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Talk:Straight-twin engine

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I changed the entry to reflect the fact that a parallel twin is NOT equivalent to a straight two. I have updated this and other articles to remain consistent with the original assertion that "straight twin" is not equivalent to "straight two" but rather means there is a common crank pin (ie making it equivalent to the true meaning of parallel twin), although I don't know whether this is true or not 220.237.161.186 14:21, 24 September 2007 (UTC)snaxalotl

And what documented evidence of this convention do you have? Respectfully, SamBlob (talk) 00:04, 27 November 2008 (UTC)

Surely not

Current article reads the left cylinder fires, then 180° later the right cylinder fires, then the engine rotates 360° before the left cylinder again fires. Ummm, you could split hairs and argue that this is true, the engine does rotate 360° before the left cylinder fires, but it then rotates another 180° before the left cyinder finally fires... 540° in all. Andrewa (talk) 07:47, 9 February 2009 (UTC)

Big Bang

The supposed firing sequence of the 270° twin is not "big bang", since it's 270° between ignitions, then 450 degrees of "rest" - that is in order to get the compromised smoother firing than a 180° crank (180°-540°), but less smooth than a 360° crank (360°-360°). Firing 90°-630° would be considered big bang, but it is unknown (to me) whether any engine actually does this, and would barely be more refined than a single.

As for the 2009+ Yamaha R1, that, too, does not use a big bang firing sequence. It is 90°-180°-270°-180°, like one bank of a cross plane V8, or identical to a 90° V4 (e.g. Honda VFR 800). Yamaha have expressly stated that they no longer believe "big bang" to be beneficial now that they have eliminated the oscillating inertial torque resulting from the periodic kinetic energy exchange between the crankshaft and pistons. See this article, and this one.

--Identiti crisis (talk) 23:04, 21 April 2011 (UTC)

Any discussion of the supposed traction / "power delivery" advantages with the 270° crank, if indeed due solely to the uneven firing interval, would surely also apply to the 180° crank, given that is more uneven; similarly, it would apply equally to a 90-degree V-Twin, as that has exactly the same inertial torque characteristics and power stroke timing. Presumably, the "power delivery" is "improved" with the 270° crank for much the same reason it was with the R1 above, simply by significantly reducing the oscillating torque resulting from kinetic energy exchange between the rotating and reciprocating parts ("inertial torque"), a characteristic it would share with the 90° V-Twin.

--Identiti crisis (talk) 12:34, 20 October 2011 (UTC)

What exactly is a parallel twin?

I have now twice tried to imply in the article something I think it ought to contain, which is the fact that some people believe that there are TWO kinds of inline twin engines,(not counting the newer 270° variant) which is the PARALLEL and the VERTICAL twin. These designations describe the positions of the crank pins rather than the placement of the cylinders. Some "experts" stubbornly state that the placement of the crank pins has nothing to do with (the origin of) these terms, but that the term "parallel twin" exclusively means that the cylinders are placed in the same parallel plane, as opposed to in a V-engine, and that "vertical twin" exclusively means merely that the cylinders are placed vertical as opposed to inclined. I find that nonsense! In case you mean the latter is true, I ask you: Why are there no such terms on engines with other cylinder numbers, where they should be fully applicable as well? And why is there no such thing as a "horizontal twin" when there is a vertical one in existence? Ever heard of a "Vertical single" or "Parallel four" used as a term? Hardly, even though they are fully existent. I have no particular "reliable source" on that my explanation is the correct one, other than articles I have read that clearly states that it is the case, without giving any "reliable source" on the origin of the term. Try to google "vertikaltwin" in Swedish pages and tell me what you find. I also read an article in Norwegian about the Jawa OHC 500, which normally was a "Vertical twin" (after my explanation), but kits for racing were available, with 360° crank and different camshaft thus making it a parallel twin. I did not read this on the net, but if I found it, could it be regarded as a "reliable source"? Can my old teacher, that was an old motorcycles nut, be regarded as a "reliable source"? He explained me the difference of a parallel and a vertical twin and why they are called so. Unfortuneately he is dead now, so I'm the only one left to tell what he told me. Does that make me a "reliable source"? Hardly, but those who advocate the other explanation does not have any reliable sources either. The truth is that there are no reliable sources on the term, only different opinions. But I think the article should contain my explanation as well, as opposed to only the other one, as it clearly seems to be two different explanations present.(and since Swedish sources exclusively use my version.) I therefore think my first version that stated that SOME SOURCES(e.g. all information in Swedish) claim that this is what the terms Vertical and Parallel twin is about. If you read on the top of this very page there is another contributor which has about the same explanation for the "True meaning of Parallel twin. Which should about state my case. Which is, that if the article cant contain both explanations, it should not contain any of them.

Arve Kvalvik — Preceding unsigned comment added by 88.84.36.158 (talk) 13:35, 25 October 2011 (UTC)

Sorry, but in WIkipedia truth is trumped by verifiability. Whatever you put in the article, without sources, is original research and therefore doesn't belong (see WP:RS). From my perspective I have seen the term used for 180, 270 and 360 degree configurations as a generic term for how the cylinders are arranged in relation to each other e.g. at Totalmotorcycle.com, at MCN, at Howstuffworks.com, by Yamaha for their 270 degree XT1200Z, etc. This book explicitly states that parallel twins can have any crankpin alignment. Similarly you can find references that use the term vertical twin to refer to engines with the 180 or 360 alignment. Try as I might I could not find a single reference that supports your assertion that parallel is 360 and vertical is 180. Most references to vertical are simply that the cylinders are aligned vertically, rather than at an angle (as they are on the BMW F800 bikes) --Biker Biker (talk) 19:00, 25 October 2011 (UTC)

Ok, take a look here: http://translate.google.com/translate?sl=sv&tl=en&js=n&prev=_t&hl=no&ie=UTF-8&layout=2&eotf=1&u=http%3A%2F%2Fmetrobloggen.se%2Fmotorblogg%2Fhonda_cb_450%2F

And here: http://translate.google.com/translate?sl=sv&tl=en&js=n&prev=_t&hl=no&ie=UTF-8&layout=2&eotf=1&u=http%3A%2F%2Fwww.classicmotor.se%2Fartiklar%2Fexperten%2F20090331%2Fhur-arbetar-en-vertikaltwin%2F%3Fpage%3D1

As you can see in the last article there is a full article on the subject in Classic Motor no. 10/1991. Is that a "verifiable source" enough to you, like that book of yours? Those who wrote them are anyway in both cases only people. My guess regarding the explanation of the terms in your books is that the authors or their source knew about these much used terms, but not really what they meant, so they stated in their scripts that they meant the most obvious they could think of. Like it has been forgotten with time so to speak. The version in the current article was even another new one, that "parallel twin" is cases where the crank sits across the frame, longtitudal ones is only an inline twin. As far as I know the term "parallel" means something very close to "in line with" so how the author figured that one I can only wonder. Anyway as you can see from these articles, there are more people that uses my explanation of the terms, so now you know that I'm not taking it out of the blue. My suggestions are to either write in the article that there is more than one explanation on the subjects vertical and parallel twin, or to simply only write that they are terms that are often used when talking of two cylinder motorcycle engines, leaving any further explanation out.

AK — Preceding unsigned comment added by 88.84.36.158 (talk) 00:25, 26 October 2011 (UTC)

Move discussion: Straight-two engine or Parallel-twin engine?

This article, Straight-two engine had been cut and pasted into the redirect Parallel-twin engine. Since the cut-and-paste move was done in such a way as to obscure the edit histories of the article and the talk page, which is unacceptable to Misplaced Pages as it violates the CC-BY-SA 3.0 License and the GNU Free Documentation License under which Misplaced Pages operates, it has been reverted.

However, the action does bring up a point. Is "straight-two engine" the best name for this article? Does it follow the naming guidelines of Misplaced Pages? It is probably best to discuss this and come up with an established consensus on what the name of the article should be.

Sincerely, SamBlob (talk) 18:44, 16 June 2012 (UTC)

The move was not done "in such a way as to obscure the edit histories". The move was done in good faith, and based on the expert knowledge of the reliable sources, by a beginner at this game who was trying his best to help and you've created a tangle of related short-cuts and talk pages now.
By all means, please work out how to transfer the page "properly" but in the meanwhile learn to speak to willing volunteers in a way likely to engender their cooperation.
Straight two? If you don't know anything about engines, try starting with Google Books or Scholar.
In the future, try approaching someone new politely and ask them, "Can I help you? What exactly was it you were trying to do?" etc instead of accusing them. You will find it elicits a far more civil response, and then you will be able to judge their intention. --Bridge Boy (talk) 00:42, 28 June 2012 (UTC)
I'd like to keep it the way it is until we can straighten out the edit histories. One might be slightly more common than the other, but I don't see a compelling reason to clobber the history over semantics. --Dennis Bratland (talk) 01:01, 28 June 2012 (UTC)
OK, I think I've sort out the tangle of all the related short cuts and have the discuss in the same place. Please don't mess with it until we resolve this issue.
As fas as I am concerned, the argument for "Parallel twin" over "Straight two" is clear.
I followed the style of other engine configurations to include the hyphenation, although I have no strong position in support of that, and tidied up many of the rest of them so that they all matched, there were obvious shortcuts, and there was some sense of logical consistency.
I suggest any changes should be conceived of in consideration of the bigger picture.
Daniel, stop your gaming. My comment to you was not "vandalism". Please learn to speak to people with civility, approach them first to see what it is they are doing and understand what is going on, try offering help before you accuse them, especially dishonesty or with prejudice. --Bridge Boy (talk) 01:28, 28 June 2012 (UTC)
O.K., since you will not go to WP:MOVE and read why you should not do this, let me bring the relevant part of WP:MOVE to you:
Please do not move or rename a page by copying/pasting its content, because doing so fragments the edit history. (Misplaced Pages's copyright license requires acknowledgement of all contributors, and editors continue to hold copyright on their contributions unless they specifically give up this right. Hence it is required that edit histories be preserved for all major contributions until the normal copyright expires.) - from WP:MOVE
I will now ask an administrator to try to undo the tangle you have created.
Sincerely, SamBlob (talk) 01:40, 28 June 2012 (UTC)


  • Sorry for coming to this so late, but isn't this a case for splitting? Straight twos are a fairly humdrum entry in the inevitable list of basic engine configs. They're found everywhere. Parallel twins though are a narrow, albeit well-populated, subset of this. They imply a timing that just isn't used for the other straight twos. The term is also, IMHE, only applied to motorbikes.
Parallel twin warrants its own article, under that title. Yet we certainly can't rename straight-two to it, as that would be way inaccurate for the others. Andy Dingley (talk) 10:48, 28 June 2012 (UTC)
Can you give us any references or citations to differentiate the two, and clarify what precisely you are talking about? I'm finding it difficult to find any reference to "straight-two" at all, except those referencing the Misplaced Pages. On the other hand, I can find plenty that use parallel twin for 180, 270 or 360 degree twins, and referred to it as "most commonly known". If you read the references I gave, you will also see it is widely used for automobiles, snowmobiles, ATV, jet skis and so on, and has been for decades.
Even if you cannot provide references, I'd genuinely like to know where and from when the term was used. (What I think you are suggesting is that parallel-twin is used only for 360 degree engines but that is just not so). --Bridge Boy (talk) 11:47, 28 June 2012 (UTC)
  • This bit of the article has not only survived B-Boy's editing blitz but seems to have actually gained a reference from it:

"Parallel twin" refers to an engine which has its crankshaft mounted transversely across the frame; and the term "inline twin" refers to exclusively to an engine with its crankshaft mounted inline with the frame, such as the Sunbeam S7. - from Straight-two engine#Motorcycle use

If this is to be believed, then the term "parallel-twin" is specific to straight-twins that are mounted transversely in the frames of motorcycles. Therefore, the more general term, "straight-twin", should be the title of the article.
Sincerely, SamBlob (talk) 12:56, 28 June 2012 (UTC)

Votes

Request page history merge

{{Histmerge|Straight-two engine}} Sincerely, SamBlob (talk) 01:47, 28 June 2012 (UTC)

Moved back

Moved back... I think. I'm not sure which page it was at originally. Let me know if I made a mistake fixing the cut-and-paste move. NW (Talk) 02:05, 28 June 2012 (UTC)

This is right. I've requested comments from WikiProjects Motorcycling and Automobiles to see where the consensus is. Thanks! --Dennis Bratland (talk) 02:09, 28 June 2012 (UTC)
Yes, you made a mistake. All Sam asked for was a history merge, not a page moving. The topic and talk page should be at Parallel-twin engine. --Bridge Boy (talk) 06:27, 28 June 2012 (UTC)
It is as it was. Discussion will (hopefully) bring consensus as to where it should be, at which time it will be put there. Sincerely, SamBlob (talk) 12:23, 28 June 2012 (UTC)
If this page is titled what it was a month ago, I'm satisfied. The move discussion above should establish a new firmer consensus. NW (Talk) 12:37, 28 June 2012 (UTC)
Do you know anything about engines? Can you supply any references to support the predominance of the term straight-two? Thank you. --Bridge Boy (talk) 12:49, 28 June 2012 (UTC)
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