Modeling headers

[Dave K]

Anyone have any tips or tricks, for modeling a set of automotive headers?

Right now I modeled a bunch of different bends, 30deg, 45deg, etc., and I'm assembling them, twisting, and swapping out, pretty much the same way you would do it in the shop. Since they are twisting and turning in 3D, I didn't come up with any other way.

Using NX5.

-Dave




-Dave
Everything should be designed as simple as possible, but not simpler.

 

[4mranch1]

I usually come up with a centerline and then a cross section (In your case a circle.) at the start of each path. Then use Insert / Sweep / Sweep along Guide...

Unite each tube into one solid that would be your header and then Insert / Offset-Scale / Hollow to get your wall thickness.

Add desired end flanges and blends (Inside and out.) and you have your header.

Hope this helps.

Gary Ashby
Designer

 

[4mranch1]

Try using Bridge Curves (Insert / Curve from Curves / Bridge / Set to tangent) to connect arcs if plain old radius curves are too simple. They can be edited to adjust the path between end points/curves (Same menu: Tangent Magnitude slider bars for First Curve and Second Curve.). This method of developing centerline pathes provides you with some flexibility.

Gary Ashby
Designer

 

[kevklem]

Also in Bridge Curve, you can modify the start or end location of the bridge anywhere along the parent curves using the Location Slider Bar. Make sure the icon at the top is selected for the parent curve you want to modify and slide away.

 

[hudson888]

Dave,

Reading what you're trying to do and some of the suggestions think first about the process that is to be used in making these things. If it's your own project that you intend to build using shop tools then your method is probably the best one described on the page for you.

On the other hand there are a number of casting and molding methods in use for making inlet and exhaust manifolds that could use more complicated geometry, but you'll need to take advice about the limits of the specific process that you're using to set the parameters of your design.

If you are bending tubes and minimum bend radii will be important to you then remember that once you start using bridge curves and/or other spline curve creation methods, (I tend to favor studio spline a lot these days), then you have to keep control of minimum radii by other means. If you do create any spline curves to use as a centerline then take care to have a minimum inside bend radius in mind and check your geometry against it. Having done similar tasks in the past it is almost too easy to create geometry that varies in 3D space and difficult to discipline yourself to check the size of radii in ALL directions.

Be careful with sweeping profiles if you're not experienced with it then I would suggest generating a spline curve as well as the centerline and one or more other guides to control your swept geometry. Otherwise what starts out as a circular profile may be distorted since even relatively sound looking inputs may not control the orientation of profile and centerline that you would wish for. We often learn how to use these tools in ways that get a result, but real life examples where you need to get the right result can prove challenging. Start by re-reading the manual about sweeping and model simple examples with a few inputs that you can vary to control and influence the outcome, you'll quickly become more confident before tacking your real tasks. Its probably going to save you a lot of grief with this job later on.

One of the simplest modeling tools to describe a tube would be a cable with an internal and external diameter. The input is a simple curve centerline. The default construction will segment the result by simplifying/approximating any input curves that are splines, but the segments will be perfectly circular in section. Otherwise you can choose single segment construction, then one tube or cable segment will be created per spline, but the swept profile will be slightly approximated.

Good Luck with you Projects.

Regards

Hudson,

 

[Dave K]

Thanks for the input.

I decided to stick with my original method, since the guys in the shop would be fabricating them from pre-bent pieces (at least this first set).

-Dave



-Dave
Everything should be designed as simple as possible, but not simpler.