Harmonic Drives explained 

Your setup was so clear that it was immediately easy to comprehend. Good teacher.

A possibly belated, but no less heartfelt and sincere thanks for taking the time and effort of making this absolutely EXCELLENT video. Explaining a complex subject matter in a VERY clear concise and approachable manner. It is in my opinion "pearls" like this video that makes Y.T. worth while. Best regards.

That's the best explanation I've seen so far. Took a good deal of effort to setup.

For years I have wondered how robots with compact reduction gear assemblies were able to work without backlash. I had always assumed there was a sun gear assembly inside, so it never occurred to me it was a "harmonic drive", which I heard of but didn't grasp the meaning. I learned so much today and it was awesome. Thank you very much, I needed that! :)

Man i wish i had a teacher like this guy, school woulda been great

Super great explanation. One would think that the flex spline gear would fatigue over a short time, but they're so widely used in so many applications that it must not be an issue. Thanks for the great video demonstration!

Great explanation. Now I understand the mechanics behind my new telescope mount drive. Very impressive!

I have never even heard of these mechanisms before but I'm super glad I stumbled on this video. That was fascinating!

I had a great “Ah Ha” moment about 6 or 7 minutes into the video. I’m a now retired electronics technician who used to work in the production of printed newspapers. Equipment from a company called Ferag used harmonic drives and when we were trained on it the instructor told us what it did but couldn’t explain how it did it. To him it was a magical engineering marvel. In the years that followed we repaired them quite frequently. Usually the Flex Ring would crack and we disassemble the unit and replace it. I had a fair understanding of how it worked after working on them but you, my friend, brought it all together. I’m going to forward your video to my former coworkers who still have to deal with it. I’m sure they’ll appreciate it. Thank you.

Easist tutoial that I 've ever got.

Zero backlash & fixed timing... 2 great attributes for a gearbox... 🤨 a lot of people don't realise just how important backlash , or rather lack of it , is.. anyone with a milling machine who trys climb-cutting better have NO backlash in their table feed... 😰 Great description, the use of the straight racks initially helped greatly to understand the theory behind these rather exotic & quite expensive units... 🤗 😎👍☘🍺

goes from stories and anecdotes about harmonic drives to explaining them at 2:00

I've read how this drive works multiple times but never were able to visualize how it works. It was a mystery to me up to now. Great teacher!

Shared this video to my robotics class. Far and away the best video explaining how these drives work from the 5 I watched before this.

Hands down ...the best video I have seen on harmonic drive.

WOW What an amazing explanation. Thank you so much.

In the '70s, as a 12 year old, I had a Visible Wankel Rotary Engine model which was driven by a planetary gear harmonic drive. I always assumed that this was how it worked, I was never sure until I saw this.

We use these drives in our surgical robots. Love the clear explanation and linear props to illustrate the basic physics. Thank you.

I understand it immediately after your demo with those straight gear. Very clear explaination.

I finally understand harmonic drives. In 12 minutes. Man that's stellar.

Considering buying a telescope mount that works on this principle and wanted to understand it. Your video helped a lot. The advantage of very low backlash in astronomical mounts is significant, as well as the reduced need for counterweights on the mount. Thanks very much.

I work for Harmonic Drive and it really doesn't surprise me that these things last. Much care an precision goes into making these.

I subscribed because you talk slow enough for someone to follow what you are saying and you leave the video on what you are showing long enough for the viewer to follow it.

Best harmonic drive mechanical explanation I've seen (out of at least a dozen I've come across)

Wow, you're a great teacher, your video is terrific and I now know something completely new about gear drives. Years ago I got a fanuc welding robot arm and was amazed at the zero backlash on the joints but never knew why it was possible until now. As for how to get 2 more teeth with the same pitch, it's hits me now that the outer ring is naturally LONGER than the inner one, hence can have 2 more teeth in its' path. However, sizing up the tooth depth to accomodate the mating, etc is a challenge.Thanks for this explanation and I'll look at more of your videos in the future.

man this was a perfect explination, very good job! amazing drive motor design... the minds that come up with these things

They are starting to be used in astrophotography-mounts, that’s how I got interested in the topic. No backlash is the magic that‘s so important in this area. Great explanation, that’s why they are so,expensive

Brilliant explanation, thank you for the clarity! This concept is really flexible (pun intended!)

Very clear, well done, finally grasp it thanks to the linear version. Thanks!

You Sir defogged my mind in 12 minutes on harmonic drives, THANK YOU.

To everyone wondering if you can use spur gears on the bearings instead of a flex spline, the answer is: yes. I was curious about this as well, so I drew up a harmonic drive in Fusion and 3D-Printed a model that uses entirely 3D-Printed parts except the bearings, which are fidget spinner bearings. My tolerances leave a lot to be desired, which may hide the reason for using flex-splines instead, but it is a fully functional gear reduction that uses spur gears all round and no belt/compliant mechanism.

Thanks for the explanation. When I took aircraft maintenance our instructor had us make our own vernier scale using two pieces of paper with marks on their edges. It opened our eyes to the concept of a vernier scale. Later we had to manipulate a vernier coupling to change timing which was very simple for us. This differential of gear teeth I instantly understood from that course I took over fifty years ago.

This is the most amazing and useful video i have seen in a long time. Thank you for explaining this. I was really struggling to understand exactly how it works. You are an awesome teacher.

I can't thank enough to the person explaining very beautifully the concept of harmonic drive so good video ❤️❤️ love it it just instantly clicked in my mind how the mechanism works after seeing the demonstration

This was fascinating. I've seen it explained a dozen or so times but this is the first time I've actually understood it. Thank you!

thank you for an excellent 👍 class, I have never seen a harmonic drive in rl, but now I know what it is. greetings from Cape Town South Africa.

This is the clearest demonstration and explanation I've seen in a long time. Thank-you.

Thank you for the clear demonstration of the harmonic drive!

Terrific illustration. Thanks for posting the video.

It looks like a perfect job for a wire EDM machine. Great explanation. Thank you.

I appreciate the clear explanation and effort of building the demo rigs.

This is an excellent video . I was having serious difficulty understanding this drive and your explanation brought it all together for me. I commend this instructor profusely.

This is the best explanation of this mechanism I've ever seen. Thank you!

The best explanation of this drive. Point! Greetings from Munich, Tom.

Superb video! Thank you! Now I know why grease for our Yaskawa robot harmonic drives costs quite a dollar. Thare is a company Harmonic drive, that is making everythig around this technology.

I have heard of this but had never had an explanation. You provided a very good explanation.

This is how the Sumitomo Cyclo drives work. Very interesting and well done

OMG THANK YOU… this actuator type has been _wrecking_ my brain for the last two weeks!

Best explanation I've ever seen!

New subscribers earned ! Much love from 🇺🇸and 🇨🇦

Amazing explanation. Thank you very much.

Love it!!! I need to make some of these but specialized use.

Thank you! Wonderful demostration!

Thank you very much for a very simple explanation of strain wave drives. One of the newer places that these drives are starting to be used is in astronomy, more specifically astrophotography. Astrophotographers are always looking for lighter weight, more powerful, more reliable and less power consumption in their gear, since often time hobbyist astrophotographers are out in the middle of some open field, far away from any power. For the most part, telescope mounts fall into two categories, Alt/Az, or Altitude Azimunth and EQ, German EQ which means German Equatorial mounts For astrophotography, EQ mounts are much more common, albeit much more expensive. You can align one axis to the North Star, Polaris, and the mount will rotate around that point in the sky, and since all the stars and things in space also rotate around it, once you've selected your target, the mount tracks around the North Star, keeping the object in the center of the scope. Strain Wave drives are now offered by two companies, ZWO and iOptron. Usually, a normal EQ mount requires a counterweight and shaft to balance the load on the 'Right Ascension axis, which is the axis pointed at the North Star. Having the system balanced keeps down tracking errors. The Strain Wave drive eliminates the need for the counterweight (up to a certain payload), thereby reducing the entire weight of the mount. It also tracks better and has zero backlash, which is something astrophotographers also are interested in. So, yeah, Strain Wave mounts are coming, and they are going to be the future of hobbyist astrophotography. Because of you, I know a lot more about strain wave drives now than I did 45 minutes ago!

Fasting drive and very clear explanation thank you!

This is the best explanation I've seen. I'm wondering why use a flex instead of just smaller gears.

This is a great explanation - well done!

It's so excellently explained! God Job!

Thanks for the concise explanation. I can see that these drives have multiple applications beyond the world of robotics. As an astrophotographer who deals with backlash on a seasonal basis (ambient temperature variations) this technology would be exceptionally well suited to telescope drives. My impression is that this type of mechanism would be less prone to backlash due to temperature variation. Chhers!

This guy is a great explainer. Thanks for the video.

Fantastic explanation and the hardware was really good. I now know 'Harmonic Drive' has nothing, at all, to do with music.

You give an excellent description of how the flexspline is a wedge that aligns the stator and output gears in the model but when you go to a real world application the stator and output are no longer wedged into alignment. Obviously they can't be as they are completely different gears. This looks like a similar but different mechanism. I would like to see a model that accurately represents the Fanuc robot drive.

Sir, you are a life saver.

You explain extremely well! And your pronunciation is so clear. Cheers mate!

Clear explaination and great video. Thank you

Fascinating. Great explanation. Harmonic drives are showing up in telescope mounts and I wanted to see how they worked.

Outstanding it is Crystal clear now

Great teaching! I have learnt a lot. Thank you.

Glad to see you up and running again. Be well.

I must subscribe to the channel. Immediately and deeply attracted by the awesome demonstration and teaching. Thank you!

Great explanation. Factories replacing every year or few years would explain cheap used robots.

Excellent, thanks for taking the time to make this!

Most detailed and easy explanation of harmonic gear i've ever seen

Cool video! Wanted to buy one of these robot arms recently but than I looked at the price... Now I’ve decided to just build one!

Excellent explanation, thank you very much!

Great model and explanation.

Your explanation was very easy to understand. Thank you

Nice video! Looking at these drives I thought that instead of having the flexible gear to wedge the stator and output gears, why not have a plantetary/harmonic hybrid? It would be like a normal planetary setup, but instead of the drive going through the planet gears, the planet gears would only do the job of the flexible gear in a harmonic drive setup, becoming the wedging force to do the reduction, while transmitting the force/torque. There would no longer be a need for the traditional sun gear as in a plantetary setup, so it could be omitted. The difference in gear teeth needed for this to work as a harmonic drive could be achieved by making the outer part of the planetary drive (is it called the ring gear?), in two pieces with a different number of teeth. These two ring gears would act as the stator and the output respectively, connected by the aforementioned planet gears (which may need to be slightly elongated to allow for adequate meshing contact between the two ring gears). By using planet gears to do the job of the flexible gear, it negates the need for it to be flexible, removing the weak link. Also, if you adjust the teeth size to outer ring gear diameter ratio, you could have more than two spots where the teeth "harmonize" allowing for greater force transfer, while dispersing the load for better longevity. Just a thought...🤔

Great explanation. Thank you for the video.

Thank you for an awesome explanation.

Thanks for the informative video! I didn't know I was curious about Harmonic Drives until I started watching your video. 8)

Thank you. I learned something new today.

Best explanation ever, thank you !

Best explanation and drive model ever!

Awesome Demonstration, you wrapped up the idea in a beautiful simple was with many tools

Excellent demonstration! Thank you so much!

One more thing I never knew I wanted to know. Thanks random smart dude on the internet.

I appreciate the effort you put on to explain. Well done!

Awesome lesson, many thanks 👏👏👏

that was interesting. never heard of a harmonic drive but could see how durable and long lasting it could be. thanks for the info!

I honestly understood in the first 40 seconds great video

Oddly enough when you were talking about that invention back in the 50s that explains probably why my father when I was a child was giving me an explanation how bigger gears than little gears if depending on what's going on with speed and motion you can probably run a car at 55 miles an hour with a toy motor it all depends on how you arrange the gears and that explains what he was trying to show me when I was a child he was trying to envelope a sense of science I guess when I was a child but it took off many years later it took off thank you

The explanation is so clear and fantastic, thank you!

Amazing gears. Thank you very much for the clear explanation.

Awesome explanation. Nothing to say other than many thanks !

Cool, simple, visual, intuitive and clear explanation, to the point I can go and build my own right now, all I need is a gear pack for SolidWorks It’s so rare, that a smart person can explain own knowledge, and you are definitely more than able to, thank you BTW, I think nylon filament can be used as a flexible part, instead of a belt (without detracting a brilliance of this solution of course, coz belt is an industrial, very reliable component)

Best explanation ever!!!

This video is incredibly well presented.

Golden Channel

Excellent explanations !!!