In true Vincent fashion I am going on a tangent here. A few years ago several motorcycle riders descended a local pass with dead engines (before the days of the dreaded BMW electronic assist brakes). Of course there was a certain amount of skill and bravery involved but the winner(s) were all the shaft drive bikes with (relatively) narrow tyres. Of course it was nothing like this:
http://www.youtube.com/watch?v=LWLbu1wIIEo
http://www.youtube.com/watch?v=LWLbu1wIIEo