I came up with this concept for a partial rotation, lubricant free, low friction bearing for a robotics application. Two complementary sets of tensioned tendon-like cables (or tapes) serve both to constrain the degrees of freedom of the joint as well as the rolling surface. Here's a render of a model I made to illustrate the idea:

I'm sure that I'm far from the first person to have had this idea, but having no clue about its proper name nor about how to describe it, I'm unable to find anything on the net. I guess it's best described as a kind of flexure, but what exactly? Has this mechanism found any real world applications?

  • $\begingroup$ Those "tendons" will have to be incredibly strong to resist torsion forces between knuckle segments. Seems to me that the red clamps will be crushing the tendon and providing a point of failure. The way this is drawn, there is no resistance to immediate tensile force between the two adjacent metal parts. In other words -- a lot of backlash between the yellow and pink hatched areas. $\endgroup$ – user6335 Feb 21 '18 at 20:45
  • 1
    $\begingroup$ ...Beautifully drawn and rendered though. Very high quality illustrations. $\endgroup$ – user6335 Feb 21 '18 at 20:49
  • $\begingroup$ I'm mostly asking about the concept (as in bearing with load bearing tendons of some kind crossing sides at the joint), not the implementation, but thanks for the feedback. Indeed this alone won't handle torsion (you'd need two of these to constrain that DOF). The red clamps are only supposed to preload the tendons (for rigidity) by pulling on them, not clamp them against the main body (even though I did misleadingly render them clamped all the way down) $\endgroup$ – jms Feb 21 '18 at 21:01
  • $\begingroup$ Okay, I see what you're getting at. In the interest of simplifying your question, I'd be tempted to omit the superfluous "furniture" that surrounds the actual joint that you're interested in. Out of interest, do you have a material in mind for the tendons themselves? $\endgroup$ – user6335 Feb 21 '18 at 21:08
  • 2
    $\begingroup$ This is how the Polynesians have been lashing rafts for a couple thousand years. Modern example on a Wharram, I think image. I built a lot of dock floats and kayak and canoe floats with this lashing and they survived many hurricanes. I've only ever heard it called a rope hinge. $\endgroup$ – Phil Sweet Feb 21 '18 at 21:23

I think it is similar to what it is called by MIT Fundamentals: Flexural Rolling Bearing or Rolling Contact Flexure in section 10.14.

As is often the case, a hybrid system can combine the best of both worlds. So it is with rolling contact flexural bearings. These bearings allow for compact rolling element joints to be designed. These joints can sustain large normal compressive forces due to the rolling contact, and respectable shear and tensile forces due to the flexible bands. This also make them inherently preloaded. Most importantly, they allow for rolling motion with a minimal number of elements and no lubrication which makes them particularly well-suited for precision instruments medical device applications.

Youtube link for a similar bearing which is called Compliant Rolling-Contact Element

| improve this answer | |

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.