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!
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.
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.
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.
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.
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.
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... for a good example of the terrain).
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?
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.
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.
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.)
That was my thought. A small amount of friction at the center of the rotation will be much less noticeable than the bearing being essentially on a lever at the edge of the wheel. Thus even small amounts of friction will make pedaling harder.
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.
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:
20 comments
[ 4.3 ms ] story [ 58.9 ms ] threadSpokes 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.
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.
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.
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.
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... for a good example of the terrain).
[1] http://www.carbonfibergear.com/peugeot-redefines-the-bicycle...
[2] http://www.reddit.com/r/technology/comments/b2g91/spokeless_...
http://www.partty.com/Home-Bike/BillyLane.jpg
[edit for better link]
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.
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.)
http://minimalissimo.com/2010/02/a-hubless-bmx-and-a-helples...