Driven – A bicycle drivechain concept without derailleurs and chains | Hacker News Reader

Driven – A bicycle drivechain concept without derailleurs and chains

ceramicspeed.com

45 pointsthatcantbeit48 comments

This company is really famous for selling really expensive "upgrades" that do very little for actual speed.

The resistance of the chain & pulleys is a very tiny percentage of the whole unless they're gunked up and not maintained/lubricated or are broken.

Pretty much all mechanical resistance on a bike is dwarfed by aerodynamic resistance. When the aerodynamic resistance is broken down the contribution of the bike is dwarfed by the contribution from the rider and his/her body position on the bike. When you start getting into the resistance from gear the helmet & clothes are more significant than the bike.

None of this stops them from selling $10,000 bikes to amateurs who are slow though.

It is free but hard work to go on a core strength + flexibility program that lets you access more aerodynamic riding posture. Working with a good fitter/coach will cost a little but help get there with less guesswork. Everything about getting fast on a bike is harder work than buying stuff.

When people start talking about bicycle upgrades to shave a few ounces here and there, I just point at my belly and the 10's of pounds I could drop from my body before I worry about a couple ounces on my bicycle.

I think the fastest bikes in a straight line are recumbent bikes because of the small frontal area. Nobody talks about it much (probably because nerdy middle age men are the only demographic with enough devil-may-care attitude to ride one in public)

The fastest bikes are fully enclosed velomobiles, but they're expensive and usually don't fit in normal bicycle parking spaces.

Also they're banned in most racing events and horrendously expensive.

that's fascinating - I think common bicycles would probably have lots more variants if these hidden administrative rules didn't exist.

I'm reminded of the look of sport motorcycles. The design has been heavily influenced by an almost unknown source - a racing rule from many years ago that said the fairing should not extend forward of the front axle.

First, from an engineering perspective, this product is really cool and maybe for some well-funded Tour de France team it could make sense to test this out. But the price point, the lack of compatibility with components of existing drivetrains and the lack of compelling reasons to make the change, are going to be headwinds to adoption.

On page 3 of their brochure (https://www.ceramicspeed.com/media/2979/driven_brochure.pdf), they're showing 0.5% - 1.0% efficiency gains over a traditional drivetrain that is cross-chained, meaning that if you use a traditional drivetrain correctly (i.e., shifting so as not to cross-chain) the gains are likely significantly smaller.

As ben7799 said, this company is primarily in the business of selling very expensive products that have minimal impact on performance.

I'm sure this is a neat system, but it's worth noting that bicycles are already very efficient, the difference between their claimed efficiency and a properly set up traditional drivetrain is maybe one or two percent.

And any weight savings are probably useless due to the minimum weight required for racing. Pro bikes are basically at the point where they're having to add weight just to pass inspection. This system might have a bit less rotational mass in the "cassette" than a traditional cassette which would help.

I've ridded a half-decent street bike a summer or two. This thing was light enough that as a tall slightly chubby man I felt uneasy just getting on it, I kept thinking "this thing will crumble from my weight". I knew it was stronger than that, but my brain kept telling me something wasn't right.

And it was a pretty mid-range bike.

As a tall, lean cyclist I'm always a bit surprised by both the extremes that people go to in weight reduction and by the palpable speed difference that you feel when riding a light bike.

When I ride a 1980s steel road bike, we (bike+rider) weigh about 75 kg. On a modern carbon-fiber bike, we weigh about 71 kg. That's a 5% difference, but the latter feels like it has rocket boosters when I get out of the saddle to sprint up a climb, while the former feels like I'm carrying an anchor the whole ride. Borrowing a friend's hill climb fixie machine well under the UCI weight limit gives even more of an exhilaration of speed. But conversely, adding 30lbs of bags to go touring doesn't feel that much more difficult once you're up to speed.

I wouldn't be surprised if most of that difference in feel could be explained by frame rigidity rather than weight. I love my steel frame but I know it's not super efficient.

IMO it’s probably that wheels are a lot lighter now. Rotational mass is a killer.

I've got two different sets of wheels for the same gravel bike. Its standard 42 mm wheels for gravel and 28 mm slick wheels I assembled for road. Same brake rotors and same gears on the back. The set of road wheels is about 1.5 kg lighter (3 pounds). The bicycle seems to fly with them. Rotational mass is really important and also slick vs threaded.

True, good point.

See also: people overinflating their tires because it feels "fast", even when measured performance on real-world roads is actually worse.

I think you could get more gains by using the restroom before a race.

chains are a pain. But belt drives have been around for 10 years now and you hardly see them.

Chains are the most complex part of the bike with the most moving parts. You have to lubricate them, they stretch.. But they work well in all variety of conditions (even rusty and squeaky) and are fairly cheap.

Sheldon Brown's (RIP) bike pages have some good articles on the good old chain.

old school html ahead: https://www.sheldonbrown.com/chains.html

https://www.sheldonbrown.com/chain-wear.html

    > Sheldon Brown's (RIP) bike pages[...]

Off-topic, but how sad to see the state of that website today. I read Sheldon's website religiously before he died, but hadn't seen it in over 10 years.

This[1] is how it looked like when he was alive. Now it's stuffed full of ads, and the first thing you see is a pop-up cookie warning about "our social media, advertising and analytics partners".

1. http://web.archive.org/web/20080111140407/http://www.sheldon...

I didn't get the pop-up, but your right, its a hard with all those ads. The info is good, but without adblockage...

There are some clasics on the archive. Browser tips: http://web.archive.org/web/20071227104629/http://sheldonbrow...

how to make a website: http://web.archive.org/web/20071227104613/http://sheldonbrow...

Sheldon Brown's wife was my CS prof at northeastern[2] and someone named John Allen[1] seems to be keeping the site up to date. Oddly John's bike blog page is pretty good and ad free. Lots of words on the old web.

http://john-s-allen.com/blog/

http://www.ccs.neu.edu/home/fell/#Courses

Chains are inexpensive, very efficient, and easy to replace or service. There's a reason bicycles have used them for over 100 years.

Belt drives are comparatively expensive and don’t work with derailleur gears. Internal gears, especially cheap systems, still cannot offer as many gears as a derailleur. Belts also need to be pretty tight and thus cannot be used on most bicycles with a rear suspension as the distance between the pedals and the sprocket changes under load. So many people opt against belts.

I have seen quite a few belts on internally geared hubs - a quick search turns up quite a few[1] commuters shipping w/ belt + Nexus internal hub.

1: https://www.bikeexchange.com/blog/best-urban-belt-drive-bike...

Absolutely: internal gear hubs are the only gears you can use with belts. They just tend to be substantially more expensive for the same amount of gears as a comparative derailleur. Internal gears also tend to have a higher friction than derailleur gears - the really good ones such as a Rohloff speedhub cost > 1000 EUR. Even a comparatively mundane Alfine 11 gear costs ~ 400-500 EUR. A pinion gear isn’t exactly cheap either.

In return you get a mostly maintenance free setup. It’s great, but I probably wouldn’t opt for it for a city commuter bike.

And most belts are a permanently closed loop, unlike chains which can be opened and closed. This means you need an special frame with an openable rear triangle.

It doesn’t actually need to open, but the frame must be built to support belts. The lower bar of the rear triangle must pass over the belt.

Interesting comments about the suspension. Several models of motorcycles use belt drive and they have both front/rear suspension.

BMW uses them on some of the F models, Buell’s where all belt drive and I think all Harley’s use a belt transmission.

There are plenty of motorcycles with belt drive, the suspension doesn't seem to be a problem.

motorcycles have different issues. The gear changes are internal inside the transmission, not in the belt drive line. Also, bikes tend to have multi-link suspension with chain growth through the travel. This allows the suspension to be reactive to pedaling forces to reduce rider induced pedal-bob that eats efficiency.

The system isn't ready for prime time, but apparently it's a great way for CS to advertise!

I'm not accusing... but I'm struggling to see how this isn't just an ad.

For what it's worth, I upvoted the 'story' because I never heard of such a thing and it looks really cool. While I'm a little sad to read that this kind of thing doesn't actually really help, it's not that unexpected. Still, it looks neat, and once the price comes down (I didn't see any prices but I'm guessing it's hundreds for a few metal parts), I might want to play around with such a bike to see for myself. It's a little like other gadgets/gimmicks. (Some gadgets have use, others don't really.)

Video of it working:

https://www.youtube.com/watch?v=UFAQ6CzNm7s

The above video doesn't show it changing gears... I was wondering how it did it. It is (sort of) covered in the "fully explained" YouTube video: https://www.youtube.com/watch?v=-9gQ1KRhesM

Explanation: very complicated with a battery powered wireless electronic shift mechanism embedded in the drive shaft. The "fully explained" video doesn't show it changing gears either, just explains how they would do it. My take-away is that it doesn't change gears as of the making of the video (July 9, 2018) but "they have a plan..."

Correct in the video you reference, they say "this is how we invision the shifting will occur"

I couldn't figure out what it was from the page, but the linked PDF has more information (rolling pinion to what looks like a driveshaft)

https://www.ceramicspeed.com/media/2979/driven_brochure.pdf

How do they keep the bearings from skipping over the rear gear/disk? That disk and driveshaft would have to be extremely stiff to avoid flexing, especially in lower gears where the contact point is further out, and it looks like just a couple millimeters of flex will give enough space to skip.

As far as I'm aware chain was introduced to allow for light weight while keeping vibration resistance.

Can't this pulley system be trimmed down even further to one bar transmission?

Based on my experience with motorcycles, chains are better than shafts for transmitting torque. Shafts tend to twist over their length in high torque settings, whereas chains just "pull" with minimal stretching.

Specific to this product, how the hell would you keep the 20-30 "gear" bearings on the shaft clean and operating smoothly in anything but lab conditions?

I have concerns about the longevity of those itty bitty ceramic bearings in real world conditions where you're hitting bumps and cracks in the road while under load from pedaling.

Also, literally every part of that page screams "expensive AF" including the part where they don't talk about the price.

You can seal the bearings, but that cuts efficiency. That's not the only problem, though. The interface between the bearing and the bearing sprocket will make it rather unusable in very dirty conditions.

Their setup seems like an answer to a question no one was asking.

The gains you could get from improving drivetrain efficiency are very marginal. Everyone else is working on improving aerodynamics. That's the actual limiting factor in cycling, and it always has been.

I was looking at them and scratching my head too.

I hope these images are just for show, and that the real product will use shielded bearings or else they are going to get crunchy and destroyed fast.

I couldn’t find it on the mobile version of the site but a video of the pinion based drivetrain showed up somewhere else the other day, I think the post is likely in reference to that chain-less system

Shaft drive bicycles had their heyday in the 19th century when chains were unreliable.

Would this system be legal in professional competition cycling?

No, this violates current UCI rules.

"The front wheel shall be steerable; the rear wheel shall be driven through a system comprising pedals and a chain"

However, the rules do change and have been recently (like the removal of the 3:1 restriction).

Probably not, the UCI operates on a policy of all new tech being forbidden until explicitly authorized.

Honestly, the price-point of these things makes it prohibitive for most people...I wish I could try one for fun though :)

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