Problems drawing connected arcs

[DickB]

I was working on a wabble drive: https://www.youtube.com/watch?v=KCLrzAtq3j4

I'm making the gears - if you can call them that - with a series of precisely-placed connected arcs:


I had lots of trouble doing this. I finally succeeded after much trial and error regarding the sequence of arcs to draw next to get it to work.

Here is an illustration of the problem. I had these two segments drawn, and I wanted to connect them together with an arc:


When I drew that connecting arc, things went haywire. Connections that were tangential clearly became non-tangential. One of the arc's radius constraint was removed. And the arc that I drew ended up with a radius constraint that I didn't specify:


I'm curious if others have this problem. I've uploaded the mpc done with Designer 3.102. I started this project with Designer 1, but it misbehaved so badly I could not get very far. At first Designer 3 worked better, but it too had issues. BTW I have had similar problems in the past when drawing other complex connected lines.

[bergerud]

I have always had trouble drawing with arcs. My method is to draw the whole thing first with segments and then convert the segments to arcs at the end. There are certain tangency conditions which cause Designer to crash when converting segments to arcs, so, save often.

In this case, I think I would have drawn all the segments to make a regular polygon. Convert every second segment into an arc (adjusting the radius of each). Then convert all the segments between.


Edit: I should also add that I stay away from constraints. I type a radius and then remove the constraint.

[SteveNelson46]

I think all of us that have tried to draw anything sophisticated using the Designer have had problems. Especially arcs. Even converting line or arc segments doesn't always work correctly. Considering time as a factor it's just easier to use Corel Draw or Adobe Illustrator and then import as a DXF.

[DickB]

My method is to draw the whole thing first with segments and then convert the segments to arcs at the end.

I went back to Designer 1 to try your method and it worked. I did also have to follow this sequence:

1. Draw a polygon with the Connected Lines tool.
2. Convert all segments to arcs, positioning each radius to approximate location.
3. Set x and y constraints on the radii.
4. Specify and constrain the radii.
5. Convert Free connections to Tangent.

If I tried converting the nodes to tangent and then setting the radii, in some cases it was not allowed. (Error message "The constraint you entered could not be completed because it conflicts with another constraint." Clearly not the case, as I was able to make the same constraints in a different order.) These constraints are all necessary to make the "gears" with the required precision.

In this case, I think I would have drawn all the segments to make a regular polygon. Convert every second segment into an arc (adjusting the radius of each). Then convert all the segments between.

I tried that and it didn't work. At one point I got the non-tangential tangents.

There are certain tangency conditions which cause Designer to crash when converting segments to arcs, so, save often.

I have not had crashes so much as misbehavior or an inability to draw correctly.

Edit: I should also add that I stay away from constraints. I type a radius and then remove the constraint.

That didn't work for me. If I removed a radius constraint, then changed the Free node to Tangent, the radius was altered.

I'm attaching the Designer 1 version of the ring in case anyone wants to play with it.

[DickB]

I think all of us that have tried to draw anything sophisticated using the Designer have had problems. Especially arcs. Even converting line or arc segments doesn't always work correctly. Considering time as a factor it's just easier to use Corel Draw or Adobe Illustrator and then import as a DXF.

Problem is I'm cheap. I don't have Corel Draw, Adobe Illustrator, or DXF Importer. And if I did there's another learning curve that will take time. I really think these bugs should be addressed. One should be able to design parts such as mine with Designer IMHO.

[bergerud]

Here is a simple crash example. Try and convert the middle segment to an arc.

[SteveNelson46]

Problem is I'm cheap. I don't have Corel Draw, Adobe Illustrator, or DXF Importer. And if I did there's another learning curve that will take time. I really think these bugs should be addressed. One should be able to design parts such as mine with Designer IMHO.

Dick,

I agree but if we carry this too far we will soon experience the wrath of LHR

[DickB]

I don't think so. Just pointing out a bug and my opinion that it should be fixed.

[lynnfrwd]

"The Wrath of LHR"

(Sorry, couldn't help myself...but this is what I conjured up in my mind. It doesn't help the arc issue, but I can't do anything about that and I don't think LHR has any plans of software updates any time soon. We will keep it in mind for when we do.)

[JLT]

Dick,


Saw your post, and took a quick hack at a Radial Vector script (see attached, which you can sinply drop into the RadialScripts folder). Basically it treats every tooth and trough as a tooth, drawing either a convex or concave arc as the tooth. (So for example, if you want a Wabble gear with 11 teeth, you need to enter 22 as the total number of teeth + troughs.) Based on the following video https://www.youtube.com/watch?v=2shapHAanIU , it appears that the outer disc is basically the same profile, with one more tooth & trough, and of course a larger diameter, but cut on the inside of the gear profile. So, when using this script to generate the outer disc, simply make the cutting bit diameter "-1/8", which will draw the cut profile on the inside of the gear...


(BTW, my apologies if I took some of the fun out this. The math was kinda interesting to me! Yes, I'm an odd duck...)


R, Jon