
startAngle=angle_offset,
|
||||
angle=360,
|
||||
count=self.n_tooth)
|
||||
.eachpoint(lambda loc: tooth.located(loc))
|
||||
.intersect(Cq.Solid.makeCylinder(
|
||||
height=h,
|
||||
radius=self.radius,
|
||||
))
|
||||
.cut(Cq.Solid.makeCylinder(
|
||||
height=h,
|
||||
radius=self.radius_inner,
|
||||
))
|
||||
.cutEach(
|
||||
lambda loc: profile.moved(loc),
|
||||
)
|
||||
)
|
||||
base = (
|
||||
Cq.Workplane('XY')
|
||||
.cylinder(
|
||||
height=self.base_height,
|
||||
radius=self.radius,
|
||||
centered=(True, True, False))
|
||||
.faces(">Z").tag(f"{tag_prefix}bore")
|
||||
.union(
|
||||
teeth.val().move(Cq.Location((0,0,self.base_height))),
|
||||
tol=tol)
|
||||
.clean()
|
||||
)
|
||||
#base.workplane(offset=tooth_height/2).circle(radius=radius,forConstruction=True).tag("mate")
|
||||
(
|
||||
base
|
||||
result
|
||||
.polyline([
|
||||
(0, 0, self.base_height),
|
||||
(0, 0, self.base_height + self.tooth_height)
|
||||
|
|
@ -131,11 +91,11 @@ class HirthJoint:
|
|||
.tag(f"{tag_prefix}mate")
|
||||
)
|
||||
(
|
||||
base
|
||||
result
|
||||
.polyline([(0, 0, 0), (1, 0, 0)], forConstruction=True)
|
||||
.tag(f"{tag_prefix}directrix")
|
||||
)
|
||||
return base
|
||||
return result
|
||||
|
||||
def assembly(self):
|
||||
"""
|
||||
|
|
|
|||
13
nhf/test.py
13
nhf/test.py
|
|
@ -13,12 +13,15 @@ class TestJoints(unittest.TestCase):
|
|||
self.assertIsInstance(
|
||||
obj.val().solids(), Cq.Solid,
|
||||
msg="Hirth joint must be in one piece")
|
||||
|
||||
def test_joints_hirth_assembly(self):
|
||||
j = nhf.joints.HirthJoint()
|
||||
assembly = j.assembly()
|
||||
isect = binary_intersection(assembly)
|
||||
self.assertLess(isect.Volume(), 1e-6,
|
||||
"Hirth joint assembly must not have intersection")
|
||||
for n_tooth in [16, 20, 24]:
|
||||
with self.subTest(n_tooth=n_tooth):
|
||||
j = nhf.joints.HirthJoint()
|
||||
assembly = j.assembly()
|
||||
isect = binary_intersection(assembly)
|
||||
self.assertLess(isect.Volume(), 1e-6,
|
||||
"Hirth joint assembly must not have intersection")
|
||||
def test_joints_comma_assembly(self):
|
||||
nhf.joints.comma_assembly()
|
||||
def test_torsion_joint(self):
|
||||
|
|
|
|||
Loading…
Reference in New Issue