Carbon Fibre Road Bicycle tube junctions... ?

Hi there

I am in the process of modelling a bicycle, and am having a lot of trouble getting started on the headtube / toptube / downtube junctions.

I want to model something where each tube flows into the next, in super smooth style like the attached picture…

Everything I try just ends up a mess of edges, and far from smooth. Is there a tried and tested way to get smooth results like this with tubes? Also, the tubes would need to change shape subtley and in symettry along the length of each tube, like a real carbon bike frame…

But, what would be the best procedure? Should I model it in 3 parts, or do it all from a single piece?

Any advice, examples, etc, would be greatly appreciated. I am new to all this, as I am sure you worked out!


more then one way but
i would try to get each parts with proper cross section
then use boolean to merge the different parts!

hope it helps

happy blendering

If you want it smooth it needs to be modeled. I’d have look at

Hi guys.

Thanks so much for reply to me.

RickyBlender; What do you mean, ‘proper cross section’ (and how can I achieve this?) I will study ‘Boolean’ in Blender to learn about that. Cheers!

eppo; Well, that certainly looks like something useful! I will install it and give it a go! Thanks!

each part dont ahve the same cross sections some are round other more like an ellipse

so each part must ahve it’s own cross section


I am sorry RickyBlender, but I don’t understand what you are saying. I understand what you are saying about each part having a different cross sections (I think!), but the bit about each part having to have it’s own cross section? What do you mean? Each part DOES have it’s own cross section, by nature of being 3D, right?

Eppo; I installed and tried that plugin. Works great on making a line where two objects meet. After I do that though, I have no idea how to join the vertices or delete the unwanted sections. The outlined part does not seem to be part of either mesh object I am trying to join!

each part has it’s own cross section and you ahve to find a way to joint them in a smooth way
may be using boolean or other methods
but that’s modelling skills


OK, so what you are telling me is to improve my modelling skills, I need to improve my modelling skills. Thanks for that.

modellng 3D is not always simple because of shapes changing
like look at your frame it has rounded circular parts conneted to elliptical one
so this is not simple to do there is a transition and this has to be somehow done manually
and you need to find trick to do it in a smooth way which i call skills
and with time your skill level will increase you learn more tricks and 3D becomes a lot easier and faster

anyway if you have other specific questions you can always ask for advice here on forum and somone will try to help you

may be open a new WIP thread for you project and ask questions there as you go along your project

happy blendering

I get what you are saying, but that is exactly what I am doing; asking for specifics on how to solve a problem, and you are only replying with confusing vagueness. Thanks anyway.

Can anybody answer my previous specific question about the plug in eppo linked me to…

“Eppo; I installed and tried that plugin. Works great on making a line where two objects meet. After I do that though, I have no idea how to join the vertices or delete the unwanted sections. The outlined part does not seem to be part of either mesh object I am trying to join!”

That line then allows for better subdivision planning, cutting with Knife tool and snapping both elements together - snap still works on it.

As Witold Jaworski says: “Ultimately, I concluded, that I need a tool, which would create the common edge of two arbitrary meshes. It was more practical to create the new faces around it manually, not spending time on removing the automatically created ones. So, here is such tool. I have found it useful, maybe you also utilize it.”

That’s all to it.

@owenjames, there is a built in addon by the name of “Pipe Joints” please enable it and you will have several T and Y types of joints, which you can use in your project. rest of the structure is just simple cylinders. you can deform them from round tube to bit flat tube with the help of proportional editing tool (Hotkey O).

@eppo Ah, thanks!

Right, to that plugin is just a tool that draws a line on an existing mesh? I was pulling my hair out trying to figure out how to delete the faces inside of the outline.

@dukejib thanks a lot for your suggestion. I will enable that addon and see how I go with it. Cheers!

@dukejib; OK, I have been using the pipe joints thing, and while at first it seemed not to be exactly what was looking for, I have now started to make some progress, so thanks a lot for that!

Currently at this stage…

It isn’t essential to have all meshes joined; meshes can be separate yet part of the same object, or even separate objects.

Use bezier curves and circles to make the parts.

  1. Add a Bezier Circle and rename it, Bezier_Item_Shape.

  2. Add a Bezier and rename it, Bezier_Item_Path.

  3. Go into edit mode on, Bezier_Item_Path; press ‘V’ and you’ll see the window as shown. This allow you various controls, for example if you select vector with everything selected, then it will prefectly straighten and align the node points as shown in ‘4’.

  4. I duplicated the, Bezier_Item_Path.

  5. Make sure, Bezier_Item_Path is selected; under Geometry, Bevel Object select the little cube area for the drop down menu; select, Bezier_Item_Shape. This will give you a tube as ‘6’.

  6. The items I call paths become the actual object that can be converted to a mesh object; they use the shape I created, in this instance I used the default circle.
7. Select, Bezier_Item_Path.001 and go into edit mode. By selecting the nodes, you can extrude (e), grab (g) and also manipulate the nodes to affect the curve. You could use that to create your handle-bars for instance.
8. I just made a curvy shape.
9. When comparing images, 8 and 9, you’ll notice one was much smother than the other; Shape, Resolution, Preview U determines this. It defaults to 12, but adjust this to suit your needs; after converting to a mesh, you might find there is too much geometry, chose a lower number.

I’d recommend duplicating the object before conversion as that is an easier way to revert. It prevents mistakes with Ctrl z, and also a blender crash messing stuff up too.

To convert a bezier to a mesh; object mode, select the bezier item, alt C and select what you require.
10. It’s possible to select, Bezier_Item_Shape, and manipulate it to change the shape even once it is being used by objects; not after a mesh has been created though.

Hope you find this helpful.

Writer’s Block; thanks for that. Good introduction for me into the world of Bezier curve modelling. I managed to follow your instructions and make a smooth curve.

Question; when I omit the stage where you instruct me to make a bezier circle before making the bezier curve, and I then try to bevel the bezier curve, there is no reference to the bezier curve on the drop down menu in Geometry. Is there a reason for this?


Anyway, here is where I am at the moment with the project. I realise there are going to be loads of obvious mistakes in there which you experts will scoff at, but I am very happy with my work so far!

MR. it looks fantastic (modeling wise). you’ve done a very good job with it.
since i am no expert. I rest my case with applause. :slight_smile:

Sorry I missed your reply; glad you found it helpful.

You need a bezier for the shape, and one for the path; the path, as I name everything, becomes the object when converted.

Looks great what you did, and true experts will never scoff at inexperienced people’s attempts to learn.

Personally, the only stupid question is the one never asked; if someone doesn’t know, then asking is one very good method of finding out - not always the best but always very good.

Looks good. A mirror modifier would make things much easier on you.