Talk:Eccentric (mechanism)

Are you tagging this article as a stub merely because it is short? It doesn't just cover bicycles. Perhaps you should read the whole thing more closely. Perhaps you can even improve it.--John of Paris 11:52, 13 September 2007 (UTC)

Hi, thanks for your work on this article. According to the WikiProject Cycling assessment guidelines, this article is a clear stub. It gives a brief definition of the term, but doesn't elaborate. There is, for example, no history section nor another subheading that treats the topic fully. One way the article could be improved by creating a structure to the article to indicate where information could be added. The article was assessed manually (if a bot had done it a notice would have been placed on the talk page, although a bot could only do it if there was a stub template) and, in my mind, there is little doubt about the validity of the assessment. Regards, Severo^TC 16:58, 13 September 2007 (UTC)

But you can't have read the whole article closely - I repeat: this is not an article on cycling. It contains a section - a very short paragraph - on the incorporation of an eccentric in the bottom bracket of a tandem for chain adjustment. But the article as it stands describes a principle. - that could be perhaps be better described, if so please help to do so. Whatever the, case it does not need to be long and may require no substantial additions - so how can it be right to rate it as stub-class?--John of Paris 19:40, 14 September 2007 (UTC)

I'm sorry but I don't understand what the issue is here. The article is within the scope of WikiProject Cycling and it is a clear stub-class article according to the Version 1.0 Editorial Team/Assessment. Regards, Severo^TC 22:08, 14 September 2007 (UTC)

OK, so I have included it in the Engineering portal where it is a clear Start class article, as I agree that it could have more references and links, although a number of internal links already lead to it which IMO is more important. However it still does not need to be very long.--John of Paris 10:45, 23 September 2007 (UTC)

uses of a eccentric bottom bracket

I think that the only thing that necessitates an eccentric BB is the need to adjust chain tension and the inability to do that from the rear end of the chain loop. While the issues mentioned in the article all can lead to this situation, they are not the prime cause. I don't see how disk brakes necessitate an eccentric when used with vertical dropouts (or other chain tensioning method). I do have an acquaintance who rides a brodie Cretin [[1]] that does have horizontal dropouts and disk brakes. (He's had it set up single speed and derailleured). I'm also familiar with the ocho[[2]] from brodie that does use the eccentric BB with disks and an internal hub, and vertical dropouts, and that makes putting the rear wheel in easier but it's just another way of doing it.--Keithonearth (talk) 07:51, 12 December 2008 (UTC)

Yes, the ability to move the rear axle is the main thing. Vertical dropouts precludes that. So does a rear disc brake or an internally geared hub, even if the bike has horizontal dropouts, as Sheldon Brown attests. I'm not sure about the internally geared hub, that's why we cite an expert, but the disc brake makes sense to me. There is very little room to position the rotor properly with respect to the fixed caliper. -AndrewDressel (talk) 14:36, 12 December 2008 (UTC)

I think sheldon's info is a bit out of date. There's now a number of ways to adjust the chain tension from the axle using disk brakes. The cretin mentioned above does it with unusual disk tabs that use slots instead of holes in the tabs that allow for significant adjustment. (I think 2006 was the first year they did that, maybe 07.) I know this is OR, but it is first hand experience. There's more elegant ways of doing the same thing, but this article isn't high enough importance for me to do much research for valid references.--Keithonearth (talk) 17:23, 12 December 2008 (UTC)

The article currently state 'the device often used on...' and then lists tandems, disc brakes, internal gear hubs, and vertical dropouts. It remains perfectly valid even if there is new technology which handles the problem differently. No one is making the claim that eccentric bottom brackets are the only way to adjust chain tension. Unless you can find a reference that says 'eccentric bottom brackets are obsolete and no longer used', no change is necessary. -AndrewDressel (talk) 04:14, 13 December 2008 (UTC)

Eccentric or not

A RTLM mechanism

This image appears to be of a complicated slider crank. In any case, it does not have a circular disk (the flywheel on the far end does not count) and so does not fit the description given in the first sentence of the existing article:

An eccentric in mechanical engineering is a circular disk (eccentric sheave) solidly fixed to a rotating axle with its centre offset from that of the axle (hence the word "eccentric", out of the centre).

Is there a source for one way or the other? -AndrewDressel (talk) 19:26, 20 September 2009 (UTC)

You are correct, the photo doesn't depict an eccentric, but a 6 bar linkage with a short link 2. I'll add a ref to the current definition. Wizard191 (talk) 18:10, 21 September 2009 (UTC)

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