ProE Spherical Constraints for Assembly

[scottyb]

Hi guys,


I am in the middle of my undergraduate thesis and am having great trouble getting ProE to do what i need it to.


I am designing an upright for a racecar, and it has three plain spherical bearing connections. These are where i am constraining the model for the analysis, and i am applying a remote load through the wheelbearings.


I have done this simulation in solidworks and it is a bit too basic in functionality and lets you constrain all 3 degrees of freedom in rotation and/or all 3 degrees of freedom in translation. In solidworks, i would fix translation at all three bearings and the model would work. I would apply the spherical constraints to the spherical face on the plain spherical bearings. This generated boundary condition errors at the top upright mount, as it is actually free to move vertically.


Following this i have moved to ProE as i can do the same thing but constrain all6 degrees of freedom at each bearing as i please.


But, it doesn't work. Below is what have tried.


spherical coordinates at the centre of the bearing and constraining all translations, and free rotations on the spherical surface.


Same again, but selecting all surfaces on the spherical bearing part.


creating a datum point at the same place as the spherical coordinate system, and applying the constraints above to it. But it says that the constraint is not applied to a geometric part.


All i need is for this to work, i can get the top mount to translate vertically, but none of the parts will rotate at all. In the pic below, i need the bit that is spherical to rotate, but it just won't happen. I am hoping you guys can pinpoint my errors easily, and that i have fallen into a trap for youg players!


Please lend a hand if you can, PM me and i will email you any more info if you need it to get a better understanding.


Thanks for your help!View attachment 2323


Scott

 

[Mloew]

Could you set-up a spherical coordinate system at the center and constrain only the radial dimensions. That should work.

 

[scottyb]

Hey mate,


thats the first thing i did, as it would obviously seem to work that way... but no...


I had a spherical coord system at the centre of each bearing, and i would use that as the coord system in the constraint setup box. i chose the outer spherical surface as the surface, and then i fixed all three translations, and free'd all three rotations.


The model does not rotate as it obviously should.


maybe it is overconstraining it by fixing one of the translations (i have tried freeing them individually, but it just doesnt work...


there has to be some little trick that i am missing...


Cheers for the response!



Scott

 

[Mloew]

Scott,

Try eliminating the ball and necking the joint down to a a point via two cones or with beams. Then if you constrain just that point in the three translations directions, you should have something. It seems that constraining the surface is over-constraining the model.

 

[scottyb]

Hi guys,


Thanks for your input!


I have found a solution by creatinga datum point at the centre of each bearingwhere the coordinate system is, and then using rigid connectors from the bolt holes top and bottom to the datum point.


I then constrained the point with the spherical coord system and freed rotations. It worked, and i could remove the bolts and spherical bit. this reduced my run time by half!


Thanks.


Scott

 

[Mloew]

Scott,

Glad it worked. What is the application? It looks like a Formula SAE upright.

 

[scottyb]

Hi Matthew,


Yep, i am doing analysis of our 2005 FSAEupright and comparing it to physical testing of the component, then with a validated model i can design the 2006 uprights using the same technique.


Cheers,


Scott