# Atmospheric four-rotor parametric CAD teaching model

This directory contains a genuine CadQuery/OpenCascade assembly, exchange files, and renders generated from its CAD solids. These model-derived views accompany the atmospheric four-rotor teaching layout on this page.

## Rebuild

Use Python 3.12, install the listed requirements, and run:

```text
python -m pip install -r atmospheric-quad-cad-requirements.txt
python build_atmospheric_quad_cad.py
```

The script recreates the 19-solid STEP assembly, STL viewing mesh, assumptions CSV, and two PNG views. STEP re-import is validated in the build itself; the STL is a faceted mesh and has no parametric feature history.

## Model dimensions and limits

All values in the CAD model are visualization dimensions in millimetres. The rotor centre offsets (±660 mm) and body, battery, arms, motor placeholders, blade placeholders, and centre marker are schematic choices. The swept-area ring diameter of 1,128.38 mm carries forward the earlier teaching diagram's label of 1 m² per disk; this is a retained illustration convention, not an aircraft requirement, design recommendation, or validated rotor choice. The ring is a CAD annotation solid, not a guard or physical component. The assumed centre-of-mass sphere is a marker only; no part masses are defined.

The blade solids do not encode an airfoil, pitch, rotation, motor selection, structural sizing, or controllability. The assembly does not calculate thrust, hover power, endurance, stability, safety, or flight performance. It is not a manufacturing design and has no flight validation. No performance benefit is claimed.

## Files

- `build_atmospheric_quad_cad.py`: editable parametric source.
- `atmospheric-quad-parametric.step`: neutral solid assembly, 19 solids.
- `atmospheric-quad-parametric.stl`: viewing mesh.
- `atmospheric-quad-cad-isometric.png`: model-derived isometric view.
- `atmospheric-quad-cad-top-mobile.png`: model-derived top view with compact explanatory labels.
- `atmospheric-quad-assumptions.csv`: dimensions and interpretation limits.