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.
Driven – A bicycle drivechain concept without derailleurs and chains
31–40 of 49 posts
Re: Driven – A bicycle drivechain concept without derailleurs and chains
#32The 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.)
Re: Driven – A bicycle drivechain concept without derailleurs and chains
#33First, 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.
Re: Driven – A bicycle drivechain concept without derailleurs and chains
#34chains 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.…
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.
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.
Re: Driven – A bicycle drivechain concept without derailleurs and chains
#35Earlier quoted context omitted.
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.
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.
Re: Driven – A bicycle drivechain concept without derailleurs and chains
#36Earlier quoted context omitted.
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.
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.
Re: Driven – A bicycle drivechain concept without derailleurs and chains
#37Earlier quoted context omitted.
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 spr…
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.
See also: people overinflating their tires because it feels "fast", even when measured performance on real-world roads is actually worse.
Re: Driven – A bicycle drivechain concept without derailleurs and chains
#38Earlier quoted context omitted.
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 spr…
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.
Re: Driven – A bicycle drivechain concept without derailleurs and chains
#39Earlier quoted context omitted.
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.
True, good point.
Re: Driven – A bicycle drivechain concept without derailleurs and chains
#40chains 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.…
> Sheldon Brown's (RIP) bike pages[...]
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...