I made a drawing. Hope this will make it clearer.

As yet explained above your sections are inclined and not perpendicular to the tube of the ring!
So that can't be circular but ellipsoïds!

So if you want the same measure between & along the 2 "perimeters" internal / external: you must draw 2 ellipses !

If I understand what you want, I think Moi3D is not done for this.

You want to have this constraints :
- having a tore with 2 diameters of sections.
- having joining size regular in measure

Moi3D is not a constraints based modeler.

The result you want to have depends on a constraints resolving. The solution depends on :
- diameter of big section,
- diameter of small section,
- diameter of the tore (or ring). The main difficulty is here. ***
- size of the junction you want.

*** in fact, as you explain it, doing it with a cylinder is easy. But with a non linear path, you have to cut the small tore (or the big one, it depends of wich one is the "reference") with different inclinaison. It's section become en elipse.


You don't have a universal solution. I think, each solution depends on the complete set of these parameters.

Perhaps I'm wrong, but I think it's not possible to give to Moi3D and let him processing to have a solution.
To do it, you have to calculate yourself all values and give to Moi3D the right measurement you have calculated before.

Sorry, I was wrong...

The WN's method gives a soluce...

I have tested and you can test it with this file.
The test uses a big size of junction (3 as radius)


The modeling is done at the end with a sweep and two rails section by section.

Sorry but where are the similar gaps between the different diameters in these soluce ?

Is this what you are after lara?

Nearly a circlular cross section, and hypoallergenic.

- B

Hi Lara,
So this: """"""How would you place at beginning the cutting objects in order to avoid the distance differents at the lofts? Ideas?"""""""

From this post and image: """""""http://moi3d.com/forum/index.php?webtag=MOI&msg=10096.37""""""""""

Is answered this way... Notice you spoke about how the result is identical, "Under and reversed" in that area...

That is because your chamfers are going in 2 different directions, so the up and down side of the "slant" is opposite.

To get the symmetry in the place you want, with equal proportions, your "cutting objects" should be a "Mirror" of each other (Not a copy). This reverses the "slants", so they are opposite, and produce results that "face and duplicate" each other...

"Copying" the cutting objects will have the "reversed direction chamfers" produce "reversed symmetries"

Let me know if this is too hard to follow.

It's all about the cutout, and the symmetry on the torus is not suitable for this form, it's good if everything turns out to be so simple...
And yes, as BurrMan says, the front view and the top view show different chamfer slopes.
It looks like you need the same chamfers in these places?

@Pilou
>>Sorry but where are the similar gaps between the different diameters in these soluce ?

sweep was an error, you're right !
using loft is better...

I redone it.
Look and say me if it's the soluce.

Yes that right but that is trivial in this case because sections are perpendicular to the perimeter! ;)
(radius from the center)
I don't believe that is this specially asked! :)

I´m not sure. I didn´t find THE solution in your proposals. Mainly I mean the ideas/constructions with 3d-files I took a look at. The others I may not verify. My english is not so good, as you noticed meanwhile.
The main problem what you perhaps not noticed is that the cutting direction is not horihzontally or vertically in 90°.
I put the ring with the cutting directions as file here...
cu...Mala

P.S.: I extractecd now the profiles. If it it would be possible to aling the littler circles to their bigger neighbour circles it could work. But how?

These are not circles!

It's like i said from the beginning Ellipses! :)

The more easy : make an Offset ineternat from the External Ellipse et voilà ! :)

Then move along the circular perimeter internal and you will have your same measures of your troncated volume wanted!

(troncated is not show here but very easy to make with all these advices :)

It's your choice after to want a circle inside but you will not have same distance between big & little section!

Here you have an ellipsoïd !

Hi Mala,

> The main problem what you perhaps not notices is that the cutting
> direction is not horihzontally or vertically in 90°.

Ok, but if a cutting direction that is not 90 degrees does not make the kind of result that you need then why do you want to use it?

As best that I can tell (I'm still not sure) it seems that a cut made with parallel planes at an angle does not produce the kind of geometry that you want.

- Michael

Hi Mala, maybe after you do the outer cut, you should construct a tapered extrusion from the resulting edge and then use that to cut the inner tube with.

That looks like this:

Cut outer ring with angled box:




Do not cut inner ring with another box, instead generate tapered extrusions from the edges:



Make one on each side, use the "Flip" option in tapered extrusion for the other one:



Now it's these tapered extrusion surfaces that are used as cutting objects and also cut by the inner tube as well. When combined after the pieces are trimmed it will look like this (3DM attached also):



Is it right? Is it a uniform angle of the transition surface the thing you're trying to achieve?

- Michael

You have exactly that you want except the little middle part is not a cylinder but an ellipsoïd!
The other part is a cylinder!
There is yes the same distance between Big "section" & "Little" section (ellipse) around it's axe

Always of that because your sections are not PERPENDICULAR to the perimeter !!!
Offset sections (ellipse) Extrude Sweep and finally Loft the little extremities between them

Hi Mala, maybe another possible method would be to make a version of what you want along a straight line so it's a cylinder and then bend that into a circle using Transform > Deform > Flow.

That would produce a slightly different result than the tapered extrusion one above, because when you cut the toroidal shape with a planar cut, that produces some asymmetry with that cut being planar but the other side where the tapered extrusion intersects the inner tube will not be planar. With a Flow method you would have both planar cuts in the base shape and they would both deform when the shape bends into a circle using Flow.

You would use curve to curve flow for that with a line down the center of your cylinder as the base curve and a circle as the target curve.

- Michael

Flow is very cool but... :)

Or maybe what you need to do is to start with a kind of center line between the cuts, construct an extended angled surface from that and then use that surface to intersect the outer and inner tubes rather than using any plane to intersect them.

- Michael

Hi Pilou, re: "Flow Not Equality", if I maybe understand now (not sure!) the desired result has to do with a uniform angle, not equal distances. It's probably not possible to have both of those characteristics at the same time, it's either one or the other.

- Michael