Hi- I have managed to get  my JCB model to callibrate, but am now having trouble knowing how to approach this complex shape! Even the wheels are causing great difficulty as when I mark modelling points and try to attach a flat circle to the outer edge, the shape will not attach to all my points, and as the wheel is at an angle to the camera, the perfectly circular shape does not fit over the oval wheel shape.
 
How do I solve this problem?  
 
Any hints on how to go about tackling the whole JCB? I am trying to split it into 4 main sections- should I be using faces or mesh or cubes.... any suggestions would be appreciated.