Stringbike: Chain-free bike
wired.co.uk
wired.co.uk
"Although, that would presumably be the least of your worries if a fast-moving, taught, metal wire lashed off its piston next to your leg. Ouch." I've had a couple chains break or skip off (especially on fixed-gear bikes, which don't have a derailleur or chain tensioner to regulate chain slack), and having a taut wire whip at my ankle sounds like a terrible idea. Getting a bit of grease on my ankle or pant leg is rare, and at most a minor annoyance.
I usually ride singlespeed or fixed (much better on snow!). I've read about modding 3-speed internal hubs into 2-speed fixed internal hubs, but haven't tried.
The design in the wired article, while interesting, seems like an overly complicated solution to the chain "problem".
> "[The] asymmetry [of traditional designs] has been the source of lots of problems"
I'd like to hear more about that. Sure, the rear wheel is balanced a little differently to account for this, and I imagine the feel is a little different if the both pedals are directly attached to the "cranks" (or their equivalent pulleys here), but I don't see a lot of problems caused by the asymmetry of a traditional design. Am I just blind to it? What are these problems?
The current system has no problems and most parts are interchangeable.
For riders who use the bike for one week/year, put it away when it rains and never touch it otherwise it's great
So, I ask HN: why aren't chain/belt bike designs symmetrical?
EDIT: as to the article -- more analysis of why symmetrical designs are superior would have been nice.
I think the advantages are because of the location of the torque. When the left pedal exerts force, it torques the left side of the bike which coincides with the the natural movement of the bike. Imagine when a cyclist pedals very hard and the bike sways from side to side from the force exerted on the pedals. Now I'm not sure if they are trying to reduce the movement of the bike, or make it feel more natural.
The thing I cannot make out is the switch from gears to a single system. Is the output of work the same as the force going in, which would mean that you have to pedal the same amount going up a hill as going down, or is there a variability of work like a rowing machine? The rowing machine system would seem to apply here but they do not address that so I'm not 100% on that.
This could be done continuously, rather than having discrete gears.
I'm not sure what causes the wire to rewrap itself around the ring on the upstroke... probably some sort of embedded spring.
The lowermost video on this page shows the real bike from an angle where you can see what happens to the wires:
http://www.stringbike.com/Internal%20symmetry%20of%20both%20...
Also, to me it looks like the two rotating cylinders next to the rear wheel are ratchets, like a socket wrench.
Non-circular gears change the gear ratio as you pedal. It effectively shifts down in that part of the pedal stroke where you have the least strength. Since the bike doesn't slow down, your feet must speed up. Then, when your feet swing around to where you have more strength, it effectively shifts up.
My argument is, if you are pedaling at the limit of your strength, you are in too high a gear. Shift down and spin your feet faster. You'll use less strength, and more aerobic capacity, enabling you to maintain an equivalently high power output, but for longer. It's easier to run a marathon at a constant speed than to sprint 100 m at a time, taking walking breaks to maintain the same average speed.
It all comes down to how good the motor (legs+lungs) is.
It's funny how people are so resistant to innovation. "Biopace chainrings are often cited as the epitome of a solution looking for a problem among the biking press." While typing on a computer that likely contains a mechanical hard drive spinning at close to 10krpm, the author complains of a slight increase in mechanical complexity that will allow him/her to generate more power. The real question is whether or not the complexity is manageable, will it break down frequently? etc.
I remember using Biopace and the part I remember the most was going up a steep hill and losing traction because of the change in torque. I was riding a bike the way I was accustomed to pedaling but the power output would surge because of the change in mechanical advantage. Maybe I could relearn how to pedal so I could take advantage of Biopace but I really just wanted to ride, not maximize every degree of the pedal arc.