Chainring Tech
Wondering if someone could help me: I had just started reading some news article about a chainring technology that increased gear range without having a front derailleur. Unfortunately, I closed the article and now can't find it, and because it was Google news it's not in my history. It was called something like bimodal gear tech, but that's not it. I can't imagine how it worked. Did anyone else see that article?
EDIT:
Apparently you can see even Google news history via: https://myactivity.google.com/myactivity
The article of interest is: https://newatlas.com/bicycles/binary-gear-bottom-bracket-gearbox/
Posted Jun 10, 2023, 3:54 AM UTC · edited
01
Instead of a front derailleur, it has a planetary gearset inside the bottom bracket that works like the Sturmey-Archer internal gear hub that gets engaged via a cable pull.
Unengaged, you are making the chainring rotate 1 revolution per crank revolution. Engage the internal gear hub with a cable pull, it switches the chainring to be driven through the planetary gear and cause it to rotate 1.25 revolutions per crank revolution.
How the Sturmey-Archer hub works: https://www.sheldonbrown.com/internal-gear-theory.html#trends
At the center of these gearboxes are the planetary gearset: https://en.wikipedia.org/wiki/Epicyclic_gearing
Planetary gears are also used in car transmissions and many other applications.