MY_Model construct not working?!?

[eluser]fatnic[/eluser]
Trying to run this bit of code (just to test) and having problems with $this->table_name.

Code:

class MY_Model extends Model {

    var $table_name;

    function MY_Model() {
        parent::Model();
        $this->table_name = 'whatever';
    }

    function getAll() {
        return $this->table_name;
    }

}

When I call getAll() the above code returns nothing. However, when I set the table name in the getAll() function it work perfectly. What am I doing wrong?!?!?