Revonte's New E-bike Motor with Stepless Gearing Eliminates the Rear Derailleur
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:
 | “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.
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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.
If it is good, it might can work as a gearbox.... ????
A chain is like, 90+% efficient.
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.
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
@Revonte: what happens when you stop pedaling, does the gear change? (in the "auto" mode)
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.
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.
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
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.
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.
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.
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.
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
Looks like fake news/sales scam to me...
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)?
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