pipe in the pipe

[themole]

I have to create another "identical" cylinder inside a sheet cylinder, given by the customer, but having smaller diameter. the only thing that in the upper part the cylinder is shaped "strange", so the inner cylinder must be such and which.how can it be done to project with the 3d? use the controls of the surfaces? thanks in advance. I attach a free hand drawing to make the idea.

greetings

 

[Catafratto]

the first thing that comes to mind is to derive the original tube by applying a scale factor: This if the scaled shape is fine...