Misbehaving spline - Locomotive model

stephen_allen

Hello all,

I'm revisiting an old project where I couldn'tfor the life of me get a spline to behave.

Perhaps it was more "modelling" than CAD, so perhaps I needed to try blender? In any event, I was modelling a British Rail Class 68 locomotive 

It has a compound curve at the front end, which creates a compex curved surface each side of the windscreen. On the 1:1 loco my gues is that this is for aerodynamics?

https://cad.onshape.com/documents/d0f408d21880972df55df2a9/w/39050cb4a967b9edb796556d/e/0a9e21ca919a5908cc99271b

I've rewatched the curves turotials, and am none the wiser how to pick this project back up. 

More specifically, I'm using splines to try and create the final curve to border the surface, but I must be getting something basic wrong, as the spline jumps about. The spline on the other edge behaved as expexted.

Any suggestions would be appreciated.

Kind regards

Steve

dirk_van_der_vaart

I took a look at your project, it looks to me as double symetric, so if I had to do this I would design a quarter of the locomotive.
And I looked at some picture's of the locomotive to see more detail's.
I think it's better to start over again and do some tutorial's on surfacing and take a look at 3D fit spline in the help files.
And you don't need Blender for this.

dirk_van_der_vaart

Here's a good example
https://cad.onshape.com/documents/de780ec49486965165c66088/w/f64eb044aeb36be91e0d17cd/e/f885b7f854227b0aa9c72853

stephen_allen

Thanks, I will start over. Like you say, it is (broadly) double symmetric.

Looks like the 3D fit spline in its current form might post-date my previous attempt at this project.

Thanks again

stephen_allen

So, I've carried on with the document, working in quarters as you suggested. I've looked up 3D spline (and fill - also new to me) and managed to get the complex shaped surface I need - but I'm still struggling with 2 things:

(1) my loft of the general shape of the front of the loco hasn't worked properly - it's gone concave underneath where I didn't expect it to; and

(2) I'm struggling to remove the shape of my complex surface from the front of the loco - I assumed that was simply a matter of thickening a lot in the correct direction, and removing.

I appreciate I'm a hobbyist, and clearly out of my depth here, so may need to abandon this project. however, any help will be gratefully received.