# How do I create a non-circular helix along a curved path?

#### marcr

##### New member
I want to model wire wound around a square u-shaped core (like a horse shoe). To do this I need to create a non-circular helix that will follow a u-shaped path. How can I do this and is it even posible?

#### ProFishent

##### New member
You need to use a variable section sweep! It would be very difficult to explain without seeing your part! I could show you how, if you e-mail me the part to be wrapped!

#### mjcole_ptc

##### New member
marcr

The general technique is to sketch the center curve for the helix as a datum curve or trajectory at the center of the horshoe.

Then create a VSS surface I think Pivot directon will work

Select the plane used for the center curve as your pivot ref.

Then in the section definition sketch a diagonal line from the orig traj.

Write a relation for the angle of the line and make it as long as the radius you want.

initial=45

sd_angle=initial+360*trajpar*N

where initial is the start angle and N is the number of loops

This will generate the curve which you can use to make a swept blend for the wire

Michael

#### ProFishent

##### New member
That will work for your initial helix, but He needs to make a non circular helix!!

My method starts the same, then you create a swept surface along the same trajectory. The 2nd surface represents the shape of the part to be wrapped! Then create a datum curve using the intersect of the 2 surfaces, and use this as your trajectory for a swept blend.

One problem is that you may have to change your models accuracy level (SETUP/ACCURACY) to a finer value!

I am trying to send you an example part, but I work on solaris and have lost mapping from my NT server. As soon as I get this fixed I will send you a part which is probably exactly what you need!

#### Rajesh

##### New member
Extrude a surface in the required shape. Then offset a plane and create formed curve so that the curve wraps around the surface. The length of the formed curve should be calculated using the formula: a^2+b^2=c^2, where a is the perimeter of the surface, b is the pitch and c is the hypotenuse. Multipy c with n(no. of turns) to get the length of the curve. (You have to give CSYS while creating formed curve). Then use swept blend with the curve as the trajectory.

Regards,

Rajesh