Why Harmonic Drives Are Awesome.

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Today we cover Harmonic Drives, Planetary Gears, and Worm Gears.
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Notes:
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[@brunonikodemski2420]

I'm one of the engineers for the actual Lunar Roving Vehicles, made by General Motors and Boeing. Harmonic drives were used on all four wheels, and were used to be able isolated the DC brush-motors from the vacuum on the Moon. Brushes do not work well in vacuum, since they are lubricated on Earth by a thin film of water, from the humidity. On Moon there is no H2O, so the brushes turn to dust and wear rapidly. The motors and the harmonic drives were half-pressurized with a partial atmosphere, with a specific humidity installed. Garrett-AiResearch did the motor assembly. Gear ratio was about 80-to-one. Motor turned up to 19,000rpm max, but usually ran at less than half of that during actual on Moon motoring. The drives would work just fine if somebody went to the Moon and energized them, but the wheel brakes are probably locked-up now, due to vacuum cold welding, so the vehicles probably could not move.

[@dfriendperc]

Very cool! Thanks for that.

[@ivanradojkovic1705]

Why not use brushless motors?

[@godfreypoon5148]

@@ivanradojkovic1705 At the time the LRV was developed, power semiconductor technology was not what it is today. Given that, and the complexity of the required control system, brush motors would have been a better option overall.

[@Keiranful]

@@ivanradojkovic1705 Additionally, semiconductors don't fare very well in space. The ISS orbits within the Van-Allen-Belts that shield a lot of radiation and still has to regularly replace laptops because they start to malfunction. The control module of a brushless DC motor would fare similarly bad or worse.

[@snakezdewiggle6084]

So how do ISS, and satellites, continue working so long, but not laptops. And don't tell me Shielding, I'm a consulting Physicist.

[@mickeyfilmer5551]

I have to say Jeremy, you are a brilliant example of a self taught engineer. You have conveyed so much info, in such easy to understand format, that I am sure (and hope) you have inspired dozens, if not hundreds of young people to take up engineering- especially robotics - as a career. I'm and old school engineer, who learned my trade "at the bench" mostly, but nowadays KZbin is a big factor in teaching people. Keep on doing what you are already a master at- and I am sure many more young potential enginners will get the inspiration and confidence- just because of you - to take up this subject as a either a hobby or a job. Well done Sir!!!

[@robert5]

Jeremy, you are a brilliant example of a self taught engineer.... And, this is why Jeremy's videos are so appealing to me and all the other "backyard" engineers. Watching Jeremy expands my realm of what I think I can do. LOVE watching what Jeremy does.

[@BeginnersLuckGarage]

Why does he not have millions of subscribers? Amazing Channel for engineers and inventors of all ages. PLEASE SUBSCRIBE!

[@esrAsnataS]

Kids don't realise how lucky they are to have people like Jeremy teaching them engineering. I'd have sold one of my brothers kidneys to have this when I was younger.

[@raav2878]

it's not too late. it's never too late.

[@The_Flying_Yeti]

And then still, Most of them would rather watch some idiot dance on tiktok 🤣

[@OsoMagna]

Absolutely agree. Fesz electronics, Eddie Woo mathematics are 2 other examples. One can self-educate now. I wish some forward thinking university would step up to coordinate areas of study built around these and other online resources, and then certify students that successfully test-out on those areas of study.

[@WesMacaulay]

If your brothers are still alive, there’s still time to sell their kidneys on eBay 😂

[@cdoublejj]

STFU and square dance! we are are learning long division today kids!!!!

[@ladamyre1]

One of my favorite uses of the planetary gear-set is the Sturmey-Archer 3 speed bicycle hub patented in 1903. It used ratchets to give an underdrive, one to one and then an overdrive giving the bicycle 3 speeds. Later a coaster brake was incorporated into the mechanism eliminating the need for a separate brake mechanism for the rear wheel. However, being a retired ASE Master Technician who ended his career as an Automatic Transmission specialist, my absolute favorite use of planetary gears is in the 700-4R/4L60 & 75 transmissions used in GM vehicles in the 80's, 90's and 2000's. Unlike all other 4 speed overdrive automatic transmissions, the 700-4R design, which continued in the 4L60/75 transmissions, uses only two planetary gears to achieve 4 forward speeds and the requisite reverse gear. All other automatic transmissions used a 3rd planetary gear-set to get overdrive. It's one of the tightest and most compact automatic transmissions ever designed and it was a huge success, once all the bugs were worked out, most of them lubrication issues.

[@brunonikodemski2420]

I have a GM 2500 van, which has a 4/80. I often wondered if it had a secret gear. Its a 1995, still works well, easily repairable. Love the van, put a Positraction into it, works in hail, sleet, or snow, and it may very well outlive me. I intend to be buried in it, one way or another. Wife says no way, but kids want it anyway.

[@billynomates920]

so that's how they work! always wondered about that as a kid but haven't even thought about sturmey archer gears as an adult. if you want a busman's holiday - precision transmission is back up and running on youtube - i think the guy has spent 46 (might be 48 now) years servicing automatic transmissions and watching him go through an 4L60E is something to behold!

[@ryszb]

Worm gears can be quite precise at high reduction ratios, but it comes with a price of small teeth and low max torque for the size. Gears like that are often used in telescope mounts.

[@JeremyFieldingSr]

Thanks for sharing.

[@carneeki]

They can be used in high precision applications like rotary tables on a milling machine where the worm is mounted in an eccentric and "cammed in" to the gear, which is how the output can also be disengaged for quickly setting up the rotary table. It won't eliminate the backlash, but it can be minimised. Typically you would only operate the input wheel in a single direction and clamp the output so the part being milled won't be shaken about in the backlash.

[@ryszb]

The backlash can theoretically be (mostly) removed by creating a ball worm gear (similar to ball screw). It should offer reduced backlash and higher efficiency compared to normal worm gear. I found some patent applications and prototypes, but no finished product. I guess it is too complicated and expensive fot it's performance or there are some other downsides to this design. Regardless I like this concept ;-)

[@gljames24]

I need a stepper reduction for an optical system and someone already mentioned a worm gear system so I'm glad to see that confirmed. Thanks!

[@jasonpatterson8091]

Harmonic drives are coming into vogue for mounts - there are half a dozen new models introduced recently because they're so compact and lightweight compared to worm driven mounts. The torque is high enough that they often don't need counterweights at all.

[@Scriven42]

You nerding out over taking that gear apart is pure joy.

[@jimsvideos7201]

Fun fact, big radial aircraft piston engines often had planetary gearsets on both ends of the crankshaft. The prop gearbox reduces the speed to keep the blade tips subsonic and the supercharger gearbox increases speed.

[@notsam498]

Makes sense, auto transmissions are often the same. An old school automatic 4spd transmission is essentially multiple sets of planetary gears that can sync up in different ways to give you different drive ratios.

[@dirtapple1716]

Hey there, I'm an IT manager at a construction company, all of our cad guys use the space mouse, and the keyboards/mice. I am just starting to deploy windows 11 to our machines. Had a guy who was having the weirdest issue with the photos app, where it would just crash when trying to open a photo. My guys couldn't figure it out, so I stepped in; the faulting module was the space mouse driver! So keep that 3dconnexion software updated.

[@Chris-bg8mk]

I was doing robotics at Carnegie Mellon in the late 80's and early 90s and I do like strain wave gearing as well. I would propose a slight revision to your description of precision. You seem to equate it to a lack of backlash. I'm sure you know this is a gross oversimplification. We were trying to do some very high precision work over long distances and this magnified the imprecision of the strain wave gearing. It turns out that due to the mechanical drive of the flex spline, there is a tiny sinusoidal error added to the output, in addition to the gear ratio function. We were measuring the input and output positions very precisely with resolvers and could characterize the transfer functions of each gearbox. Love this series Jeremy, THANKS!

[@JeremyFieldingSr]

Indeed it is a over simplification, but I still think appropriate for the conversation here. The series is a introduction to the gear types and why you would generally choose one over the other. There are many exceptions and what ifs to each gear type that would have been way too much for this series. Thanks for the input here. I love it when experts add detail and value in the comments. We all learn from each others experience that way.

[@htnowpro]

Thank you Jeremy, I need over simplification 😂​@JeremyFieldingSr

[@GunnerViggoNissen]

Very interesting and no unnecessary talk. I am impressed with the content. Thank You!

[@davidbwa]

Interesting. Thanks. And thank you for clear, no nonsense explanations with no 'background' music competing with your voice and no jerky video / needless transitions. .

[@bowieinc]

Who else goes ahead and clicks “like” right at the start because you know you won’t be disappointed and don’t want to accidentally forget to support Jeremy?

[@TheSilmarillian]

Hear you.

[@marko5766]

Not an engineer here, my usual method for disassembly of something new is brute force & ignorance. It warms me to see an experienced engineer use the same method! :)

[@markuscamenzind5510]

i never use brute force, i just use a bigger hammer and if the hammer doesnt fix it,your problem is electrical

[@theeucguy]

In a bicycle hub gear system, several types of gears are used to facilitate smooth and efficient gear shifting. The specific types of gears typically include: Planetary Gears (Epicyclic Gears): This is the most common type of gear used in hub gear systems. The planetary gear setup consists of a central 'sun' gear, multiple 'planet' gears that rotate around the sun gear, and a 'ring' gear that encircles the planet gears. This arrangement allows for multiple gear ratios in a compact space within the hub of the rear wheel. Sun Gears: These are the central gears around which the planet gears revolve. Planet Gears: These gears revolve around the sun gear and are mounted on a movable carrier which rotates them around the sun gear. Ring Gear: This is a large gear that encircles the planet gears, typically fixed to the hub's casing. Clutch: A mechanism used to engage or disengage various gears to achieve different gear ratios. Shift Ring: Used to change gears by moving the clutch to engage different combinations of these gears. Hub gear systems are enclosed within the rear wheel hub, protecting the gears from dirt and moisture, leading to less maintenance compared to traditional derailleur systems. They offer a range of gears suitable for various riding conditions and are particularly popular on urban, commuter, and utility bikes.

[@tonyrobinson1623]

E-bike motors are starting to use strain wave reduction gears. They allow a much smaller form factor and reduced noise from gear lash while coasting. Unfortunately the motors that use them are not as efficient with their use of battery power. I don't know if this is related to the strain wave gearing.

[@Redbonegapeach]

My favorite part was watching you take apart the gear box for the first time, with real live reactions 😂. ❤

[@matthewweaver1123]

I used to work in a printing facility, and was part of a crew that worked on a Heidelberg Harris m3000 printing press. There are some really really neat things about different parts of the press, but like you, one of the things that fascinated me the most was the harmonic drive used to set timing in the folder. It's been years so hopefully I'm remembering the details correctly, The cutting cylinders and delivery fans were driven by a 40 ish horsepower motor. The cutting cylinders were driven directly by the motor. The belt that drove them then continued downward and wrapped around the outer ring of the harmonic drive and the fans were attached (through additional gears and shafts) to the cup side, the eccentric side was coupled to a small motor that would freewheel when timing was good and rotate it faster than the ring or slower than the ring when timing needed adjusted which would advance or retard the fan timing relative to the cutting cylinders. Seeing the gear train and the harmonic drive opened up for maintenance was quite impressive to see in my early 20s. Thanks for doing this video. Very cool

[@theantasist]

Thanks for taking the time to disassemble the planetary gears. Great video!

[@StubbyPhillips]

Regarding the Space Mouse, *ABSOLUTELY!* Having it on my viewport camera *_(NOT the model!)_* is an absolute MUST HAVE now. It makes it SO easy and SUPER FAST to zip around and view things from anywhere in 3D space. It's also really satisfying to just fly around using a 6 axis controller. Also try it with Unity and Unreal and Google Earth and Elite Dangerous and... I see people doing things in 3D without one and feel a little sad for them.

[@tracyrreed]

I attended the SIGGRAPH conference in Las Vegas in around 1991 or so and saw one of these for the first time. The hardware was ungodly expensive back then. The concept disappeared for many years and only recently seems to have turned up again.

[@TheCynical0ptimist]

Very cool! I watched this through the lens of an amateur astronomer where these gear types are used in robotic telescope mounts. Most of the consumer grade mounts are worm gear and belt based, but there's a lot of excitement around harmonic drive based mounts that are coming onto the market, especially for lightweight, portable setups. In either type, terms like precision, backlash, and periodic error are important to consider, especially for astrophotography where sub-arcsecond pointing precision is often needed. Thanks for the awesome videos as always!

[@cornpop7805]

I used to work for a manufacturer of industrial robots. So, I have replaced many gear reducers, including harmonic, rotary vector, cyclonic, and another antiquated type I can't remember. We only used harmonic on the minor axes of small robots. Once you get to 6kg capacity robots, the major axes are RV (rotary vector) reducers. On 50kg capacity (and above) robots, no harmonic reducers were used. From there up, we used RVs. I know this is true for the two major Japanese brands. I'm not sure what the European manufacturers do.

[@JeremyFieldingSr]

That is consistent with what I have seen as well. I had one on my desk as you saw but didn’t mention it was used in robotics.

[@CatNolara]

Never heard of RV reducers, really have to look those up. I heard Harmonic Drive reducers have issues with longevity, the flex spline tends to break in the roots of the teeth at some point. Edit: seems like those are the same as cycloidal drives, right? Didn't hear them called that before, but I am familiar with those afterall.

[@cornpop7805]

@CatNolara Look up a KZbin video called "The Nabtesco RV Principle". It will give a description and animation of its operation. I understand them a bit better than this video can describe, but it's too difficult to describe with words. Hopefully, you get the concept through the video. There is nothing flexible within this drive (gear reducer). This is precisely why I have replaced so many of them. If you put the wrong grease in them, everything shatters. This is because there is maybe 0.0001" of clearance between the sprockets and the pins. Thicker grease creates too much interference, and things shatter. Contrary to what the video shows, the pins don't rotate along their axes. All the pins are mounted stationary to the outer plate. For some reason, the video shows all the pins rotating around their own axes.

[@oasntet]

@@cornpop7805 Seems not terribly difficult to grok; it's much like a strainwave gear, but instead of deforming the cup to engage teeth, it uses a cam system to move the inner gear. And those cams can be very beefy and spread the load out across many bearings, rather than just the point load behind the teeth.

[@cornpop7805]

@oasntet I suppose you could call them "cams", but I see them more as sprockets. But, instead of the rollers being attached to chain, the rollers are replaced with rigid pins. Also, there are 3 sets of sprockets, each running off center (eccentric) on their own bearings. The three sprockets are timed 120⁰ apart from each other. The sprockets are not all on the same plane, they're kind of stacked, in reference to the center input shaft. The output is basically the body of the reducer, which is the largest casting. The smallest RVs have two sets of sprockets. Regardless of how many sprockets, each sprocket only pushes on one pin at a time. The output is always fairly low speed, but high torque. There is actually double reduction, the input gear to the sprocket(s) ring gear, and the sprocket(s) to pin reduction. There is significant backlash between the input shaft and ring gears, but that backlash is mitigated by the final gear reduction. The resulting total backlash of the reducer is usually less than one arc minute (1/60⁰). Some are as low as 1/180⁰.

[@ChimeraActual]

Great video as usual! I had a 1964 flat windshield Chevy van, final drive geared for around town. I turned it into a camper and wanted to reduce RPMs for use on the highway. I could have installed a lower geared rear end, but I found a 1957 Chevy overdrive transmission first. It essentially snapped into place, all bolts and controls were identical to the original. Chevy saving a buck, updating was anathema. The point? Inside the OD transmission was a two speed planetary gear controlled by a solenoid, you pushed a button to shift into OD, and it worked for each gear. Six gears! unfortunately the lower gears were almost duplicates, still, it was useful on a snowy or Icey road. It also had a freewheeling clutch in the transmission. After first gear you didn't need to clutch to change gears! Great for learning how to double clutch on the downshift. In hilly terrain it gave surprising fuel economy. Power up the hill for volumetric efficiency, off throttle to coast down with the engine idling. It also had a cable to lock out the freewheeling clutch, very important on longer descents, the brakes were barely adequate.

[@gregweinfurtner7774]

Your explanations are so clear and educational with the gearing and at nearly 70 yrs old I've seen a lot of mechanisms. Love yer channel! I bought this hand operated chain hoist, which I will try to explain is one such type of ratio in a chain form. I was so excited once I discovered how it worked, I showed my daughter. She said, "oh. that;s nice" and walked away... ha ha! I bought a hand operated.chain hoist (with a loop of single chain) which had a top solid pulley with two parallel chain link depressions in the circumference. The one side has 10 link depressions and the other has 9 depressions, i.e. 10D or 9D.. (There is a hook on this pulley that hooks to the rafter or whatever.) These depressions fit each chain link. So, the hoist chain is able to turn the pulley with the 10D or the 9D pulley is in the single loop of the chain. Every time the pulley turns once, the chain is tightened up or loosened depending upon the the direction the chain is pulled. The ratio is 9:10 or 10:9. And idler pulley connects to the load with a hook and rides in the chain loop.. I was so amazed by that old technology that I had to buy the thing at a junk shop. I went home and immediately geeked out and took it apart to see how it worked!

[@kyleeames8229]

9:02 Wow! The confidence on display here is remarkable. Yeah, you were hesitant to begin disassembling it but you’re not even organizing and labeling all the parts as you remove them! I recently helped my brother disassemble his desk fan for maintenance and cleaning. Labeled every screw, bracket, etc. I was absolutely terrified of losing parts or reassembling it incorrectly. I’m sure glad I did it though. He was considering buying a new one and the last thing we need is more plastic in a landfill.

[@f.k.burnham8491]

Jeremy- You are a great teacher. Thank You for all the effort you put into these videos.

[@matthewlazaric3543]

Just came across your channel, the enthusiasm you have is infectious. Very good video

[@samwillard5688]

Fantastic view of the harmonic drive; I have been wondering. Good to see you.

[@teresaellis7062]

I am SO glad I found your channel. I need to show this to my son. He loves working with mechanical items. This video will make him so happy! I try to follow along with what he says, but my goodness, a lot of it goes over my head.

[@jimharmon3404]

Well Jeremy your explanation of harmonic drives really resonates with me. You are very well-spoken, organized, and clear with your explanations. It was a pleasure to learn from you. Mind you I am long retired so this is not my first rodeo. Now I want to get myself a harmonic drive to play with!

[@gregben]

Superb! Really enjoyed every word and the videography and demonstration.

[@azyfloof]

My first encounter with a strain wave gear was, of all places, in a Lego Technic motor. Part 2986. It was part of a multi model kit that came out in the early 90's I took the motor apart cause I was fascinated by how small it was (I think to this day it's the smallest motor to be produced by Lego) and was amazed by the TINY coreless motor and microscopic gearing. it was fantastically engineered!

[@rodin4429]

Love your videos. Your enjoyment in it is shared and spills out in every video. It's not often I mention the sponsor used in a video, but 3DConnexion Space Mouse is amazing. SOme years into using one, I just can't believe everyone isn;t using them ( I am sure 3DConnexion thinks the same - LOL)

[@FrankBenlin]

I love my Space Mouse. It's as close as you can get (right now) to having your hands on a digital model. Thanks, Jeremy.

[@ryanvanderpol7962]

Dude, sweet video! Love it, thanks for making and sharing!

[@scruffy3121]

Nice Video, My favorite "gearbox" is the "Constant speed drive" basically two axial hydraulic pumps acting as a gearbox to rectify for older aircraft generators. That thing is just amazing.

[@brunonikodemski2420]

Toyota has now adapted this concept into their hybrid drives. It just used two electrical motors and a gear train to accomplish the same thing. The Weber State car website has amazing details about that transmission. Will replace all mechanical transmissions pretty soon, for car-like vehicles (not heavy power).

[@Thebritcoll]

Well I didn’t need to know this for anything in foreseeable future… but you are a great teacher and i really feel like I learned a lot about gears. Can’t wait for this to come up randomly during conversation at some point in the future and feel knowledgeable.

[@christophergrove4876]

🇨🇦/🇺🇸... Hey there Jeremy! In the past I've enjoyed your many vidz about electric motors. While perusing for information about gears, looked what KZbin tossed my way. EXTRA BONUS... I had already been looking at and considering the Space Mouse and so I figured I'd give YOU the affiliate click and get the 10%! EXCELLENT! I'm quite excited!!!! Cheers, bro!

[@treepop1550]

Haven't seen your channel for awhile, glad to see your progress and number of subscribers!!!

[@SGT_RPGames]

As always, I love your way of explaining everything in a way that makes it easy to understand. Thanks for making learning fun and engaging 👍

[@jimparr01Utube]

Thank you Mr. Fielding. Very good tutorial. In respect of the harmonic gearbox, I remember seeing a documentary about 20 years ago that spawned the idea of this type of reduction. Guy having drinks in a bar. Spun a coin on the bar-top and watched as it slowly tipped over doing its wibbly-wobbly thing. He noticed the rotation of the coin in relation to the bar-top surface. The light-bulb lit up. The original concept was a little different to what you have shown in this video. It was two ring gears but one of the gears had one less tooth than the other. One of the gears was tilted on its rotational axis by a cam to mesh with only two or three teeth on the other. Same idea, different implementation. 60/61 teeth = 60:1 reduction.

[@whistle3man]

I always love you videos. Very informative. Also i have used the space mouse for many years at work and i too have several at home on cad systems. Extremely useful CAD tool for sure.

[@KC-zb1ku]

Astounded, absolutely Mind expanding… your extremely comprehensive “abstract” of these gears completely opened up a tier of mechanical knowledge I had no concept of. So obviously, I’m not an engineer; but a very mesmerized and extremely appreciative (hack-mechanic) observer, Jeremy… Thank you so much

[@deanwilliamson1373]

Thank you for the content. I really enjoyed that. I will look out for more of your content

[@michaelatherton6055]

Excellent. I'm now hearing about harmonic drives in astronomical mounts and this helped emensly. They are touted as able carry more weight in a smaller form factor with little to no backlash. They are also more expensive.

[@cymeriandesigns]

When that part went flying out of the planetary gear as you disassembled it, I got a flashback to old AvE videos.

[@wnight55]

Jeremy, that lesson was so well taught. Thank you

[@raydunakin]

This was really interesting, and your presentation was excellent!

[@Hertog_von_Berkshire]

Thanks for the video. A great set of explanations.

[@chiparooo]

Very cool! Thanks for sharing!

[@greggc.touftree5936]

Can't believe I was blessed with a J.Field video this morning. Sankyuu.

[@cashenjoe1]

Very informative video, thank you for sharing your knowledge!

[@williambaldwin2047]

Watching you take apart that planetary made me realize that we have so much in common, it reminded me of the first time I took apart a Muncie 220

[@evilotis01]

how absolutely fascinating! i knew nothing about this subject, and found it intriguing. subscribed! also, you kinda look like Andre Iguodala

[@johnnickerson6522]

Thank you very much. I'm usually entertained by KZbin videos. I rarely learn something completely new. You have added to my knowledge of the world.

[@hakonthorvaldsen4263]

Ten thumbs up Jeremy. Keep imparting your knowledge. You have an ability to convey knowledge that is absolutely fantastic.👍👍👍👍👍👍👍👍👍👍😎

[@rickmiller1425]

The video of the pancake drive did a great job showing the deformation of the gear. Very cool demonstration, thank you!

[@chriscord6524]

This is the first I’ve seen of your stuff. You’re good, I love gears. I build rc rock crawlers just to learn about the lockers and trans systems. Subscribed.

[@KarlBunker]

Fascinating stuff! I'd never seen a strain wave gear before and it's amazing.

[@propertystuff7221]

Wowzers! I've never even heard of harmonic drives except as technobabble in sci-fi. But to see the real thing in motion is a thing of beauty!

[@petesteinberg9975]

Excellent job. Love your site. I’m subscribing.

[@hottractor1999]

Very interesting, i don't really know anything about the different kinds of gear you were talking about, so it was all new to me. Thanks for the explanations.

[@JeremyFieldingSr]

Great. You would enjoy the first episode more. It is an introduction to gears overall and I also talked about the most common gears in that one. It’s a better place to start this journey 😁. This video assumes you saw the first one for the basics

[@Steve_The_Ignorant_Astronomer]

I'm glad you reviewed the strain wave gearing. I'm an amateur astronomer and I've been looking into telescope mounts that are using stream wave because they can carry so much weight and the backlash is basically nothing

[@Philip-hv2kc]

Good video , problem with worm drive might be that only on tooth is taking all the forces. On a chain and sprocket for example, the forces are evenly spread over many teeth , same for belt drive. But then a problem with chains and belts is that huge reductions or increases can't be done in a small package, and change of plane axis for the rotation can't neither be done in a small package. I love how belt drived provide a clutch function by adjustment of tension during engagement.

[@CausticLemons7]

Gears are one of those great inventions that you rarely see but when you think about it you realize they are everywhere and very important. Plus they look cool spinning around!

[@Lyle-In-NO]

Hi, Jeremy. I'm an EE not a ME, but I thoroughly enjoyed this video. I have a much better understanding of these fascinating topics. Thank you for making it!

[@joels7605]

Excellent video good sir. I really like your instructional videos.

[@kevinbowker2385]

Thank you Jeremy! It's always a joy to learn from you.

[@user-yw6ws4tk1b]

Thoroughly enjoyable videos, Jeremy! The best cycloidal zero backlash drives I have seen are the Slovakian made Spinea Drives, which has a youtube channel or series of videos describing how its patented cross roller internal power transfer member works. The two cycloidal plates and pins still provide torque increase via the gear ratio, whilst the cross member greatly increases the torque available from surprisingly compact units. They are absolute beasts. Id like to see you dissect one- I certainly cant afford to.

[@porthose2002]

Love your content, Jeremy! Thanks!

[@vog51]

I hate how youtube constantly redirects you to other videos and ignores your subscribed videos on your main page. I'm glad I found you again. Great video!

[@JimPekarek]

I have a 3D Connexion Space Mouse, and can confirm they're invaluable for 3D modeling. A little pricey, but high quality and worth it. Super cool they sponsored you, and thanks for the excellent content. I'm learning a lot about gear design from this series.

[@pauldritsas6047]

Thank you Jeremy. You are a blessing my friend.

[@stefanschneider3681]

As a hobby-astrophotographer this was very interesting! Because these harmonic drives have really introduced themselves in this area. They are installed in the mounts, that's where the telescope and camera are mounted on and correct for the rotation of the earth to allow long exposures. Thus they have to be very precise, but also withstand some pressure. Because a large telescope with a dedicated astrocamera, a second little scope and camera for guiding, an automated focuser, a filterwheel etc. can add up to quite some weight. But it makes sense why they are more expensive, because as you said: The machining and the material seems to be quite unique. Thx!

[@dansv1]

I first heard about harmonic drives when reading about the Apollo lunar roving vehicle. Each wheel had its own motor and harmonic drive.

[@blahorgaslisk7763]

In a post above one of the people working on that rover talks about the motors and hydraulic drives. From the few things I remember was that the motors were brushed, and that brushed motors didn't work well in vacuum as they require some humidity in the air that lubricate the brushes. Both the harmonic drives and the motors was pressurized to half an atmosphere using some gass and a calculated amount of humidity. He wrote that the motors and the harmonic drives were probably still fine, but the brakes were probably stuck because of vacuum welding. Sounds wrong when I write it so he probably used some other words. anyway look at the comments above. it shouldn't be hard to find the actual comment.

[@RoboCNCnl]

Great video ! Love your 3D connection, I have the small one and can not work without it anymore...

[@BBQDad463]

Thank you for this video. First time I had seen a harmonic drive.

[@BooleanDisorder]

Why was I not subbed before. I love this. 😂 Always fun to find quality channels.

[@rickanna8662]

Great channel! I graduated from two famous universities with two different engineering degrees. Every time I watch one of your videos I ask myself, why wasn't I taught that in engineering school? Kinda frustrating.

[@annalievanvuuren9415]

Great presentation. Thanks

[@sams5803]

Jeremy I love your content! I am sooo happy you’re still doing this!!!!!

[@JeremyFieldingSr]

Welcome back to the neighborhood LOL. Glad to have you

[@AlarKemmotar]

I've been playing with nutating gear trains recently, and they operate on a similar principle to the strain wave gears, where a small difference in the number of gear teeth leads to large reduction ratios.

[@danielsacks7152]

Another consideration is side loading capabilities. Such as driving a sprocket. Worm gears are used in a lot of heavy-duty pto winches because you don't want the winch spinning backward when you release the clutch and disconnect the power. They still will under severe load and have a small spring-loaded band brake on the input shaft that is constantly applied that you adjust just tight enough to hold the load. The bull gears on a worm drive are usually bronze. That's why you don't pull a vehicle by the winch cable. You use the winch to pull the vehicle. There's a shear pin in the pto drive or a set pressure limit on hydraulic driven ones. Jerking on the cable of a stopped winch can strip the teeth off the bull gear!

[@warrenjones744]

You mentioned stacking planetary gears to get the desired ratio and output. Hydraulic excavator swing gears are an excellent example of that. Depending on the size of the machine there may be one or two swing drive housings with three or four stacks aside to achieve that number. Planet drives are very cool.

[@snatchbandicoot]

I have no need for this information in my brain… but I loved watching it. You definitely earned another sub from this video alone and I will have to go back and watch some of your older videos.

[@tomperkins6389]

Jeremy you are a master communicator. Thank you.

[@ottopartz1]

I took a random chance on the algorithm and clicked on the video. Your enthusiasm and way of explaining things has earned you a neew subscriber.

[@user-rm5cc1nh2w]

Well done Sir !! Thank you 😎

[@NobleValerian]

Gears are so cool. Also, I just discovered the space mouse for the first time a few months ago on another channel and I've been on the fence about it ever since. Your recommendation with the discount finally got me to pull the trigger!

[@NobleValerian]

FYI, I placed my order on the first and got it today with free shipping. That's fast! (but if you don't live in the NE, it probably won't be that fast...) Also, the trainer tool says, "Congratulations! You are now familiar with your 3D-Mouse's basic function." And while my proficiency in the placement game was high right out of the gate, I can promise you that I am NOT familiar with it! 🤣 But it is VERY intuitive.

[@kristhomas6474]

Some great information. Compared to other occupations you dont get a lot about drives or whats out there and available per application. Its hard to find what your looking for if you dont know what to look for. Thank you

[@JeremyFieldingSr]

So true. That’s why I started making these videos. I remember what it was like trying to find and learn this stuff.

[@cdnpont]

I always wondered what kind of driven gears were in a single Fanuc robot we had at work. The amount of power contained in this robot was mind blowing for it's size. Thank you!

[@davidk1061]

Jeremy, you're the very BEST!

[@volbla]

When i was playing around with planetary gear designs i discovered something that's like a mix between a planetary gear and a harmonic drive. If the planet gears are connected to more gears that mesh with a ring gear with fewer teeth than the first ring gear, that second ring will turn very slowly in a similar way to a harmonic drive. Sure enough, somebody had already thought of such a setup 😋 They're called wolfrom drives, but even finding that name was pretty hard because there doesn't seem to be many people talking about them. I don't know what exactly their pros and cons might be. One con with my own setup is that the secondary planets and ring must have a custom tooth size to properly mesh (at least to get the greatest gear ratios), so they would probably be even more expensive than a regular planetary set.

[@YodaWhat]

@JeremyFieldingSr - Also offering large ratios in a compact package is the Cycloidal Drive, which gives *wide-ranging SMOOTHLY VARIABLE ratios.* It was invented and demonstrated by an Australian mathematician, apparently in the 1980s. It operates by taking advantage of the fact that cycloids are very nearly circular in a small part of the bumpy curve, so the mechanism cuts out those parts and stitches them back together in a system slightly resembling a planetary gear set. If I recall correctly from the magazine article, a *ratio range* of at least 1600 was easily achieved, variable between a small speed increase and a much larger reduction ratio. Definitely both extremes and everything in between were easily accessible and continuously adjustable on-the-fly by way of a single lever. The unit also acted as a clutch when that control lever was pushed _beyond max reduction_ ratio. But I never saw or heard more of it, _and I want to!_ Seems to me it would make a fascinating video for your channel. Can do? Secondly: Is it really _necessarily true_ that in the Harmonic drive there has to be a _difference of exactly 2 teeth_ between inner and outer? Never more than 2, never less than 2? Because I have excellent visual imagination (including animation) and it seems to me that other _difference numbers_ should be possible, with appropriate changes to other components. I speculate that those versions are not seen because they offer ratios that are always lower than with difference number=2, so those lower ratios are achieved by re-designing the whole drive. Makes sense to you?

[@dfriendperc]

I’m no engineer but wouldn’t a more tooth difference require a smaller inner gear and thus the outside would have to flex more causing more metal fatigue? Though I imagine tooth size and overall diameter difference might make more than a 2 tooth difference possible. ??

[@YodaWhat]

@@dfriendperc - Those concerns do not apply because this is not like any drive you've ever seen.

[@user-df3tn5lm4n]

Very informative, thank you

[@shanealexander9952]

One of my favorite content creators!

[@JD2jr.]

Yo, a spacemouse sponsorship is awesome. Been wishing for one since I first saw one. Need to get them sold in big box stores so I can play around with one

[@Poult100]

Interestingly the worm drive was the drive of choice for possibly over a hundred years for telescope drives, where the telescope is made to rotate at the same speed as the earth, to effectively track celestial objects. The backlash was always a problem if the drive was reversed or if the balance of the scope took it in the wrong direction. All sorts of compensatory mechanisms, normally microcontroller motor drives that spin to take up the backlash, are used. I think the strain wave drive is finding a place in telescope drives now.

[@jdbergan]

Taking that gear apart was a good move. Really helped me visualize the concept.

[@stephengreen3566]

I learned a lot, thanks. Great video.

[@StoneInMySandal]

The 3Dconnexion CadMouse is a great tool too. I’ve completely worn out many mice, but the CadMouse just keep going. It’s perfect with the SoaceMouse.

[@ThomasSearcy-tv7vq]

Excellent! I learned a lot.