Compliant Mechanisms that Roll Like GEARS!?! -- #VeritasiumContest

#VeritasiumContest

Since the prize money is coming from a UCLA professor who lost a physics bet to Derek from Veritasium, this is my attempt as a fellow UCLA professor to redeem my university’s reputation.

This video is about how compliant rolling-contact joints can be used to counter intuitively create compliant lattices of gears. Compliant rolling-contact joints consist of crisscrossing flexures that are deformed around cams. They achieve large ranges of deformation without increasing in stress and achieve near zero stiffness about the desired axis of rotation while maintaining high stiffness in all other directions. 2D and 3D lattices of many shapes can be designed.

My work pertaining to these lattices, which are called ‘Compliant Rolling-contact Architected Materials’ (i.e., CRAMs), is previously published in the journal Nature Communications at the following link:

If you are interested in learning more about compliant mechanisms in general, check out my YouTube Channel, “The FACTs of Mechanical Design”

and be sure to check out Veritasium’s video on the topic as well:

Acknowledge: This work would not have been possible without the help of my students, Luke Shaw, Samira Chizari, Matt Dotson, and Adam Song!

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Disclaimer: Responsibility for the content of this video is my own. The University of California, Los Angeles is not involved with this channel nor does it endorse its content.

[ahobimo]

If I understand them correctly, these mechanisms can't actually rotate continuously like a true gear. They can only rotate within a limited range (<360°). So wouldn't this be closer to a linkage, rather than a gear?

[fearalice]

"..can move 360 degrees.."
in all designs you showed, if it were to move 360 degrees it would break or heavily deform. Even the one you showed while saying that is 180 degrees of movement, not 360.

[andrewphillip]

Metal-band and roller mechanisms like this have been implemented successfully in a few niche applications requiring ultra-low friction, one of which being early automotive airbag sensor switches. Also, sometimes surface grinders use a band and roller to translate rotational motion of the hand wheels into translational motion of the table, presumably because the force vector is always exactly tangent to the path of motion, whereas with a rack and pinion the force vector is not exactly tangent, and moreover it can vary in direction and magnitude over the range of travel if there are any geometrical imperfections, which would be a problem for a precision grinder since imperfections would show up in the workpiece. I have never seen an example of band and roller used to convert rotary motion to rotary motion, but I’m sure there exist machines which could benefit from incorporating this concept

[pirobotbeta]

Zero-backlash bands have been around for a very long time.
I saw my first one tearing down a floppy-drive in 1985 or so.
The stepper has a drum, band wrapped around drum.
Band ends were on the 'sled'.
Stepper rotates, band drags sled to and fro.
Very precise movement that rack and pinion gearing would have a hard time matching.

[blazingangel]

That first demo of two semi circles in articulation could be cool as a load bearing joint in a robot arm. Could use opposing linear actuators on either end to articulate it like muscle on bone. Only challenge I can think of would be whether the surface friction and rigidity of the join constraint would be enough under load.

[getaclassphys]

One of the best videos in this contest.

[samuels]

This is more of one of those 'toothed hinges' you see on fire doors to ensure that they close properly rather than a gear

[johnborton]

// "Since the prize money is coming from a UCLA professor who lost a physics bet to Derek from Veritasium, this is my attempt as a fellow UCLA professor to redeem my university’s reputation."//

LOVE it. Showing UCLA deserves a second chance.

[pauljs]

The single one may make move obvious sense in being restricted like a knee joint. The multiple one seems a little odd, but I could still see some application if it had springs and dampeners to a mostly monostable position. (Earthquake dampener maybe?)

[jaxxonad]

This would be great incorporated into a steering column. It would be super responsive. Probably would have some furious kickback tho.

[chrispysaid]

No, your design cannot rotate 360°. At most, it can rotate 179.9̅° in one direction and 179.9̅° in the other.

[BenjaminGoldberg]

The concept is the same as a rolamite bearing or a scrollerwheel bearing, but simpler.

[kjamison]

Me: “Fascinating!”
Me: <looking at the last model> mind blown

[namthainam]

All the good without mentioning all the bad... Also how is it 360° of rotation?

[urmum]

i really hope your video wins! You made a high quality video which perfectly shows something that looks like it should not work

[jurajvariny]

How can it have 360 degrees of motion? Only 180 was shown.

[Iamwolf]

These linkages may wind up having an application in MEMS-based analog computers, if not already.

[trinsit]

This blew my mind. How much stress can it take compared to the normal gear type? Limb joints on robot possibilities?

[shirleysycamore]

Love this video. I hope this video wins. You have explained it so well.

[cyberlord]

Ok I need an extended version exploring the full scope of possibilities here