Chain

wayne_sauder

I know the subject of chains has been discussed in-depth on the forum and I think I hunted up all the posts related to it. I am wondering if anyone could give me any ideas on ways to simplify this to get better performance? https://cad.onshape.com/documents/b289e23ee832231bdd4a4708/w/7f41f4cdb4df01f33d333bee/e/4be86dd71f7768dd214c69d8  

alnis

The best performing moving chain method I've found so far is @NeilCooke's method in this thread, but I'm guessing you've probably already seen it. One difference between his method and yours is that there's a surface instead of a solid with a single face instead of multiple, but I'm not sure if this is why it performs well. Unfortunately, there isn't really a good way to make chains move in Onshape at the moment. Here are the methods I know of for making static models of chains in Onshape:

• Curve pattern in a part studio and make a composite part. This is easiest to make, but it's not accurate in the BOM for the number of chain links, can have lower performance (since you have a bunch of individual parts in a trench coat masquerading as one part), and the chain links don't quite have lined up pins because of where the curve pattern instances the parts.
• Use linear and circular patterns to precisely pattern the chain links around and between sprockets, using one last fastened mate at each sprocket to make sure the links go off in the correct direction to the next sprocket. This is a lot more work than the curve pattern, but the result has an accurate BOM, the assembly may load slightly faster, and you'll know exactly how many turns to tighten your tensioner before you put the whole thing together.
• Model it as a single solid that looks like a narrow and thick belt. This doesn't give any visual accuracy, but it's good enough for checking for appropriate clearances, is very easy to do, and is generally good enough from a functionality standpoint.

For changing the position of the chain, I use configurations for all three methods (either driving changes in the pattern/extrude sketch or in the number of pattern instances in various places). Hopefully, there will be a chain pattern like there is in SolidWorks at some point!

Hope this helps!

steve_shubin

@wayne_sauder

If you’re at all interested in simulating chain movement — and I want to emphasize simulate — because there was some optical illusion going on (I believe that’s what John called it), then you need to see what John McClary did.

Unfortunately I’m not good at searching for past posts and I have no idea where to look

@john_mcclary  —  HELP !  Where is that post

wayne_sauder

I tried working with a surface for a while, was not able to tell that that made much difference. I would like to simulate it to show the client and what John McClary did does not work for this project because the links for an attachment are only on one side and the chain never travels a full revolution, that is a neat trick though. I'll probably have a show and tell with a static chain.    

john_mcclary

Yea, every attempt at a full rotation of linked chain always ended up binding at some point. 

I'm sure if I had more patience it could be done. But I did the animation illusion instead of an actual chain animation for performance reasons.

If you need to animate other things along side that then you need to use reference parts and relations like I did with the rubiks cube example. 

If you do that then you should be able to simulate the chain simultaneously with your sprockets and packages.. But Onshape is not built for complex animation. So you would be better off exporting to another system with a more sophisticated animation tool, like solidworks or possibly fusion?? Not sure really, I only ever animated models with solidworks before.

Maybe one day Onshape will have better built-in animation tools

russell_gililland

Voting up to see onshape tackle animation solutions in 2023. Chains etc.

MichaelPascoe

@russell_gililland, that would be awesome. 
While we wait, here is a hybrid solution of real links + the animation illusion.

For the animation to work:

• The chain needs to travel at least one link
• Set the animation to loop
• Set the animation start and stop to line up with your sprocket ratio
• Set the speed to be fast (around 7 steps or so) to make it appear seamless. For this to really be seamless you would need to use a tangent path guide, however I wanted to stick with actual links for this studio

https://cad.onshape.com/documents/713f282c6a0c9a8e90b0ac19/w/f72fa6bbdf5cfa0f320837b5/e/472428fc9d95e354784d8a24?renderMode=0&uiState=63b44df015b392361559d1f6

john_mcclary

yeah, that's pretty much the trick I used too

It's ok if you just want to show the chain move, but if there are other actions, then that trick becomes obsolete 

https://www.youtube.com/watch?v=kMy4j_LYuYo