# Rack

> Component kind `rack` (category `mech`, DSL name `rack`, API v1)

Straight toothed bar. Engages a spur gear (the pinion) via `mech.rackPinion`; the pair converts rotation into linear translation along the rack local X axis.

## Parameters

- **`module`** — Tooth module (mm). Must match the pinion module for the teeth to mesh.
- **`length`** — Length along the local X axis (mm). The travel range.
- **`width`** — Face width along the local Z axis (mm).
- **`height`** — Back thickness along the local Y axis (mm).
- **`pressureAngle`** — Tooth pressure angle (deg). Standard is 20°.

## Parameters schema

| Parameter | Type | Default | Constraints |
| --- | --- | --- | --- |
| `module` | Number | 2 |  |
| `length` | Number | 300 |  |
| `width` | Number | 10 |  |
| `height` | Number | 10 |  |
| `pressureAngle` | Number | 20 |  |

## Ports

| Port | Type | Description |
| --- | --- | --- |
| `motion` | `linear` | Linear port along the local X axis. Accumulates `position` as the rack translates. |

## Kinematics

Rack-pinion rule: velocity_rack = -omega_pinion × pinion.pitchRadius. Sign flips so a counter-clockwise pinion pushes the rack in the +X direction of its local frame by convention.

## Example

```
rack "R1" {
  module: 2
  length: 300
}
```