www.ratiozero.com/ NOTE: One-way ratcheting/ motion is an essential feature of this transmission and not bicycle specific as I mentioned in the video. Wothout a one-way bearing or a ratchet or other similar mechanism the small planet gears would just roll back and forth on the ring gear leading to no output. This is something I should have emphasized more in the video. Support the channel by shopping through this link: amzn.to/3RIqU0u Patreon: www.patreon.com/d4a Become a member: ruclips.net/channel/UCwosUnVH6AINmxtqkNJ3Fbgjoin Grit: ruclips.net/channel/UCt3YSIPcvJsYbwGCDLNiIKA
@@battlebossv9219 That is a very good question. It does not seem possible to move the slot mechanism in the large planetary gears to the other side of the center, because then the small planetary gears would spin freely and have no drive. The small planetary gears must be blocked in 1 direction, because otherwise there is no drive. I have already asked how that blocking mechanism works, because it is invisible.
Rubbish. This was Hondas failed system in F1 and downhill mountain bike racing in early 2000s My gearbox Carbon fibre downhill bikes beat them. Moreover a far better way for a split cycle reciprocating system that DOES all but eliminate all leverage variation using roller followers on a cam was built by myself In the 1990s, and has been developed by many companies since.
Wow! This isn't some scam, they actually made a geared CVT! Also, your explanation was so thoughtful and precise. Explaining how these mechanisms work is often tricky, but you nailed it.
@ Doesn’t that use the electric motor in tandem with the ICE to determine the output speed/torque? It uses two inputs along with a planetary gear set to one output, I believe. The cvt in this video has one input leading to one output without the use of friction, so it is functionally true to the idea.
@@rdubs1705 @agr8trip It's a Toyota Hybrid System. If you aren't sure what it is, it's always a Toyota Hybrid System. It's "free" to use and has been the go-to for anyone cheaping out on making a compliance car in the last few years.
it's actually a ancient technology by now. it's very common just not common for cars and vehicles the public usually uses. so people don't even realize what kind of CVT trannies there are out there in the industrial and agricultural field.
Toyota's e-CVT and Ratio Zero operate on the same principle, using a single planetary gear set to create different ratios but Ratio Zero can be purely analog due to the lever arms. Toyota's e-CVT is much simpler/robust due to it having the direct drive sun gear.
When I got my Stenograph Kit with all the gears as a child, I wondered what use the elliptical gears could be used for? Nothing intuitive came to mind, as did with the round gears. The arm connectng a round gear to offset the elliptical gear it's connected to during rotation wasn't included in the kit. Had the arm been included I might have figured it out.
I'm sure they help, but I'd be hesitant to say that they "cancel" out the speed variations outright. The shape of the elliptical gears is fixed, but the speed variation depends on the currently selected transmission ratio. So, unless I'm mistaken, the elliptical gears can only cancel out the speed variation at one specific transmission ratio. If the transmission is set to any other ratio, some speed variation would still be there (though it'd probably be reduced when compared to the round-gears option). Having more "phases" (i.e. having more than three arms), though, could alleviate the problem.
@@AndreaZambon87 That applies to nearly any improvements. Nothing is perfect. Size and weight limits. Multiple compromises to get best results possible. I'm thinking possible cone shaped gears that allow mechanical contact with another gear on a flywheel that slides up and down the cone shaped gear according to centrifugal force, changing gearing ratios by changing diameter of cone shaped gear smoothly while continuously rotating.
@@d4a See, you brought a vacuumer to a tanks job. Can't merge without causing a traffic jam? Get flattened! Can accelerate at a green light? Get flattened!
@@d4a Video Idea 4 U ....I saw some 15 year old news clips & several articles about. An odd Grail 2 stroke engine made in Kansas USA that was supposed to be a huge game changer for the international combustion engine. It obviously wasn't but might be something to research as to why it isn't now in everything.......Also there's a guy with a DIY lightweight diesel engine sports car that gets 100 mpgs & does 0 to 60 in 4.7 seconds. The Omega he calls it here on RUclips.
I built something very similar back in 1998 while at university in the uk. We used one way clutches in the same way, but instead of varying the "crankshaft" throws, we used split connecting rods and moved the pivots of the conrods. this meant that the adjusters were fixed to the casing not to a moving part so less friction involved. "laminated" the transmission by keying a stack of discs for the crankshaft throws, and using thin laser cut and machined connecting rods with bronze bearings. we used 6 clutches and 6 crank throws to smooth the output. we had a ratio range if approximately 200. ie 1:1 to to 200:1
@@afterthought3341no, it was actually a variable drive for a seed drill that we were developing, and I borrowed a test rig from my university, and we rigged up a variable speed electric drive to operate it. Even with 6 elements, at the higher speed (lower reduction) part of the speed range, velocity fluctuation was an issue. More elements mask this problem. The main thing that we were trying to establish was an exact, repeatable calibration of the output to the input.
But one of the best things about this CVT is that it also eliminates the need for a clutch at all, adding 6 clutches seems like the opposite idea. I say that because clutches by nature are frictional and thus going in the complete opposite direction of what the actual featured technology is indicating.
Hey, it’s pretty important I think to people trying to understand how this works that you mention the one way gears’ main job is not to allow freewheeling, but to allow the ratchets to pull the gears in only one direction. If they were freewheeling bearings, the gears on the lever arms would roll back and forth and provide to torque transfer. The torque of this transmission is transmitted directly through that one way ratcheting gear.
I was just thinking the same thing. I am guessing those 1 way bearings are going to be a major source of friction, wear, noise, and generally just issues. I bet that's the main reason this hasn't really taken off.
In the 80's, an inventor from California developed the "Paradigm Variable Speed Transmission" for bicycles. It was a very simple, light weight, novel epicyclic gear design producing constant variable ratios from 1:1 to 1:5 output. It worked well until someone with very powerful legs decided to push on the pedals with the same torque as when he was sprinting at the end of a race. That torque caused the slipping clutches used in the design to fail, and this design used very large, heavy duty slipping clutches. If the RatioZero design is using slipping clutches, which I believe it does, I hope they are far far superior to the slipping clutches I know of. Maybe a new rachet design I'm unaware of would work. Either way, I wish the designer of this new novel device good luck.
It operates like a rowing machine... Interesting, but it looked like work to spin it without a load. And I didn't hear any efficiency numbers (they surely know the prototype's actual efficiency). I'm guessing that if they beat belts we'd have heard it (and eCVT reigns supreme anyways). But ebikes are a broad market. They could have a niche.
@@jeffrenquist5476yes. He mentions these gear-CVT eliminate the need for a clutch, but these ratchets are essentially the clutch in a round about way. There are different types of these, the common pawl and ring type no doubt used here, but also axial ring pair type and sprag type which have benefits and drawbacks over the former. The blessing here is that each ratchet-planet gear has plenty of time to seat its engagement between ratcheting and applying torque, which eliminates the most common avenue of failure for these mechanisms.
This seems like an obfuscated ratcheting CVT, these have been around for a while. There's a bunch of extra gears and levers to make it seem like something new and different, but really it's just a ratcheting cvt, the animation around 13:00 really makes it clear as thats the same motion and link as in a ratcheting cvt. The freewheeling you mentioned isn't a bicycle specific addition, it's something inherent to this type of CVT. All ratcheting CVTs unavoidably do this, sometimes it's a convenient feature, sometimes it's not.
Exactly! I was very confused that the ratchet wheels werent explained during the CAD when its clearly the way that the different small planet gears "pass the baton" to each other. The locking of the ratchet is the mechanism by which any torque is transferred to the output ring gear.
So, what your saying is "Its been around for a while, and since it is not in mass production, it means its not practical". You know, kind of like plasma propulsion!
The fact it can change gear ratio while not rotating is another advantage over traditional CVTs: they have to be under some level of rotation (even if the output is disconnected) to change ratio, otherwise it would pinch the belt.
@@YoungShul what OP is talking about is that you can change "gear" while vehicle is standing still (which you cant in "classic" CVT unless circumvented otherwise, i.e. the disconnected output stated by OP)
@@Trauerdurst_TD3D This however is pointless for combustion engines and the fact that it goes from "highest" gear to "lowest" from the neutral position is an unfortunate reality. The combination of the two makes it less straightforward.
Correct me if I'm wrong but you say the one-way ratchets are because it's on a bicycle. I can't help but think because of the dragging that the little planets have to do that a one-way ratchet is actually critical to the operation and not just for the bicycle. Otherwise when the lever arm went to pull back the little planet would just freewheel and not transfer any torque. I would love to know how I'm wrong if I am but I think that is correct.
You are obviously correct! This is just a "ratcheting CVT", ratchets(or some other type of "freewheel" mechanism) have always been an integral part of them throughout the ages.
I was wondering the same thing and I’m surprised he didn’t address this in the video. I would like to see how they achieved this inside such small gears.
I agree, as soon as I saw the initial animation, my first thought was how are they freewheeling one way, but locked and applying torque the other way? A ratchet seems the only explanation - without a sun gear (as per a standard planetary gear system), free-wheeling planets would just move back and forward in the ring gear, unless they could only turn one direction. EDIT: if it was ratchets, then I can't see this technology scaling up. The ratchets would have to be strong enough to provide peak torque through the transmission, and would therefore have quite a bit of resistance (not to mention noise). Then there's the issue of high-RPM, and the ratchet "slipping" backwards because it hasn't had time to engage. Seems great for a bicycle, can't see it on a super-car. Koenigsegg's CC850 transmission is probably a much more useful breakthrough!
In college, I had a great physics professor, Lynn Beebe, who was a wizard at explaining difficult concepts for my then young mind to understand. He also drove a 1963 Corvette coupe when it was just an old but undeniably cool car. You are the first person I feel would be better at explaining difficult concepts to what is now my old mind than Lynn Beebe could. Thank you.
I believe you failed to mention the ratcheting mechanisms necessary in the smallest gears which lock the rotation towards the arms when they are on the power stroke and thus allow power to be transferred. This has me stumped because in the animation if these didn’t exist, the small gears would simply roll back and forth on the output gear, essentially skipping over the thing that makes this work at all.
@@mrblc882 Everything has fail points. The question is, can it be made durable enough to be viable? In low power applications like a bicycle, absolutely. Simple one way bearings would be sufficient. High power applications like a race car or truck, that will be a challenge. I do think yes, it can be made durable enough but it won't be easy and your concerns are valid.
@@wingracer1614 It seems like a fundamentally more complex and intricate design, but you're correct. If it provides enough of a benefit it can succeed. I have a feeling even if it does catch off massively more well trodden set speed gear transmissions will still exist for durability and simplicity reasons. At very least it now exists and can be used for enthusiast and luxury cases!
That's the one part I saw in the first animation that made me wonder how they would actually make it. In the prototype he had, they used ratcheting mechanisms but it seemed to have a lot of noise and friction. One way bearings would be much quieter and smoother but they wear out fairly quickly. If they were to use them and make them last, they would have to be very large.
yeah it should be added to the video, I spent about 5 minutes staring at the schematic trying to understand what was stopping the gears from just freewheeling in both directions.
Agreed, however I would be concerned about the longevity of the ratchet mechanism in a car/truck application, so in my thinking (anyone feel free to correct my logic) why not -keep all 3 levers at the same position (moving together) , -lock the current 'output' gear and, and -use a 'sun' gear in the center as the output? In my half-though calcs, this would: -remove the speed variation over each revolution, and if the -sliding levers are on roller bearings, this should allow for changing ratios under high torque as well while -maintaining the ability to go 0:1 ratio. Craap, o thought some more and OK, this idea would simply make the output shaft rotate back-and-forth. For my idea to work, the levers would have to ride on a cam to flip them to the opposite side every time the slot is parallel to the ring gear... or some other lever mechanism similar to variable compression ration engines. Brain hurting now. Gotta get back to work but I still think the sun gear with a locked ring (current output gear) and the lever shift every half turn might be plausible. This would definitely reintroduce output shaft speed wobble every turn but that's easy to minimize.
am I alone in knowing that there was ratcheting from the sound at the very beginning of the video? 0:08 my first thought was "sure, split the rotation, and multiply the number of moving parts" the work it would take to refurbish one of these at the end of life would be crazy if the electronics could not be completely separated from the mechanicals. If it all comes as ONE single part? electronics integrated right alongside the inner works? They could never be rebuilt by any local.... and becomes one more short lasting part that can not be repaired.... just one more way for corporations to F you when you "buy" something
@@derricktalbot8846 I didn't pick up on it immediately, but as soon as the CAD animation started it was obvious that the gears had to only be able to free spin in 1 direction. That does open some interesting thoughts as to whether or not a gear is the optimal solution to that specific part of the device. Is there a non-rotating catch mechanism that would be just as functional with significantly fewer parts?
The ratchet means it’s technically not a CVT, since the actual number of discrete gear ratios is just equal to the number of ratchet clicks at the highest radius offset.
dont forget about the toyota hybrid electricCVT , where planetary gearset is controlled by speed variance in two electric motors. this gives the close to the same efficiency as manual transmission
No mention of Toyota's eCVT? Yes, it's electromechanical, but unlike belt driven CVTs, it doesn't rely on friction and transmits power through a planetary gear set.
@@d4a I was going to mention this as well. There's a fantastic WeberAuto video on toyota ecvt transaxles that explains the working principle. Edit, as I missed the point - for a bicycle application an ecvt would require a second input from a motor, so it'd be suited to a commuter ebike, but it can't just provide variable transmission without it. So if the goal is one input only, it's not the way to go. That said, these are really ingenious and strikingly simple. They also pull double duty providing hybrid drive, regen braking and starting the ICE in addition to being a cvt. Would love to see a video with your take on these, pros and cons.
Would love to see a deep dive into the Toyota eCVT (2010 and newer Prius). Maybe that could be scaled down to e-bike size. Brilliant design in simplicity and virtually frictionless and practically impossible to wear out.
My first dealing with a CVT type of transmission was not in a car but in the HVAC industry. A VAV(variable air volume) is used to vary the fan speed in a commercial building according to load requirements this maintains static pressure and temperature. This geared approach is an interesting application to solve the inherent limitations of the variable pully design.
I mentioned this application on another thread. I am a retired HVAC mechanic, and worked on VAV units with this drive set up. They were problematic, and we replaced them with VFDs. I don’t like these CVTs either.
@@rodgraff1782 Yeah. Much better to do it with power electronics. More reliable. You can think of the electric motor in an EV as a VFD. The battery DC voltage is used to produce a 3-phase AC voltage to drive the motor at the desired speed. So the reason you don't need this in an air handler is the same reason we don't need it in an EV.
I am sure I am not the only one who noticed this, but I have not read through all the 1500+ comments. Gear ratio is input(from engine) to output shaft(not tires) of transmission. You will always have a gear reduction on your differentials...I am fascinated by this new type of CVT though...no flimsy belt. Yay!
These transmissions have a lot of friction that generates heat. That equals lost horsepower, as it takes energy to generate heat. I’m not sold on these. I
@@unevenelephant469it's a good idea which eliminates the energy loss of slipping stretching belts and chains and could be engineered to be as durable and reliable as a manual gearbox for a car (which a belt or chain driven CVT simply cannot)
@@DJKr15py @unevenelephant469 Might even be better if the wear and overall system efficient is the same or higher than traditional gearboxes due to allowing the engine to always be in the preferred rpm at all times for either optimal torque or power
The eCVT is extremely simple in it's construction. It actually has a fixed numerical gear ratio between the ICE and the output. It can vary the ICE RPM by changing the speed of one of the electric motors (MG1 in Toyota language). The second electric motor (MG2) is fixed to ring gear of the planetary gearset and as such also directly linked to the final drive/differential. The ICE is connected to the planet carrier and MG1 to the sun gear. Since the speed of MG2 is fixed to the output speed of the transmission you can vary the ICE speed by varying the speed of MG1. By spinning MG1 in the opposite direction you can drive in EV mode since it keeps the ICE at 0rpm. There is no clutch or torque converter between the ICE and the transmission, only a fixed torque damper.
The eCVT is the reason I decided to get the Prius. The belt system that many cars use is not exceptionally reliable especially the Nissan version. The Sienna and the venza hybrids along with the Prius all use this system and it is very elegant and extremely reliable and is capable of some towing if you don’t mind pissing away your MPG.
This is the best explanation of a regular manual transmission and the interaction with variable engine speeds I have ever seen. I've always struggled to explain this to people who don't understand these concepts. You nailed it with your graphics and description. The geared CVT is an engineering marvel. I hope it makes it into mainstream usage. Well done!!!
That's what I call a genius idea, it's something out in the open for everybody and none had the idea before. It's purely mechanical a Victorian engineer could have designed and build it . Nothing fancy, no electronics, no exotic material just steel and brain
I wouldn’t be surprised if a victorian engineer actually built something similar. Here’s a video of an old Massey-Ferguson combine harvester where the reel drive works with exactly the same principle. Reel is the big pentagonal thing in the front. It has two connecting rods going back and forth and two freewheels at the shaft of the reel. The speed is varied by varying the stroke of the connecting rods. ruclips.net/video/JCySb0nTmtY/видео.htmlsi=J28SD7UxZCpI6JUz The Wikipedia article on CVTs also describes this principle: en.wikipedia.org/wiki/Continuously_variable_transmission#Ratcheting
You must have missed the part showing that it needs a motor to control the ratios, and for automotive use it will need an electronic control unit and sensors unit to control the motor.
@DonziGT230 It doesn’t need the motor and doesn’t need to be automatically controlled. It could certainly be controlled with a simple hand lever, or a knob, or any number of manual controls. The motor and automation are only there to provide for the convenience expected in modern vehicles.
informative yes but in that case it's a total useless information. this transmission is just a very nice school project but cannot survice in the real world. this size and mass just to move a 20lbs fucking bike ???? imagine the size, mass and cost of this contraption to move a fucking 3500 lbs car. the toyota hybrid cvt with just a differenital and the use of the alternator is: cheaper, lighter, stronger and simplier and for what i can imagine more efficient.
One thing that could have been explained better if I understand it correctly is the ratcheting mechanism is essential to the operation of the transmission, not because it's on a bike. That means it can't transfer negative torque back to the engine unless there's a way to reverse the direction of the one-way ratcheting mechanism.
The small gears transmit power just as long as their relative rotation locks their one-way-freewheels... As soon as the relative rotation unlocks their one-way-freewheels, they just freewheel-along. but you are right, he mentions them, while praising them for their least important role, instead of mentioning their most important role.
@@Scissors69I don’t think so. Axis offset rotation doesn’t explain how the small gears drive the ring gear. . . It has to be either a ratchet or one way bearing on each of those small gears. Or am i missing something?
My grandfather would have loved this. He was a master machinist who loved to tinker, and read up on any & every vehicular tech imaginable. He crafted a homemade gocart with a centrifugal clutch made out of a drum break which gave near-infinite gear ratio (albeit through friction), attached to a 3-speed manual gearbox. Unlike a CVT though, you could replace the pads with standard break pads in about 5 min for a dollar (at the time). And the gocart basically couldn't be flipped over. It had inverted body-lean in turns, which adjusted some suspension linkage based on speed & wheel angle both. Supercharged, limited slip... Magnetically dampened shocks too. It also had "moving" downforce spoilers. (Bear in mind, he made this in the very early 1950's) He did a lot of other things too. He liked "borrowing" from aviation tech a lot for non-aviation projects. Day job was cars and industrial machinery. But I think he poured more tinkering & experimentation into that gocart than anything else. I never saw it in a running condition, but I'm told it was "terrifyingly fast", and cornered so hard the seat straps (tie-down straps actually) could leave bruises. I suppose based on size & such, it would be regarded as a small dunebuggy really. He called it his gocart, but it was to gocarts as Doom-Guy is to a boyscout. Anyway, he would've lost sleep for days over a geared mechanical CVT.
@@Ostap..Bender afterlife isn't exclusive to Christians. Why do some people always need to hijack a wholesome story for their personal beliefs. Very unchristian. Even if it comes from a good place, it goes downhill faster than a gocart with every additional sentence you typed the ultimate insult being you speaking on behalf of millions of people. While grandpa was surely a good man, not every Christian will agree where he is. Also, it isn't relevant and we can never know.
As someone who misspent a lot of my youth building with Legos, followed by cutting gears from HDPE and fabricating manual clutches and transmissions, along with building entire remote-control tracked and wheeled models from hobby metals and wood, I so appreciate your animations and explanations of this beautiful machine. I have viewed a lot of RUclips content; this video is one I will never forget. Thank you and thanks to Ratio Zero. I can only hope that their transmission will be available in Subarus by the time I need a new car!
21:15 Finally you mention the need for one way clutches! I think these are the real killer for this design. All one way clutches I know of allow only choosing 2 from the following: - low wear rate - minimal backslash - high torque It seems that this design would need all three at the same time! Other than that, superb design and this video explains the mechanism pretty well.
I think this design overcomes the need for minimal backlash. It allows you to just add more arms and wheels to overlap each other during the phase of backlash. The prototype has 4 stages, but other than the cost of additional materials and efficiency losses from drag, there's no reason you can't have more, which would smooth out the output, and account for the backlash. I think it would also be theoretically possible with this design to use a brake mechanism instead of a one-way clutch mechanism, because the timing of it is more or less fixed (i.e. it could be controlled by a cam style mechanism or even electronically). It would add complexity to control the timing of the brakes, but it could resolve the issues with one-way clutches.
@@Old_BMWs Using a brake mechanism instead of a one-way ratcheting clutch would also allow the transmission to reverse rotation simply by changing when the brakes engage. No need for a reverse gear!
He’s not saying they require clutches or ratcheting. In fact he’s saying the opposite. The only reason why this specific model needs a ratcheting mechanism is for the freewheeling mechanism on a bicycle. Cars don’t need a freewheeling mechanism and haven’t needed one since Saab still had their 2 strokes in the 60s
@@HungrySharkMaster And he is simply wrong. The mechanism as described, both versions shown, clearly depends on a freewheel or "one-way" bearing in each of the power transfer lever modules. That is how they can spin freely when power is not being applied. Without the freewheel mechanism, with open bearings, this device would simply spin unimpeded and not function. With shaft locks it would be completely frozen and immobile. When the lever is in the reverse stroke, the gear/wheel has to be disengaged. In fact, not only in the reverse stroke, but during the transfer phase as well. Only during the solo power phase does it need to mesh, when the desired speed of the drive lever is faster than the speed of the output. I presume that freewheels are used for prototype simplicity. The first example could have used ratchets directly on the lever arms. But in both cases there is the problem of backlash. During the handoff between modules, one of them has to catch up to and overtake the other. Even if the ratchets are perfectly aligned and use the same cog, there will still be some discontinuity as the load is transferred from one to another. The ratchet cannot slip down to engage the tooth without some clearance, which the force of the system then takes out. So at minimum even if the sinusoidal oscillation of the ratchet arms is eliminated, there will still be vibration introduced at each lever "phase" transition. Introducing more lever modules decreases the sinusoidal variation by utilizing a flatter part of the speed curve (using a smaller angle of the total stroke) but at the expense of increasing the transfer jitter. Now maybe it is good enough to use a rubber flex disc on the output shaft to absorb this very high frequency jitter, but each time we add a module it also increases the complexity and number of parts, which increases the odds of some failure as well as the cost. And unfortunately I don't think any transfer mechanism (either one-way bearings or freewheel ratchets used here, or direct lever ratchets, or brake modules as suggested up-thread) can solve it. The next lever in the sequence would have to run faster than the first during the power stroke, in order to pick up the perfectly aligned next ratchet tooth, then slow down to transfer load, match perfectly during the handoff, and maintain a constant speed during its own power stroke. Quite a feat if they can figure it out!
3:11 I’m not sure the numbers entirely make sense (shouldn’t it be 2.399, 2.398,…,0.402,0.401??) But nonetheless your ability to convey information in a simple and easily digestible manner always positively surprises me :)
It's actually a variable cam coupled by gears. The slot where the actual change in ratio takes place is equivalent to a cam pushing on a lever with a moveable pivot point.
The tech has been around for ages and the main weaknesses were the one-way bearings/ratchets and the torque pulsation. And this tech has also been applied to bicycles many years ago, as a variable leverage chainless pedal drives, back when bicycles were a new thing. Nice to see this being developed further, would also be nice to see it actually coupled to an engine doing actual hard work, because many things work in concept stage and fall apart once in an actual car being driven my regular people.
So downsides will include: - only 1 small gear's teeth is engaged at a time, as opposed to load being split between all the planet gears (as in a conventional planetary drive) - thus you need more material (and weight) to transmit the same power. - the transmission is vibrating, instead of having a constant load (of centrifugal force and torsion), so fatige failure is a.much larger concern
Well realistically without freewheeling on the bicycle... ...you wont be forced to pedal faster, the pedal will instead bash your leg bone. If you are lucky it will hurt, if you are unlucky, it may break the bone
Regarding the first point: All but two of the gears in a manual transmission are sitting unused at any given time. A similar situation exists in a traditional automatic transmission. Regarding the second point: a torsion spring incorporated into the drive shaft could potentially eliminate the problem of erratic torque delivery.
I want this on a cargo bike so badly. My electric bakfiets is a rideable chain stress test right now as it quite the heavy thing to shift under load when I have the box full.
What a phenomenal video! And an amazing idea! Thank goodness for the super smart people in the world who come up with these amazing Ideas to make our lives better! I have a side X side for when we go camping. I use it as our work horse to get wood, water, and other work related projects. I had two different machines with belt CVT's and they would always burn up belts and slip when towing a heavy trailer or pulling a stump out of the ground. I ended up ordering a machine from outside of my country just so I could get a manual transmission. But with the 5 speed manual I lose top speed because it is geared towards torque! I look forward to this CVT coming out to have the best of both worlds! Very exciting!
My friend, your explanation skills are one another level. Bravo! One of the best easy to understand explanations of a complex subject I've seen. I drive a cvt on my Subaru Outback and I never want different transmition. 😉 You have to experience it for yourself to see
The transmission will likely have problems handling significant torque. It looks like at certain points in the cycle all power passes through a small bearing on the end of the arm.
And if those little planet gears have sprag clutches in them, it's not really a true gear driven CVT. It still relies on fiction. If they have ratchets, I imagine the torque delivery would stutter since the lash between one and the other wouldn't be perfect.
I am almost 70 years old, and all my working life I have driven a manual transmission economy vehicle. One thing I have always loved about these vehicles (though I didn't notice it until I drove an automatic transmission vehicle) is the instant application of power when I suddenly accelerate. Though the economy vehicle does not have a lot of power, I get all it has (in the current gear at the current speed) as soon as I press on the gas. I recently moved to the LA area and the manual transmission in the stop-and-go traffic got old really quick, so I upgraded from the 15-year-old Corolla to a 2023 Prius Prime, which has a CVT. In EV mode I still have that instant application of power. Then my beautiful Prius got rear-ended after one month of ownership and the rental Camry I was given had a standard automatic transmission. I hated it. I feel that the timing of power distribution is as important as the total power. I would be in a slow freeway lane and there would be an opening in the next faster-moving lane, and I would stomp on the gas. But instead of jumping forward the Camry would hesitate a moment, then decide to shift gears, and finally it would apply power about a second later. That spot that should have been big enough to safely move into is now not big enough because the car delayed the application of power. In my Corolla I would have already shifted gears prior to stomping on the gas, and my Prius would have instantly jumped forward with it's CVT, but the Camry lost me my safe opportunity. I would rather have lower power delivered when I need it than tons of power delivered late. I am very happy to see this development of a geared CVT. While I consider that my Prius will be the last car I ever buy for myself I am happy to see that better cars are coming.
I'm on the back end of 71 and I learned to drive in L.A. My first driving job (at 17) was delivering furniture/appliances in a 3 speed manual Chevy P-U. It was a blessing and a curse for both reasons> Positive power for the loads but a bear in the areas where an automatic would have aided finessing tight spaces and steep inclines in areas like near Dodger Stadium. And the stop and go issue too. I was lucky the guy who taught me manual insisted on keeping rollback under 3in. I think the required discipline of the responsibility at that age helped me stay out of trouble. But my thought here is with the mechanical complexity of a geared CVT, you would want the buffer of something like a torque converter ahead of it simply because it would take a little training to not apply too much power at once. On a bicycle, it's all about the initial leverage but if you have to pedal at a certain pace before the CVT engages, it kind of defeats the purpose. Looks like a great idea, but application might be limited for the sheer abuse we put our vehicles through.
@@Eric2300jeep I will comment that coming off the line at a light the Prius still has a small hesitation if I am using both engine and battery power. Say I am first in my lane, but I need to move over a lane or two within the next 1/4 mile or so. I turn on HV mode enabling the engine to start, but it doesn't start until I press the gas. Then the battery provides the initial power out of the light while the starter spins the engine to get it started, so I have a detectable delay to full acceleration, maybe a 1/4 to a 1/2 second. The good news is that the 2023 Prius is a different animal from previous years, and once the engine kicks in it scoots very nicely. If the guy next to me wants to race that is fine, he will open a huge gap behind him and I can just back off the throttle and change lanes into that gap. I am not racing, I just want to move over. But the key here is, as always, reaction time when the light turns green, most drivers don't react as fast as I do when I want to scoot, they are not in as much of a hurry at that time.
All your complaints about the Camry are likely due to dog shit tuning, not some kind of mechanical limitation with the automatic transmission. Every Toyota I have driven is tuned incredibly poorly when it comes to throttle reponse and shifting. I hated my Lexus GX460 tuning.
A few points to consider: The friction now happens on the one-way frewheeling devices, concentrated on a much smaller area than in a belted cvt; The displacement variation can and should be simplified to reach automotive industry readiness levels; The output has a strong torque ripple, and simple elliptical gears aren't gonna solve that.
@@klausbrinck2137 It's either a one way clutch or a ratchet. A ratchet would create enormous amounts of noise, so it has to be a one-way clutch. A one-way clutch causes a small amount of friction when it engages, and it is not a problem on a mechanism that engages it every few seconds, but in a mechanism that engages it several times a second, it becomes a problem very fast.
@@gsilva220 The ratchet or one-way is only intended for the bicycle application. An ICE application will likely feature a clutch or torque converter of some kind.
@@Drunken_Hamster this transmission literally needs a one way in any application. Otherwise there will be no torque or power transfer from the small wheels to the output. Without the small wheels locking in one way they are just freewheeling on the ring gear doing nothing.
@@Timmermon63NO belt inside Toyota e-CVT, neither clutch nor brake. Imo the build and working principle are simpler than even conventional manual transmission.
16:42 they are obviously not familiar with the bicycle crowd, the people with money are afraid of not losing every last gram of weight and the people without money are obviously not going to be able to afford that
There is a market for it. Zerode makes high end carbon mountain bikes that use a Pinion gearbox at the bottom bracket. It's slightly heavier than the traditional drivetrain, but it greatly reduces the unsprung weight at the rear wheel, which improves suspension performance. Bike reviewers report that they love the suspension feel. They also report that there's a slight decrease in drivetrain efficiency compared to a derailleur setup. The other main benefit is reliability. It's a sealed system that can go a very long time without service. A belt drive can be used. If a chain is used, the chain line is always dead straight, which improves chain life. If this could be built lighter or more compact than the current gearbox options, it might be the thing that brings gearboxes to more bikes.
@@ctsingletrackthat application was on a downhill bike where unsprung weight and reliability (no derailleur) is more important that the increased mass of the gear box. In addition, Honda developed a split linkage cvt in the early 2000 on the downhill mountain bike World Cup circuit. It was so prone to break that they often fell back to a derailleur in a box system.
I am afraid this design necessitates some kind of one way rotation limiter on the small planet gears, otherwise it would not drag the output shaft from the action of the arm. Claiming that the clicks from one way rotation limiter are only there because this particular example is intended for bicycle application seems to be a misdirection to distract from the that fact that the clicks exist even when rotating the input shaft in the correct direction.
yeah noticed that too. its a flaw in the design. without the one way ratchets the gears would simply act as idlers and no power would be transmitted. the other is the output speed variation, its a significant issue when it comes to automotive use where over 200 lb ft of torque and high speed will magnify those variations into high freq vibration what will be very noticeable. if a single ratchet fails or misses it will lead to major problems...
I have a CVT in my commuting car. I love it, for a commuting vehicle. My fun vehicle is the motorcycle. This would be very useful in EVs. Being able to take high torque input while keeping the motor in the efficiency band is exactly what an electric motor wants. Or one of those silly spinning triangles. They are moderately reliable with constant speed.
Just when you think all the advancements will come from the electronically designed side of the equation, this amazing bit of mechanical logic shows up. What a bit of deep thinking is involved in this thing from start to finish, each problem solved in a really unique manner. Awesome doesn't begin to describe what you just demonstrated. Thank you, nice, precise description, well done.
Simply genius design. As a teenager I had invented belt driven CVT but didn't knew that it already existed. And it looked crap because belt didn't look too reliable so I had abandon that idea. So until now I was struggling with idea of gear driven CVT but this design is so good because it is like variable crankshaft in the engine. from zero position the more far you move from center the more speed you have and less torque. The closer to center the more torque but less speed. Amazing how such simple idea appearing in these days then true principal mechanical engineering time was like 100 years ago. It is so simple that it is strange to me how such idea appeared just now.
I feel you. I had similar moment at the tender age of 15 when I realized that golf balls fly longer because of the dimples. Realized that it would make intake manifolds flow more as the air wouldn't be in contact with the surface. Talked about it with our car mechanic school teacher who was racing in Pro Stock drag car. He killed it saying it's not going to work. Now few years ago I was proved right.
@samulis8275 As child in 1960s-70s we had only 4 wheel roller skates, either plastic wheels for inside rinks or metal wheels for outside on streets and sidewalks. Then, after getting ice skates later as teen for ponds and flooded swamps in winter, I thought by 1980 that wheels could be put in line like a blade on ice skates and make it easier to avoid obstacles that 4 wheels outside are difficult to navigate. Then, years later in-line roller skates for outside started to be sold.
The concept is not simple, so much still needs to be developed. It does not seem to be as reliable as a normal automatic gearbox, for example the locking of the small planetary gears is vulnerable. It is questionable whether the presented design has real added value for cars and motorcycles, for example. Perhaps for smaller capacities and bicycles, but it seems expensive to manufacture. Mechanical engineering is much more complicated than many people think.
"It is so simple that it is strange to me how such idea appeared just now." The idea is old and "ratcheting CVTs" have been done many many times before but doesn't seem to have that much of practical applications(Which is not weird if you think about how they operate).
Mercedes did something kinda similar on their very first in the USA, lease only full hybrid. I don’t mean they used anything like this contraption but they did modify their standard 7 speed, planetary geared transmission to function as a CVT. To accomplish this they used an electric motor to turn one of the parts of whatever planetary was in use at the time. This allowed the planetary sets to function as a continually variable gear set within its maximum ratio limits. The transmission would then shift to the next gear and the motor would again work its magic. It actually worked really really well, and I never saw any issues out of it, though it was a very rare car. As I recall only something like 700 were ever built. It was basically the best of both worlds in my opinion. The strength and reliability of a “normal” planetary geared automatic transmission that functioned and felt like a CVT. If there was a failure in the motor, limp home mode was to just shut that motor down and then the transmission functioned as a totally standard Mercedes 7 speed. It really was cool, sadly I’ve never seen a transmission with that kind of tech since.
@ So I’m well aware of what the Prius is but I literally couldn’t care less about them. So I’m asking in earnest, in the Prius model you’re referring to, does an electric motor spin one part of whatever planetary gear set is in use at the time?
@@2down4up In the prius there are two electric motors: the larger one is geared straight to the differential, making it possible to drive the car on electric power for a few hundred yards and increasing regenerative braking power. The smaller one is connected to a single planetary gearset that splits the power coming from the combustion engine between the second motor and the differential, keeping the combustion engine at constant RPM and load while the vehicle speed increases.
I think you would be interested in Fendt Vario CVT. It uses one planetary gear and two hydraulic pump. There is no ratcheting mechanism here. They designed it in 60's and produced it in 90's.
He did mention it toward the end, but he said it was so when coasting downhill the bike pedals would not continue to rotate. Seems he missed the part where the one way rotation of the small gears is the basis of how the whole mechanism operates.
If i understand well, they use one way bearings on the planetary. This is usually troublesome. But this is indeed very clever. Reminds me of an evoluted ratchetting mechanism on manure spreaders. Lego have something like that.
I have seen a number of your videos. Your enthusiasm, your excitement, and your down-to-earth style makes these videos come to life. You do a great job explaining some very difficult concepts and your simulations add to the experience! Keep up the good work
This is like a Stephenson valve gear and an ratcheting CVT had a baby. Very neat! If it avoids the vibration of a ratcheting CVT that would be a major improvement! Btw, if I'm understanding it correctly, the 'freewheeling' is a requirement of the design, and would be present for non-bicycle uses (this is normal for most ratchet CVTs)
thank you was going to make the same comment this is simply a ratcheting CVT configured in a planetary orientation the second model displayed was simply a ratcheting CVT in a round ish box the elliptical gears is the only new thing here
@@oooooof5023 i have thought of this i feel like a sprag clutch could slip at vary low torque and at vary high torque depends what range they are made for i know they can be vary vary strong but why not have both, this is the week point of the system after all
The small gears transmit power just as long as their relative rotation locks their one-way-freewheels... As soon as the relative rotation unlocks their one-way-freewheels, they just freewheel-along. Look at this device to understand, focus on how the pedal changes rotating-direction on the crank, while the crank keeps turning to the same direction: YT-video d7E-3ndSG9E
Your gearing example ignored the effect of the final drive ratio on the ultimate number of rotations the tires will make. Otherwise, this was another fantastic video! Thanks for your great work.
Couple weeks ago came across a vid explaining Porsche’s six stroke engine. Two problems: 1) his accent was nowhere near as charming as our guy here and 2) 90 seconds in he’s pitching a grooming device and describing the options he has in trimming/shaving his pubes. Stopped immediately, thumbs down and searched for @driving4answers’ video on the same topic. No need to deal with any of that nonsense. Just quality gearhead engineering content.
I designed a gear based CVT decades ago. It was based on a differential, with one of the differential outputs connected to a viscous coupling anchored to the differential itself. Applying more torque would induce slip in the viscous coupling, temporarily reducing the default 1:1 ratio between the input and output of the CVT. As it turns out, Toyota used the same design for their Hybrid CVT, except instead of a viscous coupling they attached an electric motor.
I also designed a gear based CVT decades ago. My goal was to differential a differential in situ. I felt a little bit impossible, I still have the design but I never tried it IRL.
Seems inefficient to use slip to change ratios. Toyota's only will work in a Hybrid. The power used in the electric motor for adjusting the output speed is added to the engine power in the planetary gearbox - not burned up in slippage
@@el86lo36fkyNo they don't. They use a variable output hydraulic pump which uses a 'swash plate' to vary the stroke of the pump cylinders from zero to full stroke. Similar outcome, very different mechanism.
There is a wrong point about the sounds at 21 minutes. If you look closely at the animation, you should see that the gears rotate freely in one direction, but not the other, because the gears are pulling the output. So this clicking must be a mechanism in these gears that allows movement in one direction. And this cannot be eliminated from the designs of cars. Also this one direction mechanism is most unreliable part, because its not work well on high rpm or high torgue.
The clicking is the freewheel mechanism, not the gears though you are correct that those planetary gears do need a one way mechanism. Since this is a low power bicycle gearbox, I suspect they are just using one way bearings in them instead of some sort of ratcheting mechanism, thus they wouldn't click.
that´s correct, he mis-communicated it there... he mentions them, while praising them for their least important role, instead of mentioning their most important and most obvious role.
The way to describe the sensation of driving a CVT on a road (I've driven a few) is to compare it to driving a boat. You rev a boat to a specific engine speed and typically stay there as you cruise along.
this thing is so cool and ingenious , but 12:07 is seems like (from my understanding that) the gears that drag, only do so because the dragging gears has some sort of one-way clutch. and if such a thing was there wouldn't that mean that the torque would be limited by the friction of a Sprag clutch or the pedals of a ratchet. if this isn't what is happening then what causes the dragging wheels to stop?
The limit is the one way clutches, or ratchets. They are always the weakest link. I've been designing these for years. They just can't hold any reasonable torque of automotive applications and end up facing the same slippage problem of traditional CVTs. These mechanical CVTs also have a lower efficiency of traditional CVTs due to the added complexity, and drag resistance of the one way clutches.
@@sachinshinde9460 maximum indexing frequency? They don't really have one, since they have virtually no backlash, but they are susceptible to chatter and slippage. If the design is with traditional ratchets, the ratchet teeth will unavoidably wear, and they are susceptible to indexing frequencies equal to the individual ratchet dog spring rate plus the inertia of the ratcheting dogs. My guess would be roughly 100 indexes/sec. Anything faster than that, and I think the ratchets would not be able to reset in time and would skip several teeth before engagement. so basically the unit would be limited to 100RPM. This is why one way clutches are used instead in addition to having no backlash, but they have an inherently lower torque capability.
@@PrIsMaTiSmX Thanks for the prompt reply. I am little bit tangled in same situation like these guys do, but I am planning to use rollers instead of balls or sprags, will it be reliable? Intended frequency is around 150 indexes/sec.
@@sachinshinde9460 Do you mind me asking what you mean by rollers? The only ones I am aware of are the ones designed with sprags. Just guessing, I don't think it would be reliable. and 150 indexes/sec is too low for any application other than riding a bicycle or very low power applications. Traditional transmissions can operate well over 10,000RPM (166 indexes/sec) at the input, and have significantly higher output RPM. This is why sprag one way clutches are pretty much the only way to go.
I don't believe this thing is gonna be on any car. It has the same reliability issue with CVT because of those one way clutches. But do not worry, I am working on it.
You seem to have forgotten about one application of extremely high torque and work where CVTs are absolutely king and have no competition. Tractors and Farming Machines in general. Insane hours and torque loads in this field and basically all tractors have CVT these days. That huge Fendt 1167 Vario MT is pulling massive implements across the fields day and night in the season.
@@justincredible5406 As i understand its basically maintainance free because the "variable" part in a tractor CVT is a variable hydraulic pump. Power is transmitted thru a liquid. The input pump can vary its fluid output at a fixed rpm.
ruclips.net/video/68G8RyWEwzA/видео.html Its actually even smarter than i thought. The variable displacement hydraulic pump just accellerates the tractor to a fixed speed at which point a fully geared power transmission takes over seemlessly. Smart Stuff.
Hi Mechanical Engineer here. Watching this reminded me of something I looked into years ago. I was watching a youtube video about the (under the ocean) discovered Antikythera Mechanism from the greeks - made about 2000 years ago. It used meshed gears to model the eliptical orbit of the moon around the earth (as well as many other planets in the solar system). I was intrigued by this mainly to see how meshed gears could trace out an elipse, so I modelled the gears in solidworks to see if it actually worked - which it did. Anyhow, it brilliantly used an offset axle in a sliding slot to trace out an elipse following the path of the moon around the Earth - almost identical to the design you showed in this clip. Weird how our most unique new technology is replicating a mechanical concept that was figured out thousands of years ago.
I think so. And inside those I believe is a ratcheting mechanism which transfers the power to the output gear which I guess would be more limiting than the gear itself. Another potential limiting factor in my eyes would be the sliding pins connecting the arms to the 3 (or 4 in the second design) planetary gears.
Yep but guess what. MILLIONS of vehicles are on the road right now that do the same thing. Planetaries are not the only style of gearbox out there. Every F1 gearbox in any gear is just one single straight cut gear against another one.
This is a very cool concept. But I don't think manufacturers will be implementing this due to complexity. They have already perfected CVT technology that most CVT's will last more than 300k miles. Toyota also made a more robust CVT by having a geared launch or 1st gear, taking out the major stress that wears out CVT's. The no.1 thing that kills CVT's are lack of maintenance like fluid changes.
That's a point he doesn't touch on about this design. With nothing except bearings and gears being stressed, there would be little maintenance needed. Especially with synthetic lubricants.
Complexity is nothing new to automakers. Practically everything on a car is ridiculously complex. And why do they insist on using so much complexity? Fuel economy and emissions regulations. They will gladly put something hideously complex and unreliable on a car if it can last the warranty period and give a 0.1% improvement in fuel economy. This has the potential to do far better than that.
@@wingracer1614 Indeed. These things are mandated by governments and are being forced onto people who may have other concepts in mind. I think we've exceeded the point where efficiency in use provides more benefits than the costs of this complexity, and the planned obsolescence of extreme repair costs requires that even more energy and pollution be produced to replace these vehicles. I had an old Honda Civic with a carburetor that could give you almost 50 MPG. Less fuel used equals less pollution produced to be dealt with post-combustion and I really question whether the small gains of today's cars are worth it when that old Honda could be economically owned and driven for ~30 years while today's cars cost far more and give only half the service life. We need a more practical balance with the buyers deciding what they need, and the governments not setting insane goals to reach which are less than a few percent better.
You need to call several transmission shops and ask for their opinion. CVT has, and always will be, a dismal failure at best. Maintenance does little or nothing to help. You have a steel drive chain (push belt) running on steel pulleys. Every one made has blown up sooner or later. You can't perfect a flawed design.
02:49 Our 1960's Melroe Bobcat skid steere has a huge rubber belt/pulley drive system very similar to that, For "Slow'(Turtle) or "Fast (Rabbit)" speeds. But only one set of pulleys moves in & out, IIRC.
D4A became so big and popular that company sent a prototype to advertise their CVT) And that's great, because it means that you can really explain the principles and basic mechanics of such complicated thing to a big audience. Great job.
Ingenious technology, masterfully explained 👌 👏🏼 I can't wait to do a test ride on a bicycle equipped with this system! If the final product will be competitive in regards to weight, it'll be the ultimate gearing solution for many cycles, and most probably way more efficient and durable than NuVinci/Enviolo CVT, which I have tested and found to be not efficient enough for use in a non-electric-assisted bicycle. I'm excited to see if it can reach the hitherto unsurpassed efficiency of the Rohloff gearhub! Thanks for this brilliant explanation video!
You explain the rachet mechanism in the small gears as if its only use is to freewheel a bicycle, but my impression is that it is needed so the small gears can "pull" the output shaft in one direction and then freewheel to their original position. Is this correct? Does this mean that engine braking with such a transmission will not be possible?
Engine breaking is not possible with Ratchet CVTs no. This is simply a ratchet CVT reconfigured to a planetary gear setup rather than the parallel shaft setup that is more typical.
Reminds me of a linkage I saw once on a steam locomotive. It was able to rotate while the train was stationary, and it could also reverse directions. I don't think I ever knew the name of it but it was one of the many assorted linkages that were popular back in the steam days. Genius stuff.
The pulsing output will really limit use of this to relatively low speed and low power applications. The elliptical gears appear to reduce the effect by about 2-3 x but the variance is still there. This will cause significant vibrations overall and focus stress to the one-way 'planetary' gear clutches. The plot showing the elliptical gearing should have included a line for 'overall' output speed. If I understand the concept correctly the output is driven by whichever 'baton' is currently moving the fastest. The graph shows that there would be some significant changes in output speed when handing the baton. I can't imagine the one-way (sprague?) clutches will last very long under heavy load due to these shocks. Unless an elegant and 100% uniform torque transfer can be found mechanically.
You've got to remember not to let perfect be the enemy of good. The standard universal joint used on all driveshafts today pulses/ varies speed slighty when it isn't at exactly 0°, it's cancelled out by having two so only the drive shaft experiences the pulses. This will probably be corrected before the power reaches the road somehow.
Well since nearly all power sources other than turbines and induction motors have pulsed output at all speeds, I don't think it matters (internal combustion engines, human legs and DC motors are inherently pulsed). Flywheels and springs and hydraulics have been used for hundreds of years for smooting output torque of machines (for thousands of years in wind and water mills) - it's a non problem. Since sprag clutches have been used for heavy auto-transmissions and are used in the main drive of helicopters to allow auto-rotation - they seem to last just fine under very high power applications - several thousand HP per drive shaft. There is no shock when load transfers from one "baton" wheel to the next, as the relative speeds cross over, the clutch in the slower one simply stops transmitting torque - if you look at the graph, at any one time two "batons" have positive rotation and one has negative - the output is the sum of the two positive rotations (the torque resulting from negative rotation is cancelled by sprag clutch so will not retard the output rotation) - the result should be a gentle ripple of torque and speed - much smoother than a single cylinder motor cycle engine or human feet driving the input shaft, so insignificant in practice.
@@rcdieselrc only for light duty applications on vehicles without driveshafts, heaver vehicles don't even have CVs but use two uni-joints next to each other where light cars use CVs. Everything has applications and uses.
This reminds me of the string drive on bicycles , compared to standard chain or belt drives. The power and rotation is split between left and right side and you alternate between 2 to provide consistent torque. Actually really similar when you think about it. Its just the lever arms instead of the strings
So in traditional CVTs there is the concept of "weighting" or "biasing" the CVT. With a "light bias" or weights the transmission will be much more "racey" always seeking to operate in the higher rpm power band. A heavier bias will cause the CVT to more eagerly "shift up" and maintain more gently rpms in the lower end of the power band. A local workshop put the wrong weights in a 100cc scooter I had. It made it get off the line a lot faster, however it was embarressing to drive. You just couldn't drive it quietly. Any throttle at all and you were ripping it at 7000rpm. If you buried it off the line it would come pretty close to the rev limiter. The guy basically said, "But that's what every one does to them to get them to go faster." The next scooter I had went the other way. It would lock onto about 3.5k rpm and stay there all the way until it ran out of ratios and only then did you get the top end of the power band to get the 125cc scooter up to a top speed of 75mph when it hit the rev limiter making you "bob like a parcel shelf dog". In other CVT transmissions from the like of honda they use hydraulic intervention to provide "adaptive" "weighting".
@@apollonitro4802 confident in your lack of knowledge, you are. Just keep your inbred kids away from mine, and you can believe the earth is flat for all I care 👍
No it's not. This type of CVT has it's own drawbacks. Some because of freewheels (they don't work instantly and there's an angle between on and off state for a freewheeling mechanism from 3° to 15° or sometimes more and you have no energy transfer at this state. Also there's a torque output pulsation. There's a lot of things to solve but it's still better than belt/chain CVT
@teolynx3805 i think i saw similar cvt on old steam engines but in a simpler design. it basically converts rotational motion into reciprocating and then back to rotational. so you right, it has all drawbacks of both and introduces new.😃
Leonardo Da Vinci invented the CVT, a racheting model, a Loong time ago. I was really surprised when I started digging into the subject. Thanks for this video, the detail is very welcome.
I know I'm a bit off topic here, but since we're talking transmissions, I have to ask - why isn't just everyone simply doing what Koenigsegg did with their Light Speed Transmission? It's such a simple design - multiple clutches for multiple gears. No shifting rods, no planetary gears, no nothing except a mechatronics unit opening and closing clutches for each gear. When compared to all these 6-8-speed DCTs, 6-10-speed torque converter automatics and CVTs we have in cars these days, the LST just screams simplicity, speed, efficiency and reliability in comparison. So, why isn't everyone doing just that? I'm sure there's a reason for it, I just don't yet understand it. Mate, I don't know if you've already talked about the LST in your videos, but if not, a video on it would be appreciated. Now, I'll proceed with watching this.
For one this CVT need no to maybe one clutch instead of seven and only one actuator to change gear ratio instead of one for each clutch. It also seems to me like this can be put in a rather short package. Better for transversal engine layouts and especially bicycles. But with the rise of EVs we might never see this in a production car. But I see a lot of potential for bicycles.
They are. The Koenigsegg gearbox works the same as a DCT, just with three clutches instead of two. How complex and expensive do you want your car to be?
@@JSmith19858 I understand that, but the LST has no shifting rods and synchros, just gears and clutches and that makes it much simpler than a DCT. Perhaps shifting rods and synchros really aren't that big of a deal the way I imagine them to be.
@@EwiggrimmigMight still be useful for EV, should be able to let you use smaller electric motors for better efficiency, like everything it depends on cost if it's feasible.
I loved my CVT in my last big Ford wagon and drove it a quarter million miles. Ford did not implement simulated shifts and that was a good call from my perspective. It did suffer from lack of towing capacity, and has gone out of production. My current big Ford wagon is a 6 speed and can tow a plenty. Maybe my next big Ford wagon will have the best of both. Here's to hoping. Thanks for this vid.
I had Subaru with CVT and loved it. The key is never drive aggressively, never load it heavily, and never ever tow anything. I had a trailer hitch on the stern but it was for bike rack. :)
This specific objective was the source of hundreds of hours of 'mower thoughts', trying to figure out a way to do this while chasing a mower around the yard. I just knew there had to be a way. So much ingenuity and invention here, I'm just glad it's not a super simple device that I should have been able to come up with in my mind, but it's rewarding to see elements of my thoughts in there. The split rotation however is likely something I would have never come up with in my life. Amazing!
6:19 "are the only thing transferring the torque..." *INHALE* "...which means that..." That was kinda funny. Liked for the great information and still great video quality.
This is old news...Clock complications have used this movement many many years ago. The magic is getting that Mech to run at much higher speeds and for Billions of Cycles. Good luck with that. The COST would be fucking ENORMOUS. Thumbs up for the Explanation. Long time fan of your Channel
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NOTE: One-way ratcheting/ motion is an essential feature of this transmission and not bicycle specific as I mentioned in the video. Wothout a one-way bearing or a ratchet or other similar mechanism the small planet gears would just roll back and forth on the ring gear leading to no output. This is something I should have emphasized more in the video.
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Saw a commercial in the 90s about a cvt bicycle. It was an infomercial. Does anyone else remember? I always wondered how it worked.
How do you reverse?
Are there any numbers on efficiency?
@@battlebossv9219
That is a very good question.
It does not seem possible to move the slot mechanism in the large planetary gears to the other side of the center, because then the small planetary gears would spin freely and have no drive.
The small planetary gears must be blocked in 1 direction, because otherwise there is no drive.
I have already asked how that blocking mechanism works, because it is invisible.
Rubbish. This was Hondas failed system in F1 and downhill mountain bike racing in early 2000s
My gearbox Carbon fibre downhill bikes beat them.
Moreover a far better way for a split cycle reciprocating system that DOES all but eliminate all leverage variation using roller followers on a cam was built by myself In the 1990s, and has been developed by many companies since.
Wow! This isn't some scam, they actually made a geared CVT!
Also, your explanation was so thoughtful and precise. Explaining how these mechanisms work is often tricky, but you nailed it.
They actually already exist, and have for a long time. My Maverick hybrid uses a gear based cvt.
@ Doesn’t that use the electric motor in tandem with the ICE to determine the output speed/torque? It uses two inputs along with a planetary gear set to one output, I believe. The cvt in this video has one input leading to one output without the use of friction, so it is functionally true to the idea.
@@rdubs1705 @agr8trip It's a Toyota Hybrid System. If you aren't sure what it is, it's always a Toyota Hybrid System.
It's "free" to use and has been the go-to for anyone cheaping out on making a compliance car in the last few years.
it's actually a ancient technology by now. it's very common just not common for cars and vehicles the public usually uses. so people don't even realize what kind of CVT trannies there are out there in the industrial and agricultural field.
Toyota's e-CVT and Ratio Zero operate on the same principle, using a single planetary gear set to create different ratios but Ratio Zero can be purely analog due to the lever arms. Toyota's e-CVT is much simpler/robust due to it having the direct drive sun gear.
Using elliptical gears to cancel the speed variations from the levers is such an elegant solution
When I got my Stenograph Kit with all the gears as a child, I wondered what use the elliptical gears could be used for?
Nothing intuitive came to mind, as did with the round gears.
The arm connectng a round gear to offset the elliptical gear it's connected to during rotation wasn't included in the kit.
Had the arm been included I might have figured it out.
the whole construction is an elegant solution to a complicated problem.
YES I liked that
I'm sure they help, but I'd be hesitant to say that they "cancel" out the speed variations outright.
The shape of the elliptical gears is fixed, but the speed variation depends on the currently selected transmission ratio. So, unless I'm mistaken, the elliptical gears can only cancel out the speed variation at one specific transmission ratio. If the transmission is set to any other ratio, some speed variation would still be there (though it'd probably be reduced when compared to the round-gears option).
Having more "phases" (i.e. having more than three arms), though, could alleviate the problem.
@@AndreaZambon87
That applies to nearly any improvements.
Nothing is perfect.
Size and weight limits.
Multiple compromises to get best results possible.
I'm thinking possible cone shaped gears that allow mechanical contact with another gear on a flywheel that slides up and down the cone shaped gear according to centrifugal force, changing gearing ratios by changing diameter of cone shaped gear smoothly while continuously rotating.
finally my bicycle will be able to compete with cars on the road
Jokes aside, bicycles area already very competitive in city centers and during grid-lock.
@@theothertonydutch I get passed by bicycles all the time in the city. And I have a 136 hp vacuum cleaner at my disposal.
@@d4a See, you brought a vacuumer to a tanks job. Can't merge without causing a traffic jam? Get flattened! Can accelerate at a green light? Get flattened!
Looks a little bit too heavy.
@@d4a Video Idea 4 U ....I saw some 15 year old news clips & several articles about. An odd Grail 2 stroke engine made in Kansas USA that was supposed to be a huge game changer for the international combustion engine. It obviously wasn't but might be something to research as to why it isn't now in everything.......Also there's a guy with a DIY lightweight diesel engine sports car that gets 100 mpgs & does 0 to 60 in 4.7 seconds. The Omega he calls it here on RUclips.
I built something very similar back in 1998 while at university in the uk. We used one way clutches in the same way, but instead of varying the "crankshaft" throws, we used split connecting rods and moved the pivots of the conrods. this meant that the adjusters were fixed to the casing not to a moving part so less friction involved. "laminated" the transmission by keying a stack of discs for the crankshaft throws, and using thin laser cut and machined connecting rods with bronze bearings. we used 6 clutches and 6 crank throws to smooth the output. we had a ratio range if approximately 200. ie 1:1 to to 200:1
this is awesome, nice project
Did you use bicycle parts to test?
@@afterthought3341no, it was actually a variable drive for a seed drill that we were developing, and I borrowed a test rig from my university, and we rigged up a variable speed electric drive to operate it. Even with 6 elements, at the higher speed (lower reduction) part of the speed range, velocity fluctuation was an issue. More elements mask this problem. The main thing that we were trying to establish was an exact, repeatable calibration of the output to the input.
Did you discover a reason why it could notbe commercialized?
But one of the best things about this CVT is that it also eliminates the need for a clutch at all, adding 6 clutches seems like the opposite idea. I say that because clutches by nature are frictional and thus going in the complete opposite direction of what the actual featured technology is indicating.
Dude. Thats probably one of the coolest things I've ever seen.
+1
Normally I can understand what he's talking about. This is going to take me a while.
@@chazeroni455 yeah, whoever created this is a genius.
You wouldn't say that if your typical uni professor was teaching you this... Not talking about the good ones...
My ford cmax from 10 years ago had a planetary gear based cvt. No belts no chains.
Hey, it’s pretty important I think to people trying to understand how this works that you mention the one way gears’ main job is not to allow freewheeling, but to allow the ratchets to pull the gears in only one direction. If they were freewheeling bearings, the gears on the lever arms would roll back and forth and provide to torque transfer. The torque of this transmission is transmitted directly through that one way ratcheting gear.
I was just thinking the same thing. I am guessing those 1 way bearings are going to be a major source of friction, wear, noise, and generally just issues. I bet that's the main reason this hasn't really taken off.
correct, it just incidentally works to allow freewheeling.
In the 80's, an inventor from California developed the "Paradigm Variable Speed Transmission" for bicycles. It was a very simple, light weight, novel epicyclic gear design producing constant variable ratios from 1:1 to 1:5 output. It worked well until someone with very powerful legs decided to push on the pedals with the same torque as when he was sprinting at the end of a race. That torque caused the slipping clutches used in the design to fail, and this design used very large, heavy duty slipping clutches. If the RatioZero design is using slipping clutches, which I believe it does, I hope they are far far superior to the slipping clutches I know of. Maybe a new rachet design I'm unaware of would work. Either way, I wish the designer of this new novel device good luck.
It operates like a rowing machine...
Interesting, but it looked like work to spin it without a load. And I didn't hear any efficiency numbers (they surely know the prototype's actual efficiency).
I'm guessing that if they beat belts we'd have heard it (and eCVT reigns supreme anyways).
But ebikes are a broad market. They could have a niche.
@@jeffrenquist5476yes. He mentions these gear-CVT eliminate the need for a clutch, but these ratchets are essentially the clutch in a round about way. There are different types of these, the common pawl and ring type no doubt used here, but also axial ring pair type and sprag type which have benefits and drawbacks over the former. The blessing here is that each ratchet-planet gear has plenty of time to seat its engagement between ratcheting and applying torque, which eliminates the most common avenue of failure for these mechanisms.
This seems like an obfuscated ratcheting CVT, these have been around for a while. There's a bunch of extra gears and levers to make it seem like something new and different, but really it's just a ratcheting cvt, the animation around 13:00 really makes it clear as thats the same motion and link as in a ratcheting cvt. The freewheeling you mentioned isn't a bicycle specific addition, it's something inherent to this type of CVT. All ratcheting CVTs unavoidably do this, sometimes it's a convenient feature, sometimes it's not.
This comment is important and needs more likes.
Exactly! I was very confused that the ratchet wheels werent explained during the CAD when its clearly the way that the different small planet gears "pass the baton" to each other. The locking of the ratchet is the mechanism by which any torque is transferred to the output ring gear.
@@EvenLessConspicuousHandle Yeah, he called them a freewheel but glossed over it.
yeah that was what i was thinking as well from how it worked
So, what your saying is "Its been around for a while, and since it is not in mass production, it means its not practical". You know, kind of like plasma propulsion!
No wonder you have more than a million subscribers. Your explanations and enthusiasm are really number one. Thank you very much.
Imagine how efficient the next generation manual pepper grinders will be. It will really raise my molecular gastronomy.
How fast do you need the grinder to spin? It’s going to get awkward to hold with the 1 Lb extension container of pepper seeds just to fuel it.
😂
@@Cloud30000"reload!"
The fact it can change gear ratio while not rotating is another advantage over traditional CVTs: they have to be under some level of rotation (even if the output is disconnected) to change ratio, otherwise it would pinch the belt.
I might be wrong but didn't it rotate the output slightly while changing?
@@YoungShul what OP is talking about is that you can change "gear" while vehicle is standing still (which you cant in "classic" CVT unless circumvented otherwise, i.e. the disconnected output stated by OP)
@@Trauerdurst_TD3D This however is pointless for combustion engines and the fact that it goes from "highest" gear to "lowest" from the neutral position is an unfortunate reality. The combination of the two makes it less straightforward.
You cannot, because there is no clutch. If you were to try to change the ratio while stationary, the output would have to start to move.
@@mreaper2265 it goes from "lowest" gear to "highest" from the neutral position
Correct me if I'm wrong but you say the one-way ratchets are because it's on a bicycle. I can't help but think because of the dragging that the little planets have to do that a one-way ratchet is actually critical to the operation and not just for the bicycle. Otherwise when the lever arm went to pull back the little planet would just freewheel and not transfer any torque. I would love to know how I'm wrong if I am but I think that is correct.
You are obviously correct!
This is just a "ratcheting CVT", ratchets(or some other type of "freewheel" mechanism) have always been an integral part of them throughout the ages.
I think you are right!
I was wondering the same thing and I’m surprised he didn’t address this in the video. I would like to see how they achieved this inside such small gears.
@@ghall05 it is not something I would expect him to overlook.
I agree, as soon as I saw the initial animation, my first thought was how are they freewheeling one way, but locked and applying torque the other way? A ratchet seems the only explanation - without a sun gear (as per a standard planetary gear system), free-wheeling planets would just move back and forward in the ring gear, unless they could only turn one direction.
EDIT: if it was ratchets, then I can't see this technology scaling up. The ratchets would have to be strong enough to provide peak torque through the transmission, and would therefore have quite a bit of resistance (not to mention noise). Then there's the issue of high-RPM, and the ratchet "slipping" backwards because it hasn't had time to engage.
Seems great for a bicycle, can't see it on a super-car. Koenigsegg's CC850 transmission is probably a much more useful breakthrough!
In college, I had a great physics professor, Lynn Beebe, who was a wizard at explaining difficult concepts for my then young mind to understand. He also drove a 1963 Corvette coupe when it was just an old but undeniably cool car. You are the first person I feel would be better at explaining difficult concepts to what is now my old mind than Lynn Beebe could.
Thank you.
I believe you failed to mention the ratcheting mechanisms necessary in the smallest gears which lock the rotation towards the arms when they are on the power stroke and thus allow power to be transferred. This has me stumped because in the animation if these didn’t exist, the small gears would simply roll back and forth on the output gear, essentially skipping over the thing that makes this work at all.
I also believe so. Also, that ratcheting mechanism looks like potential fail point of this design.
@@mrblc882 Everything has fail points. The question is, can it be made durable enough to be viable? In low power applications like a bicycle, absolutely. Simple one way bearings would be sufficient. High power applications like a race car or truck, that will be a challenge. I do think yes, it can be made durable enough but it won't be easy and your concerns are valid.
@@wingracer1614 It seems like a fundamentally more complex and intricate design, but you're correct. If it provides enough of a benefit it can succeed. I have a feeling even if it does catch off massively more well trodden set speed gear transmissions will still exist for durability and simplicity reasons.
At very least it now exists and can be used for enthusiast and luxury cases!
That's the one part I saw in the first animation that made me wonder how they would actually make it. In the prototype he had, they used ratcheting mechanisms but it seemed to have a lot of noise and friction. One way bearings would be much quieter and smoother but they wear out fairly quickly. If they were to use them and make them last, they would have to be very large.
Make one out of wood
The explanation only makes sense when you understand that ratcheting is critical to the whole design, absolutely not just for bike applications.
yeah it should be added to the video, I spent about 5 minutes staring at the schematic trying to understand what was stopping the gears from just freewheeling in both directions.
Agreed, however I would be concerned about the longevity of the ratchet mechanism in a car/truck application, so in my thinking (anyone feel free to correct my logic) why not
-keep all 3 levers at the same position (moving together) ,
-lock the current 'output' gear and, and
-use a 'sun' gear in the center as the output?
In my half-though calcs, this would:
-remove the speed variation over each revolution, and if the
-sliding levers are on roller bearings, this should allow for changing ratios under high torque as well while
-maintaining the ability to go 0:1 ratio.
Craap, o thought some more and OK, this idea would simply make the output shaft rotate back-and-forth.
For my idea to work, the levers would have to ride on a cam to flip them to the opposite side every time the slot is parallel to the ring gear... or some other lever mechanism similar to variable compression ration engines. Brain hurting now.
Gotta get back to work but I still think the sun gear with a locked ring (current output gear) and the lever shift every half turn might be plausible. This would definitely reintroduce output shaft speed wobble every turn but that's easy to minimize.
am I alone in knowing that there was ratcheting from the sound at the very beginning of the video? 0:08
my first thought was "sure, split the rotation, and multiply the number of moving parts"
the work it would take to refurbish one of these at the end of life would be crazy if the electronics could not be completely separated from the mechanicals. If it all comes as ONE single part? electronics integrated right alongside the inner works? They could never be rebuilt by any local.... and becomes one more short lasting part that can not be repaired.... just one more way for corporations to F you when you "buy" something
@@derricktalbot8846 I didn't pick up on it immediately, but as soon as the CAD animation started it was obvious that the gears had to only be able to free spin in 1 direction. That does open some interesting thoughts as to whether or not a gear is the optimal solution to that specific part of the device. Is there a non-rotating catch mechanism that would be just as functional with significantly fewer parts?
The ratchet means it’s technically not a CVT, since the actual number of discrete gear ratios is just equal to the number of ratchet clicks at the highest radius offset.
dont forget about the toyota hybrid electricCVT , where planetary gearset is controlled by speed variance in two electric motors. this gives the close to the same efficiency as manual transmission
Or just get an EV which blows ICEs out the water smh
is the eCVT basically a electric car with a range extender?
Sadly eCVT is only possible in hybrids. If it was applied to ICE te electric motors changing ratios would kill fuel efficiency.
@@KamilKubik43 More accurately it by definition makes any vehicle with that transmission a hybrid and usually improves efficiency.
@@GewelReal in which regard?
No mention of Toyota's eCVT? Yes, it's electromechanical, but unlike belt driven CVTs, it doesn't rely on friction and transmits power through a planetary gear set.
exactly! and they don't suffer from oscilating output
ECVTs are the future.
@alucard87 and they need two inputs?
@@d4a I was going to mention this as well. There's a fantastic WeberAuto video on toyota ecvt transaxles that explains the working principle. Edit, as I missed the point - for a bicycle application an ecvt would require a second input from a motor, so it'd be suited to a commuter ebike, but it can't just provide variable transmission without it. So if the goal is one input only, it's not the way to go.
That said, these are really ingenious and strikingly simple. They also pull double duty providing hybrid drive, regen braking and starting the ICE in addition to being a cvt.
Would love to see a video with your take on these, pros and cons.
Would love to see a deep dive into the Toyota eCVT (2010 and newer Prius). Maybe that could be scaled down to e-bike size. Brilliant design in simplicity and virtually frictionless and practically impossible to wear out.
My first dealing with a CVT type of transmission was not in a car but in the HVAC industry. A VAV(variable air volume) is used to vary the fan speed in a commercial building according to load requirements this maintains static pressure and temperature.
This geared approach is an interesting application to solve the inherent limitations of the variable pully design.
I mentioned this application on another thread. I am a retired HVAC mechanic, and worked on VAV units with this drive set up. They were problematic, and we replaced them with VFDs. I don’t like these CVTs either.
@@rodgraff1782 Yeah. Much better to do it with power electronics. More reliable.
You can think of the electric motor in an EV as a VFD. The battery DC voltage is used to produce a 3-phase AC voltage to drive the motor at the desired speed.
So the reason you don't need this in an air handler is the same reason we don't need it in an EV.
The vavs I worked on just had a damper I think.
I am sure I am not the only one who noticed this, but I have not read through all the 1500+ comments. Gear ratio is input(from engine) to output shaft(not tires) of transmission. You will always have a gear reduction on your differentials...I am fascinated by this new type of CVT though...no flimsy belt. Yay!
I mean, my CVT belt is anything but flimsy since it's a chain belt, but it is indeed sluggish sometimes. I love it for the comfort tho.
No flimsy belt, a couple dozen more finnicky bits to wear out and go bad. I'm not exactly seeing a huge advantage here.
These transmissions have a lot of friction that generates heat. That equals lost horsepower, as it takes energy to generate heat. I’m not sold on these. I
@@unevenelephant469it's a good idea which eliminates the energy loss of slipping stretching belts and chains and could be engineered to be as durable and reliable as a manual gearbox for a car (which a belt or chain driven CVT simply cannot)
@@DJKr15py @unevenelephant469 Might even be better if the wear and overall system efficient is the same or higher than traditional gearboxes due to allowing the engine to always be in the preferred rpm at all times for either optimal torque or power
Ok, this is pure art. Also, have you considered making an episode about Toyota’s eCVT hybrid transmission, another marvel of mechanical engineering?
Yes, that's actually a good video idea!
@@d4a I love the eCVT! impressive and reliable design.
The eCVT is extremely simple in it's construction. It actually has a fixed numerical gear ratio between the ICE and the output. It can vary the ICE RPM by changing the speed of one of the electric motors (MG1 in Toyota language). The second electric motor (MG2) is fixed to ring gear of the planetary gearset and as such also directly linked to the final drive/differential. The ICE is connected to the planet carrier and MG1 to the sun gear.
Since the speed of MG2 is fixed to the output speed of the transmission you can vary the ICE speed by varying the speed of MG1. By spinning MG1 in the opposite direction you can drive in EV mode since it keeps the ICE at 0rpm. There is no clutch or torque converter between the ICE and the transmission, only a fixed torque damper.
A planetary gear set is a sideways differential.
The eCVT is the reason I decided to get the Prius. The belt system that many cars use is not exceptionally reliable especially the Nissan version.
The Sienna and the venza hybrids along with the Prius all use this system and it is very elegant and extremely reliable and is capable of some towing if you don’t mind pissing away your MPG.
This is the best explanation of a regular manual transmission and the interaction with variable engine speeds I have ever seen. I've always struggled to explain this to people who don't understand these concepts. You nailed it with your graphics and description.
The geared CVT is an engineering marvel. I hope it makes it into mainstream usage.
Well done!!!
That's what I call a genius idea, it's something out in the open for everybody and none had the idea before. It's purely mechanical a Victorian engineer could have designed and build it .
Nothing fancy, no electronics, no exotic material just steel and brain
I wouldn’t be surprised if a victorian engineer actually built something similar. Here’s a video of an old Massey-Ferguson combine harvester where the reel drive works with exactly the same principle. Reel is the big pentagonal thing in the front. It has two connecting rods going back and forth and two freewheels at the shaft of the reel. The speed is varied by varying the stroke of the connecting rods.
ruclips.net/video/JCySb0nTmtY/видео.htmlsi=J28SD7UxZCpI6JUz
The Wikipedia article on CVTs also describes this principle: en.wikipedia.org/wiki/Continuously_variable_transmission#Ratcheting
Simplicity almost always equals reliability and longevity, and this is a simple but ingenious design.
You must have missed the part showing that it needs a motor to control the ratios, and for automotive use it will need an electronic control unit and sensors unit to control the motor.
Steam train uses almost similar system on how it "selects" speed. It is missing the planetary gears. So you are more correct than you thought
@DonziGT230 It doesn’t need the motor and doesn’t need to be automatically controlled. It could certainly be controlled with a simple hand lever, or a knob, or any number of manual controls. The motor and automation are only there to provide for the convenience expected in modern vehicles.
I love how D4A is just a huge car/engine engineering nerd
Can't wait for him to get into watch movements
Man I love this channel. Every time he puts a video I gotta watch it they're so informative.
informative yes but in that case it's a total useless information. this transmission is just a very nice school project but cannot survice in the real world. this size and mass just to move a 20lbs fucking bike ???? imagine the size, mass and cost of this contraption to move a fucking 3500 lbs car. the toyota hybrid cvt with just a differenital and the use of the alternator is: cheaper, lighter, stronger and simplier and for what i can imagine more efficient.
Never heard of a CVT. Great explanation. Thank you.
One thing that could have been explained better if I understand it correctly is the ratcheting mechanism is essential to the operation of the transmission, not because it's on a bike. That means it can't transfer negative torque back to the engine unless there's a way to reverse the direction of the one-way ratcheting mechanism.
The small gears transmit power just as long as their relative rotation locks their one-way-freewheels... As soon as the relative rotation unlocks their one-way-freewheels, they just freewheel-along. but you are right, he mentions them, while praising them for their least important role, instead of mentioning their most important role.
@@klausbrinck2137 - It was fully explained by the Axis Offset Leverage. No ratchet necessary
@@Scissors69I don’t think so. Axis offset rotation doesn’t explain how the small gears drive the ring gear. . . It has to be either a ratchet or one way bearing on each of those small gears. Or am i missing something?
My grandfather would have loved this. He was a master machinist who loved to tinker, and read up on any & every vehicular tech imaginable.
He crafted a homemade gocart with a centrifugal clutch made out of a drum break which gave near-infinite gear ratio (albeit through friction), attached to a 3-speed manual gearbox. Unlike a CVT though, you could replace the pads with standard break pads in about 5 min for a dollar (at the time). And the gocart basically couldn't be flipped over. It had inverted body-lean in turns, which adjusted some suspension linkage based on speed & wheel angle both. Supercharged, limited slip... Magnetically dampened shocks too. It also had "moving" downforce spoilers.
(Bear in mind, he made this in the very early 1950's)
He did a lot of other things too. He liked "borrowing" from aviation tech a lot for non-aviation projects. Day job was cars and industrial machinery. But I think he poured more tinkering & experimentation into that gocart than anything else. I never saw it in a running condition, but I'm told it was "terrifyingly fast", and cornered so hard the seat straps (tie-down straps actually) could leave bruises. I suppose based on size & such, it would be regarded as a small dunebuggy really. He called it his gocart, but it was to gocarts as Doom-Guy is to a boyscout.
Anyway, he would've lost sleep for days over a geared mechanical CVT.
Thanks for sharing that story mate
Nobody never dies. Your grandpa living in afterlife. So pray about him to God Father.
Best regards from christians from the whole world.
You mean drum brake?
@@seriouscat2231 indeed
@@Ostap..Bender afterlife isn't exclusive to Christians. Why do some people always need to hijack a wholesome story for their personal beliefs. Very unchristian. Even if it comes from a good place, it goes downhill faster than a gocart with every additional sentence you typed the ultimate insult being you speaking on behalf of millions of people. While grandpa was surely a good man, not every Christian will agree where he is. Also, it isn't relevant and we can never know.
As someone who misspent a lot of my youth building with Legos, followed by cutting gears from HDPE and fabricating manual clutches and transmissions, along with building entire remote-control tracked and wheeled models from hobby metals and wood, I so appreciate your animations and explanations of this beautiful machine. I have viewed a lot of RUclips content; this video is one I will never forget. Thank you and thanks to Ratio Zero. I can only hope that their transmission will be available in Subarus by the time I need a new car!
1: Mind Blown. Thank you.
2: You are a genius at explaining this stuff.
3: I see great things in Ratio Zero's future. Hope they can get funded.
21:15 Finally you mention the need for one way clutches! I think these are the real killer for this design. All one way clutches I know of allow only choosing 2 from the following:
- low wear rate
- minimal backslash
- high torque
It seems that this design would need all three at the same time!
Other than that, superb design and this video explains the mechanism pretty well.
I think this design overcomes the need for minimal backlash. It allows you to just add more arms and wheels to overlap each other during the phase of backlash. The prototype has 4 stages, but other than the cost of additional materials and efficiency losses from drag, there's no reason you can't have more, which would smooth out the output, and account for the backlash.
I think it would also be theoretically possible with this design to use a brake mechanism instead of a one-way clutch mechanism, because the timing of it is more or less fixed (i.e. it could be controlled by a cam style mechanism or even electronically). It would add complexity to control the timing of the brakes, but it could resolve the issues with one-way clutches.
@@Old_BMWs Using a brake mechanism instead of a one-way ratcheting clutch would also allow the transmission to reverse rotation simply by changing when the brakes engage. No need for a reverse gear!
@@Old_BMWs Wouldn't brake mechanism require friction surfaces and cause lots of wear and power loss?
He’s not saying they require clutches or ratcheting. In fact he’s saying the opposite. The only reason why this specific model needs a ratcheting mechanism is for the freewheeling mechanism on a bicycle. Cars don’t need a freewheeling mechanism and haven’t needed one since Saab still had their 2 strokes in the 60s
@@HungrySharkMaster And he is simply wrong. The mechanism as described, both versions shown, clearly depends on a freewheel or "one-way" bearing in each of the power transfer lever modules. That is how they can spin freely when power is not being applied. Without the freewheel mechanism, with open bearings, this device would simply spin unimpeded and not function. With shaft locks it would be completely frozen and immobile.
When the lever is in the reverse stroke, the gear/wheel has to be disengaged. In fact, not only in the reverse stroke, but during the transfer phase as well. Only during the solo power phase does it need to mesh, when the desired speed of the drive lever is faster than the speed of the output.
I presume that freewheels are used for prototype simplicity. The first example could have used ratchets directly on the lever arms. But in both cases there is the problem of backlash. During the handoff between modules, one of them has to catch up to and overtake the other. Even if the ratchets are perfectly aligned and use the same cog, there will still be some discontinuity as the load is transferred from one to another. The ratchet cannot slip down to engage the tooth without some clearance, which the force of the system then takes out. So at minimum even if the sinusoidal oscillation of the ratchet arms is eliminated, there will still be vibration introduced at each lever "phase" transition. Introducing more lever modules decreases the sinusoidal variation by utilizing a flatter part of the speed curve (using a smaller angle of the total stroke) but at the expense of increasing the transfer jitter.
Now maybe it is good enough to use a rubber flex disc on the output shaft to absorb this very high frequency jitter, but each time we add a module it also increases the complexity and number of parts, which increases the odds of some failure as well as the cost. And unfortunately I don't think any transfer mechanism (either one-way bearings or freewheel ratchets used here, or direct lever ratchets, or brake modules as suggested up-thread) can solve it. The next lever in the sequence would have to run faster than the first during the power stroke, in order to pick up the perfectly aligned next ratchet tooth, then slow down to transfer load, match perfectly during the handoff, and maintain a constant speed during its own power stroke. Quite a feat if they can figure it out!
3:11 I’m not sure the numbers entirely make sense (shouldn’t it be 2.399, 2.398,…,0.402,0.401??) But nonetheless your ability to convey information in a simple and easily digestible manner always positively surprises me :)
I think so too
Yeah, it should be the way around... just like @ap0llo.0ne51 wrote
yup
thought so too, i'm 99% it's only a typo
yes
It's actually a variable cam coupled by gears. The slot where the actual change in ratio takes place is equivalent to a cam pushing on a lever with a moveable pivot point.
Good job, you figured it out.
I posted about zero max brand speed adjusters and my comment was censored.
Bro have been feeding us good lately. Whenever I find any niche engineering sample, bro will upload a video for it the next day.
“Bro”
🤦🏻♂️
@vincedibona4687 english isn't my first language, i just learned it from YT and insta 😅
What a brilliant explanation of a complex motion
The tech has been around for ages and the main weaknesses were the one-way bearings/ratchets and the torque pulsation.
And this tech has also been applied to bicycles many years ago, as a variable leverage chainless pedal drives, back when bicycles were a new thing.
Nice to see this being developed further, would also be nice to see it actually coupled to an engine doing actual hard work, because many things work in concept stage and fall apart once in an actual car being driven my regular people.
Was also used in machine tools, especially drill presses for an automatic variable-rate feed of the drill into the work.
It also looks like high rpm might be problematic and might result in more vibrations than you would expect from classic transmissions.
So downsides will include:
- only 1 small gear's teeth is engaged at a time, as opposed to load being split between all the planet gears (as in a conventional planetary drive) - thus you need more material (and weight) to transmit the same power.
- the transmission is vibrating, instead of having a constant load (of centrifugal force and torsion), so fatige failure is a.much larger concern
Well realistically without freewheeling on the bicycle...
...you wont be forced to pedal faster, the pedal will instead bash your leg bone. If you are lucky it will hurt, if you are unlucky, it may break the bone
this looks like a case of "just because you can, doesn't mean you should"
Regarding the first point: All but two of the gears in a manual transmission are sitting unused at any given time. A similar situation exists in a traditional automatic transmission.
Regarding the second point: a torsion spring incorporated into the drive shaft could potentially eliminate the problem of erratic torque delivery.
Something like a two piece flywheel with springs inside can smooth out the output quite a bit.
@@debtfree_2024I'm not an engineer, but personally, I'm not convinced the costs outweigh the benefits for this particular design.
Ratio Zero is definitely going places. This is amazing. I yearn for a world where this exists on a car or motorcycle that I can buy locally.
I want this on a cargo bike so badly. My electric bakfiets is a rideable chain stress test right now as it quite the heavy thing to shift under load when I have the box full.
What a phenomenal video! And an amazing idea! Thank goodness for the super smart people in the world who come up with these amazing Ideas to make our lives better!
I have a side X side for when we go camping. I use it as our work horse to get wood, water, and other work related projects. I had two different machines with belt CVT's and they would always burn up belts and slip when towing a heavy trailer or pulling a stump out of the ground. I ended up ordering a machine from outside of my country just so I could get a manual transmission. But with the 5 speed manual I lose top speed because it is geared towards torque! I look forward to this CVT coming out to have the best of both worlds! Very exciting!
My friend, your explanation skills are one another level. Bravo! One of the best easy to understand explanations of a complex subject I've seen.
I drive a cvt on my Subaru Outback and I never want different transmition. 😉 You have to experience it for yourself to see
The use of all of the overrun (sprag) clutches will be a durability challenge.
The transmission will likely have problems handling significant torque. It looks like at certain points in the cycle all power passes through a small bearing on the end of the arm.
If you don't need coast, you could do away with them.
And if those little planet gears have sprag clutches in them, it's not really a true gear driven CVT. It still relies on fiction.
If they have ratchets, I imagine the torque delivery would stutter since the lash between one and the other wouldn't be perfect.
@@johnnicol8598 On a bike?
@@absolutepressur Freewheel clutches can be spring or centripetal.
I am almost 70 years old, and all my working life I have driven a manual transmission economy vehicle. One thing I have always loved about these vehicles (though I didn't notice it until I drove an automatic transmission vehicle) is the instant application of power when I suddenly accelerate. Though the economy vehicle does not have a lot of power, I get all it has (in the current gear at the current speed) as soon as I press on the gas. I recently moved to the LA area and the manual transmission in the stop-and-go traffic got old really quick, so I upgraded from the 15-year-old Corolla to a 2023 Prius Prime, which has a CVT. In EV mode I still have that instant application of power. Then my beautiful Prius got rear-ended after one month of ownership and the rental Camry I was given had a standard automatic transmission. I hated it. I feel that the timing of power distribution is as important as the total power. I would be in a slow freeway lane and there would be an opening in the next faster-moving lane, and I would stomp on the gas. But instead of jumping forward the Camry would hesitate a moment, then decide to shift gears, and finally it would apply power about a second later. That spot that should have been big enough to safely move into is now not big enough because the car delayed the application of power. In my Corolla I would have already shifted gears prior to stomping on the gas, and my Prius would have instantly jumped forward with it's CVT, but the Camry lost me my safe opportunity. I would rather have lower power delivered when I need it than tons of power delivered late.
I am very happy to see this development of a geared CVT. While I consider that my Prius will be the last car I ever buy for myself I am happy to see that better cars are coming.
I'm on the back end of 71 and I learned to drive in L.A. My first driving job (at 17) was delivering furniture/appliances in a 3 speed manual Chevy P-U.
It was a blessing and a curse for both reasons> Positive power for the loads but a bear in the areas where an automatic would have aided finessing tight spaces and steep inclines in areas like near Dodger Stadium. And the stop and go issue too. I was lucky the guy who taught me manual insisted on keeping rollback under 3in. I think the required discipline of the responsibility at that age helped me stay out of trouble. But my thought here is with the mechanical complexity of a geared CVT, you would want the buffer of something like a torque converter ahead of it simply because it would take a little training to not apply too much power at once. On a bicycle, it's all about the initial leverage but if you have to pedal at a certain pace before the CVT engages, it kind of defeats the purpose. Looks like a great idea, but application might be limited for the sheer abuse we put our vehicles through.
Hybrid ecvt is a totally different animal than traditional cvt
Couldn't agree more with "I would rather have lower power delivered when I need it, than tons of power late"
@@Eric2300jeep I will comment that coming off the line at a light the Prius still has a small hesitation if I am using both engine and battery power. Say I am first in my lane, but I need to move over a lane or two within the next 1/4 mile or so. I turn on HV mode enabling the engine to start, but it doesn't start until I press the gas. Then the battery provides the initial power out of the light while the starter spins the engine to get it started, so I have a detectable delay to full acceleration, maybe a 1/4 to a 1/2 second. The good news is that the 2023 Prius is a different animal from previous years, and once the engine kicks in it scoots very nicely. If the guy next to me wants to race that is fine, he will open a huge gap behind him and I can just back off the throttle and change lanes into that gap. I am not racing, I just want to move over. But the key here is, as always, reaction time when the light turns green, most drivers don't react as fast as I do when I want to scoot, they are not in as much of a hurry at that time.
All your complaints about the Camry are likely due to dog shit tuning, not some kind of mechanical limitation with the automatic transmission. Every Toyota I have driven is tuned incredibly poorly when it comes to throttle reponse and shifting. I hated my Lexus GX460 tuning.
A few points to consider:
The friction now happens on the one-way frewheeling devices, concentrated on a much smaller area than in a belted cvt;
The displacement variation can and should be simplified to reach automotive industry readiness levels;
The output has a strong torque ripple, and simple elliptical gears aren't gonna solve that.
the clutches work via frictionless form-lock (positive engagement), not by friction...
@@klausbrinck2137 It's either a one way clutch or a ratchet. A ratchet would create enormous amounts of noise, so it has to be a one-way clutch. A one-way clutch causes a small amount of friction when it engages, and it is not a problem on a mechanism that engages it every few seconds, but in a mechanism that engages it several times a second, it becomes a problem very fast.
@@gsilva220 The ratchet or one-way is only intended for the bicycle application. An ICE application will likely feature a clutch or torque converter of some kind.
@@Drunken_Hamster this transmission literally needs a one way in any application. Otherwise there will be no torque or power transfer from the small wheels to the output. Without the small wheels locking in one way they are just freewheeling on the ring gear doing nothing.
@@mikosoft- It was fully explained by the Axis Offset Leverage. No ratchet necessary
Driving a Toyota CVT Hybrid since almost a year now.
Best car and transmission I ever owned.
Silent, smooth, 3.8l/100km.
Wait, the belt will go, the bills will come.
@@Timmermon63the hybrids use a "e-cvt" or something which is supposedly better.
@@Timmermon63NO belt inside Toyota e-CVT, neither clutch nor brake. Imo the build and working principle are simpler than even conventional manual transmission.
@@Timmermon63no belt, it is electromagnetic
16:42 they are obviously not familiar with the bicycle crowd, the people with money are afraid of not losing every last gram of weight and the people without money are obviously not going to be able to afford that
Probably have to make it out of PTFE for the bikers.
There is a market for it. Zerode makes high end carbon mountain bikes that use a Pinion gearbox at the bottom bracket. It's slightly heavier than the traditional drivetrain, but it greatly reduces the unsprung weight at the rear wheel, which improves suspension performance. Bike reviewers report that they love the suspension feel. They also report that there's a slight decrease in drivetrain efficiency compared to a derailleur setup. The other main benefit is reliability. It's a sealed system that can go a very long time without service. A belt drive can be used. If a chain is used, the chain line is always dead straight, which improves chain life. If this could be built lighter or more compact than the current gearbox options, it might be the thing that brings gearboxes to more bikes.
@@ctsingletrackthat application was on a downhill bike where unsprung weight and reliability (no derailleur) is more important that the increased mass of the gear box.
In addition, Honda developed a split linkage cvt in the early 2000 on the downhill mountain bike World Cup circuit. It was so prone to break that they often fell back to a derailleur in a box system.
@chriskring4709 Zerode's gearbox bikes are trail bikes. They don't currently have a downhill model in the line-up.
I am afraid this design necessitates some kind of one way rotation limiter on the small planet gears, otherwise it would not drag the output shaft from the action of the arm.
Claiming that the clicks from one way rotation limiter are only there because this particular example is intended for bicycle application seems to be a misdirection to distract from the that fact that the clicks exist even when rotating the input shaft in the correct direction.
Agree. About halfway through the video I was expecting a mention of sprag clutches on the small planet gears... 🧐❔
Correct - although it may be roller bearings in a pinch on the smaller planetary gears to provide a frictionless clutch
yeah noticed that too. its a flaw in the design. without the one way ratchets the gears would simply act as idlers and no power would be transmitted. the other is the output speed variation, its a significant issue when it comes to automotive use where over 200 lb ft of torque and high speed will magnify those variations into high freq vibration what will be very noticeable. if a single ratchet fails or misses it will lead to major problems...
Correct !
@@piccalillipit9211
To transfer greater power, that doesn't seem solid to me.
I have a CVT in my commuting car. I love it, for a commuting vehicle. My fun vehicle is the motorcycle.
This would be very useful in EVs. Being able to take high torque input while keeping the motor in the efficiency band is exactly what an electric motor wants.
Or one of those silly spinning triangles. They are moderately reliable with constant speed.
Just when you think all the advancements will come from the electronically designed side of the equation, this amazing bit of mechanical logic shows up. What a bit of deep thinking is involved in this thing from start to finish, each problem solved in a really unique manner. Awesome doesn't begin to describe what you just demonstrated. Thank you, nice, precise description, well done.
Simply genius design. As a teenager I had invented belt driven CVT but didn't knew that it already existed. And it looked crap because belt didn't look too reliable so I had abandon that idea. So until now I was struggling with idea of gear driven CVT but this design is so good because it is like variable crankshaft in the engine. from zero position the more far you move from center the more speed you have and less torque. The closer to center the more torque but less speed. Amazing how such simple idea appearing in these days then true principal mechanical engineering time was like 100 years ago. It is so simple that it is strange to me how such idea appeared just now.
@@cibimbox9195
It takes Necessity.
I feel you. I had similar moment at the tender age of 15 when I realized that golf balls fly longer because of the dimples. Realized that it would make intake manifolds flow more as the air wouldn't be in contact with the surface. Talked about it with our car mechanic school teacher who was racing in Pro Stock drag car. He killed it saying it's not going to work.
Now few years ago I was proved right.
@samulis8275
As child in 1960s-70s we had only 4 wheel roller skates, either plastic wheels for inside rinks or metal wheels for outside on streets and sidewalks.
Then, after getting ice skates later as teen for ponds and flooded swamps in winter, I thought by 1980 that wheels could be put in line like a blade on ice skates and make it easier to avoid obstacles that 4 wheels outside are difficult to navigate.
Then, years later in-line roller skates for outside started to be sold.
The concept is not simple, so much still needs to be developed.
It does not seem to be as reliable as a normal automatic gearbox, for example the locking of the small planetary gears is vulnerable.
It is questionable whether the presented design has real added value for cars and motorcycles, for example. Perhaps for smaller capacities and bicycles, but it seems expensive to manufacture.
Mechanical engineering is much more complicated than many people think.
"It is so simple that it is strange to me how such idea appeared just now."
The idea is old and "ratcheting CVTs" have been done many many times before but doesn't seem to have that much of practical applications(Which is not weird if you think about how they operate).
Mercedes did something kinda similar on their very first in the USA, lease only full hybrid. I don’t mean they used anything like this contraption but they did modify their standard 7 speed, planetary geared transmission to function as a CVT. To accomplish this they used an electric motor to turn one of the parts of whatever planetary was in use at the time. This allowed the planetary sets to function as a continually variable gear set within its maximum ratio limits. The transmission would then shift to the next gear and the motor would again work its magic. It actually worked really really well, and I never saw any issues out of it, though it was a very rare car. As I recall only something like 700 were ever built. It was basically the best of both worlds in my opinion. The strength and reliability of a “normal” planetary geared automatic transmission that functioned and felt like a CVT. If there was a failure in the motor, limp home mode was to just shut that motor down and then the transmission functioned as a totally standard Mercedes 7 speed. It really was cool, sadly I’ve never seen a transmission with that kind of tech since.
The prius is exactly like that, minus the 7 gears, as the electric motors do the full range of car speeds
@ So I’m well aware of what the Prius is but I literally couldn’t care less about them. So I’m asking in earnest, in the Prius model you’re referring to, does an electric motor spin one part of whatever planetary gear set is in use at the time?
@@2down4up In the prius there are two electric motors: the larger one is geared straight to the differential, making it possible to drive the car on electric power for a few hundred yards and increasing regenerative braking power.
The smaller one is connected to a single planetary gearset that splits the power coming from the combustion engine between the second motor and the differential, keeping the combustion engine at constant RPM and load while the vehicle speed increases.
@ Thanks for the awesome explanation! I was unaware anyone other than Mercedes did this. I guess I shouldn’t be surprised Toyota did.
I think you would be interested in Fendt Vario CVT. It uses one planetary gear and two hydraulic pump. There is no ratcheting mechanism here. They designed it in 60's and produced it in 90's.
All those moving parts, what could possibly go wrong ?😮
An extremely clear and informative explanation of what would appear to be a very complicated mechanism. Well done, excellent as always 👏
I think I may have missed it but I think you forgot to mention that the small planet gears can only rotate in one direction
Forget about that.. as always one should watch the whole video before commenting 😂
He did mention it toward the end, but he said it was so when coasting downhill the bike pedals would not continue to rotate. Seems he missed the part where the one way rotation of the small gears is the basis of how the whole mechanism operates.
@@woodhonky3890 Making this a ratchet cvt in disguise.
@@jaldo7364 Yep, that's exactly what I was thinking. Not quiet usable for heavy equipment in this form, but still pretty cool.
@@woodhonky3890 right not just me then
If i understand well, they use one way bearings on the planetary. This is usually troublesome. But this is indeed very clever. Reminds me of an evoluted ratchetting mechanism on manure spreaders. Lego have something like that.
What a beautiful piece of engineering - and you explained everything thoroughly, well done!
i like the crunching noise that this transmission makes.
I have seen a number of your videos. Your enthusiasm, your excitement, and your down-to-earth style makes these videos come to life. You do a great job explaining some very difficult concepts and your simulations add to the experience! Keep up the good work
This is like a Stephenson valve gear and an ratcheting CVT had a baby. Very neat! If it avoids the vibration of a ratcheting CVT that would be a major improvement!
Btw, if I'm understanding it correctly, the 'freewheeling' is a requirement of the design, and would be present for non-bicycle uses (this is normal for most ratchet CVTs)
A sprag clutch might work in an application where the extra weight isn't a big deal.
I also believe the same. Each of the little gear have to have a ratcheting for freewheeling when not transmitting movement to the output.
thank you was going to make the same comment this is simply a ratcheting CVT
configured in a planetary orientation
the second model displayed was simply a ratcheting CVT in a round ish box
the elliptical gears is the only new thing here
@@oooooof5023 i have thought of this
i feel like a sprag clutch could slip at vary low torque and at vary high torque
depends what range they are made for i know they can be vary vary strong
but why not have both, this is the week point of the system after all
The small gears transmit power just as long as their relative rotation locks their one-way-freewheels... As soon as the relative rotation unlocks their one-way-freewheels, they just freewheel-along. Look at this device to understand, focus on how the pedal changes rotating-direction on the crank, while the crank keeps turning to the same direction: YT-video d7E-3ndSG9E
Your gearing example ignored the effect of the final drive ratio on the ultimate number of rotations the tires will make. Otherwise, this was another fantastic video! Thanks for your great work.
Also, the dyno chart is fake. If torque and horsepower doesn't cross at 5250, it's made up.
@@ncguyredneck but it's in different units
@@G0ldbl4e they still cross at 5250 to to hp nm to kw
@@ncguyredneck NM/kW cross over at 9543
@G0ldbl4e and where does the chart in the video cross?
It is like a three phase drive with three ratchets. The ratchet you do not see is likely the point of failure.
and EACH of the ratchets must transfer ALL of the torque/power
@@bartoszskowronski Good point.
Rachet, YOU ARE THE WEAKEST LINK
It was fully explained by the Axis Offset Leverage. No ratchet necessary
@@Scissors69 so what prevent to turn small gear once right and second left?? if there isn't ratchet?
No clickbait, no 5 minute intro, all meat and potatoes.
You earned a subscription. Very nice video.
Couple weeks ago came across a vid explaining Porsche’s six stroke engine. Two problems: 1) his accent was nowhere near as charming as our guy here and 2) 90 seconds in he’s pitching a grooming device and describing the options he has in trimming/shaving his pubes. Stopped immediately, thumbs down and searched for @driving4answers’ video on the same topic. No need to deal with any of that nonsense. Just quality gearhead engineering content.
You made the mechanical principle really easy to understand for me
I designed a gear based CVT decades ago. It was based on a differential, with one of the differential outputs connected to a viscous coupling anchored to the differential itself. Applying more torque would induce slip in the viscous coupling, temporarily reducing the default 1:1 ratio between the input and output of the CVT. As it turns out, Toyota used the same design for their Hybrid CVT, except instead of a viscous coupling they attached an electric motor.
I also designed a gear based CVT decades ago. My goal was to differential a differential in situ.
I felt a little bit impossible, I still have the design but I never tried it IRL.
Seems inefficient to use slip to change ratios. Toyota's only will work in a Hybrid. The power used in the electric motor for adjusting the output speed is added to the engine power in the planetary gearbox - not burned up in slippage
CVT on Tractors used the same system but with an hydraulic unit
That sounds like an effective heater, but pretty poor at anything else.
@@el86lo36fkyNo they don't. They use a variable output hydraulic pump which uses a 'swash plate' to vary the stroke of the pump cylinders from zero to full stroke.
Similar outcome, very different mechanism.
This is beautiful. Thanks to offer us beautiful discoveries and clear explanation to our nerdy mecanical mind.
There is a wrong point about the sounds at 21 minutes. If you look closely at the animation, you should see that the gears rotate freely in one direction, but not the other, because the gears are pulling the output. So this clicking must be a mechanism in these gears that allows movement in one direction. And this cannot be eliminated from the designs of cars. Also this one direction mechanism is most unreliable part, because its not work well on high rpm or high torgue.
The clicking is the freewheel mechanism, not the gears though you are correct that those planetary gears do need a one way mechanism. Since this is a low power bicycle gearbox, I suspect they are just using one way bearings in them instead of some sort of ratcheting mechanism, thus they wouldn't click.
Yes, looks a version of Ratcheting CVT: en.wikipedia.org/wiki/Continuously_variable_transmission#Ratcheting
that´s correct, he mis-communicated it there... he mentions them, while praising them for their least important role, instead of mentioning their most important and most obvious role.
The way to describe the sensation of driving a CVT on a road (I've driven a few) is to compare it to driving a boat. You rev a boat to a specific engine speed and typically stay there as you cruise along.
this thing is so cool and ingenious , but 12:07 is seems like (from my understanding that) the gears that drag, only do so because the dragging gears has some sort of one-way clutch. and if such a thing was there wouldn't that mean that the torque would be limited by the friction of a Sprag clutch or the pedals of a ratchet. if this isn't what is happening then what causes the dragging wheels to stop?
wow, such a cool machine! Really love the way you explain things, so easy and interesting to follow along. Love this channel!
I'm on minute 5 of the video and my mind is already blown!
What an absolute beautiful piece of machinery. One of the smartest things I've ever seen. Truly amazing
The limit is the one way clutches, or ratchets. They are always the weakest link. I've been designing these for years. They just can't hold any reasonable torque of automotive applications and end up facing the same slippage problem of traditional CVTs. These mechanical CVTs also have a lower efficiency of traditional CVTs due to the added complexity, and drag resistance of the one way clutches.
What will be maximum indexing frequency for one way bearings?
@@sachinshinde9460 maximum indexing frequency? They don't really have one, since they have virtually no backlash, but they are susceptible to chatter and slippage. If the design is with traditional ratchets, the ratchet teeth will unavoidably wear, and they are susceptible to indexing frequencies equal to the individual ratchet dog spring rate plus the inertia of the ratcheting dogs. My guess would be roughly 100 indexes/sec. Anything faster than that, and I think the ratchets would not be able to reset in time and would skip several teeth before engagement. so basically the unit would be limited to 100RPM. This is why one way clutches are used instead in addition to having no backlash, but they have an inherently lower torque capability.
@@PrIsMaTiSmX Thanks for the prompt reply. I am little bit tangled in same situation like these guys do, but I am planning to use rollers instead of balls or sprags, will it be reliable? Intended frequency is around 150 indexes/sec.
This ^^^^
@@sachinshinde9460 Do you mind me asking what you mean by rollers? The only ones I am aware of are the ones designed with sprags. Just guessing, I don't think it would be reliable.
and 150 indexes/sec is too low for any application other than riding a bicycle or very low power applications. Traditional transmissions can operate well over 10,000RPM (166 indexes/sec) at the input, and have significantly higher output RPM. This is why sprag one way clutches are pretty much the only way to go.
I don't believe this thing is gonna be on any car. It has the same reliability issue with CVT because of those one way clutches.
But do not worry, I am working on it.
You seem to have forgotten about one application of extremely high torque and work where CVTs are absolutely king and have no competition. Tractors and Farming Machines in general. Insane hours and torque loads in this field and basically all tractors have CVT these days. That huge Fendt 1167 Vario MT is pulling massive implements across the fields day and night in the season.
How do they pull it off? Aren't maintenance periods very short?
*pun intended
And snowmobiles, like, forever...
@@justincredible5406 As i understand its basically maintainance free because the "variable" part in a tractor CVT is a variable hydraulic pump. Power is transmitted thru a liquid. The input pump can vary its fluid output at a fixed rpm.
@@lohikarhu734 Same class to me as are quads and mopeds. True. CVT is very common in them.
ruclips.net/video/68G8RyWEwzA/видео.html
Its actually even smarter than i thought. The variable displacement hydraulic pump just accellerates the tractor to a fixed speed at which point a fully geared power transmission takes over seemlessly. Smart Stuff.
Hi Mechanical Engineer here. Watching this reminded me of something I looked into years ago. I was watching a youtube video about the (under the ocean) discovered Antikythera Mechanism from the greeks - made about 2000 years ago. It used meshed gears to model the eliptical orbit of the moon around the earth (as well as many other planets in the solar system). I was intrigued by this mainly to see how meshed gears could trace out an elipse, so I modelled the gears in solidworks to see if it actually worked - which it did. Anyhow, it brilliantly used an offset axle in a sliding slot to trace out an elipse following the path of the moon around the Earth - almost identical to the design you showed in this clip. Weird how our most unique new technology is replicating a mechanical concept that was figured out thousands of years ago.
the total torque capability is limited by what a single one of those little planet gears can provide?
I think so. And inside those I believe is a ratcheting mechanism which transfers the power to the output gear which I guess would be more limiting than the gear itself. Another potential limiting factor in my eyes would be the sliding pins connecting the arms to the 3 (or 4 in the second design) planetary gears.
@@themiddleman9376 I was thinking the same about that ratchet mechanism, although it wasnt mentioned in the video i think
Yep but guess what. MILLIONS of vehicles are on the road right now that do the same thing. Planetaries are not the only style of gearbox out there. Every F1 gearbox in any gear is just one single straight cut gear against another one.
This is a very cool concept. But I don't think manufacturers will be implementing this due to complexity. They have already perfected CVT technology that most CVT's will last more than 300k miles. Toyota also made a more robust CVT by having a geared launch or 1st gear, taking out the major stress that wears out CVT's. The no.1 thing that kills CVT's are lack of maintenance like fluid changes.
That's a point he doesn't touch on about this design. With nothing except bearings and gears being stressed, there would be little maintenance needed. Especially with synthetic lubricants.
Complexity is nothing new to automakers. Practically everything on a car is ridiculously complex. And why do they insist on using so much complexity? Fuel economy and emissions regulations. They will gladly put something hideously complex and unreliable on a car if it can last the warranty period and give a 0.1% improvement in fuel economy. This has the potential to do far better than that.
The promise is something of a 20% efficiency increase. That's no small thing.
@@wingracer1614 Indeed. These things are mandated by governments and are being forced onto people who may have other concepts in mind. I think we've exceeded the point where efficiency in use provides more benefits than the costs of this complexity, and the planned obsolescence of extreme repair costs requires that even more energy and pollution be produced to replace these vehicles. I had an old Honda Civic with a carburetor that could give you almost 50 MPG. Less fuel used equals less pollution produced to be dealt with post-combustion and I really question whether the small gains of today's cars are worth it when that old Honda could be economically owned and driven for ~30 years while today's cars cost far more and give only half the service life. We need a more practical balance with the buyers deciding what they need, and the governments not setting insane goals to reach which are less than a few percent better.
You need to call several transmission shops and ask for their opinion. CVT has, and always will be, a dismal failure at best. Maintenance does little or nothing to help. You have a steel drive chain (push belt) running on steel pulleys. Every one made has blown up sooner or later. You can't perfect a flawed design.
3:11 should be 2.399, 2.398, ... 0.402,0.401
🤓☝️
was going to say the same thing, but someone beat me to it
You have such skill in explaining complex engineering. Thank you so much for the work you do!!
02:49 Our 1960's Melroe Bobcat skid steere has a huge rubber belt/pulley drive system very similar to that, For "Slow'(Turtle) or "Fast (Rabbit)" speeds. But only one set of pulleys moves in & out, IIRC.
A Reeves drive. --D
Heavy machinery, like metal mills tend to have this as well.
D4A became so big and popular that company sent a prototype to advertise their CVT)
And that's great, because it means that you can really explain the principles and basic mechanics of such complicated thing to a big audience. Great job.
This makes me love the simplicity of the 4 speed granny gear SM420 and foot pedal clutch on my 58 Chevy truck.
Simple, yes. Good, no.
Ingenious technology, masterfully explained 👌 👏🏼
I can't wait to do a test ride on a bicycle equipped with this system!
If the final product will be competitive in regards to weight, it'll be the ultimate gearing solution for many cycles, and most probably way more efficient and durable than NuVinci/Enviolo CVT, which I have tested and found to be not efficient enough for use in a non-electric-assisted bicycle. I'm excited to see if it can reach the hitherto unsurpassed efficiency of the Rohloff gearhub!
Thanks for this brilliant explanation video!
You explain the rachet mechanism in the small gears as if its only use is to freewheel a bicycle, but my impression is that it is needed so the small gears can "pull" the output shaft in one direction and then freewheel to their original position. Is this correct? Does this mean that engine braking with such a transmission will not be possible?
Engine breaking is not possible with Ratchet CVTs no. This is simply a ratchet CVT reconfigured to a planetary gear setup rather than the parallel shaft setup that is more typical.
Reminds me of a linkage I saw once on a steam locomotive. It was able to rotate while the train was stationary, and it could also reverse directions. I don't think I ever knew the name of it but it was one of the many assorted linkages that were popular back in the steam days. Genius stuff.
Stephenson's Link Motion.
@@jeffreythompson9549 Thank you. I should look into that. Very interesting.
Or walschaerts valve gear.
The pulsing output will really limit use of this to relatively low speed and low power applications. The elliptical gears appear to reduce the effect by about 2-3 x but the variance is still there. This will cause significant vibrations overall and focus stress to the one-way 'planetary' gear clutches. The plot showing the elliptical gearing should have included a line for 'overall' output speed. If I understand the concept correctly the output is driven by whichever 'baton' is currently moving the fastest. The graph shows that there would be some significant changes in output speed when handing the baton. I can't imagine the one-way (sprague?) clutches will last very long under heavy load due to these shocks. Unless an elegant and 100% uniform torque transfer can be found mechanically.
I came to the comments to say this.
You've got to remember not to let perfect be the enemy of good. The standard universal joint used on all driveshafts today pulses/ varies speed slighty when it isn't at exactly 0°, it's cancelled out by having two so only the drive shaft experiences the pulses.
This will probably be corrected before the power reaches the road somehow.
@@stainlessteele5which is why universal joints were dropped in favor of cv joint in most cases
Well since nearly all power sources other than turbines and induction motors have pulsed output at all speeds, I don't think it matters (internal combustion engines, human legs and DC motors are inherently pulsed). Flywheels and springs and hydraulics have been used for hundreds of years for smooting output torque of machines (for thousands of years in wind and water mills) - it's a non problem.
Since sprag clutches have been used for heavy auto-transmissions and are used in the main drive of helicopters to allow auto-rotation - they seem to last just fine under very high power applications - several thousand HP per drive shaft.
There is no shock when load transfers from one "baton" wheel to the next, as the relative speeds cross over, the clutch in the slower one simply stops transmitting torque - if you look at the graph, at any one time two "batons" have positive rotation and one has negative - the output is the sum of the two positive rotations (the torque resulting from negative rotation is cancelled by sprag clutch so will not retard the output rotation) - the result should be a gentle ripple of torque and speed - much smoother than a single cylinder motor cycle engine or human feet driving the input shaft, so insignificant in practice.
@@rcdieselrc only for light duty applications on vehicles without driveshafts, heaver vehicles don't even have CVs but use two uni-joints next to each other where light cars use CVs. Everything has applications and uses.
This reminds me of the string drive on bicycles , compared to standard chain or belt drives.
The power and rotation is split between left and right side and you alternate between 2 to provide consistent torque.
Actually really similar when you think about it. Its just the lever arms instead of the strings
So in traditional CVTs there is the concept of "weighting" or "biasing" the CVT. With a "light bias" or weights the transmission will be much more "racey" always seeking to operate in the higher rpm power band. A heavier bias will cause the CVT to more eagerly "shift up" and maintain more gently rpms in the lower end of the power band.
A local workshop put the wrong weights in a 100cc scooter I had. It made it get off the line a lot faster, however it was embarressing to drive. You just couldn't drive it quietly. Any throttle at all and you were ripping it at 7000rpm. If you buried it off the line it would come pretty close to the rev limiter.
The guy basically said, "But that's what every one does to them to get them to go faster."
The next scooter I had went the other way. It would lock onto about 3.5k rpm and stay there all the way until it ran out of ratios and only then did you get the top end of the power band to get the 125cc scooter up to a top speed of 75mph when it hit the rev limiter making you "bob like a parcel shelf dog".
In other CVT transmissions from the like of honda they use hydraulic intervention to provide "adaptive" "weighting".
0:18 It’s magic!!,
No, it's not
Yes, it is
@@apollonitro4802 whatever floats your boat, just keep your dumb ass kids away from mine 🤣
@@apollonitro4802 confident in your lack of knowledge, you are.
Just keep your inbred kids away from mine, and you can believe the earth is flat for all I care 👍
It's a joke so overdone it makes you look almost as bad as if you meant your comment literally.
expectations: combines benefits of both
reality: combines downsides of both
same old story😄
No it's not.
This type of CVT has it's own drawbacks. Some because of freewheels (they don't work instantly and there's an angle between on and off state for a freewheeling mechanism from 3° to 15° or sometimes more and you have no energy transfer at this state. Also there's a torque output pulsation. There's a lot of things to solve but it's still better than belt/chain CVT
@teolynx3805 i think i saw similar cvt on old steam engines but in a simpler design. it basically converts rotational motion into reciprocating and then back to rotational. so you right, it has all drawbacks of both and introduces new.😃
Leonardo Da Vinci invented the CVT, a racheting model, a Loong time ago. I was really surprised when I started digging into the subject. Thanks for this video, the detail is very welcome.
well done, the cad model really helped , very very well explained.
I know I'm a bit off topic here, but since we're talking transmissions, I have to ask - why isn't just everyone simply doing what Koenigsegg did with their Light Speed Transmission? It's such a simple design - multiple clutches for multiple gears. No shifting rods, no planetary gears, no nothing except a mechatronics unit opening and closing clutches for each gear. When compared to all these 6-8-speed DCTs, 6-10-speed torque converter automatics and CVTs we have in cars these days, the LST just screams simplicity, speed, efficiency and reliability in comparison. So, why isn't everyone doing just that? I'm sure there's a reason for it, I just don't yet understand it. Mate, I don't know if you've already talked about the LST in your videos, but if not, a video on it would be appreciated. Now, I'll proceed with watching this.
For one this CVT need no to maybe one clutch instead of seven and only one actuator to change gear ratio instead of one for each clutch. It also seems to me like this can be put in a rather short package. Better for transversal engine layouts and especially bicycles.
But with the rise of EVs we might never see this in a production car. But I see a lot of potential for bicycles.
They are. The Koenigsegg gearbox works the same as a DCT, just with three clutches instead of two. How complex and expensive do you want your car to be?
Because it's still not continuous and therefore engine runs in sub-optimal regime most of the time... during acceleration that is.
@@JSmith19858 I understand that, but the LST has no shifting rods and synchros, just gears and clutches and that makes it much simpler than a DCT. Perhaps shifting rods and synchros really aren't that big of a deal the way I imagine them to be.
@@EwiggrimmigMight still be useful for EV, should be able to let you use smaller electric motors for better efficiency, like everything it depends on cost if it's feasible.
Due to the warning at 9:20 I was forced to pause the video to roll a joint before moving on
I loved my CVT in my last big Ford wagon and drove it a quarter million miles. Ford did not implement simulated shifts and that was a good call from my perspective. It did suffer from lack of towing capacity, and has gone out of production. My current big Ford wagon is a 6 speed and can tow a plenty. Maybe my next big Ford wagon will have the best of both. Here's to hoping. Thanks for this vid.
I had Subaru with CVT and loved it. The key is never drive aggressively, never load it heavily, and never ever tow anything. I had a trailer hitch on the stern but it was for bike rack. :)
i love the beauty of your videos so much, it is full of brightness , and gives great hopes about the potential of mankind's spirit
This specific objective was the source of hundreds of hours of 'mower thoughts', trying to figure out a way to do this while chasing a mower around the yard. I just knew there had to be a way. So much ingenuity and invention here, I'm just glad it's not a super simple device that I should have been able to come up with in my mind, but it's rewarding to see elements of my thoughts in there. The split rotation however is likely something I would have never come up with in my life. Amazing!
it's beautiful. My Dad often pondered the idea way back in the day, but he never had the 'spare' time to allocate to it - C'est la vie.
6:19 "are the only thing transferring the torque..." *INHALE* "...which means that..."
That was kinda funny. Liked for the great information and still great video quality.
This is old news...Clock complications have used this movement many many years ago. The magic is getting that Mech to run at much higher speeds and for Billions of Cycles. Good luck with that. The COST would be fucking ENORMOUS. Thumbs up for the Explanation. Long time fan of your Channel
Awesome! I'm fascinated. Thank you very much for this explaining video! I've never saw something creative like that.