Revonte's New E-bike Motor with Stepless Gearing Eliminates the Rear Derailleur

Mar 1, 2019
by Revonte  

Revonte
A New E-bike Motor with Stepless Gearing
Motor and battery: Revonte's CVT transmission automatically synchronizes your desired pedaling torque with power assist across the entire speed range - uphill or downhill.

The e-bike market carries a significant potential in several domains, like getting more to people ride bikes and making modern mountain bikes even more versatile. In the technological side however, the progress has been incremental at best. We at Revonte are about to change that by providing an e-bike motor option that differentiates itself clearly from the existing options. Please continue reading to see why and how.

CVT - A Brief Background

If you aren't well versed in automotive or industrial world, the three-letter acronym CVT might not be familiar. It stands for continuously variable transmission – a technology which has been used in a wide range of industrial applications. In the car manufacturing world, heavy hitters like Subaru, Nissan, Toyota, Honda, Mitsubishi, Volkswagen, Audi and Mercedes have made their own versions. We have implemented the time-tested technology to two wheeled and (mostly) human powered vehicles. CVT offers significant and even unheard benefits and ride qualities when it comes to e-bikes in particular

What Is It?

We at Revonte have created a new type of e-bike motor and drivetrain construction which is based – you guessed it right – on CVT technology. The technology principle itself can be considered quite old. In this case that comes with a considerable advantage. If a technology has stood the test of time, it means that it is highly functional and in this case, robust. The former can be said about the conventional rear derailleur as well. The latter? Well, let´s leave that for you, the reader, to decide.

The principle behind our CVT motor could be described as elegant in all of its simplicity. Besides the ingenious principle behind the CVT technology, we’ve made a considerable effort to make it light and compact by means of mathematical modelling, simulation, and good old-fashioned engineering. After all the hard work, we can say that the result is very pleasing.

The “hardware side” is only half of the equation, although an important one. Besides that, the technology is more robust than any other existing one in the e-bike market, our motor ride qualities are highly adaptable via software. This means two things, which are very profound:

1) More adjustability and choices for the rider – more on this later.
2) One motor can be used in all bikes, no matter the intended use and application. This will make a very happy product manager, no matter the size of the company he is working in.

The Benefits – What It Does?

The term “continuous” behind the acronym C in CVT gives a strong clue what’s to come. Taken straight from the CVT motor Wikipedia page:

bigquotes“Shiftless transmission, single-speed transmission, stepless transmission, pulley transmission, or, in case of motorcycles, a ‘twist-and-go’, is an automatic transmission that can change seamlessly through a continuous range of effective gear ratios.”

Yes, you read it right. Our motor has stepless gearing which means that the bike can be ridden with constant, self-selected cadence – everywhere.
No matter if you’re sprinting towards a double with a high gnar factor, pedaling up the hill for the next dose of ascending fun, or riding casually along the local trail, changing between coasting and pedaling modes. No gear or cadence changes are needed, if the rider does not wish so. The motor and software do the work for you in that department – continuously – and will serve its duties in any type of bike, whether it would be hardtail or a heavy-duty rig that lives for downhills.

However, if the traditional indexed shifting is preferred, that poses no problem. The software can be adapted to any number of gears. The current “standard” of 12-speeds is just an arbitrary number, certainly not the limit. With our system, one could go as low as 5- or as high as 20-speed, for example. Once again, this is only a matter of software preferences.

Time to Ditch the Derailleur

The current derailleur is a respectable feat of engineering. It has served it´s time though and one could argue that the existing potential has been used for the most part. Broken derailleurs, bent hangers, rattling chains and clutches worn too loose will be a memory in the past, located in the same bin next to cantilever brakes.

Our drivetrain employs a single-speed setup. All the gear ratios, automatic transmission or indexed gears are achieved by use of a single chain (or belt, if that's what you like to roll with). This brings the drivetrain complexity down by several magnitudes, meaning fewer braking parts, less need for maintenance and therefore, less unwanted headaches. Frame designers and even whole engineering departments will most likely welcome this change with open arms as well. The end users, meaning the riders, will benefit the most though, with a significantly improved riding experience.

Locating the motor around the bottom bracket is non-negotiable. This keeps the center of gravity at the center of the bike and as low as possible, which produces superior handling characteristics. There aren’t any other options for motor placement when it comes to riding characteristics and simplicity of construction. Messing this setup by attaching a derailleur and a heavy cassette to the rear wheel is poor choice which has the default option for too long.
Placing the motor around the bottom bracket is the superior choice in every aspect. Leaving the derailleur out makes it even better.

What Will Follow?

We are working extremely hard to get the finalized product out to daylight. News about further details, photos, blog articles and most importantly release dates (when confirmed) can be found at our site Revonte.com.

Pay us a visit and stay tuned. It´s about to change how e-bikes are made and ridden. We are not here to add small incremental improvement to the already stacked pile. We prefer a complete revolution.

Posted In:
eMTB



61 Comments

  • 18 1
 The big 'S' brands probably make far too much money from replacement derailleur sales to spend the R+D on phasing them out. E-bikes badly need this though, those things rinse drivetrains for fun!
  • 12 1
 May as well go buy a nissan micra.
  • 1 2
 With GTR engines
  • 6 0
 I don't think the loss of efficiency is nearly as big of a deal when you look at the Pros: less unsprung weight, less maintenance, no loss of drive power during shifts, etc...

Combined with a top of the line motor that can make up for the loss in efficiency at a very minor weight penalty, this seems like a good program.
  • 4 0
 Would the system work without the motor or is there too much drag- Jukka, Revonte..?
  • 2 0
 Exactly. The idea is good, but what about those wasted watts?
If it is good, it might can work as a gearbox.... ????
  • 3 0
 I can't remember any exact figures, but in heavy off-road equipment it it generally accepted that a CVT transmission equipped machine will be markedly less efficient than a similar machine specced with a normal gearbox (in terms of HP to the wheels) Will be interesting to see ho this one has been done.
  • 1 0
 The development is focused only to the e-bike side of things at the moment.
  • 1 0
 @Revonte: my Yamaha scooter is said to make 15.5 horse at the crank, and 11 at the wheel. That's a big loss.
A chain is like, 90+% efficient.
  • 4 3
 @jaame: A brand new, clean, well lubricated, well adjusted, non-bent, derailleur setup with a good chainline is 90+% efficient. The majority of bikes out there fail to meet these standards though, and even if they do at the beginning of a ride, they almost certainly don't by the end.

A gearbox setup of some description will be less efficient in perfect conditions, but much more consistent in real world conditions. I absolutely agree that a derailleur setup is still probably best for xc whippets and TdF guys. But I'd hazard a guess that most everyone else will get places faster and more reliably with a gearbox.

Just my 2c.
  • 1 0
 @gabriel-mission9:
What is the power loss during gear change? The efficiency of a cvt won't change during gear changes, and you can change gear whenever you want. (you don't really have gear changes, but it is something else Smile . )
@Revonte: what happens when you stop pedaling, does the gear change? (in the "auto" mode)
  • 3 0
 @shaked: Who cares how efficient it is while you're shifting...? That's like 0.01% of the time?

To be fair I see this making sense on an e-bike where any power loss can be more than made up for by the motor, but the kind of efficiency loss you get with a CVT really can't be justified on a regular bike.
  • 1 0
 @gabriel-mission9: I agree with everything you say.
I also think CVT is excellent for some applications, for example scooters and ebikes. I would even try it on a motorbike or car. Yes, it's really inefficient, but the upside is that it's almost maintenance free and you're always in the right gear so your brain is free to do the other jobs it needs to do. I see cars are getting more and more gears because the engines are getting smaller. For example, the new ford ranger has a 2 litre engine and a ten speed box because the engine only has a 2000rpm spread of good power. When I saw that I immediately thought of CVT, because my Smax literally holds the engine revs at 7000 all the time when I'm gassing it, until I get right to the top end on speed and then engine speed is allowed to rise.
It makes a lot of sense. Even a 190hp superbike with CVT would put out 120 at the rear wheel, which is still a lot.
  • 3 0
 @jaame:
If my 190bhp bike dropped down to 120 I'd by fricking furious .That and the engine braking, throttle response, speed , fuel efficiency and weight would be a disaster.
Typical superbike gbox and chain takes about 10-15bhp off crank power.
Plus controling engine speed to alter the bikes handling via the gbox is essential at speed. Can't do that with cvt.
120 at the wheel isn't alot at all. That's 600 cc bike levels from a 1000
  • 1 1
 @markg1150: It wouldn't be for everyone. If you can use 190hp on the road then it's not for you. In my case, a 600 is on the limit of what I would want on the road. They make closer to 100hp at the wheel, even though they reckon over 120hp, it's not accurate because that's at the crank with ram air. I would be perfectly happy with 120 horse but I guess it would be more aimed at commuting or touring. Working the box is fun and fast, but after four hours my clutch hand, or wrist I guess, gets almost too crampy to change gear. I end up having to lock my fingers and move my whole arm back instead of just squeezing it.

I know Suzuki was testing a GSX-R1000 with CVT some years ago. Obviously they didn't think it was worthwhile on that particular bike. There are some other bikes out with semi auto boxes and stuff.

I think a bigger factor is the unsprung weight being very high on a CVT when compared with a chain.

Still, that would not be an issue in a car. One could even use a CVT with chain final drive like the TMAX.
  • 1 0
 @jaame:
Agree 100 is fine for the road these days but I'm a trackday addict. de cat and mapped r6s+ zx will put 110+ down easy.
Sore wrist after 4 hours? Do you clutch on the up shift? Or got a heavy one and them daft stubby pazzo levers. Seems unusual.
  • 1 0
 @markg1150: Yeap - there is more to riding a motorbike than many think. A 190+ HP liter bike on a track, you have many factors at play of which the traditional gearbox, sprocket/chain combo come into play It is about control, input and feedback through ones whole body and also many forces at work that keeps the bike on track at high speeds under a symphony of differing and opposed forces.

Quite different to mountain biking but just like mountain biking, a lot of fun - just with different rewards.

Sure there is alternative tech that can be used but for some reason - it hasn't seemed to taken hold, just like upside down telescopic forks have not been replaced by anything else on mass in Sports Motorcycles and subsequent racing. The Britten from New Zealand was the odd exception and it is just a footnote in the history of Motorcycle Racing.
  • 1 0
 @jaame: Well, there is a reason CVT was banned from F1.
  • 5 2
 Will be major losses in efficiency at least 20% but is heading in right direction for gearing for e-bike, but no way would be efficient enough for non e-bike?
  • 5 0
 First of all, efficiency has naturally been considered from the first design stage. There will be losses, but they're certainly in the acceptable range. More specific details are to follow later on. We would also like to point out that our motor is designed from ground up to be used with e-bikes without the traditional consideration that bicycle industry carries, which might limit the resulting design. The design fulfills it intended purpose very well.
  • 2 1
 Can anyone actually find any evidence of this company “Revonte” having made any physical product whatsoever? I can’t see any prototyping or engineering drawings that show this company has actually worked out how to make this product yet...

Looks like fake news/sales scam to me...
  • 2 1
 Technical drawings are a trade secret. More info, photos and material of working prototypes are to follow later. Stay tuned.
  • 1 0
 @Revonte: was that your kit in the carbon fibre gearbox e bike at the trade show last year?
  • 1 0
 We knew this was coming. I like the idea, and sure a real e-mtb needs a stronger drivetrain than normal but this solution poses many new problems. All possible mechanical problems aside, having a motorized bike with an automatic transmission may change the legal category of the vehicle to a moped. In my state Pennsylvania I think one of the only technical differences is that a moped has an auto tranny and the class one e-bike does not.
  • 1 0
 Nuvinci has a CVT hub, it’s heavy and there it has significant drag, spongy feel, and it is not 100% engaged.

It’s like comparing manual and automatic transmission, loss of engagement is not an issue when you’ve got lots of horsepower, but humans ain’t got even a single horsepower.

Makes sense for an ebike and that’s about all.
  • 1 0
 I just checked the website and they describe using a planetary gear system with two motors for the CVT similar to a Toyota Prius. I am familiar with that type of cvt and is about as simple as you can get. If you're going to ride an e-bike this is the way to do it. Shouldn't have any more drag than the gear reduction used in other e-bikes. Plus you can ditch the cassette and build a strong symmetrical rear wheel.
  • 4 0
 What happens if your battery runs out
  • 10 0
 Obviously you drag that POS home.
  • 3 0
 cvt gearboxes in cars are horrible to drive, dull witted and slow. hopefully this will work out though,
  • 1 1
 Cvt with a combustion engine is more fuel efficient, yet far from ideal performance. This is not entirely comparable to electric brushless technology, or have you found an optimal rpm range for your motor in order to maximise range and if so does the Esc keep the motor in this range at all times?
Also, in cars, some manufacturers have had serious teething issues with Cvt boxes.
What warranty and service requirements do you foresee.
Final one. Will you have a mode that will allow fixed gear ranges simulating traditional gears?
Really interesting proposal and perhaps we have finally found a better use for a cvt box in sport.
@revonte
  • 1 0
 Well would want a high torque motor that runs at quite a slow RPM speed too work with CVT good too see it happening but not the most efficient design, but does that really matter on an e-bike?
  • 1 0
 @aljoburr: well with current ranges of batteries a more efficient design is paramount would you not say? Not just in ebikes
  • 2 0
 There is no mention of range or price...two important factors for me. The Revnote website has 0 info on it. This product may as well be shown on a napkin.
  • 1 1
 CVT was banned from F1 before it's debute. The car equipped with CVT was faster by a a good margin on the entire lap, while testing it.
CVT feels slow because there is no bang between gears, actually is more efficient and faster on the equiped gasoline cars because it has a power band to adapt to the speed.

While with humans, you have the powerband of the human to adapt to the speed of the bike, so it's a win. If you had pegs, just the motor woud be good.

There are a lot of ways to make a CVT gear. You just need the right design to reduce the drag. And this is my question. Is the drag better or worse than a Effigear (todays most efficient gearbox for bikes)?
  • 1 1
 Only problem I can see with this is if you suddenly crank hard, it might take a while for the gearbox to catch up with your speed depending on the speed of the software, leaving you spinning away for a second or 2
  • 2 1
 Take a look how fast Fox Live suspension can react to external feedback. Electronics is fast!
  • 1 1
 A modern phone will wipe the floor with a computer from the 1980's no problem, so I think it should be fast enough. Look up the size of a Snapdragon 855. It can easily fit in a bike.
  • 2 0
 @Pavel-Repak: There is always a delay in electro-mechanical systems. Your comment about processing power is valid, but it boils down to the speed of the actuator/motor/solenoid that moves the gears. The Magura Vyron dropper is a case in point, few seconds delay with it. Also look up cvt gearboxes in cars, this is a common problem with them.
  • 1 0
 I think the most common problem is the ratio being too hard when coasting high speed into a steep hill. The good thing is that since there is no changing of gears the CVT can change the ratio very fast and under power. So if it was in a too easy ratio compared to the speed i do not think you would consider it a problem even if you could notice it. I think this technology will be most effective in roadbikes and commuter bikes at first, untill they have perfected the technology for mtb. The downside for CVT is that it is not as effective as a normal gearbox or derailleur gearing, but it kind of makes up for this shortfall by letting the engine work at its most effective range at all times or peak power when needed. This is most definetely the future for most e-bikes.
  • 1 0
 @AD4M: I think the new wireless Reverb is supposed to be much quicker so maybe it is doable.
  • 5 2
 Waiting for combustion ”motor” pedal bikes reviews
  • 2 0
 I wish this was in the North American pinkbike news feed............ Cool product
  • 2 0
 Great to see! We need companies like Revonte to seriously disrupt the drivetrain space, especially for ebikes.
  • 1 0
 Thanks. Smile And that is we are about to do.
  • 1 0
 @Revonte: So, you pass the speed limit. How is the drag? This is my main question so far.
  • 1 1
 Looks like a cool development. I wonder if it is compatible with a regenerative braking system. That is lacking on e-bikes thus far, and would dramatically extend their range.
  • 2 0
 Scotty Kilmer says no to a cvt
  • 1 0
 The word "automatic" is worrisome.
  • 2 5
 This will never work as in a pedal application. Replacing a derailleur transmission with a heavy cvt box seems counter-intuitive. The transmission will be another bulky component mounted close to the motor. What's next a remote operated sequential box for bicycles?
  • 1 0
 What's the service interval to change ATF?
  • 2 1
 @polebicycles A bike for people lacking stamina in the pipeworks?
  • 1 0
 great idea, all the best!
  • 1 0
 Very nice product. Keep going!
  • 1 1
 CVTs are normally know for their lack of efficiency. How low is it here?
  • 1 0
 Please see the reply above to question from @aljoburr.
  • 1 0
 But Before dismiss this idea for lower efficiency all gearing has losses in efficiency & no motor will run at 100% efficency anyway,
but what you want too think about when using a motor that can run 30-40 times faster than driven wheel and how efficient you can make that change, but not that easy too do without major losses?
But most efficient way will win out
  • 3 4
 CVT gearboxes SUCK. Then again, the sort of people that like CVT gearboxes likely are the type to ride an ebike.... Hmmm
  • 1 3
 Me n my friend will prohibit this thing ride our trail... Coz it will looks like a moto... You know that thing will ruin the trail in second
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