How to make different mates to revolve at same time?

johannes_sheya

hello, I am drawing a flip braai stand and cant just manage to make my mates works together. i want the braai grid to be flipping in 360 degree.

 the link of what I am trying to draw https://www.youtube.com/watch?v=aN8QujqNSxs

my drawing https://cad.onshape.com/documents/17e8fd9946020e0164c772f6/w/c906df306a4a7f7b0183c017/e/db45f76ed6ae63c4f32b87c4

mahir

This is a four bar linkage. All the rotations are related, not independent. Therefore, you don't really need to control more than one mate. Add the necessary rotational mates to constrain one side of the mechanism (3 revolute + 1 cylindrical). The other side can be constrained similarly or by using 3 planar mates; you have options. Then, animate one of the rotational mates, or drag the handle. All the parts will follow along if mated correctly with no extra degrees of freedom. I'd fix your model, but the link you shared is read only.

mahir

Here's an example. Dragging parts works fine, but animating a mate isn't working well though. @philip_thomas, any ideas why the other assembly mates aren't solved while animating one the revolute mates?

https://cad.onshape.com/documents/57acdfaae4b005c413ed9b6f/w/3fd585a46d3af1b3ba413c53/e/a0dbd0a7933376281df9dd34

philip_thomas

@mahir - there is nothing wrong with your mating strategy - your problem is geometry

When all 4 links of your 4-bar linkage are the same length, there are certain positions when there are at least two and (possibly) infinite solution - this is why they flip. 
Here is the same assembly with the length of one of the linkages shortened - there is only a single solution for any angle.

https://cad.onshape.com/documents/e5e84c47a25e36e41646b69c/w/954234f34249675006ca96ee/e/c4e24c2bcfd383487904d022

This animates very nicely

mahir

Duh! Fixed the example.

But I'm still seeing some unexpected behavior. If I right-click>Animate a mate, all's well. If I edit a mate and click the Play button, only the part being mated moves. I would expect to see the total effect on the assembly, not the isolated motion. Is this behavior as designed?

philip_thomas

@mahir - editing a mate only solves THAT mate, not the entire system - that's what the SOLVE button does (pressing the Solve button is a one-time solve of the entire assembly).

mahir

Gotcha.