The Möbius Gear | Hacker News Reader

The Möbius Gear

robotics.eecs.berkeley.edu

164 pointspmjordan21 comments

I was trying to view the description of the entire process (using this link http://robotics.eecs.berkeley.edu/~ahoover/CS285/FinalProjec...) but I get a 404 error.

I don't know if this is only for me, but I found a report regarding this project here

http://www.cs.berkeley.edu/~sequin/CS285/PROJ_06/A_Hoover/AH...

I like this quote from the conclusion:

"The most important lesson to be taken from my experience with this project is that no single tool is suﬃcient to solve a reasonably complicated engineering problem"

"SLIDE proved to be diﬃcult because adding additional sweeps to the existing ﬁle began to cause SLIDE to crash."

"In an ideal world an open standard interchange format that allows users to move between diﬀerent modeling packages, leveraging the strengths of each to solve complex design problems, would be available and implemented by all major modeling packages." That was interesting to read in the article. Having never worked with solid works or Slide, it was nice to be made aware of the issues faced in that field of work.

But I want to see it turn!

Have a gear cube as a consolation prize: http://www.youtube.com/watch?v=qfspDCpVDTw

Agreed. Video or I say it doesn't rotate!

Second that. But I would would settel at least for more angles of this.

I'd like to know where I can buy one, I don't have access to any 3D printers and I think this looks like something I'd like to have in my office.

Looks like the 'planetary' gears should be conical instead of cylindrical?

I saw the leading photo (no supporting text) on a disreputable image board last week. OP was asking what it was, everyone else was getting their minds blown. I went right to Google, typed "mobius gear" and found out.

The image did spur a few mental gusts but seeing it here a few days after seeing it there... mind blown.

What are the applications of this? Or is that a blasphemous question to ask?

I know that Möbius strips have applications in real engines. Fanbelts for example are möbius strips because they get worn equally over the whole surface that way.

Perhaps there could be a similar use case for a gear like this,but I have never heard of any.

Usually gears have a prime number of teeth on the cogs involved if possible, and different prime numbers at that.

This ensures that wear is even which helps with the longevity of the parts and also ensures smooth-running as there will be no uneven wear on one part of a cog. Another side effect is to spread oil evenly across all teeth in a reasonably short running time.

I cannot see how a mobius gear would offer any significant benefits over this. Most cogs are already machined to fit each other neatly, and the problem with fan belts (uneven wear) doesn't really apply to gears.

Why would a prime number of teeth be beneficial? Every full rotation, all n teeth should have the same amount of wear.

It's a cool insight that I just learned, but if the two gears share a multiple, then the same teeth will engage with each other over and over leading to uneven wear pattern. If the gears are relatively prime (e.g. 6 and 17) then each tooth will touch each other tooth before repeating the cycle.

Try it out on a piece of paper and see for yourself (that's what I did).

http://en.wikipedia.org/wiki/Coprime

Presumably the desired condition is that gcd(n,m) = 1 (the number of teeth be relatively prime) so that each tooth of one gear meets with each tooth of the second gear, cyclically. If there are variations/defects in teeth, this might help them wear more uniformly.

In an ideal world every tooth on the gear is exactly the same, but in the real world they have slight differences that wear each tooth differently. So by having a prime number of teeth, the teeth of two gears don't mesh with the same teeth on the opposite in a short repeating pattern. The gear teeth wear more evenly this way and imperfections are worn off over time instead of worn in.

I'm not saying that it doesn't exist in perhaps specialized applications but ... I have never ever seen an automotive fan belt that was a möbius strip. Older cars (and other belt driven machinery like drill presses and band saws) use v-belts and newer cars use serpentine belts. Having installed new belts in both my older and newer cars (as well as the drill press and band saw in my shop) I have seen exactly zero that could be called möbius. In fact, I don't recall seeing one at the parts store that was möbius. In fact, now that I think about it a serpentine belt comes in contact with rollers on both faces anyway and would not have to be möbius to wear more evenly.

I don't know where you're based but they were never common in the USA, and where they were common they have since been replaced by modern materials with a clear inside and outside and no twist.

There have been several technical applications for the Möbius strip. Giant Möbius strips have been used as conveyor belts that last longer because the entire surface area of the belt gets the same amount of wear, and as continuous-loop recording tapes (to double the playing time). Möbius strips are common in the manufacture of fabric computer printer and typewriter ribbons, as they allow the ribbon to be twice as wide as the print head while using both half-edges evenly.

from http://en.wikipedia.org/wiki/M%C3%B6bius_strip

Reply on news.ycombinator.com