Motorcycle CAD Assembly

This example demonstrates the complete visualization of a motorcycle CAD model, highlighting its front, rear, and central assembly structures. Detailed here are the crucial kinematic points used throughout internal analyses, defining everything from the steering axis to the swingarm connections.

By orchestrating discrete components—such as forks, shock mounts, and custom-oriented wheels—the script illustrates how the discrete mechanical sub-systems seamlessly combine to form a full 3D representation of the motorcycle chassis.

Import necessary libraries

import numpy as np
import pyvista as pv

from pymycar.Cad.MotorCycle.front_assembly import fork_front_suspension
from pymycar.Cad.MotorCycle.rear_assembly import swingarm_cad_base, rear_suspension_cantilever
from pymycar.Cad.MotorCycle.frame import frame_cad_base
from pymycar.Cad.MotorCycle.wheel import motorcycle_wheel

Define the Motorcycle Configuration

A dictionary containing the coordinates (x, y, z) in mm for key points across the motorcycle chassis. In this example, all the points are refering to the center of gravity (point 0, 0, 0)

data = {
    # --- Front assembly ---
    "wheel_center_front": np.array([650.0,   0.0,   -520.0]),
    "STEERING_AXIS_BOTTOM": np.array([650.0, 0.0,  -100.0]),
    "STEERING_AXIS_TOP":    np.array([570.0, 0.0,  250.0]),
    "fork_right_upper":  np.array([570.0, -110.0, 250.0]),
    "fork_left_upper":   np.array([570.0,  110.0, 250.0]),
    "fork_right_bottom": np.array([650.0, -120.0, -520.0]),
    "fork_left_bottom":  np.array([650.0,  120.0, -520.0]),
    # --- Rear assembly ---
    "wheel_center_rear": np.array([-600.0,   0.0,  -520.0]),
    "SA_RIGHT": np.array([-100.0, -90.0, -300.0]),
    "SA_LEFT":  np.array([-100.0,  90.0, -300.0]),
    "sa_right_outer": np.array([-600.0, -110.0, -520.0]),
    "sa_left_outer":  np.array([-600.0,  110.0, -520.0]),
    "U_SPRING_MOUNT": np.array([-150.0, 0.0,  50.0]),
    "l_spring_mount": np.array([-420.0, 0.0, -350.0]),
}

Build the 3D Assemblies

# --- Front Assembly ---
# Create the front wheel and the steering/fork assembly
ringradius_front = 300.0  # Example ring radius for the wheel
crosssectionradius_front = 65.0  # Example cross-section radius for the wheel
wheel_front = motorcycle_wheel(data["wheel_center_front"], data["fork_right_bottom"], data["fork_left_bottom"], ringradius_front, crosssectionradius_front)
steer_axis, U_form_upper, U_form_bottom = fork_front_suspension(data)

# --- Rear Assembly ---
# Create the rear wheel, swingarm, and rear suspension system
ringradius_rear = 330.0  # Example ring radius for the wheel
crosssectionradius_rear = 105.0  # Example cross-section radius for the wheel
wheel_rear = motorcycle_wheel(data["wheel_center_rear"], data["SA_RIGHT"], data["SA_LEFT"], ringradius_rear, crosssectionradius_rear)
# pv.Cylinder(center=data["wheel_center_rear"], direction=(0, 1, 0), height=50, radius=200)
swingarm = swingarm_cad_base(data, index=None)
rear_suspension = rear_suspension_cantilever(data, index=None)

# --- Frame ---
# Build the main motorcycle chassis
frame = frame_cad_base(data, index=None)

Visualization setup

Display three separate plots sequentially: 1) Front Assembly 2) Rear Assembly 3) Complete Model

Front Assembly

plotter_front = pv.Plotter(title="Front Assembly")
plotter_front.add_text("Front Assembly", font_size=14)
plotter_front.add_mesh(steer_axis, color="darkred", name="Steering Axis F")
plotter_front.add_mesh(U_form_upper, color="silver", name="Fork Upper F")
plotter_front.add_mesh(U_form_bottom, color="gold", name="Fork Bottom F")
plotter_front.add_mesh(wheel_front, color="black", opacity=0.3, name="Front Wheel F")
for key in ["wheel_center_front", "STEERING_AXIS_BOTTOM", "STEERING_AXIS_TOP",
            "fork_right_upper", "fork_left_upper", "fork_right_bottom", "fork_left_bottom"]:
    plotter_front.add_mesh(pv.Sphere(radius=8, center=data[key]), color='red')
    plotter_front.add_point_labels([data[key]], [key], point_size=15, font_size=14, text_color='black', shape='rounded_rect', shape_opacity=0.6, shape_color="white", always_visible=True)
plotter_front.show()

Static Scene

Interactive Scene

Rear Assembly

plotter_rear = pv.Plotter(title="Rear Assembly")
plotter_rear.add_text("Rear Assembly", font_size=14)
plotter_rear.add_mesh(swingarm, color="steelblue", name="Swingarm R")
plotter_rear.add_mesh(rear_suspension, color="teal", name="Rear Suspension R")
plotter_rear.add_mesh(wheel_rear, color="black", opacity=0.3, name="Rear Wheel R")
for key in ["wheel_center_rear", "SA_RIGHT", "SA_LEFT",
            "sa_right_outer", "sa_left_outer", "U_SPRING_MOUNT", "l_spring_mount"]:
    plotter_rear.add_mesh(pv.Sphere(radius=8, center=data[key]), color='red')
    plotter_rear.add_point_labels([data[key]], [key], point_size=15, font_size=14, text_color='black', shape='rounded_rect', shape_opacity=0.6, shape_color="white", always_visible=True)
plotter_rear.show()

Static Scene

Interactive Scene

Complete Model

plotter_comp = pv.Plotter(title="Complete Model")
plotter_comp.add_text("Complete Model", font_size=14)
plotter_comp.add_mesh(frame, color="darkorange", opacity=0.9, name="Frame")
plotter_comp.add_mesh(steer_axis, color="darkred", name="Steering Axis")
plotter_comp.add_mesh(U_form_upper, color="silver", name="Fork Upper")
plotter_comp.add_mesh(U_form_bottom, color="gold", name="Fork Bottom")
plotter_comp.add_mesh(swingarm, color="steelblue", name="Swingarm")
plotter_comp.add_mesh(rear_suspension, color="teal", name="Rear Suspension")
plotter_comp.add_mesh(wheel_front, color="black", opacity=0.3, name="Front Wheel")
plotter_comp.add_mesh(wheel_rear, color="black", opacity=0.3, name="Rear Wheel")

for name, coord in data.items():
    plotter_comp.add_mesh(pv.Sphere(radius=8, center=coord), color='red')
    plotter_comp.add_point_labels([coord], [name], point_size=15, font_size=14, text_color='black', shape='rounded_rect', shape_opacity=0.6, shape_color="white", always_visible=True)
plotter_comp.show()

Static Scene

Interactive Scene