Modify width of object in specific area

Hello group!

I am creating a curve for my son’s hot wheels track builder.
After various prints, I identified that I need to increase the space in the middle section of the curve to allow the cars take easily the curve.

All my curve is the same width. How to increase the width in the middle like the attached image? From 40 mm to 45?


Note: I am a beginner, the curve was made by a simple revolve of a sketch.

You will likely have to use sweep tool. Change the middle section of the curve to reflect you width requirements. The end and beginning will be identical, the middle cross section must reflect the width change. For smoother transition, more cross sections to sweep from will be better. Not easy, but it is what it is.

As @Oregonerd stated, Sweep is the tool to use. Here’s what I did.
First, I made a 90° sweep of the cross section of track just to show what you did when you used Revolve, then deleted it.

I made a new sweep with wider track minus the upper rail. I sketched a larger circle away and 90° to the center of the track. Then I use Project to create an arc so that the center of the curve at the arc is higher than at the ends. Now I used Sweep to make the upper rail. Then I did a Union of the outer rail and curved track. To finish I subtracted the non-essential extra curved track beyond the upper rail. Hope this helps.


Very elegant sir! :clap: :clap: :clap:

Using the method I described above, here’s a way to make it more dimensionally accurate.
My track is at an angle of 45°. I made a plane at 45° and normal to the center of the track.
Sweep a temporary track where you will only need to use the upper curve. Project that surface to the plane. Add a line of specified length that you wish to increase at the center. Draw a new arc. Delete the temporary curve. Sweep a new extended width track and finish like I did in the previous video. Now you should have your curve with a specified wider track at the center of the curve.

1 Like

@TigerMike thank you so much for your tutorial. I am very new in design and using Shapr3D, and explanation by text it is really difficult, however I try hehe. @Oregonerd thanks for your explanation too.

I want to know if you could help me with a new requirement in this model. Hot to do the same in the upper wall? I mean, to start in some height but when reaching to the middle, it is going increasing?

Here I used a similar method as before. The plane is at the same angle as the upper ramp. For simplicity, I just used a straight line instead of an arc at the projected curve. Hope this helps. BTW, I worked on several Hot Wheels sets back in the day.

1 Like

@TigerMike thank you so much again! You make it so simple! I wish Shapr3D YouTube videos explained this kind of things, because the examples are from more complex topics.

@TigerMike sorry to bother you, but could you help me with a new situation. My curve as you suggested is working good, however is not what I expected. How to convert the ends to plain, I mean, no degrees? But keep the 45 degrees ramp in the middle?

Hi Sebastian,
Glad to help. I believe the solution is to use Loft in addition to what you already have. I don’t have time right now but will look into it later. Others can chime in and give it a go.

@TigerMike thank you. I tried but It was horrible hehe. Do I need to create progressive skectches?

I used Loft and it sort of worked. I had the same problem you encountered. My problem is that I used the modified 45° curve with the extended curve at the center and higher outer rail at the center.

To set up the loft, I rotated the sketches from the upper inner corner. The middle sketch is 22.5° and the two end sketches are 0°. Upon completion you can see that the inner rail has a nice transition while the outer rail is way off. The issue here is that the outer and inner rail contours need to be reversed. Meaning, the opposite of the original construction. This way the outer rail should transition smoothly. I say this without trying it so caveat, it may not.

On the other hand, it may work on your curve as it appears you are using the original banked curve without the extended middle part the curve. Let me know if you need further clarification as this may be a bit confusing.

1 Like

@TigerMike thank you! I use the normal curve as example because I did not want to affect the final version, but then I will have that problem too hehe. But your approach gave me an excellent understanding to know the process. I will try with more sketches to get a smooth transition.
Thank you so muuuch! You are the best!

1 Like