A Look Inside the Automatic & Stepless Revonte ONE Drive eMTB System

May 29, 2020 at 7:26
by Revonte  
Revonte ONE Drive Unit
The Revonte ONE Drive System provides unprecedented ride-characteristics in the world of e-bikes, thanks to the combination of the Drive Units unique inner workings and sophisticated control software.

PRESS RELEASE: Revonte

Since the launch of the Revonte ONE Drive System, the inner workings of the Drive Unit have raised a lot of interest. And rightly so, since the technology we use is unprecedented in the world of bicycles! Our novel and patented solution for setting the correct gear in a stepless fashion is a robust, time-tested, and highly adaptable. Read further to learn what's hidden underneath the hood of the Revonte ONE Drive Unit, and most importantly what makes it the drive system of choice for e-bikes all types & sizes, including high-performance eMTBs.
Revonte Facts
• A company founded in 2018 with a mission of in taking e-bikes to the next level.
• The Revonte ONE Drive System can be run in two gearing modes: fully automatic & stepless or indexed shifting.
• Highly configurable by software, the Revonte ONE Drive System type can be used in all types of e-bikes.
• Robust and reliable construction with a single-speed drivetrain.
The 1st wave of partners using the Revonte ONE Drive System was published at the beginning of 2020. More will follow soon.
• For more info, see our previous press release and visit Revonte.com.



About Gears


The purpose of a gear set is to transfer torque (force with rotational direction) from one component to another. Changes in the speed of rotation, torque, and direction of power can be modified as well compared to the original source are possible. Often, changing these variables is the sole reason for using gears whereas the transmission of power can be almost trivial.

Bicycle gears are quite a straightforward affair compared to the gear technologies found elsewhere. For example, changes in the direction of torque and power in the form of angular or bevel gears aren't needed in traditional bicycles. When it comes to e-bikes though, the story can be somewhat different since space inside the drive unit housing is at a premium, and engineers might need to resort to quite cunning solutions in delivering the watts from the drive unit to the rear wheel.

The main idea behind the bicycle gears is to vary the size of the front sprocket and rear cog according to the capabilities of the rider, speed, and gradient (which can point up or down). Wheel size and the mass of the bike are also a thing to consider, the bigger the wheels and the higher the mass, the lower the available gearing usually needs to be.

An early (and very simple) way to modify the gear ratio was to run two cogs in the back wheel, one on each side. Changing gear meant taking the rear wheel off, flipping the wheel, adjusting the chain tension, and tightening the lock nuts and resuming riding. Until 1937, this was the only way to use gears in the Tour de France. A far cry from the technology available today. Back then, changing a gear had a considerable element of tactics involved, resembling a pitstop in Formula 1 racing.

A couple of decades forward and derailleur gears have become the standard. A respectable piece of engineering in itself, but a technology that has been milked dry as a raisin, especially when the requirements of modern e-bikes are considered, not to mention mountain bikes. The need for a new solution is needed. A good indicator of the current state of affairs is that gearboxes enter the discussion virtually every time when mountain bike gears are talked about.

Making the gear system more robust, reliable, nearly maintenance-free, and with a similar gear range to the current offerings (e.g. around 500%) is a solution that the market and most importantly, everyday users have been longing for.

We are about to answer the call.



Setting the Record Straight with CVT's


CVT stands for continuously variable transmission which has been a widely used technology in many industrial applications, take the automotive industry for example. The basic function of the CVT is included in its name; it varies the gearing continuously based on the inputs and desired outputs. The classification of different CVT types is as follows:


CVT types
Different types of CVT motors. Adopted from Crolla & Mashadi (2012). Vehicle Powertrain Systems. John Wiley & Sonds Ltd.

In bicycles, CVT's carry a bad reputation because of the efficiency losses in previously presented applications. Transferring the watts from the rider to the rear wheel as efficiently as possible is of the essence when designing a bicycle drivetrain. Lack of enthusiasm towards everything that does not fulfill this condition is understandable. The game is quite different though when electrical assistance is added to the mix since there are more watts to work with. Still, we don't want to waste any of those ever-important watts – a requirement that the Revonte ONE Drive Unit passes with flying colors since it has considerably higher efficiency numbers compared to traditional CVT-based solutions!

We have intentionally moved away from using the term CVT with our system since it carries too much baggage in the form of past technologies, misunderstandings, and prejudices.



The Design


It's about time to get into the heart of the matter! What's inside the Revonte ONE Drive Unit? The short answer is a planetary gear set.

The gear set consists of the following components:
• Sun gear – the cog in the middle.
• Ring gear – the big outer ring.
• Planetary gears – the three cogs which transfer power between the sun and ring gears.
• Planetary carrier – a connecting member between the planetary gears.

The function of the gear set is relatively simple once getting familiar with the mechanism. The main challenge with gears is in the engineering and setting the dimensions in a way that fulfills the intended goal with high reliability and within the space constraints given.
A schematic photo of a planetary gearset. Adopted from Beernaert Torben Dekkers E Besselink Igo. 2016 . Gear transmission design and in-wheel packaging for a Formula Student race car.
A schematic photo of a planetary gear set. Adopted from Beernaert, Torben & Dekkers, E & Besselink, Igo. (2016). Gear transmission design and in-wheel packaging for a Formula Student race car.

Part of the secret sauce is that instead of one electric motor, our drive unit has two of them! The more detailed inner workings of the Revonte ONE Drive Unit, including the roles and functions of the two motors, connections of shafts, and sizes of the gears are left to be filled by the reader's imagination. It's a worthy puzzle to be solved since a relatively simple gear set layout like this produces an almost infinite number of possible variants. Add the other constraints to the mix, like Q-factor, desirable chainring size and you’ve got your hands full of variables sooner than you realize.

We have resolved the most optimal variant for the mechanical gear sets with carefully done iterations which is further enhanced with sophisticated control software. These features combined make the core of the Revonte ONE Drive System with its unprecedented features and ride-characteristics.



Highly Reliable


The working principle of a planetary gear set is quite simple which makes it already very reliable. Decades of engineering, advances in materials, and simulation power have further enhanced its functions to the extent that it has a highly proven track record.

When it comes to power transmission, a planetary gear set relies solely on metal to metal contact. We have done our due diligence in choosing the best materials and choosing the right parameters in building a gear set that has very high-efficiency numbers, low wear-rate, and high safety coefficients. All of the design choices and raw engineering are first done by careful iterations which are later tested with simulations, and finally in real-life situations. The latter consists of two parts: day-to-day riding in varied conditions and testing done with a purpose-built test bench which puts the Revonte ONE Drive Unit through a truly grueling workload.

In practical terms, these properties and thorough testing manifest themselves as a Drive Unit which is low-maintenance, highly reliable. There are no components, e.g. small belts, which have limited mileage by nature and therefore a recurring need for service or replacement.

The gear set and all the engineering that has gone into it forms the sturdy mechanical legs which the Revonte ONE Drive System stands on. The control software gives the “brains” for the Revonte ONE Drive System and gives all the finishing touches which makes it the smartest drive system around.



Other Benefits


The upsides of using an internal gearbox instead of external derailleur-based gears are clearcut. If you've followed us – or the talk in the industry in general – you might be familiar with some of them.

Optimal weight distribution. The total amount of weight, whether you fancy measuring in pounds or kilograms (as the rest of the civilized world), matters but it's just as important where the weight is located. Centered and down are good. High, up, and back or forward is bad. Placing the heaviest components of the bike around the bottom bracket produces the best ride-characteristics possible.

Minimized unsprung mass. Moving the gear elements from the rear wheel not only simplifies things and makes a more robust drivetrain, but it also enhances the function of the suspension by minimizing unsprung masses. It does also make a tidier looking bike, which is nice.

Software-first approach. While the mechanical design provides a sturdy pair of legs on which the Revonte ONE Drive System stands on, the real magic happens on the software level. The ride-characteristics, wide range of configuration, and tuning capabilities are all made possible by the highly developed software.

Clean cockpit. Current drive systems have added complexity to the cockpit by introducing one more remote to the already packed handlebar area. We are taking the opposite route by freeing up space, not occupying more of it! Since the traditional shifter trigger is left redundant, we are able to combine that and the Controller in a single unit. Less is more and also clean looking in this case.

Solid performance metrics. Even though ride-experience a lot more than watts and newton meters, we can more than hold our own when it comes to pure numbers.

Option to choose. Besides the automatic & stepless mode, the Revonte ONE Drive System can be run in an indexed shifting mode in which the control software emulates the function of traditional gears by dividing the gear range into the number of chosen gears.



In Closing


Hopefully, you enjoyed this peek behind the hood of the Revonte ONE Drive Unit. Our solution is unique and ingenious in all of its simplicity. We are changing how e-bikes are being built, ridden and seen in the industry and society level. The first prototype full-suspension bikes are in the works.

Follow us on our social media feeds to stay on top of the latest developments in the arena of e-bike drive systems!

Revonte on Facebook
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23 Comments

  • 8 0
 Really think this could be the future for a lot of bikes by combining gearing and assistance into one package that can be tuned as required for the specific duty. The dual motor set up makes a lot of sense here, similar to some very clever and efficient industrial gearboxes such as a voith vorecon ( voith.com/ita-en/214_e_cr168_en_vorecon-variable-speed-planetary-gear.pdf ) but instead of power splitting from one source, a second motor is used and can be tuned independently, very clever! I even like the design of the remote, screens just get in the way and ask to be smashed one way or another.

We need to embrace this new kind of thinking and step away from the incremental improvements of traditional bike design, just think of the money you'll save on cassettes, chains and smashed derailleurs!
  • 1 0
 Exactly. Our goal is to change how e-bikes are ridden and thought of and this does not happen by incremental steps. Our Drive System offers clear advantages even before considering the robust and low-maintenance nature of a single-speed drivetrain.
  • 2 1
 I am a big fan of bike/ebike technology, especially internal geared tech. I have used CVT in several different platforms and they work very well. However, most CVT systems are very heavy so I would be keen to see how this one enters the market. If executed as planned this could change the game.
  • 2 0
 Yes, indeed. Changing the game is something that we have been aiming for from the start. Thank you for the nice feedback!
  • 1 0
 @Revonte: I'm all about this. Ebikes are getting more popular and to me it seems silly to have a powerful motor with a wide torque spread and then sticking a traditional gear set and derailleur on the hub. Especially given how big they have become.

I'm all about CVT, having owned several CVT scooters. What's not to like about a system that always puts you in the optimum rev range? Friction and weight I guess. Friction is counteracted by the motor. Weight is the last big hurdle. Compared to a low spec SRAM cassette at 615g and a crappy SX or Deore derailleur, I think the market perception of acceptable weight will open up a lot.

Thumbs up.
  • 1 0
 @jaame: Thanks for the thoughtful comment. Weight is one factor, but the optimal weight distribution makes a lot in counteracting that. Grams are grams, no matter how you look at them, but then again, there several aspects to consider.
  • 1 0
 @Revonte: I wish you the best of luck and one day, when I buy an ebike, I hope it will be a cvt design.
  • 1 0
 @jaame: Thanks and we are very happy to hear that!
  • 1 0
 So is the second motor strong enough to hold up and not let the transmission slip if the rider stands up on the pedals putting maximum torque (around 100Nm) on the drivetrain?
  • 1 0
 Certainly.
  • 2 0
 If batteries run out of power, would the rider still be able to pedal this system and change gears?
  • 1 0
 can't change gear on this system, but can pedal in the easiest gear (which may be faster than walking depending on if you have it geared for commuter use, but possibly slower if geared for MTB)
  • 1 0
 @uphillsg: If that's true, this is a significant disadvantage compared to e-mtbs with derailleurs.
  • 1 0
 Yes, this is the case. However, the chance of this happening has been made as minimal as possible by control software design.

This exact question was addressed previously on our blog. If you're interested to learn more, check the whole text. revonte.com/revonte-qa-you-asked-we-answered
  • 1 0
 From the link: "Because of the design on the drive unit, it can only be run with the lowest gear if the battery has run out completely. To counteract this, our software has been developed to conserve battery life to control the gears as long as possible."
  • 2 0
 @Revonte: so you're using the planetary gear set as a differential of sorts, with the first motor applying direct torque to the output and the second motor acting as a speed/torque ratio modifier? That's a really cool idea. Would be sweet if there was a mechanical lock or something as a user-applied failsafe if the battery dies so you're able to use something other than the lowest gear though.
  • 1 0
 @Socket: Unfortunately, we can't go into that much detail when it comes to the construction and technical solutions of the drive unit. Very good reasoning on your part, though!
  • 2 0
 So, I assume the 2 motor setup does something similar to the Toyota hybrid systems?
  • 2 0
 pretty much exactly the same
  • 2 0
 Very interesting. I'm definitely for getting rid of the the metal chain and derailleur, if the weight is similar.
  • 2 0
 This is definitely the way to go with ebikes! Get rid of the fragile rear derailleur.
  • 1 0
 Happy to hear that you agree!
  • 2 0
 Changing the game of changing gears, looking forward to seeing this on the market since CVT is a great system!

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