Driven – A bicycle drivechain concept without derailleurs and chains(ceramicspeed.com) |
Driven – A bicycle drivechain concept without derailleurs and chains(ceramicspeed.com) |
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.
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.
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.
And it was a pretty mid-range 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.
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
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..."
Can't this pulley system be trimmed down even further to one bar transmission?
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?
Also, literally every part of that page screams "expensive AF" including the part where they don't talk about the price.
Their setup seems like an answer to a question no one was asking.
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.
"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).
> 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...
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.
1: https://www.bikeexchange.com/blog/best-urban-belt-drive-bike...
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.
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.
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.