I am having assembly issue.

robert_lyons820

I am a new user (one week) coming from Sketchup and have gone through all the initial self tutorials and I am having a basic problem with attachments in an assembly.  I have a control arm successfully attached at one end, but when I attach the second end to  its mating surface it attaches successfully but the first attachment snaps to the other end of the new mate.
The drawing is a shock absorbing structure on the nose gear strut of an aircraft called a "knee" spring assembly that attaches to an oleo strut. There is only one assembly tab, perhaps someone would be kind enough to look at it and tell me whats wrong.
https://cad.onshape.com/documents/d68f6239732b430d2573253e/w/59bf15a1cc74460ddde3c8a0/e/7160df705ce6bf657f07a454

Thank you in advance.

steve_shubin

@robert_lyons820

Theoretically, you would think that the revolute mate should work at all three pivot points. But when you try to do certain things using the revolute mate only, sometimes it just doesn’t work. There have been discussions about this elsewhere in this forum

.

steve_shubin

@robert_lyons820

It’s a matter of degrees of freedom regarding the mates

In essence — certain mates are more restrictive than others. And when you start deploying various mates in particular combinations, it can cause things to bind up. So you have to switch to mates that are less restrictive

So a cylindrical mate is less restrictive than a revolute mate. And a ball mate is less restrictive than a cylindrical made — at least I think that’s the proper amount of degrees of freedom of each mate

So for example — you can use a couple ball mates in place of a revolute made

https://cad.onshape.com/documents/47a1f2783fe23478fd770fd2/w/1a13856dbd99184cdb5fe3a2/e/121c05158389501cda6a4f96

matthew_stacy

Hello Robert,

I was able to make Assembly1 work by changing the Slider1 mate to 'Cylindrical'.  I think that the slider mate was conflicting with the slider mate was conflicting with the joint between the upper and lower knees.  If I understand your intent, it is the knees that constrain the strut from rotating in the main bracket.

Let me know if this works for you.  If you want to share edit privileges (matthew.g.stacy@outlook.com), I can get into the document with you to figure this out.

Sometimes it's helpful to reorder the component tree, starting with the fixed component (main bracket) and then proceeding in the order that it would be built in the shop.  Mimic realistic constraint with your mates as you go.

Cheers,

-Matt

steve_shubin

@robert_lyons820

Theoretically, you would think that the revolute mate should work at all three pivot points. But when you try to do certain things using the revolute mate only, sometimes it just doesn’t work. There have been discussions about this elsewhere in this forum

.

steve_shubin

@robert_lyons820

The original document I posted was modified more than what is showing above now