
Invention of the day: A spokeless bicycle - geekpressrepost
http://www.crunchgear.com/2010/02/16/nine-mechanical-engineers-build-a-spokeless-bicycle/
======
matthiasl
On a normal wheel, the bearings travel a much shorter distance than the wheel.

On this wheel, the bearings travel the same distance as the wheel. That makes
me wonder if the friction due to bearings is much larger in this type of
wheel. I have no idea if that's an important factor or not.

(A normal wheel is, say, 700mm diameter and the bearing race maybe 20 or 30mm,
so the bearing surfaces move 20 or 30 times more slowly than the bicycle. On
this spokeless bicycle, the bearing surfaces move at about the same speed as
the bicycle.)

~~~
pedalpete
Not only friction, but rotational weight. I would have to assume the rim in
this design is much heavier than that of a spoked bicycle, and therefore
you've moved the weight of inertia (?) to a point further from center axis.
This takes more energy to spin.

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rimantas

      It’s a very impressive project, and make sense when
      you think about it.
      <…>
      Keep in mind, this is a prototype so it’s a little rough
      around the edges, but the concept is sound.
    

Actually no. I don't think it makes much sense and I don't agree that the
concept is sound. Spokes distribute load and allow for lightweight rim, this
construction just concentrates load on few points—looks like it is just asking
rim to be squashed. Another case of the solution for the problem nobody has?

~~~
by
The rim squashing problem can be solved by having a point of contact
immediately above where the rim touches the ground as in the Peugeot concept
bicycle [1] linked from the Reddit page [2]. You can then have a light-weight
rim.

[1] [http://www.carbonfibergear.com/peugeot-redefines-the-
bicycle...](http://www.carbonfibergear.com/peugeot-redefines-the-bicycle-with-
the-b1k-concept/)

[2]
[http://www.reddit.com/r/technology/comments/b2g91/spokeless_...](http://www.reddit.com/r/technology/comments/b2g91/spokeless_bicycle/)

~~~
pedalpete
But aren't you continuing to add complexity to solve an issue which was
created by adding complexity to an already simple system.

------
akgerber
Q: How do you improve a mechanical device so simple and efficient that it's
had largely the same form for the past 100 years? A: Make it more complex and
expensive!

~~~
IgorPartola
Is it a fact that it's more expensive? I would imagine that lining up the
spokes is harder than making bearings and circles.

~~~
Groxx
Straight lines are harder than circles?

Spokes are super-simple and really cheap. It's just a tensile wire with a
threaded end (for adjustment) and a bent end. Even ridiculously high-tension
metals (in bike terms) are cheap. Plus, spokes don't move, bearings do, and
for a setup like this they'd have _really_ high rotational speed compared to a
spoked wheel's bearing.

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jrockway
At least someone can't shove a stick into your spokes and make you flip over
the handlebars. Oh wait, it's the rear wheel, where that can't happen anyway.

I agree with rimantas that this doesn't make much sense. The reality is that
the average mass-produced $10 rear wheel is lighter and stronger than this
thing. Maybe if they made the rim out of carbon fiber... but then going over a
rough road is going to shred your $500 novelty wheel and send you to the
hospital. (And speaking from personal experience, a failed wheel is no fun.
Walking home in cleats sucks...)

The bicycle wheel is a really elegant design. There is not a whole lot of
improvement to be made.

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huhtenberg
Not two weeks ago, a more polished, designer version has been making rounds on
twitter, sometimes going as far as asking for donations to help with making a
prototype:

[http://minimalissimo.com/2010/02/a-hubless-bmx-and-a-
helples...](http://minimalissimo.com/2010/02/a-hubless-bmx-and-a-helpless-
designer/)

------
raganwald
I like the look, and the aerodynamic possibilities are intriguing. That being
said, spokes play other important roles in current wheel designs.

For one thing, a typical spoked wheel uses spokes that are tightened until
they stretch a small amount. When the rim is subjected to stress, it can bend
a little and be pulled back into true by the spokes.

A spokeless wheel would probably need a very stiff rim that could resist
deformation. This would produce a harsh ride, but problem can be solved with
suspension.

~~~
bmj
Your comment about aerodynamics is interesting. Generally, time trialists use
a disc rear wheel and a minimally spoked front wheel (typically with bladed
spokes, or even a tri-spoke composite wheel). While these designs have proven
to be the best for pure aerodynamics, they are obviously very susceptible to
cross winds--the reason why racers don't use two disc wheels on the road. I
suppose this design could make sense for a course that is buffeted by cross
winds (even with a minimally spoked wheel, steering is compromised).

As for comfort, this would be more of an issue for recreational riders. The
deep dish or disc wheels that racers use for speed already give a fairly rough
ride.

~~~
raganwald
I agree with your comment.

FWIW, shock absorption has implications for control on uneven surfaces. A very
stiff wheel bounces on obstructions while a flexible wheel deforms and
maintains contact. Thus, softer tires and suspension font forks are extremely
useful for off-road bikes.

Really stiff wheels work well on extremely smooth surfaces, so time trialists
and track riders love them. Weirdly, cyclo-cross riders also love the "deep
dish" rims, although more for their ability to resist mud build-up than
aerodynamics.

~~~
bmj
Yep. I think 'cross racers choices are influenced by their ability to ride
really, really low pressure tubulars, which mitigate the effects of the deep
dish wheels.

It's also worth noting that many PRO teams run very, very standard wheels
(aluminum rims with 32 spokes) for the roughest classics, like Paris-Roubaix
(see [http://froggy100.files.wordpress.com/2009/04/paris-
roubaix.j...](http://froggy100.files.wordpress.com/2009/04/paris-roubaix.jpg)
for a good example of the terrain).

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towndrunk
Billy Lane built a motorcycle with this concept long ago:

<http://www.partty.com/Home-Bike/BillyLane.jpg>

[edit for better link]

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tsuraan
So it looks like there are two bearings on the inside of the wheel, and
probably a third against the tire? I wonder how wobbly that gets when the tire
pressure drops. I would think that just having a triangle inside the wheel
with bearings at each of the points would do the same job without the wheel
being pinned along only a quarter of its circumference. Cute bike, anyhow.

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jcromartie
It seems to me that this design could put an excessive amount of stress on the
bearing that holds the wheel in place compared to a traditional hub.

