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As soon as SRI explained how their new Abacus transmission worked, we were absolutely sure that it was cool enough to share. In a nutshell, here's why: It's the first new rotary transmission design since Harmonic Drive introduced its revolutionary gear system in the 1960s*, and it might give harmonic gears a literal run for their money.
Harmonic gears are great, but they're also super duper expensive, because they require all kinds of precision machining. Alexander Kernbaum, a senior research engineer at SRI International, has come up with an entirely new rotary transmission called the Abacus drive, and it's a beautiful piece of clever engineering that offers all kinds of substantial advantages:
The Abacus drive (named because it has components that look like the beads of an abacus) is what's called a pure rolling transmission: there are no parts that rub or slide against each other (like gear teeth), only parts rolling against other parts. Rubbing and sliding result in wasted energy, and in fact, conventional transmissions are typically only 50 percent efficient. Kernbaum says that Abacus has an efficiency "in the high 90s," a massive improvement.
[Video]: SRI Abacus Rotary Transmission [Javascript required]
* Harmonic drive gears are based on an ingenious mechanism known as a strain wave gear, which was invented in 1955 by a prolific engineer named C. Walton Musser (his other numerous inventions include the recoilless rifle and the ejection seat).
(Score: 0) by Anonymous Coward on Friday October 21 2016, @08:06PM
Yeah and I find this part rather hard to accept:
The physics of most electric motors generally dictates that the motors are happiest when they’re spinning very fast. Unless you want to use them to simply spin a thing very fast, you’ll need to add a rotary transmission that can convert low torque, high speed rotation into higher torque, lower speed rotation.
ORLY? Is that why diesel electric locomotives use electric motors instead of transmissions for high torque low rpm?
https://en.wikipedia.org/wiki/Diesel-hydraulic#Diesel-mechanical [wikipedia.org]
Diesel-mechanical propulsion is limited by the difficulty of building a reasonably sized transmission capable of coping with the power and torque required to move a heavy train. A number of attempts to use diesel-mechanical propulsion in high power applications have been made (e.g., the 1,500 kW (2000 horsepower) British Rail 10100 locomotive), although none have proved successful in the end.
In contrast diesel-electrics can easily handle much higher torque levels.
But I suppose it's in the context of servos where precision in movement/position is important. But I wonder how much torque can this "abacus" design handle in practice? The contact area good enough?
They mention robotics but there are other approaches - like robots using direct-drive motors (with the motors acting as sensors too):
http://www.ghostrobotics.io/minitaur/ [ghostrobotics.io]
https://www.youtube.com/watch?v=_YrWX9ez3jM [youtube.com]