No, I copied the first tank. I went to the file where Tank#1 lived, selected it, did a CTR_C, Then did a CTL_V and pasted a copy right into the same folder. So now I have T-1.car, and T-1copy.car, then I renamed my copy. So in all important respects, T-1 and T-2 are the same tank. Then I cloned the treads and built a new body for T-2.

What strikes me as weird, is that both tanks animate just fine in their own documents. Then each tank got dragged into the browser. When I retrieved them and inserted them into the city scene, Tank#1 runs fine, and Tank#2 has lost all its keyframes. Why did I lose the keyframes in one case, but not the other?