# Modeling Bent Corrugated Pipe

Question asked by Garrett Shank on Feb 20, 2018
Latest reply on Feb 20, 2018 by Garrett Shank

I have to make a model of a bendable metal bellows for an animation.

I'm having problems making a solid shell between my 2 guide curves.

Is it possible to make a solid shell with the sketches i have?

Attached is my attempt and a picture of how it should look.

If it is not possible to make a solid shell from my current sketches, can someone suggest a way i can do this?

Here are my requirements:

The model must be as geometrically accurate as possible to a real world bellows movement.

• It must bend in a smooth curve
• The convolutions must compress on one side and expand on the other as the bellows angulates
• This happens when the curves at the top and bottom of each convolution change radius.
• The radius' on the convolution curves will change with compression or extension, but will always be the same arc length.
• The radius at the top and bottom of the convolution will be the same (ie. top of bellows has one radius (top and bottom of con the same) and bottom of bellows has a diff. radius (top and bottom of the con the same)
• The lengths of the straight segments in each convolution are always the same.

The model must move so that i can animate it.

• I have built a skeleton on a curve constrained by an arc length. The end points of the skeleton control the top and bottom of each convolution as it moves when the bellows center line bends.
• One dimension must control the angle of the bellows, so it can be removed leaving the sketch under defined.
• I have achieved this in my current model by placing an angle between the 2 straight ends on the skeleton sketch. When this is removed i can mate the right end of the skeleton sketch to the center line of a pipe and it will follow the pipe as it moves.