Hi all
I am currently in PTSI preparatory school and I have started my TIPE (supervised personal work). The theme this year is the ocean. So I found a topic that is about RAD (rotary actuated dodecahedre). Here is a link explaining to a large extent what this system consists of:
https://www.researchgate.net/publication/326487928_Rotary-actuated_folding_polyhedrons_for_midwater_investigation_of_delicate_marine_organisms
So let's get straight to the point: my goal was to make the system you see in Figure 2 and Figure 4 of the previous link directly on solidworks. To start with, I tried to make only two arms to get after 3D printing something that looks like what you can see in the following video: http://www.zhiernteoh.com/harvard-university-2d-to-3d-by-synchronized-folding.html
As you can imagine, this is my very first year of Engineering Science. I have accumulated a lot of knowledge in a short time and I am probably missing the practical aspect. I only have a very low level of SolidWorks and that's why I'm coming to ask for your help.
So I made the sketch of a single arm by separating it into 3 pieces that I then assembled and tried as best I could to constrain it. You can have access to my progress on the attached image.
I would like to move forward while understanding and progressing (because it must be said I really love what I do and it's frustrating to be stuck without being able to move forward).
Thank you in advance for your help,
bras.png
Hello
I don't really see what you expect from us, because as much as your project is explicit, your request for assistance is not crazy.
I think your problem is less a solidworks problem than a rigorous observation because the first thing we see in your attached JPG is that your parts are too thick and that in addition you have not put any hinges. Indeed, curiously enough, and in an archaic way, the Harvard University model still uses hinges (yet at Harvard, they are not Mickeys in principle.)
In my opinion, before jumping on the assembly, you have to make the three pieces correctly. The success of this project lies in a rigorous cinematic (which is not as simple as it seems). And for a kinematics without any defects, i.e. without snagging or jamming in the movements, you need to have so-called mechanical parts.
By mechanics, I mean a mechanic made according to the rules of the art, so with perfectly calibrated parts and with games adapted to the stakes, which is not a game for young people.
To Plutarch ;-) For the continuation of the discussion
Kind regards
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Hello
First of all, thank you for your answer!
I would like to remind you that I am a beginner in this field but that I intend to learn quickly. Serte, it's not a young problem, but I'll have to deal with it if I want conclusive results.
For the realization of the 3 pieces, I started with a sketch of each of the 3 pieces of an arm of the image at the top right of the attachment. I am aware of the mediocre result, even if it is only a draft.
On the other hand, even if I know that this is too broad a question, I ask more for a common thread, what are the steps to follow to make an arm or two?
You say that you have to make perfectly calibrated parts. The problem is that from a sketch I doubt my chances of succeeding. So I create these 3 pieces myself millimeter by millimeter?
I don't know if my questions are stupid or not, please excuse my cruel lack of knowledge about it.
Yours truly,
figure_1.jpg
2 Likes
Good evening
the questions are not stupid and I understand that you are starting with Solidworks.
You have to make a single piece with a hinge to start.
Do not make the outer parts which are only used to open and close the polyhedron which, if you look closely, is only made up of pentagons articulated together by the edges. We can first disregard triangles that only have stop functions (if I saw the principle correctly).
Once the template exists, it's much easier to copy it.
I'll show you the principle in a few minutes under solidworks.
Kind regards
1 Like
Good evening
Here is a first approach
Only one piece is missing to make an arm: knowing that the missing piece is common to all 5 arms.
One of the pieces must be modified because the triangle is deliberately missing.
I'll show you a little later the method to get the result in solidworks. Tonight if I have time
Kind regards
polyhedre_ebauche.jpg
1 Like
Hello
Thank you very much for your precious help, I'm quickly tackling it today (I couldn't do too much yesterday). I think I understood the principle better.
Looking forward to hearing from you,
Yours truly,
Good evening @adrien
Attached are two images of your system. The triangle that closes the polyhedron on the blue pieces is deliberately missing.
Identical pieces have the same color. As I said earlier:
- A green coin (which is the central folding link)
- Pink five-piece
- Blue five-piece
These triangles are an impact on the kinematics and it seems easier to me to see the parts.
In my first post I said that precision was needed because due to the shape of the volume, the slightest error in the dimensions prevents the edges from joining correctly.
Let us know if you continue with your project.
PS: which version of SW do you have?
@tous the pieces are not that trivial to draw, you need a little method before getting started otherwise it's guaranteed to be a souk (hihihi!!!!)
Kind regards
rotary-actuated_folding_polyhedrons_-_two_arms_closed.zip
1 Like
Hello @Zozo_mp,
Excuse my 3-day delay. I still have classes until the end of June and therefore still DS on Saturday mornings. My revisions therefore prevent me from being very present on the forum.
However, I didn't do anything. I searched the Internet to find out if there was ever any clue about a potential realization of this system. I found a previous work on the same system: https://www.thingiverse.com/thing:3375148/comments
Maybe it will help us better understand the system being studied. In particular, we see "ball joints" everywhere: https://atazi45ab651jeqs63s8vnp1-wpengine.netdna-ssl.com/wp-content/uploads/2016/06/HD-Lower-Ball-Joint.jpg
These include the five pink pieces, the five blue pieces and the central piece (the green one) that you mentioned earlier.
Thank you very much for your patience and help. Of course I am continuing my project (I still have time ahead of me).
Please note that I am using SolidWorks 2017. I can't open your SVPJ file. The files I open with SolidWorks are usually in SLDASM and/or SLDPRT.
Yours truly,
Adrien
Good evening for the SVPJ file you have to open it with SOLIDWORKS eDrawings
Look here it's a free software
https://www.solidworks.com/fr/category/technical-communication
Kind regards
