Assembly 4 workbench

Discussion about the development of the Assembly workbench.
Syres
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Re: Assembly 4 workbench

Postby Syres » Wed Jan 29, 2020 11:27 am

Zolko wrote:
Wed Jan 29, 2020 11:03 am
what does that suspension type look like on a real car ? Do you have an image of a real suspension system ? I don't even know what to search for.
Have a look at http://what-when-how.com/automobile/ind ... utomobile/ and scroll down to Semi-trailing Arm and Coil Spring.
I think that's what @gozlikehell is trying to replicate.
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Zolko
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Re: Assembly 4 workbench

Postby Zolko » Wed Jan 29, 2020 12:02 pm

Syres wrote:
Wed Jan 29, 2020 11:27 am
Semi-trailing Arm and Coil Spring.
that should be feasible to model in Assembly4: draw a sketch representing the axis of the swing-arm and also the axis of the gear-box output (suppose they on the same level, if not make 2 sketches), draw a sketch marking the vertical (or a datum axis maight also do), attach LCS_arm to the axis and the vertical, offset the LCS_arm from the vertical by some angle (that you place in the Variables), attach a sketch to LCS_arm, draw the triangle of the arm and especially the axis of the wheel (which will have a funny 3D movement), attach an LCS to the output vertex of the gear-box and pointing towards to edge vertex of the wheel axis (and a horizontal if necessary). Attach also of-course an LCS to the wheel axis.

Now, if you want the wheel to rotate ... that might be trickier


suspension.jpg
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try the Assembly4 workbench for FreCAD v0.19
install with Tools > Addon Manager > Assembly4 — tutorials here and here
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ppemawm
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Location: Manhattan New York

Re: Assembly 4 workbench

Postby ppemawm » Wed Jan 29, 2020 12:57 pm

Thanks for providing your file for study.
gozlikehell wrote:
Wed Jan 29, 2020 10:39 am
All 3D models that I see are animated in 1 plane.
Please see also https://forum.freecadweb.org/viewtopic. ... 20#p360586
"It is a poor workman who blames his tools..." ;)
gozlikehell
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Joined: Sun Jan 26, 2020 11:47 pm

Re: Assembly 4 workbench

Postby gozlikehell » Thu Jan 30, 2020 12:28 am

Thanks from everyone. Syres, that's a good page link of examples. Zolko, you obviously know your code and can make it work. And yes, Ppemawm, I did see that example. I can model the suspension in whatever crazy path it takes. I want to model how the CV axle moves and plunges along the given suspension path.
So, we're on the same page, what I would typically call an A arm style suspension, that would be a parallel link style on the page mentioned, or an IFS from a truck, or even a McPherson strut from FWD cars. All of these suspensions travel in the same vertical, or YZ plane as the CV axle.

https://forum.freecadweb.org/download/f ... &id=102536

What suspension I'm trying to rough sketch model for the path of my CV axle is what I would call a trailing arm. Examples would be early Porsche 911 (or 930 body) rear suspension, sand rail trailing arms, or micro stub trailing arms. The suspension travels through the XZ plane and can swing either in front of or behind the inner CV joint. When the suspension is compressed, the hub is typically behind the inner joint. When extended, it's inline with the inner joint. That means the shaft moves along a 3D path while the inner joint plunges. Hence, the sketch flipping that I was experiencing.

https://forum.freecadweb.org/download/f ... &id=102538

https://forum.freecadweb.org/download/f ... &id=102537
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images.jpg
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clip_image0023.jpg
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gozlikehell
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Re: Assembly 4 workbench

Postby gozlikehell » Thu Jan 30, 2020 12:43 am

These master sketches are just that-master sketches for animation. This way I'm not uploading or linking to the whole model (at least not yet). How do I represent these 3 lines without having a sketch flip? I know I've got to modify the tripod joint plunge later for accuracy. This is just a really rough idea. Once I fix the bugs, you guys can run with it. Zolko, you can host it as another example, if you like.
gozlikehell
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Re: Assembly 4 workbench

Postby gozlikehell » Thu Jan 30, 2020 11:14 am

I think I understand what I have to do to correct it to get a full suspension sweep through the XY plane without flipping. Any ideas? Let me know. Otherwise, I'll be back in a few days.
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Zolko
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Re: Assembly 4 workbench

Postby Zolko » Thu Jan 30, 2020 11:35 am

gozlikehell wrote:
Thu Jan 30, 2020 11:14 am
I think I understand what I have to do to correct it to get a full suspension sweep through the XY plane without flipping.
Are you sure it's a pure movement in the XZ plane (XY → XZ ?) ? If the axis of the swing-arm is not at 90° from the car symmetry plane then it will not be.

EDIT: I might have been confusing with:

gozlikehell wrote:
Thu Jan 30, 2020 12:28 am
All of these suspensions travel in the same vertical, or YZ plane as the CV axle.
try the Assembly4 workbench for FreCAD v0.19
install with Tools > Addon Manager > Assembly4 — tutorials here and here
gozlikehell
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Re: Assembly 4 workbench

Postby gozlikehell » Fri Jan 31, 2020 12:38 am

The parallel systems or A arm based systems are in the same plane as the CV axle (YZ plane).

The trailing arm type system like I'm using travels in the XZ plane while the CV axle is primarily in the YZ plane.
gozlikehell
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Re: Assembly 4 workbench

Postby gozlikehell » Sun Feb 02, 2020 1:18 am

Well, I managed to fix my sketch flipping. Zolko, you were correct. I had to basically pick a different plane and stick with it. I had to take my CV path sketch and try to keep it in the YZ plane and adjust the angle of it with plenty of use of the Pythagorean theorem. I added a sketch to figure out the angle to maintain for the CV path. My range of travel is now the full length of Axle_height. The range is from -273.05 to 0.
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CV Master Sketches.FCStd
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gozlikehell
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Re: Assembly 4 workbench

Postby gozlikehell » Mon Feb 03, 2020 11:55 pm

If you'd like to see the working file, let me know. Obviously it's too big to upload as an attachment. My next step would probably be to write a script to animate it.
Attachments
CV Axle Model 2.png
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