Push on or hang from spokes?
 

I saw a show recently where a guy had replaced all of the spokes in his wheels with string / thin rope. Essentially, the bike was hanging by the string spokes as he rode (Yes, he was able to ride the bike). He said that bikes don't really push down on spokes (from center down to the ground), they actually hang from the spokes (from the center upward).

This was news to me. Is this true?

:twitchy:

Broadly speaking, yes. Tension in the lower spokes reduces, but they are still in tension AFAIK. The exception to this is wheels like the (controversial, unsuccessful) Mavic R-Sys which has spokes that also work in compression, in the manner of an old fashioned cart wheel.

Oh boy.... :popcorn:

Here's a somewhat recent "discussion" from the mechanics forum. It started picking up steam on page 3

http://www.bikeforums.net/showthread...Spoke-pattern/

Hang from :-)

Now that I think about it, I guess it makes sense.

Think about it for a second. Do you honestly think that those skinny wires will stay straight if you push down on them?

of course they push. they just don't push enough to overcome the pull from the tension.

Push, pull, whatever. It's all a matter of semantics. The short version is that all the spokes remain in tension (except under extreme circumstances), but that the tension in the bottom spokes changes more than the upper spokes.

That is, the three or four spokes near the ground contact point lose a lot (but not all) of their tension, while the tension in most of the other spokes increases slightly. Some claim that this means the hub "stands on" the bottom spokes (because they react more); others say that since everything is in tension, the hub must be hanging. I'll let you decide which way you want to present it.

String? Like 80s style? Flock of Seagulls and Tioga Disk Drive

http://members.home.nl/children-of-t...0Tioga%201.jpg

^^^ that is not an 80s bike, right?

No, the wheel predates the bike. I'm not even sure the wheel is from the 80s, but I know it was around in '92 when I rode with Tomac briefly in Durango.

This again? There is no way that a bicycle rim can stand on a spoke or 10 spokes. the nipple will simply push into the rim and puncture the tube.The spoke/rim interface is not made in a way in which a spoke could hold up the hub in this manner.

The hub is suspended in the rim by all of the spokes under equall (respectively) tension on all of the spokes. Yes, the spokes on the bottom may unload in tension partially but that is how they work together. And one more thing. The ground does not push up on the wheel. The load pushes on the hub which transfers the load to the rim via the spokes on the top of the wheel,which pushes down on the ground. The rest of the spokes keep the rim from deforming/collapsing through tension.
So, yes it can work if the "string" is strong enough, and can be properly tensioned or if the rim is strong enough to not deform.

Even if you replace the spokes with a disk you get the same thing the material of the disk at the bottom would not be in a s high of a tension as the material at the top.

If you had a rim, sufficiently strong enough to support the load without deformation, just in static, you could cut out the spokes on the bottom of the wheel with little effect. But if you were to flip that wheel 180 degrees it would collapse. Spokes are not strong enough in compression to support the load of the bike let alone my carcass.

The Mavic R-Sys would like a word with you...

As mentioned above, when it's not blowing up, the spokes work in tension and compression. The only holes it pokes are a huge swirly one in the air (the biggest I've seen tested), and the holes in your legs when the spokes all eject during a spontaneous de-lacing.

I'll give you the "bicycle rim" technicality on the R-Sys. It's more of a wagon wheel than a bicycle wheel. Probably higher drag though.

or the HED3 or the Rev-X

HED3 is a licensed copy of the specialized tri-spoke
Rev-X were known as death stars, because they kept blowing up.

So the only really successful compression wheel for bikes would be the tri-spoke.

What about the LEW wheels?

Interesting. :popcorn

Even the Rev-X "hangs" from the spokes, as they give under compression a little.

I will award you a good try on this one however I must point out as you have alluded to, it has not been a great success, if that is what you get with a wagon wheel design, no matter how light, I think I will pass. Also and this is just a personal theory, I believe they were forced into using spokes that would also be used in compression do to the amount that carbon spokes elongated under load in tension. I believe it was a design compromise. We already know that stainless steel will after a time fatigue and break eventually. Now we will replace the stainless steel with carbon fiber, a substance that is even more brittle under certain conditions. Then, if that wasn't enough, we will double its work cycle to include opposing forces, compression and tension. Just sounds like a recipe for disaster. This being said I have never looked at one up close or anything just something my brain was chewing over while I was riding.

carbon fiber spokes can be strong and not spontaneously collapse. LEW wheels for example, are done right.

Why? to simple for you?

Someone makes (or made) replacement spokes that could be thrown in a bag. Some kind of wire, IIRC. Also, Spinergy manufactures wheelchair wheels that use spokes made of a fibrous material.

:lol:

You could be right, heck I really dont know. I am not familiar with those wheels are the spokes used in compresion and tension also? What are the differences between the two? Carbon is a great material with mucho promise but I think i has limitations just like any other material. I think the compromise between safety and performance has to be re exanined. The lighter we make a bike and the more we use exotic materials narrows the performance/saftey envelope.
But this isnt really what the question was either. could string be used instead of spokes. Yes due to the way a traditionally spoked wheel works.
If you want to use string to replace the spokes in a wagon wheel......... well good luck.

I think LEW spokes only act in tension.