Help. I'm playing around with animating the construction of things and then applying gravity to one object after its built.

I first animate the construction of a portion of a nurbTorus. Then a few frames later, I animate the construction of a nurbSphere. I then make the nurbTorus a Rigid Body so that the sphere, once gravity is applied, will collide with the torus and ultimately drain through the center. Pretty straight forward.

I apply the gravity field to the sphere and get nothing. I once had it to where the sphere would react to gravity field, but was falling while it was being built and I would like to have it fall AFTER it is built.

Any suggestions? Scene file attached.