It's not every day that you can come up with an improvement on a tech that's remained mostly unchanged for the better part of a half a century, but that is what the folks at the research institute SRI International appear to have done. Their new Abacus transmission is quite likely the first new rotary transmission system to be designed in 50 years.
Designed to translate the low torque, high speed rotation of a typical electric engine into a lower speed, higher torque rotation, this transmission—dubbed the "Abacus drive"—uses a series of beads that roll in and out of indentations built into the machine's outer ring. One of the project's chief engineer's explained the system in detail to IEEE Spectrum:
The other main solution to this problem are "harmonic gears," first patented in 1957, which use an elliptical disk inside a metal ring that flexes, which then interacts with another metal ring using a series of teeth:
The Abacus drive, named for the shape of its not-quite-ball bearings, offers a number of advantages over harmonic gears, chief of which is that its internal components only ever roll across each other. This generates much less waste heat and friction than harmonic gears, which flex and have teeth that crash against each other, making the Abacus more efficient.
The idea of manipulating ball bearings through the use of precisely machined grooves is not completely novel; it's the same trick we've seen at work in some brilliantly-designed greaseless bearings. But this new application proves that there's always room for innovation, even if you think you've got everything figured out.