Recently I have been doing a lot of work in Fusion 360, and when it came to modeling I found very few resources online to guide me. I saw a couple of Inventor tutorials (by James Pearman and Nathan Nolte) modeling how to constrain chain systems, and I came very close to doing it myself on Fusion, but I never got the links to line up. I’m pretty sure I’m overthinking this, so if anyone has any simple solutions to chain systems, that would be amazing.
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In assemblies menu you can tie the sprocket motions to each other. It’s an obvious name, but I can’t remember it and will have to check tomorrow. That is what is truly needed. I read a past comment from someone today that recommended using bands instead of chain to make the thing look more realistic because chain will drastically increase the effort the processor has to make for animation.
Now that I’m back on my computer… You want to use Assemble > Motion Link for the sprockets. Make sure their ratio matches up properly. You’ve got two “Angle” boxes there where you can set the angles to be unequal to make sure they rotate the appropriate relative amount. Once you’ve done that, you get the functionality of chain.
Now, the chain itself is tougher. From the advice I saw, just sketch a band and let it sit still. But I’ll assume you want more. I don’t know for sure what to do from here. The easy part is that you want Assemble > Motion Link to make your chain move as a sprocket turns. You want a planar joint for the whole chain, so it can move in one plane (two dimensions) and rotate around a single axis perpendicular to that plane. But I haven’t figured out how to apply the joint limits to the chain yet. I’m going to try fiddling with this part next in my own model. I’ll let you know when/if I figure this bit out.
Alright, thanks for the help so far. I’ll be able to use the proportional rotation to model chain and gear systems.
So, I’ve gotten further. I’ve laid out a chain properly linked up. I’ve managed to place it properly on sprockets. But I don’t have the whole system moving properly. Here are some tricks for laying out the chain:
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There is no good way to immediately connect the links. Happily, they’re already individual links. But there is no second cylinder to match the first of the next link to. First I made a new component and stuck the chain’s link in there. Then I worked within that component. I made a midplane between the two openings. I pushed/pulled one opening to find its projection on that midplane. I then drew a circle (diameter doesn’t really matter) on the midplane, centered on that projection. Afterward I erased the cylinder I’d created with the push/pull. Finally, I connected my construction and sketch to the original body as a single rigid object. That component (VEX link object plus midplane construction plus circle sketch) are one link of the chain for me and will be what I refer to here on out as a “link.”
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Build the chain by copying a link repeatedly. For each link use revolute joint to connect the center of its cylinder (marked with a triangle when you hover over it) to the circle sketch on the other link. You can confirm you get nice chain behavior out of this by grounding one link and manually moving other links. (Notice I haven’t told you how to close a loop of chain yet, just make a single strand of chain.)
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Wrapping the chain around the sprockets. I actually did this while doing #2, going back and forth, but it’s easier to write about it as an individual step. Move point-to-point the cylinder of a link onto the sprocket. You can select the centers of the cylinder and the space on the sprocket using their triangles as noted above. It helps a lot if you can get the first link place in a nice orientation (like horizontal), preferably the orientation in which you built the chain. That will make the second link’s cylinder immediately line up. If not, you’ll want to make sure the link you’re moving has the correct orientation before moving it. Now you ground that link. This is very important. After doing so, move onward similarly around your sprocket, moving the cylinders point-to-point and grounding the links. Once it leaves the sprocket, you don’t need to be so finicky. You can just build or drag the chain in roughly a line to the next sprocket. Repeat the process with each sprocket and gap.
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Closing the chain loop. Even though everything seemed to line up, I couldn’t get the same revolute joint to work when connecting the last link to the first one. Maybe this was particular to my setup. Maybe it’s more general. I did use the computer to automatically line everything up, so it’s not that. And as far as I could tell from measurements I got them perfectly placed. But it wasn’t happy with that last revolute joint. So what worked instead is that I placed the last link so that it was properly positioned with the first link. I then chose made a revolute as-built joint between them. That way, even if there is some minuscule little deviation, maybe from a computer artifact, they’ll still behave properly since they’re so incredibly close to how they should be.
Problems with the sprockets moving:
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I currently have it working nicely with the sprockets and axles spinning in the bearing flats and with the two motions linked. It looks funning with the chain sitting in place while the sprockets move, but it’s pretty good and gives the proper behavior outside of the chain itself.
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With a limited number of links I’ve been able to use contact sets, linking them to a single sprocket. But once I go much further everything seems to stop working.
