when i make a new mesh in blender it moves in game

Hi. CAS item are intended to move, morph, display textures, etc, so everything you create must be adapted to function as intended.
The mesh is flying because it is not rigged, meaning you did not tell it how it should move, what bones should it be affected by.
You can try assigning the whole mesh to b__ROOT_bind__ or b__Pelvis__, whichever will give you the result you are going for. To do this:
- do you have anything in the list of vertex groups? If yes, it means you transferred the weights wrong. If no, it means you did not rig the mesh. Judging by you description, it seems that you did not rig it at all, so let’s do this;
- select the tube. See the big + button to the right? Click on it to create a new vertex group. Double click on the name and paste b__Pelvis__
- switch to edit mode (TAB), select the whole mesh with A. Press Assign to assign the whole mesh to the pelvis bone.

- you should also disable morphing by vertex painting the whole mesh with black (only do steps 2,3,5)


Bear in mind that it may not move the way you want. To not clip into the body, the tube must be affected by the same bones as the body in the same way. If you will do this, the shape of the tube will not be maintained.