Talk:Bicycle and motorcycle dynamics#Spinning engine parts and stability

I'm a bit astonished to see no reference to Robin Sharp's work on motorcycle dynamics? I mean in the text itself - in the history section it reads as if the 2007 work was the first time the equations of motion have been written down. Black bird blue (talk) 13:54, 5 December 2008 (UTC)

:The history doesn't mention Cossalter, either. If you think it should, please just add it without all the hysterics. 2007 was the first time the equations have been written down with a comprehensive literature review and verification by other means. At least that's what the reference says. If you think we've done a bad job, you can always just cut our budget. -AndrewDressel (talk) 15:29, 5 December 2008 (UTC)

::Sharp is added. Cossalter can add himself, his work isn't widely regarded as credible although his pictures are pretty. 88.108.190.85 (talk) 00:06, 6 December 2008 (UTC)

The stability of the bicylce and its equations of motion were already analysed by Felix Klein and Arnold Sommerfeld in their 1910 monograph "Die Theorie des Kreisels", pages 863-884, see http://www.archive.org/details/fkleinundasommer019696mbp.

BSpringborn (talk) 21:23, 14 October 2016 (UTC)

Article has these two statements:

1. At normal bicycling speeds on level ground, aerodynamic drag is the largest force resisting forward motion.

2. At faster speed, aerodynamic drag becomes overwhelmingly the largest force resisting forward motion.

One of the references to "aerodynamic drag" must be wrong.

Mesdale (talk) 18:10, 16 August 2016 (UTC)

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In the main article in the section Longitudinal Dynamics the picture caption reads "a rider performing a wheelie", this is incorrect, the picture clearly shows a BMX rider performing a manual. A wheelie and a manual are not the same thing, the mode of balancing is different between the two, the former is reliant upon torque/brake whilst the latter is solely reliant upon balance, achieved by moving the centre of gravity (the riders body) forwards and backwards. The difference is such that a rider who can perform a wheelie may not be able to manual, and vice versa. Please fix! 80.229.162.156 (talk) 00:05, 30 December 2016 (UTC)

In the Real Wheel Steering section the article mentions the, as yet unclaimed prize (offered by Rainbow Trainers), for successfully riding a bicycle with rear wheel steering. However, there are endless clips on YouTube showing people riding conventional bikes backwards. As this is evidently possible then surely riding a "rear wheel steered" bike is similarly equally possible?! Sorry, this is more of an observation on this (interesting) section than a request for an edit, but just a point for consideration! 80.229.162.156 (talk) 00:17, 30 December 2016 (UTC)

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Some issues with the following paragraph:

{{Quote|text=If the steering of a bike is locked, it becomes virtually impossible to balance while riding. On the other hand, if the gyroscopic effect of rotating bike wheels is cancelled by adding counter-rotating wheels, it is still easy to balance while riding.[5][6] One other way that a bike can be balanced, with or without locked steering, is by applying appropriate torques between the bike and rider similar to the way a gymnast can swing up from hanging straight down on uneven parallel bars, a person can start swinging on a swing from rest by pumping their legs, or a double inverted pendulum can be controlled with an actuator only at the elbow.[33]}}

• Regarding balancing a bike with locked steering, there is a contradiction: it both says it is "virtually impossible" and says how it can be achieved. -FrankSier (talk) 21:58, 17 July 2020 (UTC)

::"virtually impossible" means "[https://dictionary.reverso.net/english-definition/virtually+impossible in effect though not in fact; practically; nearly]" impossible, which is thus not contradicted by "it can be achieved". If you think there is a better way to make this point, feel free. -AndrewDressel (talk) 17:59, 18 July 2020 (UTC)

:::Thank you for the definition link, for what "virtually impossible" means literally, but I think people sometimes use this type of term a bit loosely. I have not managed to find this particular claim ("If the steering of a bike is locked, it becomes virtually impossible to balance while riding.") in the references. I think it is possible that the editor that inserted it was talking from their own experience or beliefs. I have tried to trace the editor using WikiBlame http://wikipedia.ramselehof.de/wikiblame.php but have not managed. (I think I have found that it was part of cut and paste from Bicycle. WikiBlame came up with "history messed up" message. Either the info on the editor has been lost, or I don't understand sufficiently how to use WikiBlame.) Going back to how to make the point clear, replacing "virtually impossible" with "very difficult, but not impossible" would be clearer, if that was in fact the case, but I do not feel I know what the facts are (or what the references are) so I do not feel that I should make this change. FrankSier (talk) 15:00, 27 July 2020 (UTC)

• It refers to a gymnast and a person can start swinging, presumably both from rest, and both not pushing against the ground. I have never seen this, nor can I find any example of these being done. I have tried myself to start on a swing from rest without pushing against the ground and not managed it. There is also a claim about the behaviour of a double inverted pendulum. I cannot find any evidence in the references or the articles linked to in support of these claims. -FrankSier (talk) 21:58, 17 July 2020 (UTC)

::I cannot tell what you mean by "these claims". The linked article states "a gymnist [sic] (or acrobat) on a parallel bar, who controls his motion predominantly by effort at the waist (and not effort at the wrist)." [https://www.youtube.com/watch?v=ayMsVWvj9lg Here's a video demonstrating it]. Is the issue that the source doesn't specifically mention cyclists? It is the best acceptable source I've found so far that can explain this [https://i2-prod.dailyrecord.co.uk/incoming/article9020432.ece/ALTERNATES/s615b/Danny-Macaskills-Wee-Day-Out.png feat] -AndrewDressel (talk) 17:59, 18 July 2020 (UTC)

:::I have no problem with the source not mentioning cyclists. The claims are stated to be about things that are "similar", and that is fine I think.

:::The claims that I am referring to:

:::*"a gymnast can swing up from hanging straight down on uneven parallel bars". I take it that this means swinging up from stationary from hanging straight down, and without pushing against anything, and not by applying torque with the hands on the bar they are holding. (If you did not mean "from stationary", then I think it would difficult to see the relevance of "hanging straight down"). The quote you give from the linked article does not mention about starting from stationary, or from hanging straight down.

:::*"a person can start swinging on a swing from rest by pumping their legs". The linked article does not mention a person on a swing.

:::*"a double inverted pendulum can be controlled with an actuator only at the elbow". A search of the linked article does not find the text "double inverted pendulum"; it is possible that it talks about this device using different words, but this is too technical for me to judge.

::: Unfortunately when I try to view the video you linked, I get the message "Video unavailable. The uploader has not made this video available in your country." (I am in the UK.)

::: The link from the word "feat" for me goes to a still photo of a cyclist, cycling along a rail. I see that this is a difficult feat, but I am not clear of the relevance of this to what we are discussing. I can see that the steering would be fairly restricted under these circumstances, but not actually locked (if that is the proposed relevance).

:::FrankSier (talk) 15:52, 27 July 2020 (UTC)

This recent addition:

:"A technique used on poor surfaces is to alternately (and gently) pump front and back brakes so that if they start to break away they can rapidly regain traction while the other wheel continues to contribute a stopping force, this technique also reduces brake heating, reducing brake fade.[https://bike.bikegremlin.com/813/bicycle-braking-technique/]"

has several issues:

:#Wikipedia is not a how-to manual

:#The cited "source" is "[https://bike.bikegremlin.com/author/relja/ Relja, a quite decent bicycle mechanic]" on what appears to be his personal blog.

- AndrewDressel (talk) 21:01, 26 June 2021 (UTC)

{{reflist-talk}}

{{Wikipedia:Good article reassessment/Bicycle and motorcycle dynamics/2}}

The article is over 11k words, per WP:Article size, the article needs to be split or trimmed. ReyHahn (talk) 18:31, 15 January 2024 (UTC)