assembly 3: connection to parallel groove in an elliptical plate

[eefweenink]

I have this plate with an elliptical groove in it. Now I want to make an assembly (I choose assembly 3 for that. So maybe there is a subforum where this question should be placed?)

The rectangle plate is attached into the groove of the elliptical plate (see image).

Schermafbeelding 2022-10-21 om 22.45.54.png (51.59 KiB) Viewed 1374 times

When moving one of the plates, both should stay in the same plane, but be free to move, sliding the cylinder around in the groove.
I think I tried about all types of connection, but no succes yet.
I was hoping that connecting a line/point on the cylinder to the edge of the elliptical groove would do the job, but no luck.

Attached in zip the files I use to test the available connection types.
Hopefully some of you might know a way, how to find a solution for this.

regards, Eef

[chrisb]

Moved to Assembly forum.

[jpg87]

I was hoping that connecting a line/point on the cylinder to the edge of the elliptical groove would do the job, but no luck.

hello, I'm afraid that for the moment there is no solution available :
- the PointOnLine constraint requires the line to be a segment or a circle ;
- the PointsDistance constraint with the center of the board would require expressing that distance mathematically as a function of the angular position around that center...
- but a freedom of movement in the groove which would require a tangent of the cylindrical stud against a sidewall of the groove is not yet supported (to my knowledge).

[eefweenink]

hello, I'm afraid that for the moment there is no solution available :

Maybe I have to go to one of the other workbenches for assembly?

[dtay]

HI,

Perhaps this will achieve the result you are looking for? https://wiki.freecadweb.org/Tutorial_KinematicSkeleton

[eefweenink]

Perhaps this will achieve the result you are looking for? https://wiki.freecadweb.org/Tutorial_KinematicSkeleton

At first glance I would say, the quest may still be: "how to let something slide along an elliptical curve".
But I will study this. I try to find a way.

PS: It made me scroll through the SolveSpace tutorial, and my eye fell on this:
"Other mechanisms with linear slides may have more interesting geometric behavior. For example, we can model an elliptical trammel by constraining two points on a line to lie on the x and y axes. Any other point on that line will trace out an axis-aligned ellipse:"

linkage-ellipse.png (13.9 KiB) Viewed 1191 times

Thank you for pointing me there. Regards, Eef

[eefweenink]

I wonder if it is possible working with "hidden" objects.
Maybe it is possible to create an elliptical movement, using a sliding rod connected to vertical and horizontal horizon (see image above).
And connect the point of the rod to the cylinder sliding trough the groove.
That way it looks like the cylinder is kept in place by the groove, but in fact it is done by the hidden object.

Any experience/ideas/suggestions?

[dtay]

I fiddled around with this for a while and found a solution.

Ellipse_Skeleton_Sketch.FCStd

(28.36 KiB) Downloaded 34 times

Find theses formulas inside the "Line" property -> Start -> x & y dialogues.

Code: Select all

Ellipse.MajorRadius * cos(atan2(Wire001.Shape.Vertex3.Y; Wire001.Shape.Vertex3.X)) # Line start position for X
Ellipse.MinorRadius * sin(atan2(Wire001.Shape.Vertex3.Y; Wire001.Shape.Vertex3.X)) # Line start position for Y

https://youtu.be/GBIjRhXQca0


*edit, code typo

[eefweenink]

I fiddled around with this for a while and found a solution.

Looks great. Now I have to learn, how this works, and do it myself (but that is the nice part )

Thank you very much. Eef