A New E-Bike Drive System Ditches the Classic Chain Design | Hacker News Reader

A New E-Bike Drive System Ditches the Classic Chain Design

interestingengineering.com

19 pointsmardiyah19 comments

The pedals turn a generator that produces electricity that drives the motor on the rear hub. One need not be much of an engineer of any sort to count the points of efficiency lossiness in that system. This, versus chain drive which for all it’s maintenance and fiddliness, is still the most efficient drive for bicycles and motorcycles. Even if one is fine carrying the weight of a shaft drive (say, a BMW motorcycle), it isn’t as efficient. Who cares, on a 125 bhp motorcycle? You will care on that next steep hill you have to climb with this Rube Goldberg bicycle.

And how much does this weigh in comparison to a chain drive? I don’t want to piss on anyone’s idea, but the single selling point I see is not having to clean or replace a chain. Otherwise, I assume it weighs more, and isn’t as efficient. Throw me a bone here, what makes this better other than “no chain”?

If it's an electric bike, one might care a lot less than on a bike that runs on meat power only. You may consider the battery to be the primary energy source, and pedal power a supplement.

Which works until you are out of battery, and then you have a lot of extra weight to carry uphill with greatly reduced peddling efficiency. At that point why not just have an e-bike with no peddling at all? Saves weight, battery lasts longer, can still walk it up hills.

You don't worry about being out of battery on a Tesla, so why would you on an e-bike? Clearly you need to fit the drivetrain to the expected use case, but there are plenty of people who might ride the bicycle down the street to the grocerist, but would never even consider going on a ride lasting more than half an hour.

Sure, but then... why the peddles at all?

I guess I just can't see a reason anyone would ever choose this drive-train over any other for any purpose.

In some places, the pedals hold legal weight to mark it as an "e-bike" (legal) as opposed to a "motorcycle" (illegal without appropriate license, registration, insurance, tax, inspection etc).

> chain drive which for all it’s maintenance and fiddliness

Belt drives already solve this problem. A lot of single-speed e-bikes come in belt drives. Zero rust, zero maintenance, zero oily pants.

That being said, I don't know if anyone has managed to put gears on them yet and their gearing ratio tends to be really high.(power intensive). So, they might not be great as a non-electric bike on steep slopes. I ride my belt-drive ebike without charge on flat surfaces pretty comfortably though.

Belt drives are typically paired with internally-geared hubs (or even crank cases). While not providing as many gears, they can cover the same range of gearing. There's even brands of belt-drive mountain bikes out there, like Zerode.

That's actually awesome. I was purely thinking from the POV of a derailleur.

Skipping the derailleur protects away yet another complex external part that may be prone to failure. I like it !

Wouldn't that create a strange feeling of being disconnected from the driving wheel?

It might be strange for die-hard pedalists, but not necessarily anyone else. Motorcycles do fine w/o after all.

I actually like the idea of separating exercise from locomotion. I am worried about the loss of efficiency though.

Here's a prototype of this style of drive on an e-bike (2016), killer feature is smoother gears and potential for better designed bikes, it'd be perfect for the Convercycle Extendable E-cargo without crazy long chains everywhere.

https://youtu.be/4JKOKpg21dQ

High-quality drivetrains in bicycles can have an overall efficiency of up to 95%, can this system beat that? Of the force that someone puts on the pedals, how much of that drives the rear wheel in the end?

> High-quality drivetrains in bicycles can have an overall efficiency of up to 95%, can this system beat that?

It almost definitely cannot. I tried researching efficiency of suitably small generators some time ago but it was surprisingly hard to find useful numbers; however, I'd assume combined generator + motor efficiency won't be better than 70%. Add in conversion efficiency (for charging the battery), it's even worse.

However, that's not necessarily a problem if you consider the battery to be the primary power source and pedal power as something like a opportunistic range extender. If your battery can take you there and back, then does it matter if pedal power is only 50% efficient? I would consider such a tradeoff for the joy of not ever having to clean or replace a chain (or listen to it squeak), put it back on when it drops, or getting jeans stuck in it...

Reminds me of this project I saw a while ago on youtube: https://www.youtube.com/watch?v=7hfClQh3rxM

Mutually exclusive? Flywheel or something needed? I don't think it would need one...

Im more interested in that 300km range bicycle they mentioned in the article

Article from 2021, i have not seen any bikes actually using this. So my bet is that its a fad which didnt work. Prove me wrong.

2021 is not ancient history. We’re only on the 3rd month of 2022.

Reply on news.ycombinator.com