jur

You missed the quote marks I placed on 'stands'. The emphasis I placed on exactly was meant to emphasise that the bottom spokes are doing the work, exactly like in a wagon wheel. I did explain this earlier as well, apparently you missed that also.

But the whole idea of taking into account the absolute tension of a spoke as the starting point of which word (semantics) you should be using is not so appropriate. In a wooden wheel the tyre is doing the work of pushing the rim towards the hub. In a steel spoked wheel the tension in the spokes is doing EXACTLY the same thing. In both cases the bottom spokes are going through a compressive transient as the wheel rolls.

You can't think reductionistic of spokes as individual items doing work, it is the whole that works and only the whole. The 2 cases work in EXACTLY the same way, only the absolute tension in the spokes is negative for wooden spokes and positive for steel spokes.

Your remark of 'diagonal tension' and of the rim doing the work is off the mark. Again, it is the whole. The practice of making the spokes tangential is to strengthen at the hub or the spokes will rip out of the hub.

cooker

I still disagree. Perhaps you should also have put quotes on the phrase "doing the work" which is more metaphor than physics.

A bicycle wheel is under internal tension. Normally all spokes are pulling the hub outwards, and pulling the rim inwards. When external forces are applied to the wheel, namely rider weight pushing down through the fork onto the hub, and fixed resistance by the ground pushing up below the rim, the main change in the internal tension in the wheel occurs in the lower spokes which relax partially, not in the upper ones, which retain full tension.

The engineers in the article you cited refer to that as the lower spokes "carrying the load". To me that is an extremely misleading choice of words, because it implies the lower spokes are subject to weight bearing compression (which they certainly are not), but I don't know if it is technically incorrect, because I don't know if that is how engineers talk about these concepts.

You refer to it as the lower spokes "doing the work", and that for sure is not technically correct, because as scientifically defined, work has to include movement.

The bottom line is that wooden spokes work in a wagon because they resist compression. Steel spokes work in a bike wheel because they resist stretching. How can you say that objects chosen for the opposte reason work in "exactly" the same way?

Absolutely not. This is my bag handle example. It's a variant of the very important nth law of physics: you cannot push a rope. You cannot, to any meaningful degree, longitudinally compress a bicycle spoke. Lessening the tension on something is not compression.

Yes.

No.

The diagonal I was referring to is not the tangentiality of the spokes, but rather their dishing. By having spokes pulling the rim to both the left and right, the rim doesn't fold easily under load.

jur

OK. Let's agree to disagree about how to describe it. We do fully agree that all spokes never relax tension fully and become 'pushers' (unless in extreme not-designed-for cases).

None of what I said is really my 'own' 'wisdom' anyway, I would never have guessed how spoked wheels work had I not seen that paper written on it.

In connection with this, check out the thread on airless tires, there is a Michelin tyre dubbed 'Tweel' with a spoked structure. I have no idea if those spokes are under compression or tension but there are some pics of how the bottom ones buckle under load.

I wish you were my neighbour, I could invite you over for a beer.

cooker

It's been fun

cyclistjohn

On reflection, maybe this thread would have been more appropriate for that link, but it's so easy to go off topic ;-)

Here's a bit more on the Tweel:

https://www.gizmag.com/go/3603/

Jur, I've been trying to find out more about plastic spokes, as fitted to our Stridas, but haven't found out much yet. There's obviously no way for an "end user" to tension these spokes, & I'd be interested to know what happens during manufacture of these wheels. We certainly find them very robust when it comes to baggage handler time :-)