Question Model incorrectly affected by bones on import...

Hello, ive made a simple model for a flying enemy, which is basically just a box with a propeller sticking out of the top... i dont have any bones in the box part, only the propellor, which i rotate for my animation. Ive made sure all my vertex groups are correct and none of the vertex groups include the lower part of my model, and in blender the animation plays correctly, but when i import my model into Unity and look at the animation preview my entire model is rotating. Any ideas why this might be happening? Thanks

 

Ive also made sure my animation is set to generic (even tried legacy) but this didnt change anything. I just cant figure out why Unity is assigning weights on import and how to make it not change my rigging... Anyone?

 

I cant find any answers anywhere online and the manual doesnt tell me why unity wants to automatically assign weights to some of my vertices and/or how to change it.

 

Whats making this even more confusing is ive already imported several other models that ive animated no problem, so why is unity suddenly screwing up this one?

 

Sorry for the spam, im just confused why this isnt working and trying to be thorough. Everything ive looked up says to create an armature in blender then rig it by clearing the armature/mesh's parent then parenting the armature to the mesh and assigning automatic weights. When i did this it created vertex groups, which i checked to make sure were assigned to the appropriate bones, then used to create my animation. I then played the animation to make sure it was correct, then exported my model as an fbx. But when I import the model into unity it moves my entire model (even parts that had no bones and no vertex groups). Why is this suddenly not working when ive done the same thing with other models no problem? Is there some import setting that might be different than now these others were imported? I cant find any information elsewhere about how or why that might be the case.

 

Also each of my vertex groups (and each corresponding bone) only has a weight of 1, and i only have one bone per vertex group. Also trying to tweak this in unity doesn't change anything either

 

How do you stop Unity from auto assigning vertices? Why does it even do that in the first place? I have my model rigged based on what im animating, why is it trying to force me to add the entire model to my armature when im not animating my entire model? How do i fix this?