I've watched and re-watched Aaed's videos on the capstan drive, it's great stuff. High speed, high torque, compliance, effectively no backlash. It's fascinating to watch a legit engineering mind at work.
Lerc · 4h ago
I recently found his videos also. It's one of those things that gets my mind bubbling with ideas for things I want to make, never enough time to do them all though (and this breadboard beside me is asking for attention)
It does make me wonder about the algorithm, Quite a lot of things I find on Youtube turn up on HN a week or two later. I'm not sure if this is an indicator of the effectiveness or failure of the algorithm. It is definitely succeeding in finding videos popular with some people and showing it to more who might share that interest. The question is, are the things I (and consequently many others of similar interests) see the best of all there is, or a subset of the excellent videos out there that happen to get noticed.
I sometimes find channels that are years old with a goldmine of good information. That suggests that there is more good stuff out there than what I see. Were they just unlucky that I didn't see them before? Am I lucky to be seeing them now? It also might be that it is not luck but the algorithm has arbitrarily decided that the video has some special factor that requires promotion or that I have passed some arbitrary threshold of perceived character development that makes me supposedly now interested in such things.
Keyframe · 1h ago
"back in the day", we used capstans to drive film (movie) rolls around the scanning aparatus. Both high speed and precise without backlash. Great stuff. Somehow I always thought maybe lack of high torque is the issue more people aren't using them or wear and tear.. but, apparently not?
DeepSeaTortoise · 5h ago
He's easily one of my favorite content creators. Ofc, there are much better engineers, domain experts or more entertaining people on youtube, but he strikes a very enjoyable balance.
I wanted to start writing a list of other tech related, pop-sci and industrial-design Youtubers I kinda enjoy, but noticed just how many channels I'm subscribed to... If there's any interest, I'll drop it, just tell me. Meanwhile I have some filtering and sorting to do.
noman-land · 28m ago
I am interested. I love these builder channels.
adolph · 3h ago
I haven't watched the one about the dog, but the one with the initial explication of capstan drives [0] was excellent. I've been dreaming about it for the last year, especially since about the same time another person started working with the da Vinci robot actuators which use cables to generate find motion.
I watched this last week and my jaw was on the floor. He's both a great technician, and he has the personality to make it interesting. He walked through his testing strategy far enough that you could understand his methodology and the thought process behind it, but didn't belabor it by making us watch it all. Banger!
AIorNot · 6h ago
Amazing presentation! - somebody hire this kid asap
I'm going to tell my 12 year old that when he leaves education he wants something like this on his personal web site:
"CARA (Capstans Are Really Awesome) is my latest quadrupedal robot, following ZEUS, ARES, and TOPS. Built over the course of a year, CARA is easily my most dynamic and well-designed quadruped yet."
abtinf · 3h ago
That would be a terrible path for someone with this extreme level of demonstrated talent, motivation, and follow-through.
Much better for someone to fund a startup run by him.
andrewstuart · 6h ago
He might be perfectly happy doing projects and YouTube.
dvt · 6h ago
Likely makes more money, too!
geerlingguy · 3h ago
For many, no; taking on lots of sponsorships, you can make a good amount of money (especially the ones where you agree to do X posts across Y social media accounts for Z period of time, essentially being fully sponsored across a large swath of life).
But for a lot of tech/engineering channels, it'd be immensely difficult to make the same salary as you could working at a FAANG or the like. (I'm making about half what I made when I had a W-2, but it's enough).
abtinf · 3h ago
Do fun projects of your choosing vs the grind of corporate life.
The former has a rather large non-pecuniary component of total compensation.
MiguelHudnandez · 1h ago
Thank you for taking a pay cut to do what you do, I'm so glad your channels exist. Also please remember to take vacations! (trade shows don't count)
sitkack · 3h ago
You just need to start selling supplements, anti-aging creams and time shares.
busymom0 · 3h ago
His current Patreon has 57 paid members. Unless he has another revenue stream, I think he'd need more paid members.
ekianjo · 2h ago
youtube ads and sponsorship are his additional revenue streams
mikewarot · 6h ago
It's amazing what he's done in terms of the robotics, and the presentation of it to the viewer. I'm amazed at the quality of cinematography on the internet these days.
The implications of the tools we now make available for use in our own personal workshops are still being discovered, and will be for some time.
srameshc · 2h ago
I remember a post previously related to him here on HN but I am surprised at how I forgot about him and how cool he is to build all these incredible stuff and also teaches in his videos. I am subscribing so that I never miss anything from him again.
mnurzia · 1h ago
Wow! I actually met Aead last week while he was printing parts for this project (we both work at the same place). Surreal to see it at the top of HN.
Why spend so much effort to achieve an "exact" gear ratio? Having more zeros does not equal to being more "precise".
Also, I wonder how resistant this mechanism is to wear and fatigue.
michaelt · 5h ago
Well, it probably wasn't that much effort. When you're 3D printing you're going to end up printing everything 2-3 times anyway, so why not dial in the ratio while you're at it?
And you can't really declare your design is "high precision" and present yourself as someone others should take transmission design advice from if you aimed for a gear ratio of 8 and achieved "somewhere around 7.9 to 8.2"
LeifCarrotson · 4h ago
It probably doesn't matter so much whether it's 7.913 or 8.186, but it would be important to know the exact value for kinematics. One way to do that is to build an object very accurately, the other is to build inaccurately and then measure the result after the fact.
It's also interesting because competing actuators with strain-wave, cycloidal, or planetary gearboxes will state exactly what the ratio is. The actual gear teeth may not be spaced out perfectly around the circumference, but the number of teeth is an integer with an infinite number of zeros.
tonyarkles · 4h ago
Yeah, I think one of the nice things about making it a "clean" number (either an integer or a rational with a small integer denominator) is that you can easily validate it without needing high-precision measurement equipment: put a mark on both gears (maybe even embedded in the 3D print), line up the marks, rotate the large gear 1 full rotation, and count the number of rotations the smaller gear makes. Check to see if the marks line up perfectly after those rotations.
throwawayffffas · 3h ago
I think it's about kinematics, the more precise your gears the better the model fits the real world.
That's why pro crews don't use gears and ropes. At high impulses deformations and elasticity throw the kinematics off what's actually happening. Modeling the deformations and the elasticity is a computational no no. Instead what you see is the motors right on the joints.
At least that was the case last time I had a look at robotics.
michaelt · 2h ago
> That's why pro crews don't use gears and ropes. [...] Instead what you see is the motors right on the joints.
The answer here, as with so many things in robotics, is: It Depends.
UR10e robot arm that can lift a 4kg object with a reach of 1m and has sub-1mm repeatability? Strain wave gears in the base and shoulder joints, 100:1 ratio.
MIT Mini Cheetah robot dog that can do backflips? 6:1 planetary gearbox.
Shadow Hand with 20 degrees of freedom? Tendon driven, with the 20 motors in the forearm to keep the fingers slim.
Little dinky Huggingface SO-101? Servo motors, integrating 1:345 gearing with a series of 6 tiny brass gears.
Mid-price CNC milling machine, if you call that a robot? Really long ballscrews, driven by stepper motors.
kragen · 2h ago
Surely you mean driven by closed-loop servos with encoders, don't you? Jacques Mattheij wrote a long post about how he ended up having to replace all the CNC machines he sold that used stepper motors because he didn't know any better at the time, and brushless motors are a lot faster and more powerful as well as not losing steps.
Joel_Mckay · 2h ago
In general, for some platforms each gear mechanism adds backlash precision loss, lower energy efficiency, and might not be back driven.
>Mid-price CNC milling machine
A ball-screw is mostly decorative on small machines... =3
michaelt · 2h ago
On the other hand, a 100:1 gearbox gives you much-needed torque if you're lifting a load at the end of a long arm, it makes your encoder 100x more precise (in terms of repeatability) and it makes your motor brake 100x stronger.
Back-drivability is the enemy of precision, so many robotic applications can do without it.
Joel_Mckay · 1h ago
Almost all modern servo driven units I've seen prefer to allow some compliance in the end effector. The UR5 and UR10 series for example can use force limiting control loops, and are safer to use around people.
The old "fast, cheap, or good... choose any two joke is mostly still true. =3
michaelt · 1h ago
The UR10 uses 100:1 strain wave gearing in the base and shoulder joints.
You’re right that it has a freedrive mode, and force control modes. But it’s a rigid, low-backlash robot with the compliance achieved in software afterwards.
Expensive, naturally, but none of the problems that come with things like series elastic actuators.
PaulDavisThe1st · 3h ago
more than 30 years ago I was writing code for a "robotic" device that used motors, directly on the joints.
the motors were so sloppy the company wasted a ton of money [0] having me write heuristics to tackle the errors they accumulated over several hours.
one of his whole points is that by using dyneema (rope), there's almost no elasticity at all in the capstans.
[0] relative to the cost of better motors
skeeter2020 · 6h ago
>> Having more zeros does not equal to being more "precise"
Isn't having more decimal places the exact definition of precision (vs accuracy)?
munchler · 4h ago
The point is that those decimal places don't have to be zeros. 7.893 is just as precise as 8.001.
a3w · 2h ago
Yet for some reason unknown to me, people get annoyed when you tell them „let us meet at 13:37. that is no more accurate than let us meet at 14:00 hours”
sabareesh · 6h ago
That was confusing part of this video . May be there are some limitation on the tools he uses to tune
dvt · 5h ago
I don't think the number of the gear ratio really matters, what matters is that you know what it actually is (since every IK calc depends on said ratio); 8:1 is probably arbitrary and/or looks nice & might simplify some stuff.
eichin · 5h ago
It might be a lot easier to check the ratio "by hand" (by counting rotations etc) if it's numerically simple. (IIRC in some earlier videos he noticed that the pulley size ratio wasn't producing the expected movement ratio, because they were built as an obvious 8:1 or 10:1 or something, and didn't match - which led to him figuring out the subtleties of the design - I can easily imagine wanting to preserve that aspect just for debugging, at that point, even if you now have correct math.)
TheBozzCL · 6h ago
Thanks for sharing this! What a treat of a video. It's a fun project, and it's presented very well. This guy has a talent for communication - the video was super clear and well explained. I really admire that ability and I want to get better at it.
heap_perms · 5h ago
Fascinating! I want to get into this type of stuff. But I have no idea where to start, I just have just a CS degree and 3 years experience as a developer.
adolph · 3h ago
I recommend a Brachiograph build. It will introduce you to some fundamentals of PWM and inverse kinematics. It is well documented but not cookie-cutter. Using a Raspberry Pi will give you more direct access to running the servos than the microcontroller experience. All the parts are infinitely reusable afterward if you don't want to keep it around.
Sample Supply List for $80 budget:
Pi Zero with header $20: https://www.adafruit.com/product/6008
Power supply $9: https://www.adafruit.com/product/1995
SD Card $10: https://www.adafruit.com/product/1294
Three hobby servos $18: https://www.adafruit.com/product/169
Breadboard wires $5: https://www.adafruit.com/product/153
Breadboard $5: https://www.adafruit.com/product/64
Glue, popsicle sticks, pen and paper $10
taneq · 4h ago
Arduinos and hobby servos. No, neither of them are "industrial grade" and yeah, you'll reach their limits pretty quickly, but building a physical thing that does stuff is (in my experience) a huge motivator.
Or if you're already all over the basics, figure out what kind of stuff you want to build and then try and build it. :)
Paddywack · 4h ago
Can you recommend where to find beginners projects that “do stuff”.
Retr0id · 3h ago
Just like the article, there's a huge amount of hobbyist-accessible projects on youtube, you can click around the recommended videos.
sitkack · 3h ago
Grab a servo and start playing with it.
yrcyrc · 1h ago
This is absolutely amazing, awe inspiring.
ZeWaka · 5h ago
Just saw this at Open Sauce last weekend! Super cool project, looking at all the gearing was fascinating.
s_dev · 3h ago
Cara is the Irish word for 'friend'. Not sure if thats what was intended or is just a coincidence.
kragen · 2h ago
Also the Spanish words for "face" (no me gusta tu cara, boludo) and "expensive and female" (esa computadora es re cara, boludo). https://en.wiktionary.org/wiki/cara tells us it also has meanings in Aragonese, Asturian, Catalan, Crimean Tatar, French, Galician, Indonesian, Italian, Latvian, and another couple dozen languages.
Keyframe · 1h ago
Male genital organ in few of the balkan languages (spelled with K), pronounced the same. So, there's that too.
mikestaas · 1h ago
> Programming takes the cake for what is both my most and least favourite part of any build. Nothing quite makes you pull out your hair and ask yourself, 'What the heck have I gotten into?' Like spending weeks programming a robot that just won't work. Eventually though, you fix that one line of code that makes all the difference. And then it's smooth sailing. Well, kind of.
I feel this deeply, also this whole video is quality content.
A4ET8a8uTh0_v2 · 7h ago
There is a weird mixture of hope and dread in me as I watch this. I am ridiculously excited over a person like me being able to mess around with something that, until recently, was gated behind, well, a lot of hard problems to overcome ( I am only now slowly getting through old Peter Scott's robotics to get some perspective ). By comparison, it should be so much easier to explore aspects of robotics that may go beyond strict math and engineering.
bmau5 · 6h ago
Why dread?
kragen · 1h ago
Land mines have been killing people by surprise for decades. Flying drones, some of them dropping land mines and others lying in wait for incoming convoys, produced 70% of the casualties on both sides in the Ukrainian invasion last year, and a few weeks ago the Ukrainians shipped some drones to near a Russian airport several thousand kilometers from Ukraine to blow up a bunch of airplanes. This betokens a future of borderless warfare in which probably most of your family members will be killed over the next few decades, by one or another type of semi-autonomous or fully autonomous weapon.
CARA is a super cool project which is never going to kill anybody, but it's another piece of evidence that the cost of the technology for such weapons has decreased enormously.
That said, talking about the dread is going to get boring fast, because nearly every story on the HN front page is catapulting us toward that future.
A4ET8a8uTh0_v2 · 1h ago
Good point. If we do press panic button each time, the word will lose its meaning. Naturally, it does not help that this particular community did happen to catapult us towards the future a fair bit over the past years.
andrewstuart · 6h ago
He’s got the magic combination of tech skill plus ability to make and edit entertaining videos.
micromacrofoot · 6h ago
I'm so excited for a smaller open source version of this, I'd love to make one. What a great project.
Ai, robots, where are we heading? Not far until ai + robot will replace humans
A4ET8a8uTh0_v2 · 7h ago
I don't think it is fair to downvote this comment. It is a genuine concern and should be addressed. Amusingly, given that the thought has entered mass consciousness by means of question on 'whether all this is a simulation', matrix ( the animated series ) explored this question a little and it is interesting in how the timeline aligns with what the movie presented.
asoneth · 6h ago
> It is a genuine concern and should be addressed.
No disagreement, but does the comment meaningfully contribute to the discussion about this particular project?
A4ET8a8uTh0_v2 · 1h ago
Fair point upon reflection.
zuminator · 2h ago
It's absolutely a legitimate concern but since this robot project has no chance of replacing humanity, it seems like a derail in terms of the subject matter of the video. It's as if someone posted a link to an incremental advancement in graphene aluminum-ion battery tech and a person chimed in with a general lament about heavy metal battery toxic waste disposal.
falcor84 · 4h ago
That's an interesting reference, but do our timelines really align with what was presented in (ani)matrix? Their timelines are quite murky, but it seems that in their universe things only started getting problematic between humans and AIs around 2090 and The First Machine War started in 2139 [0]. With how fast things are progressing, it's not clear to me that we have so much time.
On the flip side, capitalistic / private / special interests both controlling the progress and having the most ability to utilize it to further centralize power and wealth is deeply concerning. We can already see more controversial figures involved in AI using it to spread their personal viewpoints.
It feels really easy to see how our jobs/labor and therefore our capital and therefore our value in the modern system are being directly attacked by these capabilities and deeply concerning to imagine how further centralization of power could be good for the masses.
It does make me wonder about the algorithm, Quite a lot of things I find on Youtube turn up on HN a week or two later. I'm not sure if this is an indicator of the effectiveness or failure of the algorithm. It is definitely succeeding in finding videos popular with some people and showing it to more who might share that interest. The question is, are the things I (and consequently many others of similar interests) see the best of all there is, or a subset of the excellent videos out there that happen to get noticed.
I sometimes find channels that are years old with a goldmine of good information. That suggests that there is more good stuff out there than what I see. Were they just unlucky that I didn't see them before? Am I lucky to be seeing them now? It also might be that it is not luck but the algorithm has arbitrarily decided that the video has some special factor that requires promotion or that I have passed some arbitrary threshold of perceived character development that makes me supposedly now interested in such things.
I wanted to start writing a list of other tech related, pop-sci and industrial-design Youtubers I kinda enjoy, but noticed just how many channels I'm subscribed to... If there's any interest, I'll drop it, just tell me. Meanwhile I have some filtering and sorting to do.
0. High Precision Speed Reducer Using Rope: https://www.youtube.com/watch?v=MwIBTbumd1Q
1. Building a DIY Surgical Robot https://www.youtube.com/watch?v=d_8rHKrwr-Q
https://www.aaedmusa.com/
"CARA (Capstans Are Really Awesome) is my latest quadrupedal robot, following ZEUS, ARES, and TOPS. Built over the course of a year, CARA is easily my most dynamic and well-designed quadruped yet."
Much better for someone to fund a startup run by him.
But for a lot of tech/engineering channels, it'd be immensely difficult to make the same salary as you could working at a FAANG or the like. (I'm making about half what I made when I had a W-2, but it's enough).
The former has a rather large non-pecuniary component of total compensation.
The implications of the tools we now make available for use in our own personal workshops are still being discovered, and will be for some time.
Also, I wonder how resistant this mechanism is to wear and fatigue.
And you can't really declare your design is "high precision" and present yourself as someone others should take transmission design advice from if you aimed for a gear ratio of 8 and achieved "somewhere around 7.9 to 8.2"
It's also interesting because competing actuators with strain-wave, cycloidal, or planetary gearboxes will state exactly what the ratio is. The actual gear teeth may not be spaced out perfectly around the circumference, but the number of teeth is an integer with an infinite number of zeros.
That's why pro crews don't use gears and ropes. At high impulses deformations and elasticity throw the kinematics off what's actually happening. Modeling the deformations and the elasticity is a computational no no. Instead what you see is the motors right on the joints.
At least that was the case last time I had a look at robotics.
The answer here, as with so many things in robotics, is: It Depends.
UR10e robot arm that can lift a 4kg object with a reach of 1m and has sub-1mm repeatability? Strain wave gears in the base and shoulder joints, 100:1 ratio.
MIT Mini Cheetah robot dog that can do backflips? 6:1 planetary gearbox.
Shadow Hand with 20 degrees of freedom? Tendon driven, with the 20 motors in the forearm to keep the fingers slim.
Little dinky Huggingface SO-101? Servo motors, integrating 1:345 gearing with a series of 6 tiny brass gears.
Mid-price CNC milling machine, if you call that a robot? Really long ballscrews, driven by stepper motors.
>Mid-price CNC milling machine
A ball-screw is mostly decorative on small machines... =3
Back-drivability is the enemy of precision, so many robotic applications can do without it.
The old "fast, cheap, or good... choose any two joke is mostly still true. =3
You’re right that it has a freedrive mode, and force control modes. But it’s a rigid, low-backlash robot with the compliance achieved in software afterwards.
Expensive, naturally, but none of the problems that come with things like series elastic actuators.
the motors were so sloppy the company wasted a ton of money [0] having me write heuristics to tackle the errors they accumulated over several hours.
one of his whole points is that by using dyneema (rope), there's almost no elasticity at all in the capstans.
[0] relative to the cost of better motors
Isn't having more decimal places the exact definition of precision (vs accuracy)?
https://www.youtube.com/watch?v=u4Jh1daCl60
https://www.brachiograph.art/
https://github.com/evildmp/BrachioGraph
Or if you're already all over the basics, figure out what kind of stuff you want to build and then try and build it. :)
I feel this deeply, also this whole video is quality content.
CARA is a super cool project which is never going to kill anybody, but it's another piece of evidence that the cost of the technology for such weapons has decreased enormously.
That said, talking about the dread is going to get boring fast, because nearly every story on the HN front page is catapulting us toward that future.
No disagreement, but does the comment meaningfully contribute to the discussion about this particular project?
[0] https://screenrant.com/matrix-timeline-year-future-when-sett...
It's intellectually exciting.
On the flip side, capitalistic / private / special interests both controlling the progress and having the most ability to utilize it to further centralize power and wealth is deeply concerning. We can already see more controversial figures involved in AI using it to spread their personal viewpoints.
It feels really easy to see how our jobs/labor and therefore our capital and therefore our value in the modern system are being directly attacked by these capabilities and deeply concerning to imagine how further centralization of power could be good for the masses.