Revonte's powerful ebike motor has a built-in stepless transmission
Finnish company Revonte has given us a glimpse into the future of ebikes with a new compact drive system that integrates a motor, automatic stepless transmission and a bunch of electronics into a single tight unit with open control software.
Many regular ebike riders, including myself, are starting to run into problems wherein the "e" part and the "bike" part collide. Chains, gearsets, derailleurs and sprockets that were designed to handle the power of a muscular set of legs are often struggling to cope with the high-torque output of electric motors – even ones that are EU-legal at a rated 250 watts. Personally, I've been through two chains and one rear cassette in fairly short order thanks to a Bafang Ultra 1,600-W system that can contribute up to 160 Nm (118 lb-ft) of torque on top of whatever my legs are doing. Never mind that I run it on its lowest setting most of the time.
Ebikes are going gangbusters all over the developed world, and this kind of issue won't be allowed to persist for long. Evolo is dealing with it via an electronic automatic transmission integrated into the rear hub, but Revonte is going a step further and sticking the transmission in the main drive unit.
Thus the motor runs directly through a set of planetary gears not dissimilar to the system that drives the Toyota Prius; there's one electric motor putting torque in, and another spinning to control the speed of the output drive. A chain links the crank to the rear wheel in a clean, fixie-lookalike design that should eliminate chain jumping and skipping while lasting longer, as the links never need to bend. Personally I'd have preferred a cleaner carbon belt drive, but maybe I'm being greedy.
A rider can either leave the thing in auto mode, where it'll measure your torque and smoothly alter its ratios to keep you at your preferred cadence, or else put it in "manual" mode to have it shift between a bunch of virtual gears as if it's a normal shift. Similar things have been done in the motorcycle world for some time now.
One wonders if this cheeky little arrangement might allow Revonte to skirt around ebike power output regulations; it's rated at 250 watts nominal, but makes a whopping 90 Nm (66 lb-ft) of torque and can peak at 1,500 watts. Power output being torque multiplied by RPM, you'd think an integrated drive unit like this might be able to pound out a lot of torque at slower cadences in high gears and feel a ton stronger than other 250-W motors without integrated gearboxes. Anyone who's ridden a bunch of 250-W bikes back to back will tell you there's a massive difference between 250 W and 250 W when the torque ratings are different, and I suspect the difference between a Revonte One and a regular Bosch-drive bike might be pretty epic.
On top of this, it's got other fun bits and pieces baked in; a GPS chip, Bluetooth comms and of course a computer to run it all, complete with open, secure APIs and a bunch of plug-in pre-written modules that bike manufacturers can choose to add as they program and customize the system for various bike models. For example, it's trivial to add a "find my bike" feature to your smartphone app, or a "warn me if the bike moves and I don't," or a "remote wheel lock." You can use Revonte's own dash and hand controls, or program it to accept whatever else you like.
Indeed, Revonte sees itself mainly as a software company that happens to be building a drive unit for that software to run on. The company has no interest in making the bikes themselves, and wants to act simply as a drivetrain supplier. To that end, it's already signed up Tunturi from Finland and Lavelle Bikes in the UK, each of which is building a bike to take advantage of the Revonte One drivetrain.
It looks to us like a terrific system, and we'd love to take one for a spin. Revonte expects to have bikes on the road this year, and to ramp things up significantly going into 2021. With some US$2 million in the kitty following the company's seed funding round, scaling will be a challenge. We wonder how long it'll take Chinese giant Bafang, or Bosch, or any number of other manufacturers to produce something similar, and whether Revonte's pockets will be deep enough to defend its intellectual property. But such things are mere speculation. The take away here is that the next generation of ebikes are going to be considerably better than the current generation – and the current generation is already pretty damn awesome.
Check out a video below.
Source: Revonte via Good News Finland
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(The same thing happens with Priuses - my Prius has a 53 kW MG2, but the battery can only supply ~30 kW or so. The rest is coming from MG1, which is taking it off the engine.)
I look forward to seeing and testing the actual bikes.
The dream is to be able to maintain a near constant pedal cadence within the two main variables - speed and steepness of the road. But also to keep the motor spinning at higher speeds more of the time where it has higher power, enables use of the smallest motor. This approach can give all of this. And yet its probably the simplest mechanical setup of any ebike I've seen. No gears and yet one of the most compact ebike motors around. Look at that sleek compact driveline. Stunning.
I'm not saying this Revonte model is the answer - the 250W rating "but there's more" thing raises some questions. The Euro motors all end up underpowered. And how much will it cost? This is not a finished bike but rather a motor company. But the engineering concept is certainly bang on.
I have a 750W Bafang equipped eMTB and I can certainly say that gear change is the biggest issue to me. I have set it up as a 5 speed rear derailleur, and can also manually change two front chainrings. But it's still a near constant issue to be changing gears. Also the Bafang is oversped, under geared. The crank speed at max motor speed is more than most riders would want to cadence.
I would add that the chain drive is VERY smart here. Chains especially non-derailleur type single speed setups like this are extremely robust, cheap, compact. The strength allows for small sprockets like this to stay out of the way, whereas the equivalent belt would be very wide, or need larger dia. sprockets. A correctly sized chain here could last the lifetime of the bike. A chain can be dismantled with a master link and replaced easily, unlike a belt. At motorcycle speeds chains are noisy but at pedal speeds, silent.
Just need a 500kW motor and a belt drive and it would be perfect.