Joints with two line contacts?

[Muzzerboy]

I'm trying to mate 2 bodies where there are 2 line contacts, eg a nut contacting the faces of a wrench. I can create a revolute joint at one of the line contacts but if I try to create a second revolute joint it gets upset - you can only have one joint it seems. Although I could fiddle the result, I want to do FE analysis on the resulting assembly, so the joints need to be hinges. And I'd like the assembly to remain intact if I change the dimensions of the compts.

You have a similar joint requirement if you try to create joints between a rod and a vee-shaped valley. Again there are 2 line contacts, so the same problem arises. There are other examples like this.

Another challenge might be getting a sphere to mate with the end of a round hole. In this example the contact is circular. Seems to be a similar challenge in some ways. Try this example http://a360.co/1OVMmsd or fit a rod into a vee-shaped valley so it is kept in contact with the sides of the valleys - 2 lines of contact.

I tried inserting a plane from one of the edges of the hex nut body etc but I couldn't make it coincident with the face of the other body. The nut remained hinged from the first revolute joint (between one jaw and one of the 6 edges of he nut) but I just coudn't create a second joint between another of the 6 edges and the opposite jaw of the wrench.

Any ideas how I could mate these parts successfully? Hopefully I'm just missing something....

Thanks for any help you can give me.

[TrippyLighting · Accepted solution]

I believe what you might be looking for are contact sets.

[Muzzerboy]

Aha! That did it. I'd started looking at contact groups towards the end but didn't see how to use them and by this point I was starting to lose direction.

I created a nut to fit inside my jaws, used a planar joint to constrain their faces to the same plane, then Assemble > Enable All Contact and New Contact Set. Then selected the jaws and nut. This allowed the nut to slop backwards and forwards within the jaws, stopping when they made contact.

In simulation, I locked the end face of the wrench handle and applied 2 equal and opposite forces to generate the applied torque (1 o'clock and 7 o'clock positions - possibly not the perfect solution but it worked for test purposes. Might have been better applying them at the 11 o'clock and 5 o'clock positions. This worked nicely. It's not a pretty wrench but I was simply trying to get the simulation to work rather than spend hours trying to model up something fancy.

It's frustrating to spend ages trying to find the features you want but really helpful when you can post something here and get fast helpful responses. Really appreciate the support and hope someone else finds this heelpful / interesting.

Thanks again!

[TrippyLighting]

Kudos to accomplishing you goal. Looks nice.

I've taken the liberty to also mark my answer as the acepted solition 😉

[Muzzerboy]

Yes, good stuff. Just took a little nudge from someone who knows what they are doing!