
Driven – A bicycle drivechain concept without derailleurs and chains - thatcantbeit
https://www.ceramicspeed.com/en/driven/
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ben7799
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.

~~~
m463
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)

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

~~~
m463
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.

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freefal
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](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.

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rhinoceraptor
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.

~~~
folkrav
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.

~~~
LeifCarrotson
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.

~~~
davidbanham
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.

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

~~~
pmontra
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.

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acomjean
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/chains.html)

[https://www.sheldonbrown.com/chain-
wear.html](https://www.sheldonbrown.com/chain-wear.html)

~~~
Xylakant
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.

~~~
blacksmith_tb
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...](https://www.bikeexchange.com/blog/best-urban-belt-drive-bikes-2018)

~~~
Xylakant
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.

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mbritton72
The system isn't ready for prime time, but apparently it's a great way for CS
to advertise!

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

~~~
lucb1e
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.)

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kitd
Video of it working:

[https://www.youtube.com/watch?v=UFAQ6CzNm7s](https://www.youtube.com/watch?v=UFAQ6CzNm7s)

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gvb
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](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..."

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

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aidenn0
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](https://www.ceramicspeed.com/media/2979/driven_brochure.pdf)

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GhostVII
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.

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AstralStorm
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?

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falcolas
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?

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AmVess
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.

~~~
rhinoceraptor
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.

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jtms
Would this system be legal in professional competition cycling?

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joerickard
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).

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

