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posted by martyb on Thursday October 20 2016, @07:21PM   Printer-friendly
from the circular-reasoning dept.

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.

http://spectrum.ieee.org/automaton/robotics/robotics-hardware/sri-demonstrates-abacus-rotary-transmission

[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).


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  • (Score: 3, Informative) by bzipitidoo on Thursday October 20 2016, @08:06PM

    by bzipitidoo (4388) on Thursday October 20 2016, @08:06PM (#416909) Journal

    Conventional transmissions are only 50% efficient? Really? I'd heard the typical manual transmission in a car was 98% efficient. Automatics can be that efficient too, unless they have a typical older style torque converter without a lock, in which case the efficiency is about 80%. That's still far better than 50%.

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  • (Score: 3, Informative) by fishybell on Thursday October 20 2016, @08:40PM

    by fishybell (3156) on Thursday October 20 2016, @08:40PM (#416922)

    They mention low backlash [wikipedia.org], which for some applications is extremely important. They specifically mention electrical feedback [wikipedia.org] from the motor as a application that this type of transmission.

    That said, I've written software for robotic devices that have gear driven motors that use back-emf for position information. It worked perfectly fine without a — I can only assume — substantially more expensive transmission.

  • (Score: 0) by Anonymous Coward on Thursday October 20 2016, @08:41PM

    by Anonymous Coward on Thursday October 20 2016, @08:41PM (#416924)

    They are even better than that. See http://spiff.rit.edu/classes/phys216/workshops/w10c/car_engine/efficiency.pdf [rit.edu] for an example of freely available research.

  • (Score: 2) by frojack on Friday October 21 2016, @05:15AM

    by frojack (1554) on Friday October 21 2016, @05:15AM (#417115) Journal

    I'd heard the typical manual transmission in a car was 98% efficient.

    Pretty Close, Its actually closer to 91% for front wheel drive, 94% for real wheel drive. [rit.edu]

    Oddly, chain drive in bicycles [wikipedia.org] do reach 98%.

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