Driven – A bicycle drivechain concept without derailleurs and chains • Hacker News Board

Re: Driven – A bicycle drivechain concept without derailleurs and chains

#21

Post by rhinoceraptor » Wed, May 08, 2019, 8:50 PM UTC

AmVess wrote: post #17

falcolas wrote: post #6

Earlier quoted context omitted.

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?

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.

Re: Driven – A bicycle drivechain concept without derailleurs and chains

#22

Post by ben7799 » Wed, May 08, 2019, 8:51 PM UTC

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.

Re: Driven – A bicycle drivechain concept without derailleurs and chains

#23

Post by LeifCarrotson » Wed, May 08, 2019, 8:55 PM UTC

folkrav wrote: post #9

rhinoceraptor wrote: post #3

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 mi…

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.

Re: Driven – A bicycle drivechain concept without derailleurs and chains

#24

Post by blacksmith_tb » Wed, May 08, 2019, 8:55 PM UTC

Xylakant wrote: post #11

acomjean wrote: post #10

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.…

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...

Re: Driven – A bicycle drivechain concept without derailleurs and chains

#25

Post by gvb » Wed, May 08, 2019, 8:56 PM UTC

kitd wrote: post #5

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..."

Re: Driven – A bicycle drivechain concept without derailleurs and chains

#26

Post by evandev » Wed, May 08, 2019, 9:01 PM UTC

gvb wrote: post #25

kitd wrote: post #5

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-aw…

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

Re: Driven – A bicycle drivechain concept without derailleurs and chains

#27

Post by asynchronous13 » Wed, May 08, 2019, 9:04 PM UTC

ben7799 wrote: post #22

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…

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.

Re: Driven – A bicycle drivechain concept without derailleurs and chains

#28

Post by Xylakant » Wed, May 08, 2019, 9:04 PM UTC

blacksmith_tb wrote: post #24

Xylakant wrote: post #11

Earlier 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.

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.

Re: Driven – A bicycle drivechain concept without derailleurs and chains

#29

Post by cladari » Wed, May 08, 2019, 9:09 PM UTC

Xylakant wrote: post #11

acomjean wrote: post #10

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.…

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.

Re: Driven – A bicycle drivechain concept without derailleurs and chains

#30

Post by davidbanham » Wed, May 08, 2019, 9:10 PM UTC

LeifCarrotson wrote: post #23

folkrav wrote: post #9

Earlier quoted context omitted.

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 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.