

Stringbike: Chain-free bike - Maro
http://www.wired.co.uk/news/archive/2010-09/20/hungarian-stringbike

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silentbicycle
Chain-free bike designs (and other major hardware changes) come up
periodically. Typically, they're belt-driven. While chains and cables for
brakes seem inferior to cables and hydraulic brakes, they degrade for more
gracefully. It's not a perfect solution, but it's a reasonable local maxima
for most people. Professional racers can get away with equipment that's wildly
impractical for commuters, mountain bikers, etc., though.

"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.

~~~
spokey
There's also shaft driven bikes:
<http://www.google.com/images?q=drive+shaft+bike>

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?

~~~
coryrc
For people going for the lightest bike possible, the spokes in the driving
direction of the wheel are a smaller gauge (heavier)-- not one side or the
other, as the hub is a single piece. The frame is reinforced slightly on the
chain-side of the bicycle. But these modifications are for racing bikes,
normal bikes have no special reinforcement because the weight difference is a
couple ounces.

The current system has no problems and most parts are interchangeable.

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nuriaion
I don't see where this design has a big advantage above a traditional chain.
Maybe their is less oil/grease so your trousers will be happy. But the
efficiency of a chain is something around 97% (IMHO). I think with so much
moving parts etc. the efficiency will be lower. And i think that the forces
will be problematic to handle.

~~~
rtyuioikujhy
It's zero maintenance. For 'serious' bike riders who care about efficiency and
clean/oil chains it's useless.

For riders who use the bike for one week/year, put it away when it rains and
never touch it otherwise it's great

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JoeAltmaier
Movie is confusing - do the wires change length? How is the leverage applied
to the hub? Why not a movie of the bloody bike?

~~~
rsbrown
Also, there's no explanation of the symmetrical aspect of the design. I'm
intrigued by it, but other than vague allusions to its superiority over
asymmetrical designs no analysis is given.

So, I ask HN: why aren't chain/belt bike designs symmetrical?

~~~
oconnore
The chain goes on one side of the bike.

~~~
rsbrown
Sorry, my question was unclear. Why do traditional chain designs only have the
chain on one side? If symmetrical designs are more efficient (as the article
claims) why couldn't the same thing be accomplished with a chain/belt design?

EDIT: as to the article -- more analysis of why symmetrical designs are
superior would have been nice.

~~~
silentbicycle
The added weight from a second complete drivetrains (chains, gears,
derailleur) and/or extra mechanical complexity would probably negate the
efficiency gained by better transmission of force.

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nkassis
Not sure I see the advantage of this design. I'd try a belt driven bike first:
<http://en.wikipedia.org/wiki/Belt-driven_bicycle>.

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eli
Couldn't you just put a second chain on the other side? Or am I missing
something in this "symmetry" argument?

~~~
Tichy
Perhaps it would be difficult to keep them in sync, and if they are not in
sync, chaos ensues. No idea, though.

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oconnore
Neat. I wonder if creating a vertical elliptical pedal path, or even a linear
path would be an improvement. That way the cyclist would have more leverage on
the down stroke, since at the bottom of a circular stroke you are forcing the
pedal mostly rearwards, not downwards.

Also, to me it looks like the two rotating cylinders next to the rear wheel
are ratchets, like a socket wrench.

~~~
jacquesm
That's been done on regular gears, I'd imagine it would work much the same:

<http://en.wikipedia.org/wiki/Biopace>

~~~
oconnore
Thanks for the link.

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.

~~~
adolph
"People are so resistant to innovation" is one way to look at it. Another way
to look at it is that sometimes innovation gets far enough ahead of
expectations that it can't overcome challenges with user education and
linkages to present technology.

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.

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JoeAltmaier
Much of the complexity seems to be directed at keeping the pedals going around
in a circle. Why not levers or some other reciprocating motion? ANything would
work with cables.

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babo
Some more videos at <http://www.youtube.com/user/stringbike>

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eldenbishop
The only drawback I can see to this system is that you can't spin the pedals
backwards while coasting. I do this a lot to stretch my legs and just to pass
the time on hills when I don't feel like speeding up. Peddling backwards will
engage the forward motion "but along a miserable curve".

~~~
utexaspunk
I don't see any reason why one couldn't put a ratcheting hub in the crankset,
allowing backward pedaling...

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babo
The inventors talks about similarity with current hard drives where he got the
original idea. While this design sounds complicated, it replaces the whole
drive chain, including gear shift.

