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Double Curved Top Tube?

I have just started using Bikecad pro and I love it! I have the latest version. My problem is designing a double integrated seat tube and top tube, like on the Budnitz (see pic). I understand that I have to use a workaround and connect the seat tube to the head tube. That works OK but I then want to adjust the curvature and I can't work out how. I see in an older post that you can adjust a field called tire clearance to change the curvature, but I can't find that. Any help gratefully appreciated.



Curved top tube/ seat stay

I just created the following model as an example: bikecad.ca/1394342428378.

As you suggested, the best way to do this is to attach the seat stays to the head tube. With the seat stays now also serving as the top tube, you can remove the normal top tube by unchecking the box in the Tubing dialog box as shown below:

I've also attached a screen shot of the seat stays dialog box. Note how the Curved stays option has been selected and a 200mm deflection has been applied to the middle of the stays.

When applying curves to tubes like this it is handy to use the Problem Curves checker as described at: bikecad.ca/problem_curves.



Brent, thanks! That works great.


The result is shown below.


Now I am trying to design the ladies version, along the lines of the old French frame I have pictures. It has two sets of seat stays as you can see. Any suggestions?


Many thanks!


Photos Here

Designing a Mixte

I modified my earlier example to create a mixte model at: bikecad.ca/1394460510493.

The key is to select Symmetric (double) in the seat stay menu. This will create two separate pairs of seat stays. One can be straight and attach to the seat tube. The other can be curved and attached to the head tube.

For more on Mixte frames see: bikecad.ca/mixte.


Now I not only know how to design it, I know what its called.

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