Constantly move physics based object

Hi,

iv have a tank that is physics based. I want the tank to move on its own when i hit a button. Iv tried applyForce and it does all sorts of wierd things. Take at look at http://www.youtube.com/watch?v=yGU1E6wQFqE for the type of movement im aiming for.

Can anybody help at all? [import]uid: 162458 topic_id: 30960 reply_id: 330960[/import]