To do this type of deformation you need to create middle member in context with rotating part (disc)
Changes done in your model:
1. Delete sweep feature
2. Create a sketch on disc(part)
3. Edit Part 1 in context > Create new sketch by converting sketch created in step 2
4. Create Loft feature using both sketches
5. In Motion Study > Select motion type animation > Move Time bar to 2 sec
6. Rotate disc > Calculate study
>>Middle bar should twist<<
See video
Once again,
what is the source of your information?
Or are you really tackling this one on your own? (no YouTube?)