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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: 3, Insightful) by ledow on Thursday October 20 2016, @07:41PM
Reads like a slashvertisement.
The first design might have been around since the 50's but I've never seen it anywhere useful (looks like it needs incredibly ratios to be useful).
The new design looks unneccessarily precision and complicated and looks like it wouldn't work properly under tension.
Fail to believe it's ever as efficient as stated.
A quick google says that most gearboxes are 70% of higher in efficiency, so even the summary is overblown.
(Score: 0) by Anonymous Coward on Thursday October 20 2016, @08:05PM
it looks like something out of a sci-fi movie though, pretty!
(Score: 0) by Anonymous Coward on Thursday October 20 2016, @08:11PM
Why aren't there any wikipedia links to provide additional citations beyond the rather short list on that site.
Also: it is fucking NOISY. Wikipedia does a much better job of getting the basics to you without looking all over the place.
(Score: 5, Interesting) by physicsmajor on Thursday October 20 2016, @08:45PM
So... a couple things.
First: this was just announced. Not available yet. Hard to wield the slashvisemnt card in that context.
Second: I assume you aren't familiar with this entire field. And likely didn't read or watch the video. Rotary transmissions - which are basically an inline widget to downconvert a higher RPM to a lower one - are hugely important anywhere servos/motors are in use. This isn't a new transmission for your car, it's to improve what we can do with robotics and mechanical engineering. Where they aren't, the main reason is usually cost. Which brings me to...
Third: Have you SEEN the Harmonic Drive? That's the current state of the art, and it's bonkers more complicated and way harder to manufacture than this.
It's no IndieGoGo CGI hype video either, they've got a bunch of actual demos undergoing actual testing. I've played the armchair skeptic plenty enough, and sometimes it is appropriate. From what I'm seeing here, this isn't one of those times.
(Score: 1, Interesting) by Anonymous Coward on Friday October 21 2016, @02:11AM
Why are we calling these things transmissions? They don't switch gears.
The proper term is "reduction gear", or perhaps "reduction roller" for this one.
(Score: 3, Informative) by frojack on Friday October 21 2016, @05:17AM
Variable ratio reduction gear. Tapered roller thingies do that.
No, you are mistaken. I've always had this sig.
(Score: 2) by ledow on Friday October 21 2016, @03:56AM
1) Doesn't matter. It's a commercial pre-order, if you want to be fussy.
2) I watched and read. Their previous thing is on a Mars Rover. It's a limited-scope, fixed gearing reduction that seems to use or specialise in extremely high ratios in compact spaces (basically relying on the natural motion / sliding wobble of a metal band tied around the moving gears to form the outer "gear"). Specialist stuff exists and is boring precisely because it's limited in its scope to specialist uses. I'm sure I can find an ultra-efficient motor if I spend millions of pounds, it doesn't make it interesting - same kind of thing.
3) Yeah, I saw it. It looks fancy. This thing looks fancy. Like ultra-precision-milled double-conical bobbins running in a matching cut-out around the periphery of the gearing that - one slip - and the whole thing falls apart or jams. That kind of stuff is "pretty" but also so far into the "it costs money to get it THIS right" category that it's not interesting again.
"Actual demos"in "actual testing" just means a prototype to me.
It's a cool-looking, impractical, rare-use, specialist prototype that doesn't have a way to extend it to generic use such that you'll EVER see one in real-life. There's plenty of that kind of thing about. Like most of the stuff on the Mars rover.
(Score: 3, Interesting) by frojack on Friday October 21 2016, @02:03AM
Looks basically similar to a swashplate engine found in US Mark 46 Torpedo.
https://www.youtube.com/watch?v=eRCUqcwqu5w [youtube.com]
There is really very little new in this field, but great if they can manage to make it hold up in the real world and still maintain 90% for a couple hundred thousand miles.
No, you are mistaken. I've always had this sig.
(Score: 3, Interesting) by Hairyfeet on Friday October 21 2016, @04:16AM
The rolling motion also looks like the Duke Engine [youtube.com] but as with all these things until I see them being used commonly in the field? Yeah gonna withhold judgement one way or the other. After all we've been told about all kinda of killer tech that is "just about to come out" from PRAM to multiTB holodiscs that for one reason or another just never seem to get past that prototype stage so I've found it best to just take a "wait and see" approach.
ACs are never seen so don't bother. Always ready to show SJWs for the racists they are.
(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]