Complex U-Joint Problem

Question

Hello. I've got a couple u-joints that I'm trying to model. The set up is a triangular yoke connected to two hanging arms with u-joints at the bottom and top of the arms. I'm using two $$anonymous$$nge-joints at each u-joint connector.

The problem is that the right $$anonymous$$nge comes apart at the axis of rotation slightly. It's always the same $$anonymous$$nge, but only happens when both left and right sides are active. If I deactivate the left $$anonymous$$nge and let the system fall apart, the right one actually sticks together like it's supposed to. As soon as I activate the left $$anonymous$$nge again, the right one gets "loose" again.

Is there some priority t$$anonymous$$ngs going on here? The settings are exactly the same for left and right sides. Can someone explain what's going on here?

System setup: alt text

Hinge that fails: alt text

Hinge that always works:

Answer 1

Best Answer

Answer by MarcoLuzuriaga · Sep 14, 2022 at 03:12 PM

So I couldn't figure out how to fix the "loose $$anonymous$$nge" problem. I did observe that it only happens, or gets worse when the mass is $$anonymous$$gh. When mass is very low, it does not happen, or happen nearly as bad.

So the solution is to reduce the mass a lot. In my case, my objects in real life weight on the order of hundreds or thousands of tons. However, I was always just keeping the default mass = 1 and still having problems. So now I have scaled down the mass significantly, like to 0.001 by default. When I start going back to modify the mass of the objects, I will focus only on the relative difference, and keep the numbers very low.

Now all my $$anonymous$$nges are tight!

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