Is it possible to model kinematic linkage simulator ?
1 Like
YES!.. and no one talks about this which I find quite surprising.
I found a Youtube video which showed how to do it in Fusion360 and it works equally well in Shapr3D.
All you have to do is draw a four bar linkage with lengths specified (otherwise they’ll be stretchy and won’t behave like solid material.)
And you have to lock the two ground points of the linkage so they don’t move.
Then simply click on one of the two joints that do move, and drag it to make it pivot and see the whole linkage operate.
(Note that while you are dragging, you will see all of the dimensions, but when you click on the background, the dimensions go away and your linkage is in the new position.)
If you want to simulate a sliding joint like a hydraulic cylinder, just don’t specify the length of that line and it will stretch dynamically.
If you want to represent a bar as more than a single line, you can draw a structure of triangles of fixed lengths and even arcs with angle and radius specified, as long as the elements only reference that one bar. So those lines and arcs will act as one part.
It’s all about constraining the drawing to make the parts you want.
Then by tapping and dragging an endpoint of a bar (which is a joint of the linkage) you can see the full motion of the linkage.
It won’t plot the paths of joints but you can duplicate the parts to show the linkage in a series of positions.
And if you want see the linkage in a series of positions, you make a stack of linkages by copying the linkage in the Z axis. Unfortunately, once copied, you have to click on each line in each copy and lock the lengths again manually.
And you can make a gradient by sandwiching construction planes between the copies. The construction planes have a translucency which lightens the lines of each subsequent copy, when viewed parallel to the Z axis.
I hope all of that makes sense.
Someone should teach this in a Shapr3D tutorial.
(I suppose that could be me if Shapr3D is interested.)
1 Like
I would find it very useful…
1 Like
Here is the link to the YouTube video where I learned the concept.
https://youtu.be/rAktZZSBHnA?t=633
I bought Mahmoud’s video series on Udemy because I’m not a mechanical engineer but I needed to learn core concepts of four bar linkages and it was tremendously helpful. It showed how to create linkages that start, end and pass through a midpoint, precisely where needed. Well worth the $95 cost for my needs. But this video shows all you’d need to know, to make linkages move interactively in Shapr3D.
You mean in 2D, right?
Yes Istvan (it’s an honor by the way) yes this would only apply to basic 4 bar linkage schematics within 2D range of motion. But I’ve designed some very helpful prosthetics with this method, working solely with Shapr3D to establish the linkage geometry.
Then I used that layout to build the forms and rotational joints for the 3D model in the same Shapr3D drawing. I duplicated the model in the Z axis and rotated the parts to their fully flexed positions so I could see the linkage in its flexed and extended positions.
I exported as STLs and of course the prototype prints worked perfectly (thanks to the magic of 3D modeling)
1 Like
Yes, that’s very cool. DCM (our 2D constraint solver) is literally the best solver in the world, amazing what you can do with it.
I think all of us here would love to see what you did with it.
1 Like
Great. I’ll put together a tutorial video. I can’t show the actual prosthetics I designed because of NDAs but I’ll make a model that shows the functionality of this design approach.
2 Likes
Looking forward to your video. Thanks in advance.
Happy holidays to all…
Tommy
1 Like
Here’s the link to the video. It’s thrown together very quickly and the audio is far from ideal, but it covers some important details for any user who is new to this process, so it’s good enough for now.
(Note that it’s published at 1024 HD but users might have to select that higher resolution, because when I tried the link here, the default resolution was 320.)
6 Likes
Wow that is fantastic, very clever, maybe one day I MIGHT be able to do something like that
1 Like
Wow. Very very cool. 
1 Like
Yes it is! (You guys need to promote this functionality heavily.)
It’s a vitally important function for my needs.
Also, if you can make it so that mirroring or duplicating a sketch will preserve the constraints in the copy, that would save a lot of time.
In fact if a copy could be an Instance, that would be even better. So if you edit the length of the rocker on the stacked linkages, the other four copies change too.
Instances have a HUGE variety of applications. I use them in Modo all the time.
At some point I want to remake this video with much higher production quality. It’s rough but the content is probably useful for a lot of users.
7 Likes
Very cool!
I’ve done a similar thing with a motorcycle swingarm sketch and suspension linkages to calculate angle and visualize it’s travel, however…
I’m more so wishing I could do the same with extruded bodies, not just sketches.
I’ve tried to figure out a way to achieve this but haven’t been successful.
1 Like