Optimizing a universal joint design

AI Thread Summary
The discussion focuses on optimizing a universal joint design for a wireframe project, specifically a cube-like structure requiring compact joints that can deflect at least 45 degrees in any direction. The current use of universal joints is deemed unsuitable due to their bulkiness and design limitations, prompting a search for more efficient alternatives. Suggestions include using cup magnets and steel bearing balls as vertices to enhance compactness and functionality. The need for minimal play and durability in the joint design is emphasized, with various concepts like ball-and-socket joints and springs already explored. The conversation highlights the importance of practical construction methods alongside innovative design solutions.
DaveC426913
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TL;DR Summary
Looking for a hinge-joint that has the required freedom of movement in a compact and practical design.
First, a caveat: this is one component of a project, which is difficult to describe without quite a but of digression. If my descriptions seem illogical, it may be because I haven't described the function of the component in its proper context. I assume it will take a little bit of back-and-forth before I'm understood. For those of you who have known me online, this is a revisitation of my tesseract project.I'm designing a wireframe of a ... "cube-like thing" from hollow tubing (may be brass hobby tubing, may be 3D printed). It needs to have joints - actually vertices - that can deflect by at least 45 degrees in any direction.

I have been using universal joints, like they use in automobile drivetrains, but they are not ideal. U-joints are meant to undergo rotation, and mine does not need to. MY problem with the u-joint is that it's bulky. The actual length of the joint mechanism (vertex) takes up more of the cube's edge that I can afford.

What I want is a compact design. By that I mean I'm not concerned about the width, just the length that the parts of the joints take up (independent of scale).

Every vertex is a sphere with 4 (four) of these universal joints merging from it equally. (only one shown here).
1615755222483.png


I am looking for a joint design that:
- provides a deflection of at least 45 degrees in any direction
- is as compact as possible (i.e. short along its primary axis)
- provides minimum play (eg. a piece of string provides unlimited deflection but can just as easily collapse)
- is robust (string for example, will break over time)
- can be practically constructed

I've tried several designs - everything from ball-and-socket joints** to string to springs.

**interestingly, a ball-and-socket joint can't deflect by 45 degrees at all.

Looking for suggestions.
 
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Cup magnets in the ends of the tubes. One steel bearing ball as the vertex.
Maybe glue ball to one tube to prevent loss/injestion.
 
Baluncore said:
Cup magnets in the ends of the tubes. One steel bearing ball as the vertex.
Maybe glue ball to one tube to prevent loss/injestion.
Yeah. Good idea. Those neodymium magnets are pretty strong, but I'm not sure they're strong enough. Might be worth an experiment.
 
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