80 lines
2.6 KiB
Python
80 lines
2.6 KiB
Python
import math
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from typing import Optional
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from dataclasses import dataclass
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import cadquery as Cq
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from nhf import Item, Role
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@dataclass(frozen=True)
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class TorsionSpring(Item):
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"""
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A torsion spring with abridged geometry (since sweep is slow)
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"""
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# Outer radius
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radius: float = 12.0
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height: float = 20.0
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thickness: float = 2.0
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# Angle (in degrees) between the two legs at neutral position
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angle_neutral: float = 90.0
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tail_length: float = 25.0
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right_handed: bool = False
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torsion_rate: Optional[float] = None
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@property
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def name(self) -> str:
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return f"TorsionSpring-{int(self.radius)}-{int(self.height)}"
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@property
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def radius_inner(self) -> float:
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return self.radius - self.thickness
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def torque_at(self, theta: float) -> float:
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return self.torsion_rate * theta
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def generate(self, deflection: float = 0) -> Cq.Workplane:
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omega = self.angle_neutral + deflection
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omega = -omega if self.right_handed else omega
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base = (
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Cq.Workplane('XY')
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.cylinder(height=self.height, radius=self.radius,
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centered=(True, True, False))
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)
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base.faces(">Z").tag("top")
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base.faces("<Z").tag("bot")
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tail = Cq.Solid.makeCylinder(
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height=self.tail_length,
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radius=self.thickness / 2)
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# points cylinder to +X
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dy = self.radius - self.thickness / 2
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if self.right_handed:
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dy = -dy
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loc_dir_x = Cq.Location((0, 0, self.thickness / 2), (0, 1, 0), 90)
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loc_shift = Cq.Location((0, dy, 0))
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loc_top = Cq.Location((0, 0, self.height - self.thickness), (0, 0, 1), omega + 180)
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result = (
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base
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.cylinder(
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height=self.height,
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radius=self.radius - self.thickness,
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combine='s',
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centered=(True, True, True))
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.union(tail.located(loc_shift * loc_dir_x))
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.union(tail.located(loc_top * loc_shift.inverse * loc_dir_x))
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.clean()
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)
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r = -self.radius if self.right_handed else self.radius
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plane = result.copyWorkplane(Cq.Workplane('XY'))
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plane.polyline([(0, r, 0), (self.tail_length, r, 0)],
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forConstruction=True).tag("dir_bot")
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omega = math.radians(omega)
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c, s = math.cos(omega), math.sin(omega)
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l = -self.tail_length
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plane.polyline([
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(-s * r, c * r, self.height),
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(c * l - s * r, c * r + s * l, self.height)],
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forConstruction=True).tag("dir_top")
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return result
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