How this bizarre pericyclic transmission works? What makes them so cool?

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Pericyclic or nutational gears/transmissions typically consist of 4 bevel gears and thanks to their nutational motion, they provide extremely high gear ratios while also ensuring a high tooth contact ratio. This allows them to transfer high torques smoothly, making them competitive compared to other traditional gears. In this video, I discussed 3D printed pericyclic/nutational gears, their designs, working principles, and issues.
STL files: coming soon

[@Irontygre]

I've seen high torque gearboxes before, and now I've seen a high twerk gearbox.

[@blackflagqwerty]

Work it baby, work, work, work.

[@teplonosia420]

that was my nickname in highschool

[@MatrixRay19]

The issue you noticed on the end is related to a tiny flaw on the design, you should use tapered roller bearings on the ends! There is force being applied axially as well as radially, thus it requires tapered roller bearings instead of just standard radial ball bearings.

[@yasirrakhurrafat1142]

Might as well make the gear teeth like the cycloidal gears as well.

[@jasonwhite2028]

Didnt know tapered roller bearings were for multi directional loads, explains why you see them in automotive drivetrain applications. Good to know thanks for the info

[@dennis-nz5im]

Slab bearings. Barrel shaped like old right axles on Mercedes swing axle

[@I.no.ah.guy57]

​@@jasonwhite2028 yes but they have a large nut or snap ring to hold it in place, so it's not the bearing on its own, and it's only in certain cars, possibly just trucks, I believe. The hubs of most cars are just a large straight bearing that gets pressed into the knuckle. While trucks and anything larger has tapered bearings that are made to come apart so you can pack grease into it and then pop it back together and fasten it down

[@firstmkb]

I hear mention of tapered roller bearings mentioned around machinist lathes. Depending on what angle you’re cutting the load could be axial, radial or a mix of both.

[@misuyikillu]

i think this was genuinly one of the least annoying sponsor presentation ive seen,nice job bro

[@mspeir]

I don't know if it's useful, but it is hardly unnecessary. It may lead to a more advanced design. Try it with beveled helical gears and increase the gear contact by increasing the length of the gear teeth. You have a rather large gap between the teeth and shaft. More contact may increase stability.

[@jamesjonnes]

Recreate this with magnets. No friction.

[@ParaBellum2024]

I don't quite understand what you mean. Can you make a model in your workshop to illustrate the principle, and then upload a video showing how it works?

[@mspeir]

@@ParaBellum2024 That's a weird way to troll. 🤔🤨

[@user-gi7vi9gm4t]

@@mspeir i just looked at your channel bc i was interested if you had a workshop due to parabellums comment , you earned a new sub.

[@mspeir]

@@user-gi7vi9gm4t I haven't posted in years, but thank you.

[@aterxter3437]

If you want it to operate smoothly, three things are to take into account : 1) the distance of each nutation gear to the nutation point depends on several factors such as tha nutation ratio and the difference in tooth count in each gear mesh, if not followed, the gears don't mesh perfectly 2) 3d printed gears need to be work smoothed by runing them with an abrasive to eliminate surface artifacts 3) greasing the gears is key in smooth and qiet operation. Back to the first point, all herringbone gears have an average contact point wich describes a circle, the center of the fear being the center of this circle. With a nutation angle α, and an offset of a nutation gear from the nutation point (where the oblique and straigt axes cross) δ, and a meshing gear of radius r1 the nutation gear average radius needs to be r1/cos(α) + δ*tan(α), if you trace the simple meshing on a piece of paper to find the proper dimensions, you will find this formula with simple trigonometry. On a side note, having the same nutation gears and meshing gears will simplify the design as the nutation gears will bea simetrical to the nutation point

[@DaveEtchells]

So it’s possible to avoid the pulsing entirely if you design the gears to meet the constraints you described? I wonder if it would be zero-backlash like harmonic drives?

[@Roobotics]

Very interesting and bizarre stuff, I think the biggest shortcoming it has, is that the output is basically getting 'twitched' between gear meshes as a means of moving. So your output side isn't able to deliver a consistent level of torque in a direction. Also I think this means that despite the <a href="#" class="seekto" data-time="2401">40:1</a> ratio or so, the mechanical advantage is actually lower, each time it steps back it is undoing the mechanical advantage, then the forward stroke has to put it back that much further, so that's a sort of continuous movement ineffeciency. So it's mechanical advantage factor would be measured in the forward-wobble and advancement region only, if that makes sense. Basically it will act like a <a href="#" class="seekto" data-time="2401">40:1</a>, but the input torque used to move it, will take the effort of something more like a <a href="#" class="seekto" data-time="1801">30:1</a>.

[@MatrixRay19]

It's very much like on a worm gear reduction, friction takes away quite a bit of the performance.

[@TheTechnopider]

This was my initial impression but actually I don't think this is a fundamental problem of the mechanism, but the tolerances/manufacturing of the part. Like, its not like contact is made to force the gear once per per rotation, the contact is made cyclically around every contacting gear tooth in rapid succession. I think that there are also ways to optimize the tooth design. Before involute gear tooth, the same (or similar) criticism could be made for simple gears!

[@TheTechnopider]

​@@MatrixRay19I am unsure of this. I think at first glance you'd assume something similar of cycloidal gearboxes

[@jasonwhite2028]

I was thinking the same thing with the engage and disengage being horribly indirect compared to planetary or worm etc, but it also looks like it could be constantly engaged with just a portion of the gear as it wobbles rotating the contact position? Not sure but the vibration alone makes this seem pretty unviable, still cool to learn about

[@f.d.6667]

Maybe. But the real show-stopper is friction. Properly designed gear trains have friction only in the bearings but never on the teeth (rolling motion via evolute geometry). Here, there teeth are sliding into position. Big no-no in engineering and the reason why worm gears wear out so quickly.

[@Laroete]

as you mentioned, a solid casing made of thick steel plate, machined solid steel parts, some grease and this thing would genuinely be useful in a lot of industrial applications

[@christiangray7826]

I would love to see a really high load on this gearbox. Maybe test its limits with what 3D printing material and precision you have, until a gearbox of a certain size fails. I bet if you optimize it as much as you can, it may be capable of producing much more torque for its size and mass than other more commonly used gearboxes.

[@notamouse5630]

Cool, another gearbox that acts like a cycloidal gearbox. I already have a functioning print of a harmonic drive and a cycloidal drive.

[@KeithOlson]

<a href="#" class="seekto" data-time="372">6:12</a> FWIW, the teeth on *BOTH* sides of the center gear are engaged, so the total force is _really_ spread out.

[@GavinBath]

You have amazing skills in explaining things clearly. Well done.

[@ThreenaddiesRexMegistus]

I’m very impressed by the finish on that clear cover! I used to work with acrylics and polycarbonate many years ago. That looks as good as an injection moulding. The gearbox is an impressive force multiplier! 👍🏻

[@goliath9081]

Thank you for sharing your knowledge on the gearing

[@marco_gallone]

It’s easy to see that for a continuous input you have a pulsing outout. Even In the double gearbox configuration. You can improve the smoothness of the output by offsetting the mirrored gearbox by 90 degree rotation.

[@ParaBellum2024]

I'm struggling to understand what you mean. Can you make this design in your workshop, and then upload a video showing how it works?

[@marco_gallone]

I am not sure how to explain it, referencing 8:32 But if you install the right side transmission to be 90 deg out of phase with the left side, that will it switch which side does the pushing. Essentially you can smoothen the output motion by making it so that the push (instead of being in sync) happens twice per rotation instead, right left right left…

[@user-gi7vi9gm4t]

@@ParaBellum2024 bot

[@ParaBellum2024]

@@user-gi7vi9gm4t Wot?

[@htheorylab]

@@marco_gallone I'm not sure if you are referring to the smoothness of the axial movements. But if you picture the circular motion, your suggested offset of 90 degrees or pi/2 is equivalent to the sum of a sine and a cosine, which results in a larger amplitude, which means more axial vibration in both directions. Mathematically, as you know, only a phase shift of 180 degrees or pi will cancel. Here are two examples in Desmos: 'qfcs5camdc' (180 degrees) and 'kkvv0zanus' (90 degrees).

[@LateralThinkerer]

Sort of like a harmonic drive that doesn't require the fragile circular spline element. Cool!

[@KnooBill]

They are very interesting and you have great physics and cad skills

[@Robothut]

Excellent job on making this video and explanation. Thank you for sharing with us.

[@Chris-bg8mk]

Similar to a strain wave gearbox, it should have extremely low backlash due to the large number of teeth engaged.

[@splynncryth]

Yes, but this design is much more 3D printer friendly. James Bruton did some experiments with a printable hamonic/strain wave drive but ultimately settled on cycloidal drives for his projects because of issues he had. kzbin.info/www/bejne/h6ClmIaNoK-sg5Y Maybe someone will see a solution to the balance issue other than using a second gearbox and a better system of bearing (or maybe even something like a delrin bushing) might further improve things.

[@Luftbubblan]

Yeah, looks interesting

[@creativusme]

This broke my mind a bit but it is awesome

[@BonesyTucson]

Very cool! I have never heard of pericyclic transmissions before

[@fernandoandaluz2281]

Brilliant, thanks for sharing

[@AllToDevNull]

cool idea. maybe the center gear could be balanced by modulating the infill percentage at least a bit.

[@haroldsmith45302]

Excellent work! I hope that students pursuing advanced degrees in mechanical engineering will consider focussing on this concept for their research thesis.

[@itonylee1]

seems like a good application for differential gear

[@erkintek]

In practical sense, all tork is on one/ two teeth , balance can be mitigated, nice work thanks for knowledge

[@f.d.6667]

Certainly a nice gadget but not a solution for real-life problems: the show-stopper is friction. *Properly designed gear trains have friction only in the bearings but never on the teeth* (rolling motion via evolute geometry). Here, there teeth are sliding into position. Big no-no in engineering and the reason why worm gears wear out so quickly.

[@vincentbarkley9121]

Great work. If you use a much finer gear pitch, the distance of nutation can be reduced greatly, reducing imbalance forces. If you casually look at a harmonic drive, the gear pitch more closely resembles a straight knurl rather than gear teeth.

[@martynridley3671]

With just a pair of metal worm/gears in series like the ones you showed at the start, you'd get 16<a href="#" class="seekto" data-time="1">00:1</a>. Metal, simpler, stronger, quieter, cheaper, so, ...! Great to explore this kind of stuff, though!

[@marcseclecticstuff9497]

Just a different form of what I know as a harmonic drive, only a lot worse performance. Harmonic drives have high gear reduction, they're relatively compact, have close t0 0 backlash, run smooth/quiet, and are robust. They are commonly used on CNC machine centers to drive automatic tool changers. We have a bunch of Toyoda's that use them, a few machines are over 30 years old, never had to touch the harmonic drive sections.

[@inthefade]

Thanks I will look those up

[@I.no.ah.guy57]

What an interesting little gearbox. Im sure theres a few applications for it

[@joewoodchuck3824]

This is great for high ratio needs.

[@stefanguiton]

Excellent

[@RobertWill-uq3iv]

If you can imagine it, it's probably already been done. Fascinating stuff, but he mentioned the practical, real world solution at the start of the video: the worm gear drive.

[@Kargoneth]

Fascinating. I think that, with a different way of meshing the teeth, the engagement could be gentler, like helical gears, though the vibration will remain an issue.

[@toomdog]

That reminds me of how hydraulic pumps and motors work. Frankly, I'm thinking of all the times I wish I had known about this in my special project at work.

[@K-Effect]

These would be great to have in the hubs of each wheel on a vehicle with the proper gear ratio

[@WhyplayGaming]

3D printing is showing us so many new systems.

[@resetatan500]

Sürekli kendini geliştiriyorsun dostum tebrik eder başarılı işler dilerim.

[@Jim202030]

I like this. Still not sure about it vs worm drive but either way I will take the extra arrow for my quiver. The one thing I can say is worm drive vs this has a perpendicular input naturally so this might have some advantage for situations.

[@vitorvilasanchez]

seems like a fun concept but must be one helluva thing to balance properly

[@r.j.bedore9884]

I'm sure the angle for the shaft needs to be big enough for the gear teeth to pass by each other as it spins, but reducing this angle as much as possible will reduce the vibrations as well.

[@enderoftime2530]

There should be a counter balance weight installed to keep the center of mass around the center of rotation.

[@ericbrodersen3666]

Superb! I wonder how well this would work in low speed conditions like bicycle gearing? I’m looking forward to see more. Thanks

[@mishkamcivor409]

Since the input and output are co-axial I think you could make a cool clock design with this, with a 1rpm input that gives you your minute hand with the input shaft going all the way through to the front and then with a design with a <a href="#" class="seekto" data-time="66">1:6</a>0 reduction then the output wraps around the minute hand and gives you the hour hand and the low speed means that the noise and balance is not so much of an issue

[@user-hy4jq3pe4y]

Very inspiring! Ever considered to make a calender clock this way?

[@lordfly88]

Definitely interesting, but I think the Split Ring Compound Planetary gearbox is a much more useful design. Equally compact, practicality unlimited ratio options, and balanced.

[@ZacLowing]

Keep in mind, mirroring the gear boxes doubles the gear contact area. 2x the strength, or same strength, half the weight neaded in materials

[@nogum9763]

in praxis you can make the wobblator and its shaft out of 1 part, id opt for a much larger shaft thoug, id go so far to increase its diameter to the point where its just a bit smaller than the inner diameter of the ring. stator

[@ekaggrat]

you could make it half the size and 3d print it in metal to get strength and precision . great work!

[@ZanarkandAce]

Omg this is exactly what I need

[@BRUXXUS]

I've been addicted to videos of all the various gearing and drive mechanisms , and this is the first of this kind that I've seen! I wonder if these are used in any real products? The geometry doesn't even seem too hard to machine with standard lathes and mills. 🤔

[@OskarPuzzle]

You can make the gearing ratio even slower if you have 1 tooth difference between the two yellow gears, and each orange gear having 1 tooth more than its yellow mate.

[@retsetman9698]

Exactly, the ratio increases as the number of teeth get closer together.

[@AlRoderick]

I think even though it looks like there's a lot of teeth engaging it's still only one at a time. The teeth in front of and behind the one in contact are about to touch but aren't touching yet.

[@basquo2]

Pretty damn cool, but I have to imagine that this would be pretty high wear, no matter how refined it gets. But if it's made with easy to change setup, might be a pretty nice alternative

[@fraudbuster1456]

It’s an interesting concept. Have you done a comparison with a traditional gear with the same ratio for friction? I have a feeling the friction may be too high for practical purposes. Adding bearings to the shaft to reduce the friction there was a great idea, but as you mentioned in the video, there are multiple teeth meshing simultaneously instead of just one and that means more friction.

[@CONCEPTUALMAN]

That is interesting. In a sense , it looks like a mechanical relative of the planetary gear, or even the differential, If the output is the center and you hold one shaft while spinning the other. Perhaps counterweights in the nutating gear would cure the problem of being out of balance.

[@TheTechnopider]

I think that this should technically be backdriveable. The fact that it isn't I think implies that there are inneficiencies in the gear tooth designs. Reminds me a lot of cycloidal gears! I think this idea is very cool and potentially practical!

[@szki272]

I had a winch that used a planetary drive but it was unusual, It had the motor connected to the planet gears and no sun gear. It drove between 2 ring gears which had a different number of teeth. One was mounted to the housing the other to the drum.

[@Raye938]

Does an involute gear work best on this gear box or is there another gear geometry that would work better?

[@sugoijan]

Would it be possible to play with the weight distribution of the wobbling gear to make it stable? I guess that might be more dependent on manufacturing quality compared to adding a mirrored gear, but at least it would only be one unit

[@fralinsandfriends]

My husband would understand this. It is interesting. 😊😊👋👋❤❤

[@keenheat3335]

i don't know why, but I'm getting a constant velocity joint vibe from it.

[@Roobotics]

But is it though? the output shaft literally moves forward and back, it jitters and isn't constant at all, much more obvious on the higher ratio box, fyi.

[@bsebastiannwlange3529]

it looks interesting, i would like to see it build like an elektrik high tourq rewnch like the used for automotive for example

[@jakubpollak2067]

How does it compare to compound planetary gearbox? That one also achieve huge gear ratio and have many teeth engaged for the torque, but also have more moving parts (planetary gears)

[@IO-zz2xy]

Increadably high gear wear but good potential. Regards from South Africa

[@Nderak]

im curious about application what machines use these

[@honkie_kong1689]

I wonder if you can scale that down to be used in something like a model train locomotive? It could give it true scale speed operation smoothly.

[@creeib]

Clever 👍

[@VANdeVice]

Try swapping the incoming and outgoing rotation. In order not to slow down the final rotation, but rather to accelerate it. Is it possible to create a propeller based on this transmission mechanism ? For example, for "pedal catamarans".

[@lunarz7117]

Maybe use a counter weight like in car engines crank shaft to balance the gearbox without adding a mirrored gearbox?

[@robblerouser5657]

Something like this would be perfect for a home telescope.

[@Mcnoklacyphie]

How to create a rotor for locomotive, thank you the sound remains

[@hetrodoxlysonov-wh9oo]

What is it supposed to replace, we have small reduction gearboxes, stepper motors, variable speed drives etc.

[@piconano]

Very interesting. Question: What is the benefit of this design?

[@vangildermichael1767]

I saw a generator that operated on gravity. Just like a pendulum clock, the weight is hoisted up in the day. And at night as (the weight) "slowly" descends, A high gear ratio generator makes power from the potential energy of the big (weight). Only trouble was, no gear could hold all that weight on one tooth. It looks like your gear has solved that problem. ur oh, maybe not. I remember you say your gear, jams up if you try to "back drive" it. And that is exactly what that gravity generator project needs. A slow (rpm) into a fast (rpm)

[@tylerferrusi7652]

Maybe good for solar panel tracking because of the slow movement required. Could probably have the gearbox sealed and filled with oil for low maintenance since solar arrays are pretty remote sometimes

[@tylerferrusi7652]

Idk about the torque situation - I'd say it's only actually engaging on or two teeth at a time, a lot of other teeth are really close, especially the closer they are to the contact point but unless the gears are flexing, no additional teeth are actually making proper contact. I'd think a next step could be to compare and contrast the design to a planetary configuration to see if there are any benefits but it's definitely interesting either way.

[@Gugernoot]

Might have a use in gear reduction socket drivers unless planet gears are still better.

[@geniferteal4178]

I think you just said it, but do you get the same torque? Multiplication with limited teeth engagement?

[@gormauslander]

I feel like you could mechanically tether a counterweight to be driven by the same motor to oscillate at the same speed.

[@jacksparro3150]

The main advantage of a pericyclic gearbox is vey high output torque because several gear teeth are in contact at the same time. Because of its inherent design, we have this vibration problem causing the gearbox to self destruct. The only way to cancel out the vibration is by adding a "mirror image" of the gearbox. But then the output is now in the center of the whole gearbox which leaves us no other option but to use a spur or helical gear which is quite counterintuitive.

[@Blarrrgum]

Usefull in the circumstances you don't have access to flexible material for an harmonic drive. Harmonic drive don't have the wobbling of middle gear, much greater ratio and tooth engagement.

[@g_glop]

can you add weights to the nutation gear to balance it out? adding a mirror copy is one way but dynamic balancing is possible with just one

[@retsetman9698]

Yes, that's a way of balancing.

[@kushpacsmike]

DOPE

[@lancethrustworthy]

I think this is useful. Perhaps we will see this in microscopic form. Nanogearing.

[@marks7502]

cool

[@jamesgaither2069]

I have an idea for a clutch mechanism, that would require a lot of pressure but not a lot of parts.

[@Abmotsad]

Ultra-high gear ratios are not difficult. Three worms, labeled A, B, C. Three 100-tooth gears, labeled 1, 2, 3. Worm A drives gear 1, which is coupled to worm B. Worm B drives gear 2, which is coupled to worm C. Worm C drives gear 3. 1,000,000 to 1. Very compact. Nothing wobbles. Off-the-shelf parts.

[@bjoern_eberhardt]

This looks similar to the vibration motor mechanisms used in optical lenses

[@davidschwartz5127]

What are the results when a reverse torque load is applied to the output shaft?

[@retsetman9698]

3:45

[@iggypeters5564]

I could make that gear/axis ofset blindfolded if I wanted to

[@TashiRogo]

Would be interesting to see how this sounds and operates if it was submerged in a heavy oil.

[@wingcommand24]

Wait, even crazier. Make this a mobius strip.

[@DrewTeter]

What kind of tooth geometry do these gears use? They look kind of like involute gears but the mechanics remind me of a cross between a cycloidal gear and a harmonic gear.

[@jakubpollak2067]

Looks like bevel gears to me, he showed 4° offset, so maybe 88° bevel gears?

[@Joe-rp8fd]

what if those gear tooth are rounded , probably would be much smoother and wouldn't skip since many are engaged at the same time

[@user-vb9hh6us7s]

what happens if you make them helical?

[@thedolenorway]

I think that is the least intuitive gearing mechanism I've seen so far. I like it!

[@Mernom]

What happens if you add rotation to the input fixed gear?

[@retsetman9698]

That's something that can be done and in that case it would be a kind of variable-speed, variable ratio transmission

[@RickySupriyadi]

in my imagination this is might really works well with gravity battery.... I would like to hear from experts on my opinion. using very fast wind input to lift heavy gravity battery concrete.

[@colinellicott9737]

These are very interesting, but I think durability will be its biggest drawback. The teeth are not true gear teeth as they slide instead of rolling which the involute provides. Great vid though, thx.

[@siegfriedschlag4353]

Hallo, sehr interessant vielen Dank 👍 wünschen dir eine schöne neue Woche ❤ danke für gegenseitige Unterstützung 🔔 Siggi & Anne 👍