> For the complete documentation index, see [llms.txt](https://docs.andymark.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.andymark.com/robits-build/intermediate-and-expansion-kits/mobility.md).

# Mobility

The [AndyMark Robits Intermediate Mobility Kit](https://andymark.com/products/robits-intermediate-mobility-kit-v2) is designed to provide the components needed to expand the mobility system of a robot. It focuses on intermediate level drivetrain and movement components, allowing teams to move beyond just a functional robot base and develop more advanced mobility configurations.

The kit uses four-inch ball-bearing mecanum wheels and four NeveRest Hex gearmotors with encoders. The drivetrain can be assembled in several different configurations depending on the desired motor placement and available space for mechanisms. This is intended to work with the Robits building system and can be combined with structural components to create a complete robot drivetrain.

### Drivetrain Configurations

#### Horizontal Motors

<figure><img src="https://2060440806-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2FcQgnvayQud3Xf5sZi0wz%2Fuploads%2Fyw3Ukjtbj8FPELDzmWmw%2Fimage.png?alt=media&amp;token=9ff66e3d-0aa9-4095-8427-dcc2ea647165" alt="" width="350"><figcaption></figcaption></figure>

The horizontal motor configuration mounts the motors horizontally on the inside of the chassis.

This arrangement can help conserve vertical space above the drivetrain, leaving additional room for mechanisms and other components.

#### Vertical Motors

<figure><img src="https://2060440806-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2FcQgnvayQud3Xf5sZi0wz%2Fuploads%2F4llqG9DasCztujliyM0h%2Fimage.png?alt=media&amp;token=feb9b755-3b2d-4a52-8f51-f6e4e7d85dee" alt="" width="350"><figcaption></figcaption></figure>

The vertical motor configuration mounts the motors vertically on the inside of the chassis.

This arrangement provides greater flexibility when positioning the motors and wheels from front to back. It also opens additional space in the center of the robot for mechanisms and other components.

#### Motors Between Wheels

<figure><img src="https://2060440806-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2FcQgnvayQud3Xf5sZi0wz%2Fuploads%2FVYAV2bOjB2a2cX4lbYEw%2Fimage.png?alt=media&amp;token=d19433c8-00c4-4fde-89f0-654005192ef3" alt=""><figcaption></figcaption></figure>

The motors-between-wheels configuration places the motors between the wheels and uses belts to transfer power.

This configuration can provide a large open area inside the chassis, making it useful when a robot requires additional space for mechanisms or other components.&#x20;

### Bevel Gear Drive

The kit includes bevel drive components that allow power to be transferred from the motors to the wheel shafts. The pass through housing allows the motors to be positioned away from the wheel while still transferring rotational power to the wheel.

### Mecanum Wheels

The drivetrain uses four 4 inch ball bearing mecanum wheels. Each wheel assembly uses a wheel plate, wheel hub, rollers, roller bearings, and roller axles. The ball bearing rollers allow the rollers to rotate smoothly while the mecanum wheel provides omnidirectional movement.

Omnidirectional movement has become a standard in FIRST Tech Challenge for navigating the field. However, these require a higher level of upkeep, controls, and investment, and it is recommended that teams with less experience begin with a simple tank chassis.&#x20;

Correct wheel orientation is important for mecanum drive. The rollers on the four wheels must be arranged in the proper "X" pattern so that the drivetrain can move forward, backward, sideways, and diagonally.

<figure><img src="https://2060440806-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2FcQgnvayQud3Xf5sZi0wz%2Fuploads%2FMJJgTMbk5WYq1Xkjefvl%2Fimage.png?alt=media&amp;token=4382b18e-9080-430a-b7c2-2a4df6ebed20" alt=""><figcaption></figcaption></figure>

Before powering the robot, verify that the wheels form an "X" shape when viewed from the top.&#x20;

If the wheels are installed incorrectly, the robot may move in an unexpected direction or may not be able to translate correctly.