Talk:Pulley

Vandalism question

This page seems to get an unusually high incidence of vandalism. Normally, a page has to be either a featured article or a very public and controversial topic to be vandalized this regularly. Any hypotheses about why this page is so regularly attacked? Rossami (talk) 20:21, 28 February 2006 (UTC)

Theory of operation

I added a theory of operation section, and used two of the pulley system images from the original article. I have removed the simplest compound pulley image, because its practical implementation is not different from the diagram, which is the case for the other two - they are different from the diagrams. I also removed the "historical images of pulleys" because it didn't seem to add much, without an explanation. Maybe it could go back in under a history section? PAR 04:51, 5 March 2006 (UTC)

how about the diameter of the wheel? doesn't that have something to do with the force necessary to lift an object? —Preceding unsigned comment added by 208.71.200.85 (talk • contribs)

Nope, nothing. The forces on either side of the pulley are the same regardless of the radius of the wheel.
Okay, actually that's for a theoretical pulley. A real pulley will suffer some slight amount of friction between the fibers of the rope as it goes around the pulley. A larger diameter pulley will deform the rope less resulting in slightly less friction. But that is a miniscule effect compared to the normal forces used on the pulley. Rossami (talk) 00:24, 8 September 2007 (UTC)

Bicycle chain pulley?

Is it correct or incorrect to call the non-driven wheels in a modern bicycle rear derailleur pulleys? The chain is kept in place by its side-plates and small "near-teeth" in the pulley, rather than by fitting in a groove. This particular application also involves no mechanical advantage--just tension adjustment. Are there other applications where chains and wheels function as cables and pulleys?--SportWagon 23:28, 18 August 2006 (UTC)

In the context of the six simple machines, yes, a derailleur would be considered a pulley - specifically a "class 1" pulley with a mechanical advantage of 1. The fact that the "groove" is on the chain rather than on the wheel is a minor variant. The definition of something as a simple machine is based on how the force is transformed as the force does work. Any situation where the force is being carried through tension and where the direction is changed would probably count as a pulley. Rossami (talk) 12:13, 19 August 2006 (UTC)

Sheldon Brown had these entries in his glossary: -AndrewDressel (talk) 21:43, 4 June 2010 (UTC)

• Idler: "An idler is a pulley or roller that does not produce any mechanical advantage, nor transmit power to a shaft. Idlers are used to lead a chain around a bend (as in short wheelbase recumbents), or to take up slack in a drive chain (as in a tandem chain tensioner, or the pulleys in a derailer."
• Chain pulleys: "Most rear derailers use two pulleys in a spring-loaded cage to regulate the tension of the chain as it runs over different sized sprockets. The upper pulley is called the "jockey" pulley, the lower one is the "tension" pulley."
• Jockey pulley: "The upper pulley on a rear derailer. This is the pulley that actually guides the chain from one sprocket to another. Shimano jockey pulleys are designed with a "Centeron®" mechanism that allows a small amount of sidewards motion to compensate for imprecise index adjustment."

Additional Information Needed

I think information should be added to this article to recognize a "sheave" as a type of pulley. I'm probably not the right person to add this, but I do know that they are commonly used in oceanic applications suspended from an A-frame on a ship and also for oil drilling. 65.165.72.203 17:17, 18 October 2006 (UTC)Tired_Angel

Regarding Pictures

Bad picture. The pulleys shown are what are called belt pulleys. A rubberized loop of belt wraps around both pulleys. One pulley is the source of power, the other receives power through the belt. This was a common way to transfer rotational power prior to about 1940. Threshing machines received power through the belt and belt pulleys from the steam engines.

A picture of the type of pulleys described in the article is needed. Also the article should also mention belt pulleys as well. --69.5.156.155 06:22, 24 Sep 2004 (UTC)

Diagram 2a is INCORRECT. The upper arm to the left holding the upper left pulley is labeled with W. It does not support W, it supports W/2. I will attempt to fix and submit corrected image. Also, the Image to the right, the "Practical Compound Pulley" system is not the same as shown in Diagram 2a. Further examination also reveals that the next set of diagrams is incorrect. As I cannot seem to upload images yet I am hiding the content that is incorrect. —Preceding unsigned comment added by 71.186.138.85 (talk) 11:00, 24 April 2009 (UTC)

You didn't add this comment at the bottom, so I missed it, I thought the article was being simplified rather than an attempt at correction. Diagram 2a is CORRECT. The total upward force is 3W/2, the total downward force is 3W/2 (you probably neglected the W/2 force downward on the rope on the left which causes the entire system to be in equilibrium.) Regarding the "Practical Compound Pulley", the key word is "Practical". This is not the same as "Identical". The rope connecting the right pulley to the upper support is instead connected to the axle of the left pulley, which is in turn connected to the upper support. There is no essential difference here as far as the tensions in the ropes or the advantage of the pulley. The same is true of figures 4a and 4b. PAR (talk) 19:34, 24 April 2009 (UTC)

PAR: I am an idiot. Please excuse my misguided attempt at "fixing" the article. —Preceding unsigned comment added by Legrand68 (talk • contribs) 14:01, 25 April 2009 (UTC)

LOL - No problem, if making a mistake makes one an idiot, then I'm in BIG trouble. PAR (talk) 11:32, 26 April 2009 (UTC)

Re:Leavenworth Arrangement

Rossami: I am not quite sure how to use this system, but the Leavenworth Arrangement has not been known since Archimedes. It took me a year to discover, and I am an intelligent fellow. You will not find this knowledge in books, because this is the first time it has been published. If you are of the opinion that knowledge is never lost and rediscovered, or that such a thing could not be discovered in this day and age, I challenge you to find fault with the math, with the arrangement, and a previously published source describing the arrangement. Besides those objections, there can be no reasonable objection to the additions.--MarkLeavenworth 03:01, 19 October 2007 (UTC)

@Mark: wikipedia has a very strict policy about original research: it is not accepted. See this page Wikipedia:No original research. VanBurenen 07:52, 19 October 2007 (UTC)

I'm sorry you've misinterpretted the meaning of 'verifiable'. 1)The math does not warrent the necessity of citing for verification on the grounds that it is too simple. 2)The arrangement does not necessitate citing for verification on the grounds that it is too simple. 3)Only you can dispute my right to name the arrangement, if you can provide enough verifiable citations in the public domain to dispute my claim that I have rediscovered this technology. —Preceding unsigned comment added by 66.81.190.202 (talk) 15:32, 19 October 2007 (UTC)

You have been asked several times now to go read the Wikipedia policy against original research. It does not matter how obvious or self-evident you think this is. Encyclopedias are, by definition, tertiary sources. We synopsize the writings of others. Until it is verifiably published in a reliable source, it has no place in the encyclopedia. Either cite your sources or stop adding this content. Rossami (talk) 21:47, 19 October 2007 (UTC)

"The threshold for inclusion in Wikipedia is verifiability, not truth." OH, I see this is not an encyclopedia of knowledge, but an encyclopedia of that which is verifiable. I'm sick to my stomach and ALARMED to learn that so many Americans have been tricked and trapped into believing that TRUTH is not VERITY. Especially since this Wikipedia effort was launched to open the way for the free exchange of knowledge. You people, having taken over the effort through subtlety, are proving to be a CLEAR and PRESENT danger. If my concern is not warrented, I suggest you open an editorial chain of command for original contributions that claim to be self-evidently true.—Preceding unsigned comment added by 66.81.191.38 (talk) 04:10, 20 October 2007 (UTC) --66.81.190.29 19:10, 22 October 2007 (UTC)

Uhm, maybe this is just too obvious, but isn't this entire entry made up original research? There isn't a single source sited on it. If the Leavenworth arrangement works, then it is just a valid as all the other unsited information on this page. Siting sources is important but there isn't there some allowance for the duh factor? Should the number 10 entry and all its occurrences be removed from wikipedia because there are no references sited? Does someone need a reference to say the sky is Azure on a clear bright day? Come to think of it, there are no references to indicate user:VanBurenen even exits, or user:MarkLeavenworth, or myself for that matter. We need to all be deleted from wikipedia promptly. —Preceding unsigned comment added by 76.191.180.179 (talk) 10:30, 29 February 2008 (UTC)

Weston Differential Pulleys

i see nothing on these fascinating pulleys. would anyone be willing to write anything?

Chris(talk) 18:03, 23 October 2008 (UTC) —Preceding unsigned comment added by 86.28.101.3 (talk)

See differential pulley. (I'm not familiar enough to know if the Weston design is significantly different from the generic "differential pulley" design.) Note: That article could probably use expansion if you have time and interest. And this article should probably include a "see also" link. Rossami (talk) 18:19, 23 October 2008 (UTC)

Ahh yes, that the one. my google search with wiki at the end failed me! Still, I'm surprised its not mentioned in this article. And I don't think I'd be a good person to contribute to this article, my grammar is terrible! Thank you Dyslexia. Chris(talk) 23:52, 23 October 2008 (UTC) —Preceding unsigned comment added by 86.28.101.3 (talk)

New images

Made following new images, could be implemented to article: thumb|right|75px thumb|right|75px

Timing belts

Belt-drive on a belt-driven bicycle, but is that a sprocket or a pulley?

Do timing belts, and other ribbed belts run on sprockets, notched pulleys, or something else by another name? What distinguishes a pully from a sprocket? The teeth, the flanges, or what runs on them, a belt or a chain? Does anyone have a definitive reference, or is this just a murky area?

This is essentially the same question as was asked about bicycle chains above, I think. So in the context of the six simple machines, yes, a timing belt arrangement would be considered a pully with a mechanical advantage of 1. The Oxford English Dictionary (the only citation currently on the page) sets a different definition - one based on a perceived need to differentiate between specific kinds of things that act as a pulley. OED requires a pulley to have flanges. The simple-machine definition is based more on the transformation of forces. Rossami (talk) 21:25, 4 June 2010 (UTC)

Similar, but that was asking about wheels over which a chain runs. This is asking about wheels over which a belt runs. I believe the context of simple machines is no help in this case, because pulley and sprocket appear to be the same simple machine. OED does not require pulleys to have flanges. See definition "c. A wheel or drum fixed on a shaft and turned by a belt, cable, etc., for the application or transmission of power, or to guide the belt." -AndrewDressel (talk) 21:38, 4 June 2010 (UTC)

I misspoke about OED requiring flanges. Thank you for the correction. Nevertheless, my point is that a pulley and a sprocket are the same simple machine. Modern usage carries the connotation of ribs or chains for "sprockets" (fairly strictly) and relatively smooth ropes or belts for "pulleys" (more loosely) but they share exactly the same mechanical concept and can both be referred to as pulleys in the larger sense. Rossami (talk) 21:52, 4 June 2010 (UTC)

Mounting

A very large section was recently added to this article focused on the "Methods of mounting" a pulley wheel to a shaft. I have removed the section pending discussion here because

1. It is not unique to pulleys. Any structure fixed to a shaft would use the same techniques.
2. The level of detail is disproportionate to the rest of the article
3. The writing style encroaches on the WP:NOTHOWTO prohibitions

If anyone can recover useful content from the section, it can be found in the collapsed content immediately below. Rossami (talk) 21:44, 4 June 2010 (UTC)

I agree with point 1, disagree with point 2, and strongly disagree with point 3. As such, I think the above text should just be moved to drive shaft. Wizard191 (talk) 18:10, 6 June 2010 (UTC)