Talk:Reaction to a radial load (tensioned wire spoked wheel)

Do hubs hang from the wheel?

The physics is a bit too complex to me, but it seems that it's all a matter of point of view. It's the reduction of tention on the lower spokes that allows the (almost unchanged) tention on the upper spokes to bear the load. I imagine I am over simplifying this. In any case the article seems to be very unclear on the matter, and I would love to see it improved, but I am unsure if my understanding is accurate.--Keithonearth (talk) 03:30, 28 December 2008 (UTC)

Bicycle wheel has a couple of concise sentences with plenty of references. -AndrewDressel (talk) 17:58, 28 December 2008 (UTC)

I don't think the two articles should be merged, but I would like to see just one copy of this topic with all the best references. Arguably, it belongs here, in the more general article, but all the sources are specific to bicycle wheels. I'm tempted to suggest that both these aritlce link to a new, specific article, but I don't think there is enough material to warrent a stand-alone article on the subject. Anyone have a preference or an even better idea? -AndrewDressel (talk) 14:27, 29 December 2008 (UTC)

The current consensus among sources seems to be that under load, the few spokes at the bottom reduce tension and the rest only slightly increase tension. Jobst Brandt and Ian somebody interprets this to mean that the hub stands on the few spokes directly below it. Tom Fine interprets this to mean that the hub hangs from the rim. It seems to me that we should state something like the first sentence as fact with multiple references, and then quote specific authors semantic interpretations as exactly that. -AndrewDressel (talk) 14:49, 29 December 2008 (UTC)

I'm not sure where the best place to put the references/discution would be either, I kind of think not that many people would be reading the Wire wheels page, and way more will be reading the bicycle wheel page. Would it be possible to keep the discusion brief enough (Like two Sentences) that redundancy wouldn't be too tragic? Putting that aside for now, the way you phrase it above, seems to me to be by far the best I've heard so far, and is way better than on the article page.--Keithonearth (talk) 19:44, 29 December 2008 (UTC)

Having seen some flame wars on the the subject, I'd suggest stating something like the first sentence as the classic or conventional view, then that some using FEA argue the contrary, and finally that the argument hinges (buckles?) on whether a reduction in tension implies structural support. Nice work on the subheadings, btw. NebY (talk) 09:00, 30 December 2008 (UTC)

To say the tension changes as a fact, then the two interpretation (as you say Andrew) should avoid an edit war, no? How about: "Under load, the few spokes at the bottom reduce tension and the rest only slightly increase tension. This has been interprated as either meaning that the hub is supported by the spokes under it, (ref,ref) or that the hub "hangs" from the rim (ref). I think that fits with NebY's suggestion too. The main thing as far as I'm concerned it to remove the unattributed quote. --Keithonearth (talk) 20:10, 30 December 2008 (UTC)

Done. Thanks for your help. -AndrewDressel (talk) 12:48, 31 December 2008 (UTC)

Thank you. (didn't see the change till just now) Great job!--Keithonearth (talk) 04:21, 4 January 2009 (UTC)

I do not want to start an edit war, but there is less controversy about this than you seem to imply by your attempt at even-handedness. You might consider the following thought experiment when deciding which viewpoint to prefer. If the hub hangs from the upper spokes, then you might expect that decreasing the tension in the bottom spokes to zero would not matter much. --AJim (talk) 00:53, 9 September 2010 (UTC)

Someone might expect that, but they would be incorrect. -AndrewDressel (talk) 15:08, 24 June 2012 (UTC)

This also suggests that you ought to be able to set the spoke tension really low. --AJim (talk) 00:53, 9 September 2010 (UTC)

It might suggest that to someone, but they would also incorrect. -AndrewDressel (talk) 15:08, 24 June 2012 (UTC)

From the hanging point of view, you should need only enough combined tension in the upper spokes to support the load. --AJim (talk) 00:53, 9 September 2010 (UTC)

I see nothing in the "hanging point of view" that limits spoke tension in this way. -AndrewDressel (talk) 15:08, 24 June 2012 (UTC)

I believe there is good evidence in the references that the bottom spokes must stay in tension or the wheel will fail. Brandt devotes the first part of his book to explaining the idea that the bottom spokes support the load; see pages 6-32. Consider this quote from p 28: "Wheel Collapse ... a bicycle landing from a sufficiently high jump, could untension its bottom spokes on impact and leave its rim laterally unsupported. At this moment the wheel is unstable and will collapse to the side." He also says earlier, on p 10, "Of course the wheel is not supported by the bottom spokes only. Without the rest of the spokes, the bottom ones would have no tension. Standing, in this case, means that the spokes at the bottom are the ones that change stress; they are being shortened and respond structurally as rigid columns. They are rigid as long as they remain tensioned (my emphasis)." --AJim (talk) 00:53, 9 September 2010 (UTC)

The issue is exactly his assertion that the bottom spokes "respond structurally as rigid columns". They simply do not, by any definition of "rigid column" that I can find. They are not in compression unless the wheel fails, and the way that most spoke nipples simply press towards the hub against a hole in the rim, or Euler's buckling criteria, depending on how one prefers to look at it, prevents them from ever being in more than a tiny fraction of the compressive force that would be required to support the loads that most wire wheels support. -AndrewDressel (talk) 15:08, 24 June 2012 (UTC)

Most people would agree, based on their own experience, that a wire will not behave as a rigid column when in compression. --AJim (talk) 00:53, 9 September 2010 (UTC)

I don't believe I follow your point here. In the previous sentence, you appear to be supporting Brandt's position, but you seem to be opposing it in this sentence. -AndrewDressel (talk) 15:08, 24 June 2012 (UTC)

I really think you could have a more enlightening discussion of this subject in the article. --AJim (talk) 00:53, 9 September 2010 (UTC)

I believe that citing sources on both sides of the argument and trying to explain their positions is about enlightened as this is going to get. I don't believe there is any controversy about what actually happens as wire wheels support a load. Instead, the controversy lies simply in what words we use to describe it. -AndrewDressel (talk) 15:08, 24 June 2012 (UTC)

Forester

I've taken out the addition, provided below, with the edit comment that "the reference is fine, but we don't need the details."

Forester demonstrated this by direct measurement of change in spoke length as the wheel rotated under load. Spoke length decreased between the 5 o'clock and 7 o'clock positions with a maximum decrease of about 0.004 inch at 6 o'clock. The reduction in downward pull on the hub, calculated from the dimensions of the spokes, closely equaled the load carried.

What I mean is that the testing methodologies of none of the other sources are discusses. Readers looking for such details can check the sources directly. Also, details such as the investigator's name and the measured displacement without the total spoke length or other details necessary to interpret the number seem out of place. -AndrewDressel (talk) 03:10, 5 July 2010 (UTC)

Maximum load

From the Analysis for design of spoked bicycle wheels article, I think that the maximum load is around 490N (=?kg) (more load is possible by increasing the spokes. Also, from what I read at wikipedia, the load can be increased by reducing the wheel size. Having some formula's for this would be useful to integrate to the article.

Generally, the maximum load for the tyre is far less, around 145kg per tyre (or 290 kg for a person sitting on a bicycle since it has 2 wheels, see http://www.bikeforums.net/archive/index.php/t-320799.html ) 91.182.215.56 (talk) 09:37, 30 August 2010 (UTC)

That would be a little hard to come by. The maximum load will be a function of the rim material and cross section; the spoke material, size, and number; and the wheel size. Good luck finding a formula for that. -AndrewDressel (talk) 14:18, 30 August 2010 (UTC)