The Front Castor can easily be removed from the chassis by pulling up on the castor.

The Castor should be able to spin freely. A quick flick of a finger should give you multiple revolutions of the wheel and several up/downs of the wire at the top of the Castor column.

The castor can be pried apart for cleaning. The wheel is built like a Yo-Yo but the center axel is a bit off center. Use a small knife to cut away the hair or thread.

The Up/Down motion of the wire is detected in a sensor in the RCON tower and this helps determine if the Scooba is moving or not.