I was watching this video made with IForce2D, its about creating soft bodied wheels in box2D.
I wanted help in being able to increase the Radius of the Wheel gradually.
I tried increasing the natural distance of spring joint (Distance Joint) between central body and outer body. But since outer bodies are connected by revolute joint, which force the outer bodies to not change their positions.
I then changed the Anchor Points of Revolute Joint to match the increase in Radius of Wheel. Now, the outer bodies start moving away from center body towards their natural Distance. But gradually some outer bodies rotate and move away from each other.
Check out this video i made showing what i have done:
Note:- I am using Unity3D 4.3.4 with 2D Physics, Gravity is Off.