I came across a bug where wheels gain phantom physics when in direct contact with a steering hinge. Its hilarious, however it probably is unintentional. Unfortunately I am unable to upload a screenshot or schematic as I had hoped due to a forum error so here is a "drawing".

         O[]O              O=powered wheel
           H                []=starting block
           w                w=wood block
       OwwwO           H=steering hinge        
 
    Best of luck 

Windows 7
Besiege version 0.05