lifting the construction

[Anonymous]

How can i simulate that the construction is getting lifted in robot. The construction i have build is going to be lifted onto an oil rig. how do i simulate this in robot?

[Rafal.Gaweda · Accepted solution]

This was example how to properly rotate support. 

As Rafacascudo said :  "No ,just Ux ,as long as you set the support local direction like I recommended"

[Anonymous]

why exactly just ux?

[Rafacascudo]

Hi Tony, If you have a small free height to lift the structure ,the angle the cable will do with the horizontal will be smaller and the horizontal forces can be very significant! For example if you have an 45 degrees angle(which is not rare) ,horizontal forces will be equal to the vertical force lifted on that point. Anyway , even if the angles are closer to 90 degrees, I believe this is the exact solution for the problem. Hard work?? I´m pretty sure an user as well skilled as you can set these supports in less than 30 secs!! And it is a fun solution!! If you change the lifting point coordinates ,you´ll will notice the 4 supports automatically pointing toward that single lift point/node. 😉

[Anonymous]

Agree with your thoughts.  However I'm lazy sometimes 😞

Actually though, we normally add another member to the system, called a "spreader"  The additional beam takes a compressive force, and leaves the actual structure to be picked up with a vertical force only.  

I can send you a picture if you're not sure what it is.  

Tony

[Anonymous]

i would like a picture plz 

[Anonymous]

When i calculate the file after i have added the supports on each corner I get a warning of instability on node 52... see the attached file. Should i take this to consideration or is it nothing to worry about?

[Anonymous]

can you post the model?

[Anonymous]

there

[Anonymous]

model attached

[Anonymous]

Why should I only cross off on the UX, and not UY? I attached my file, could you see if it looks like iam simulating a lift?

[Anonymous]

normally, just use the spreader on two sides, it will be stable for regular shaped geometry.  

[Anonymous]

we are not supposed to use spreader bars, but we have added a support in one of the corner were we have cross checked RX, RY and RZ. This worked with the instabilty in node 52 😉

[Rafacascudo]

Mortel09 ,No instabilities on your original model if you use the multi-threaded solver.

[Anonymous]

the multi-threaded solver? I added a support in on of the corner so hold the rotation (RX, RY and RZ), will this be wrong to do?

[Anonymous]

My opinion is that if you have an instability in a model, using multi threaded to avoid it is un-conservative and not recommended.  The model should run fine on automatic before switching to multi thread. 

[Rafal.Gaweda]

Multithreaded solver may not report instabilities that's why it is recommended to find all model instabilities (esspecially of type 1 and 2) using different solvers.

[Anonymous]

Iam not sure what to do, I attached the file, when you hit calculations you get a warning of instability in node 52. What should i do?

[Anonymous]

it's type 3, so may just be large differernce in stiffness.  

[Anonymous]

Okei, thanks alot guys. The both of you have been really helpfull. I appreciate your help.

[Artur.Kosakowski]

Please check the displacements and rotations for case 1 (self-weight) before ignoring the reported instability.