FR link to original: http://www.freerepublic.com/focus/f-news/903195/posts
The link may only last for one hour, since it's an archived article. If so, use the FR search for Keyword - either MDM or COG. Title: Lights! Camera! Retake! (check out this cool video)
(snip) At one point three tyres, amazingly, roll uphill. They do so because inside they have been weighted with bolts and screws which have been positioned with fingertip care so that the slightest kiss of kinetic energy pushes them over, onward and, yes, upward. During the pre-shoot set-ups, film assistants had to tiptoe round the set so as not to disturb the feather-sensitive superstructure of the arranged metalwork. The slightest tremor of an ill-judged hand could have undone hours of work.
Thanks for that! That is really neat!