FreeCAD as pre-post processor for MBDyn

About the development of the FEM module/workbench.

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JamesLiu
Posts: 20
Joined: Sat Apr 28, 2018 6:23 am

Re: FreeCAD as pre-post processor for MBDyn

Post by JamesLiu »

Hey josegegas, would you please make a tutorial on cycloidal gearbox simulation? It is helpful to understand force interactions between disks and pins.

phpBB [video]
josegegas
Posts: 187
Joined: Sat Feb 11, 2017 12:54 am
Location: New Zealand

Re: FreeCAD as pre-post processor for MBDyn

Post by josegegas »

JamesLiu wrote: Thu Jan 06, 2022 6:18 am Hey josegegas, would you please make a tutorial on cycloidal gearbox simulation? It is helpful to understand force interactions between disks and pins.

phpBB [video]
Hi. Sorry but what you see in the video is just an animation, not a MBD simulation. I basically just programmed a script to move the parts as they would in a real cycloidal gearbox.
JamesLiu
Posts: 20
Joined: Sat Apr 28, 2018 6:23 am

Re: FreeCAD as pre-post processor for MBDyn

Post by JamesLiu »


Hi. Sorry but what you see in the video is just an animation, not a MBD simulation. I basically just programmed a script to move the parts as they would in a real cycloidal gearbox.
OK, understood. Do you think the latest MBDyn WB is ready for this simulation? I want to try it myself as part of learning process.
josegegas
Posts: 187
Joined: Sat Feb 11, 2017 12:54 am
Location: New Zealand

Re: FreeCAD as pre-post processor for MBDyn

Post by josegegas »

JamesLiu wrote: Sat Jan 08, 2022 1:18 am

Hi. Sorry but what you see in the video is just an animation, not a MBD simulation. I basically just programmed a script to move the parts as they would in a real cycloidal gearbox.
OK, understood. Do you think the latest MBDyn WB is ready for this simulation? I want to try it myself as part of learning process.
It depends on what exactly you would like to model. It is for sure ready to model all the mechanism but not the contact between parts. Contact is not a very mature part yet. To model the motion you only need the motion equations of the gearbox, which can be found easily on Internet or derived from the gearbox design, and then use the existing joints... It would be interesting to model it as in this example:

https://www.sky-engin.jp/en/MBDynExampl ... /ex11.html

So you can get the input and output torque, and probably the efficiency as well, assuming some coefficients.

You may want to have a look at the "Wankel engine" example:

phpBB [video]


it is somehow similar to the cycloidal gearbox. You will find the example on GitLab.
JamesLiu
Posts: 20
Joined: Sat Apr 28, 2018 6:23 am

Re: FreeCAD as pre-post processor for MBDyn

Post by JamesLiu »


It depends on what exactly you would like to model. It is for sure ready to model all the mechanism but not the contact between parts. Contact is not a very mature part yet. To model the motion you only need the motion equations of the gearbox, which can be found easily on Internet or derived from the gearbox design, and then use the existing joints... It would be interesting to model it as in this example:


Thank you for the instruction! However, my primary interest is the contact force vector between cycloidal disk and pins.
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