> For the complete documentation index, see [llms.txt](https://yams.yassrobotics.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://yams.yassrobotics.com/api-reference/c++-reference/gearing/sprocket.md).

# Sprocket

**Namespace:** `yams::gearing` **Java equivalent:** [Java Sprocket](/api-reference/java-reference/gearing/sprocket.md)

`Sprocket` models a chain or belt drive stage. The API is identical to `GearBox`; the distinction is semantic. Use `GearBox` for meshed gears.

***

## Constructors

```cpp
explicit Sprocket(double reductionStage)
explicit Sprocket(std::initializer_list<double> reductionStages)
explicit Sprocket(const std::vector<double>& reductionStages)
explicit Sprocket(const std::vector<std::string>& stages)  // "IN:OUT" format
```

***

## Factory Methods

```cpp
static Sprocket FromStages(std::initializer_list<std::string_view> stages)  // "IN:OUT"
```

{% hint style="info" %}
`Sprocket` does not provide `FromTeeth`. Use `FromStages` with tooth-count strings (e.g., `"18:36"`) to express the ratio directly.
{% endhint %}

***

## Methods

| Method                                     | Returns     | Description                                                    |
| ------------------------------------------ | ----------- | -------------------------------------------------------------- |
| `GetInputToOutputConversionFactor() const` | `double`    | Mechanism rotations per motor rotation (OUT/IN)                |
| `GetOutputToInputConversionFactor() const` | `double`    | Motor rotations per mechanism rotation (IN/OUT)                |
| `Times(double x)`                          | `Sprocket&` | Multiplies the reduction by `x`. Returns `*this` for chaining. |
| `Div(double x)`                            | `Sprocket&` | Divides the reduction by `x`. Returns `*this` for chaining.    |

***

## Exceptions

| Exception                                | Thrown When                                |
| ---------------------------------------- | ------------------------------------------ |
| `exceptions::NoStagesGivenException`     | Stage list is empty                        |
| `exceptions::InvalidStageGivenException` | A string stage is not in `"IN:OUT"` format |

***

## Example

```cpp
// 18T driving sprocket, 36T driven sprocket = 2:1
auto s = gearing::Sprocket::FromStages({"18:36"});

// Multi-stage belt drive
auto s2 = gearing::Sprocket::FromStages({"18:36", "12:24"});
```