Anything with proper steering knuckles on one axle is going to follow a track such that the rear unsteered axle is aligned with the geometric center of the turn, each of the front wheels' centerlines intersect the rear wheel centerline at the center of the turn, and the center of the front axle follows a circular track a little larger than the circular track followed by the center of the rear axle. There used to be nice diagrams in the SAE bible.
Now, there are more geometric elements in play. The tongue that steers the front trailer axle should be always tangent to the front axle center track, which means the hitch ball/ring on the trailer in front has to swing the hitch point outside of its own track, which happens if the hitch is mounted to the rear of the trailer, some distance behind the rear axle. So the tongue length and the hitch overhang have to be accounted for.
( I'm supposed to be doing something else now; anybody want to make a diagram? )
Mike Halloran
Pembroke Pines, FL, USA