[ODE] Two body problem

[Jotham]

Hi,

Before I explain my problem I would like to provide this diagram:

http://the.fieldsofnoise.org/Archive/temp/ODE-Problem.png

Right now I have a Hinge Joint between Anchor 1 and Body 1.  This
Hinge has stops near to 0 and its axis is (0,0,1).

If I run my simulation and apply a small amount of torque to the Hinge
Body 1 it moves slightly to the left or right and stops at the defined
Stop.  The Hinge Joint maintains the same radius as it started with.
This is what I would expect to happen.

Now,  I add Body 2 and connect a new Hinge Joint between Body 1 and
Body 2.  I set the axis of the new hinge to (0,0,1) and apply stops at
-45~ degrees.

When I run the simulation Body 1 moves counter-clockwise as expected
*but* Body 2 also moves in toward Body 1 until both bodies overlap.

I am only working in 2D and am wondering if Body 2 is falling forward
or backward through the Z axis?... and if there is any way to stop
Body 1 from rotating freely and constraining it to the Z axis of
rotation.

My aim here is to create a wire frame tree shape with a certain amount
of springiness on all of its limbs.  Am I going the right way about
doing this?  Do hinge joints maintain a consistent length/radius?

Regards,
Jotham Read.