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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)

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)
I will try to explain this to you: The page has been brought back to where it *was*. Where the page *will be* depends on the outcome of the above discussion. Until the above discussion is concluded, the page will remain where it *was*, regardless of where anyone, including you or I, thinks it should be. Do you understand this? Sincerely, SamBlob (talk) 14:06, 28 June 2012 (UTC)
There is no point in feeding this troll any longer. He doesn't listen. --Dennis Bratland (talk) 15:11, 28 June 2012 (UTC)
A troll? No, he is not a troll. I'm pretty sure he is upset because he is a bit new. Don't bite the newcomers. --J (t) 00:22, 29 June 2012 (UTC)
He's not that new. There have been repeated discussions where he simply doesn't care to listen to other editors. For example, numerous requests to not leave all his edit summaries blank. He's been told at least a half dozen times by different editors that the problem here is that this page was moved incorrectly, and his response is "do you know anything about engines?" He's repeatedly been asked to supply sources for his POV-pushing edits, and all he offers is bluster. For example, do you see one single source cited to support the move to "parallel-twin engine"? None. Just bluffs about sources that we never see. And then there was this.

It's like talking to a brick wall. Someone whose comments are not constructive, and only serve to draw out pointless replies, and who does not respect the collaborative editing process, is a troll. --Dennis Bratland (talk) 00:35, 29 June 2012 (UTC)

Just the sort of answer I would have expect from you Dennis, and precisely the same manner and attitude others users have complained about you too.
Half a dozen times?
Prove it. I see one, and it's from you. You are trying to prejudice others against me, here and on my talk page, with falsehoods.
The problem was, Dennis, you "told me". You did not "ask me". You did not politely explain why or show me as a newcomer. My response, at that time, was your attitude, and you need to modify it. I inferred that "you were not paying me", so don't speak to me as if you are my boss. This isn't your website.
I'll respond to anyone that approaches me reasonably and intelligently in a reasonably and intelligent manner, but what you are doing is gaming, as with your misrepresentation and little "tell-tale" above. I read your talk page and elsewhere. You have a history of doing this to others.
FYI, I added 35 references to the article. How many did you check and how many did you add?
I encourage others to check the other articles I have worked on and again you will find a very high proportion of edits with good references, so please allow me to politely call BS on this one and let's all move on.
If you all care so much about policy, what offends me, as someone who does know a little about engines, is the ridiculousness of the title of this topic. Despite all the quibbling, not one of you has been able to support it with references, how absurd is that? All someone had to do was merge the history, one person one click. It's SamBlob you should be pissed at, not me. --Bridge Boy (talk) 05:40, 29 June 2012 (UTC)

What the trade, manufacturers, experts etc call them

OK, as promised. With links to the international websites where possible. This is what the trade and manufacturers call them.

If you disagree with the use of parallel-twin, please provide your evidence or otherwise justify your opinion.

If I have missed out any important reference, please correct the list.

Thank you. --Bridge Boy (talk) 07:44, 29 June 2012 (UTC)

BTW, for each of these searches I did two searches; one for "parallel twin" and one for "straight twin", using Google to search the site, e.g. site:xxx.com. In every case, one or more variation of parallel twin came up and none for straight twin. --Bridge Boy (talk) 01:56, 30 June 2012 (UTC)
Source Terms used Alternative? URL
* Honda parallel-twin, parallel- twin engine, parallel twin-cylinder engine Straight twin - zero bit.ly/LkrxDz
* Kawasaki parallel-twin, parallel twin, parallel-twin engine, parallel twin cylinder engine Straight twin - zero bit.ly/LyTEgz
* Yamaha parallel twin, parallel twin engine Straight twin - zero bit.ly/METfxN
* Suzuki parallel twin, parallel twin-cylinder Straight twin - zero bit.ly/NURI71
* BMW parallel-twin, parallel twin engine Straight twin - zero bit.ly/LyVMoL
* Triumph parallel-twin, parallel-twin engine, parallel twin Straight twin - zero bit.ly/MbkkKv
* Norton parallel twin Straight twin - zero bit.ly/LUWhfk
* Polaris parallel twin Straight twin - zero bit.ly/KH9Tbz
* Ducati parallel twin-cylinder, parallel twin Straight twin - zero bit.ly/LIbUKY
* Husqvarna parallel-twin Straight twin - zero bit.ly/MDxKMx
* Motorcycle News parallel-twin, parallel-twin-engine, parallel twin [1] Straight twin - zero bit.ly/OGZjsq
* Motorcycle parallel-twin engine, parallel-twin, parallel Twin Straight twin - zero bit.ly/N2spPC
* Cycle World parallel-twin Straight twin - zero bit.ly/LIcMPH
* National Motorcycle Museum parallel twin engine, parallel twin Straight twin - zero bit.ly/Qxrmb4
* AMA parallel-twin engine, parallel twin, parallel twin engine Straight twin - zero bit.ly/LUYN5r
* DOT parallel twin Straight twin - zero dot.gov
* Nat. Museum Motorcycling, Aus parallel twin Straight twin - zero bit.ly/L71fJB
* International Motorcycle Show parallel-twin, parallel twin Straight twin - zero bit.ly/NJbBdL
* Cycle Trader (181,000 bikes for sale) parallel-twin, parallel twin, parallel twin-cylinder Straight twin - zero Link
* Ebay parallel twin Straight twin - zero [2]

Do I really have to go on? Oh, why not ...

The trouble is that they're all motorbikes - the term parallel twin is used around motorbikes, there's little question of that. However two cylinder engines have broader uses than that. Can you show any use of "parallel twin" in a non motorbike context? Andy Dingley (talk) 09:42, 29 June 2012 (UTC)
Polaris isn't. Please read the references already given on the topic. I am sorry Andy, I've done my work and all I have to prove is a reasonable preponderance, not document every case. If anyone can better it in other areas, please do. Otherwise it's a a ridiculously clear slam dunk.
I've added plenty of references regarding cars to the article itself, e.g. NSU related, John Deere. It's the same again. Parallel twin.
But I am looking forward to seeing how the other motorcyclists enthusiasts argue otherwise. It'll be good for a laugh. I tried. There are basically no references to back alternatives up.
Thank you. --Bridge Boy (talk) 10:39, 29 June 2012 (UTC)
Again, so what? No-one is disputing that parallel twin is in use (there's some question as to just how broadly). Your assertion though is that this is the only name used for any two cylinder inline engine, and so the article should be renamed throughout. Go back to pre-war diesels and the Junkers HK series - you won't find those described as parallel twins. Look at half a century of medium-sized stationary and boat engines with two cylinders inline. The "parallel twin" designation just isn't used here.
What's the most common (only common?) two cylinder car engine at present, the Fiat TwinAir. Now find a decent source describing that as a parallel twin and you'll see that it's also a 360°, with a balance shaft. A parallel twin, but just that type of engine that is (I think generally) agreed to be the classic "parallel twin", balance problems and all. Hard to find a god picture online, but try this [3]
Are there any two-strokes ever described as parallel twins?
Of the four strokes, how many are 360° apart? Looking back at '50s & '60s motorcycles, what's the relation between the "parallel twin" designation, and it being reserved for 360° four strokes, even if this has blurred since?
There's also the issue that you appear to be citing eBay as a source, and others no more credible. That's the "billion flies" argument. Of course there are "sites on the web" that will call anything anything, but that doesn't mean they're correct to do so. Andy Dingley (talk) 12:10, 29 June 2012 (UTC)
Yes, if you read the references you will find two-strokes named as parallel-twins, e.g. Japanese Grand Prix Racing Motorcycles. Mick Walker. Redline Books, 2002.
No, I did not assert it is the "only". I assert that it is the predominately Recognizable, Natural, Precise, Concise and Consistent title inline with Wikipedia title naming policy.
I have presented a balance of evidence that it is impossible to argue against honestly. Way beyond what is necessary.
Neither you, nor anyone else, are offering any alternative reliable sources at all. Nor the greater balance of evidence to counter my position which you now need to. The fact is, you cannot. I've looked. (And, as it is general and not specific topic, the Wikipedia is not bound by what an engine may or may not have been called in the Victorian or Edwardian period).
I am sorry but by having to latch onto and exaggerate the very final of 64 fair to excellent new references in order to establish any weakness to my argument, you've damaged the credibility of your opposition. There is no onus on me to do any more work.
If the alternative titles were in anyway common one would have expected to see evidence of it all over the place. They are not and the fact that you are all willing to sit there, dig your heels in and argue because WP:IDONTLIKEIT instead of go and add reference to a topic such as Straight engine that had none until I add ones says it all really.
So what is this really about? WP:IDONTLIKEIT, or a little gang of 2 or 3 people who think they own motorcycle related topics (and I am not including you in that statement) not liking someone new on their block?
Show us your references. --Bridge Boy (talk) 17:31, 29 June 2012 (UTC)
List of refs for straight-two, inline-twin, straight-twin, etc
  • Crouse, William H. and Anglin, Donald L. Motorcycle Mechanics. McGraw Hill. ISBN 0-07-014781-7. 1982. p. 19-20. "Engine classification by number of cylinders… 2 in-line, v-2, flat-2…Two cylinder engines are called twins. The two cylinder can be arranged in line (a vertical twin) or in a V, or opposed…"
  • The original Subaru vs. Mitsubishi faceoff. Import Tuner. 134 (May 2010): p16. ""1958 SPECS SUBARU 360 … LAYOUT STRAIGHT TWIN"
  • "They can't all be GTOs." Motor Trend Oct. 2007: 118. General OneFile. Web. 29 June 2012. "Not everything Ferrari touches turns to blazing scarlet. In 1955, for instance, engineer Aurelio Lampredi--working with Enzo and son Dino--creates an experimental inline-two-cylinder F1 engine (the theory being that two large cylinders would provide enormous torque for tight circuits like Monaco). "
  • Husick, Chuck. "Rally Round The Outboard." Yachting Mar. 2007: 118. General OneFile. Web. 29 June 2012. "The choices in outboard power include 11 models in Bombardier's Evinrude's E-TEC series; inline, two- and three-cylinder units ranging in power from two to 75 hp, a 60-degree, 115 hp V-4, and 60- and 90-degree V6s from 150 to 250 hp." :::::*note the sentence parallelism as the reason for this construction"
  • "Emission-compliant diesel engines cover 83 to 1,350 bhp in 10 models." Oil, Gas, & Petrochem Equipment May 2006: 18. General OneFile. Web. 29 June 2012. "Cat petroleum diesels line includes eight inline two, three, and four-cylinder engines with such features as single-side service access, 500-hr oil change intervals, compact injection pump timing devices, closed circuit breathers, improved governing systems, optimized injectors, and very low idle noise levels.
  • Watanabe, Laurie. "That magnificent man on his riding machines." Dealernews Nov. 1996: 26+. General OneFile. Web. 29 June 2012. "If you press him, though, Jim is likely to expound on his 1947 S7 Sunbeam - "twin-cylinder, rubber-mounted engine. They were an inline two-cylinder, not crosswise in the frame, like conventional twins are. It's like new, because it's been in a museum all its life.""
  • Tata Motors Limited Files Patent Application for a Novel Inline Two Cylinder Multi Point Fuel Injection Four-Stroke Reciprocating Piston Internal Combustion Naturally Aspirated or Turbocharged or Turbocharged Intercooled Spark Ignition Engine. "...application for a novel inline two cylinder multi point
  • Preview Tata Motors Limited Files Patent Application for a Novel Inline Two Cylinder Direct Injection High Pressure Common Rail Four-Stroke Reciprocating Piston Internal Combustion Turbocharged Diesel Engine. Indian Patents News [New Delhi] 17 Dec 2010. "…application for a novel inline two cylinder direct injection"
  • SUSAN CARPENTER / THROTTLE JOCKEY; Bike 101: Choosing your ride; Don't be intimidated. These four motorcycles are geared for beginners.: [HOME EDITION] Carpenter, Susan. Los Angeles Times [Los Angeles, Calif] 10 Jan 2007: G.1. "A high-revving, inline twin with four valves per cylinder, the 250R isn't especially torque-y, which is why it's great for beginners. "
  • PSA fires up two-cylinder turbo. Anonymous. Automotive Engineer33. 9 (Oct 2008): 5. "…baseline, it selected the inline-twin configuration as offering"
  • AMERICAN BEEMER Edwards, David. Cycle World 46. 12 (Dec 2007): 73. "...inline-Twin engine. With no racing pretensions, Wood initially had a problem..."
  • Steaming into the future... Barnett, Colin. Commercial Motor 209. 5322 (Mar 12, 2009): 44-45. "…will use the latest 800cc inline twin, which is much more compact"
  • Cruiser comparison: Kawasaki Vulcan 500, Anonymous. Cycle World 33. 2 (Feb 1994): 47. "…V-Twin class, so the little inline-Twin Vulcan doesn't exactly fit"
  • Toontown twin. Thompson, Jon F. Cycle World 34. 11 (Nov 1995): 44. "…rubber-mounted, sohc, 487cc inline-Twin, was the result."
  • Océ ColorStream 3500. Severs, Jon. Printweek (Dec 17, 2010): 16-17. "...configurations, so as a single unit, inline Twin or L-, H- or U-Twin for simplex"
  • Tuttle, Mark, Jr. "BMW F800S." Rider Dec. 2005: 15. General OneFile. Web. 29 June 2012. "BMW will tackle the middleweight market in the late spring/early summer of 2006 with a new F800S sport tourer, powered by the first inline twin-cylinder engine in BMW's history. The 800cc parallel-twin is produced in cooperation with Bombardier-Rotax…"
  • Miller, Nancy. "Highway stars." Wired Nov. 2007. General OneFile. Web. 29 June 2012. The $6,300 Aprilia Scarabeo 500 i.e. glides at 80 mph on freeway and still can zig-zag through street traffic. The Vespa GTS 250 sells for $5,999 and weighs 300 pounds but delivers a top speed of 76 mph. The Honda SIlver Wing sells for $7,999 and can easily top 100 mph with its inline twin engine.
  • "BMW AG adds scooter to 2012 range." Auto Business News [ABN] 9 Dec. 2011. General OneFile. Web. 29 June 2012. The new scooters are to be equipped with a 647-cc inline twin cylinder engine that delivers 60bhp and reaches a top speed of around 100 miles per hour.
  • "MZ introduces third 1000cc unit." Powersports Business 16 May 2005: 30. General OneFile. Web. 29 June 2012. In fact, the frame and fairing of the Super Traveller are to a large extent identical to the MZ 1000 S that has been produced at the Zschopau factory since 2004. And, the four-stroke inline twin engine is identical with the MZ 1000 SF. The engine puts out 113hp at 9000 rpm.
  • Harrisonburg Daily News Record - June 2, 1989, Harrisonburg, Virginia. Kawasaki Motors Corp., U.S.A. (advertisement) "Like an 8-valve, in-line twin engine with 454cc's of torque and mid-range punch." --Dennis Bratland (talk) 19:17, 29 June 2012 (UTC)
  • Mick Walker's European Racing Motorcycles Mick Walker. Redline Books, 2000. ISBN 9780953131136. p.20 "the Rotax 256 inline twin would not be produced." p.25 "Rotax 256 inline twin… the Model 256 inline twin designed by…" p. 26 "Rotax 256 inline twin-engined Armstrong…" p. 28 "…Armstrong's version of the Rotax inline twin. "
  • Italian Racing Motorcycles Mick Walker. Redline Books, 2000. ISBN 9780953131112. p. 25 "Aprilia had seen how the inline twin cylinder two-stroke disc valve Rotax engine had performed…" p. 27 "…since the introduction of the old inline twin back in 1985…"
  • Popular Mechanics - Feb 1989 - Page 109. Vol. 166, No. 2 - 136 pages - Magazine "Also new from Suzuki are the inline twin 15 and the inline 3-cylinder 25. Both are equipped with loop- charging, oil injection and external- mount tilt and trim. The 25 also has pre-atomized oil injection and an overrev limiter."
  • American Motorcyclist - Dec 1990 - Page 47. Vol. 44, No. 12 - 60 pages. "… its spirited 248cc four-stroke inline twin engine, with twin cams and four valves per cylinder."
  • 365 Motorcycles You Must Ride - Page 43 and 44. Dain Gingerelli, Charles Everitt, James Manning Michels - 2011 - 320 pages "OHV, two-valve-per-cylinder, four-stroke, inline twin Horsepower: 51"
  • The Motor: Volumes 133-134; Volumes 133-134. 1968 "The Fellow 360 is an all independently sprung car with a watercooled 2- stroke inline twin at front driving the rear wheels via a 4-speed gearbox, in normal tune, it is a pleasant runabout. And now Daihatsu have added an SS version, …"
  • Antique Cars. Lord Montagu, Lord Montagu - 1985 - 80 pages -"The V-twin gave way to an inline twin, still made under Daimler license"
  • Snowmobile Service Manual Intertec Publishing - 1986 - 488 pages"Engines consist of two types; the axial fan, inline twin and the simultaneous firing opposed twin. "
  • Automobile quarterly: Volume 29, Issue 1. Princeton Institute for Historic Research - 1991 - "Note the incredibly narrow angle that makes the unit appear more like an inline twin than a V4. one."
  • Automotive engineering: Volume 102, Issues 1-6. Society of Automotive Engineers - 1994 "... and an outright miser working with two cylinders with somehow motorcycle-like inline twin thumps."
  • Classic Cars: 50 Years of the World's Finest Automotive Design. Brazendale - 1983 - 368 pages "They were vee-twin-cylinder engines designed by Daimler, which were replaced by the inline, twin-cylinder unit as used in the Phonix of 1 895."
  • Ultralight aircraft Michael A. Markowski - 1982 - 320 pages - "The Cuyuna 430-D is an inline twin cylinder of 30 hp."
  • Machine Design: Volume 54, Issues 1-6; Volume 54, Issues 1-6 1982 "A modified snowmobile power plant, the 30-hp inline twin has been detuned by lowering the compression ratio and modifying the carburetion"
  • Antique cars Michael Sedgwick, 1980 - 93 pages "The engine, an inline twin, lived in a box like a meat-safe at the rear."
I think it's notable here that so many of these sources are motorcycle-related. The use of 'inline twin' is not uncommon. It's also notable how many of them, like Mick Walker, are British. DK is German, and I wonder if the use of "straight two" isn't influenced by that language. Not that it matters how something got into English. It's here now.

Parallel twin is probably the dominant term, and the page should probably be moved there. But expunging all other variants, particularly inline twin, but also straight two and inline two, is not justified. --Dennis Bratland (talk) 21:14, 29 June 2012 (UTC)

  • " 2 or 3 people who think they own motorcycle related topics"
Why do you think this is a topic only about motorcycles? Andy Dingley (talk) 09:42, 30 June 2012 (UTC)


A number of those sources, which you don't properly reference, are merely blogs or PR releases (primary sources) and so would fail "reliable sources", Dennis, but thank you for conceding parallel twin is the most common use as I suggested. However, the use of term inline is normally used to describe a sub-set of parallel twin engines where the crankshaft is inline with the chassis instead of across is. In short, an inline twin is a parallel twin but not all parallel twins are inline twins hence we cannot use inline as the dominant term, see below (e.g. you will also find references to "inline parallel twins").
No offence towards you intended at all Andy. We've never encountered each other before and you seem to be perfectly reasonable and polite. I am sorry if I was blunt to you. You are, of course, perfectly correct, the topic is not only about m/cs, however, it is pretty much only m/c and related product manufacturers that make and use parallel twins now and that is born out in the references. Believe me, I probably spent hours looking over references.
I actually expected to find more use of other terms but I did not, not even amongst small marine engines which was the only other area I could of think of where they are used, e.g. [4]. It seems only a simple non-descriptive two- or twin-cylinder are the only other commonly used terms.
Yes, I agree I was expecting to find more references to inline twins and was surprised by the predominance of the term parallel. The use of the term inline is more commonly used as a reference to the relationship of the crankshaft to gearbox and drive rather than the engine itself. "Inline", aka longitudinal or tandem parallel twins (Sunbeam S7, Rotax 256, Kawasaki KR250) are far less common. Given that the policy states "consistency", if we look at the V-twin page, longitudinal V-twins occupy a subordinate position reflecting that relative rarity. Actually, there are probably enough sources to split both transverse and 'longitudinal' parallel twins and transverse and 'longitudinal' V-twins into separate topics, if someone could be bothered to write them
I cannot because I have had too much of time wasted by the stupidity and ignorance of having to question a choice as poor as "Straight-two engine", and all the bitch slapping and conniving that has ensued since. Something these people don't seem to realise detracts from the job at hand.


I have had run ins with some of these other bods before and can see the psychology and the games that are being play. I find it tiresome and counterproductive to engendering voluntary cooperation in this project, and beyond what I consider to be reasonable. The system appears to defend ignorance and reward irrationality if expressed in the terms of various policies, and benefit those with a willingness and knowledge of who and where to rat on others.
I have no idea why Dennis has fixated on me and was working up such a case, because he is obviously otherwise well informed and intelligent. Yes, I challenged his knowledge or prejudices in other areas but I don't see that as a good enough reason to be "punished" by him, or have him build up "bad marks" against me, often very falsely. He came out with strong statements elsewhere that led me to question his judgement.
Of course, people do use the internet to behave in a manner towards other people that they would never do or get away with in real life. Perhaps it is just an unconscious sibling rivalry? --Bridge Boy (talk) 12:52, 30 June 2012 (UTC)
You still don't see it, do you?
"Having to question a choice as poor as 'Straight-two engine'" is one of the cornerstones of Wikipedia. Action is based on consensus, and consensus is gained from discussion.
Had you figured out, or asked, how to move a page properly, there would have been no time lost in trying to undo your cut-and-paste move that obscured the edit histories whether you intended to or not.
Had you presented your arguments in the talk page instead of going on a unilateral vendetta, you would have achieved exactly the same results you are achieving now *without* an edit war and tons of acrimony, and you would have achieved it faster.
Unless something radical that I can't foresee shows up, this article is going to be moved where you wanted it to be moved. This is because of the validity of your arguments and *despite* your contentious actions and behaviour. It is very refreshing to note that the discussion system actually works to find a valid answer despite attempts to undermine the system even when the attempts to undermine the system are coming from the editor *with* the valid answer.
I would hope that you learn from this that the system of discussion works and achieves better results than charging around like a mad man. I understand, however, that this is a slim hope.
Sincerely, SamBlob (talk) 14:51, 30 June 2012 (UTC)
Moving the page to Parallel-twin engine is probably a slight improvement, and that was mostly a result of my searching google books. Irrelevant links to ebay didn't convince me of anything. I have to go on record as saying that almost all of Bridge Boy's edits here have been harmful, and it is delusional to think he's won much support from me. The slight improvement gained by moving the page does not in any way justify the edit warring and the tirade of personal attacks and unjustified recriminations against SlamBob, NuclearWarfare, Andy Dingley, Biker Biker and me. --Dennis Bratland (talk) 15:09, 30 June 2012 (UTC)


Well then, if we are all agree we are all agreed and there is nothing to argue about. No need to thank me for the "slight improvement". ;-) --Bridge Boy (talk) 12:19, 1 July 2012 (UTC)
Wouldn't it have been easier, Sam, just to have done this ...
We don't all agree. Biker Biker does not agree, and it's not clear where Andy Dingley stands. --Dennis Bratland (talk) 14:01, 1 July 2012 (UTC)
I'm still against this move to parallel twin, although I'm not tied to any one particular version of inline/straight two/2/twin.
The issue is that I see a need for this to be the "top level" description of such engines, not the "most popular". If all such engines are "inline twos", and most (but not all) are "parallel twins", then the canonical title should remain at the broader scope, even if most of the article (where appropriate) describes them with the narrower term. We would still need to express coverage of those that aren't parallel twins.
This is not simply a motorcycling article. It has to cover the engines throughout: from the early examples, through the large pre-war twins, through boat and generator stationary engines, through motorcycles to microlight aircraft and small cars.
IMHE, I've only ever used paralllel twin for those engines where the pistons moved in parallel, rather than in antiparallel, i.e. 360° four strokes. These are an interesting group of engines, owing to their balance (and would justify a wiki article), and there is clearly a need for a term to identify them specifically (rather than the arse-themed colloquialisms coined by some Britbike riders) - parallel twin does seem to have served as such. My understanding is that this was common use in 1960s Britain for this specifically, although the term does seem to have broadened since. However checking some two-stroke refs, I don't find anything to support that: Irving doesn't seem to use the term and in Smith, Philip H. (1965). The High-Speed Two-Stroke Petrol Engine. p. 287. it's very clearly used to refer to 360° & 180° four strokes, with the two stroke (thus not having the four's balance choice) being contrasted with them, and all three clearly under the same "parallel twin" name. As such, I'd have to concede that the term is indeed used like this, by WP:RS.
I've never heard "parallel twin" used as an identifier for specifically transverse engines in motorbikes, but I have heard "inline twin" used specifically to distinguish those that aren't (and similarly for the BMW Ks, with their side-mounted triples and fours). Generally these transverse engines have been called "transverse", when needed. I thus wouldn't support that as an interpretation of "parallel".
As probably the most common use, the transverse-mounted two-cylinder motorcycle engine easily deserves its own article. That might be termed "parallel twin", but I'll leave that up to its writer.
Overall, I still prefer some name other than "parallel twin". Parallel twin seems unclear: the scope of the article is necessarily broad (this shouldn't become a motorbike-only article) and if parallel twin also implies connotations (even if incorrect) of transverse layout or firing order, then we should avoid that. I'm a lot happier though for parallel twin to be used within the article as an alternative name, even the primary alternative name, and not keeping it merely for a narrower scope.
As to ideal naming, then I slightly prefer inline-twin engine over the other straight-/2- variants, but don't care strongly either way. Andy Dingley (talk) 10:18, 2 July 2012 (UTC)
"Inline-twin engine" seems reasonable as it fits with the existing inline-four engine. I'm not sure about your comment regarding two articles though - everything could and should be kept within the same article. --Biker Biker (talk) 12:52, 2 July 2012 (UTC)
Whether you have "heard of it or not" Andy, there are now more than 60+ references to support the use of it, including manufacturers themselves. That you have not heard of it raises questions of credibility in your knowledge or judgement. See the list of major manufacturers above and references on the page all of whom do seem to have heard about it.
You will find "inline" or "in-line" twin with confuse matter with the common terms used for longitudinal parallel twins. Common use has established various conventions in the use of the terms parallel, inline and straight. It is not for Wikipedia to set its own but for us to follow the most common usage. --Bridge Boy (talk) 13:19, 2 July 2012 (UTC)
Apart from simply being too damned rude to even read what I wrote, just what are you griping about this time?
If you think that "parallel" as a shorthand for "transverse" is the right scope for an encyclopedia, then that's just sloppy wording by (many) other writers and we certainly shouldn't propagate it. Andy Dingley (talk) 13:42, 2 July 2012 (UTC)
@Biker Biker. Agreed. The two articles - even three - are because we obviously need the top level covered as "two cylinder engine with them next to each other". There's also a lot of potential in why the transverse vertical twin with integrated gearbox and chain drive became such a significant layout for motorcycles. After all, there are many, many possible ways to arrange this and yet most of the world's motorbikes are transverse crank verticals with 1,2 or 4 cylinders. How many inlines are there? I'd even like to see an article on 360° four stroke twins, because it's such an interesting layout technically.
Per ANI, Bridge Boy seems to be thinking of an article split too and a new article under inline-twin engine, recognising that nearly all of this existing straight-two engine is actually about the motorbike situation specifically. Provided that we tag the histories correctly, that might be the simplest way forwards. Andy Dingley (talk) 13:42, 2 July 2012 (UTC)
Just want to point out that Mick Walker was cited to support use of "parallel twin", but this is grossly misleading. In the very same book, he uses "inline twin" interchangeably. Walker does the same in [5][6] European Racing Motorcycles. It's strong evidence that there is no real distinction in the minds of the foremost experts today. Similarly, see Tuttle, Mark, Jr. "BMW F800S." Rider Dec. 2005: 15. General OneFile. Web. 29 June 2012. "BMW will tackle the middleweight market in the late spring/early summer of 2006 with a new F800S sport tourer, powered by the first inline twin-cylinder engine in BMW's history. The 800cc parallel-twin is produced in cooperation with Bombardier-Rotax…" Literally in one sentences it's inline, the next it's parallel. A historical distinction might be noted, but today they are equivalent. Historical sources also have placed more emphasis on whether the cylinders were vertical or horizontal than crankshaft orientation or firing interval (see Page, Victor W., Early Motorcycles: Construction, Operation and Repair. Dover Publications, 1924. 2004 reprint. ISBN 9780486436715. p. 122).

I don't favor these kinds of subject splits. I'd rather see these different issues, comparisons of firing intervals, and different opinions in terminology, historical and current, explained to the reader in one umbrella or parent article. There's a risk the reader will read one article and not the others, and fail to understand that experts don't all agree. If the article grows so large and unwieldy that something must be done, then multiple child articles can be spawned. Not content forks, but sub-articles under the main subject. We have a long way to go before it comes to that. --Dennis Bratland (talk) 14:58, 2 July 2012 (UTC)

I forgot to reply to the nonsense about "A number of those sources, which you don't properly reference", regarding my sources listed above. Not a single one is a blog, and not a single one is a press release. Exactly one is a newspaper ad. And what's wrong with press releases in this context, since supposedly manufacturers' language is relevant? After that annoying bit.ly/LkrxDz link to a list of Honda PR is cited as a source? Absurd.

Read Wikipedia:Citing sources and Wikipedia:Offline sources. There's nothing wrong with the citations I've given. Some of them are offline. So what? --Dennis Bratland (talk) 23:24, 2 July 2012 (UTC)

Dennis,
no one questioned offline sources. That is a fallaciously distracting argument.
However, I noticed that one of your "inline twin" references [7] was for an office printer.

Océ ColorStream 3500. Severs, Jon. Printweek (Dec 17, 2010): 16-17. "...configurations, so as a single unit, inline Twin or L-, H- or U-Twin for simplex"

The one I queried is straight off a PR release from Caterpillar Incorporated of Mossville IL USA.

"Emission-compliant diesel engines cover 83 to 1,350 bhp in 10 models ..."

Please be less rash and more careful. All of the bit-ly links point to manufacturers only specifications list. All of them use the term parallel twin.
Anyway, I have no further argument. The term parallel twin has clearly been proven to be the most commonly use term and meets all the policy requirement for renaming. --Bridge Boy (talk)
Sorry about the printer thing. The "manufacturers only specifications list" is a list of press releases, company-owned web sites, and advertisements. There is no logic of saying the diesel engine citation is flawed in some way while anything you find at honda.com is acceptable.

This isn't only about renaming. The changes you made to the article need to be reverted so that it's clear that parallel-twin isn't the only term, that manufacturers have used inline-twin interchangeably, and so have top experts like Mick Walker. Wikipedia articles should not make new distinctions that don't exit in minds of expert sources. Speaking of expert sources, I still haven't seen where Cycle World's Keven Cameron stands, and I'd like to wait to find out.

As far as consensus, without Biker Biker's Andy Dingley's support, a move is unwise, even if I think parallel-twin is the common name. Waiting for consensus means respecting the opinions of other editors. And there is no harm in leaving the page where it is.— Preceding unsigned comment added by Dennis Bratland (talk • contribs) 15:27, 3 July 2012‎


Dennis, I am going to make you a set of colors and instead of a skull and cross bones, its going to have an laserjet printer in the middle. WikipediaMC, Motto: "We are the Wikipedia Larry Sanger warned you against".
Now, read carefully. Where you are raising this point of Walker and "interchangeability", your lack of knowledge is letting you down. The Rotax engine is an inline twin, not a parallel twin (P.25) which is clarified further when he talks of the KR250 which is also an inline twin, not a parallel twin. In fact, both are "tandem" inline twins.
So, please strike out, "It's strong evidence that there is no real distinction in the minds of the foremost experts today." It's strong evidence he knew the difference and was sticking to common nomenclature.
There were a number of copies all based on the Rotax 256 engine format and, funnily enough, I actually know about all this stuff partly because I am old enough to have been around and involved when it all happened. Here's what they look like [8]. --Bridge Boy (talk) 22:08, 3 July 2012 (UTC)

Attempting to clarify naming

Just what is known here? What can we actually source?

The scope of both articles is limited to two cylinder IC engines where the cylinders are mounted alongside each other. This includes two and four strokes, petrol and diesel.

All layouts and orientations should be covered somewhere within this group of articles, although just where is up for debate. Similarly applications: as motorcycles are such a major market for two cylinder engines, a separate article for some or all motorcycle applications is a possibility.

Beyond this, both the name, scope and even the number of articles is contended.

The name appears to be a composite of two parts. Both, particularly the first, are contentious. The first is mostly technically contentious, the second a stylistic issue. Examples seen so far are:

  • Straight-
  • Inline-
  • Parallel-
  • Transverse-
  • Longitudinal-
  • Tandem-
  • -2
  • -four
  • -twin

To look at each term in detail:

  • "Straight" is the current name, and appears to be unpopular, yet relatively uncontentious. It appears to have no connotations other than the engine being neither a V nor a radial. I think we can all agree this one.
  • "Inline" starts to become a problem. Does this mean no more than straight (i.e. not a V), or does it also imply a longitudinal tandem arrangement? In general engine use, it means no more than "straight" does. In motorcycle use, an "inline twin" has sometimes been used to distinguish longitudinal arrangements specifically from transverse. However it's also cited above that it has been used for transverse engines too.
  • "Parallel" is contentious. It is not widely used outside of motorbikes. Sourcing shows that it is used, to a notable level, in the same context as straight and inline, i.e. any two cylinder.
AD's past claim that it referred to 360° four strokes specifically has been withdrawn, as sources showed good cites for this in the broader context too.
Bridge Boy seems to have claimed it as synonyms for both straight (i.e. any non-V) and transverse (i.e. crosswise only). There is no sourcing to support this narrow use: cited examples of it applied to the narrow use (most motorbike twins are simply transverse) do not indicate that it is only applied to the narrow use.
There is still no enthusiasm, except Bridge Boy, for renaming any article to parallel-twin, or for using it as a name in any article. Its meaning is just too ambiguous for us to use freely.
  • "Transverse" has a clear and simple meaning, with wide currency in motorcycles and cars. It means a transverse crankshaft, i.e. non-longitudinal. If there is to be an article on transverse twin motorcycle engines (this is a possible topic with clear notability and reader value) then the term "transverse" is clear and unambiguous.
  • "Longitudinal" also has a clear and unambiguous meaning and is commonly used with cars. It is not widely used in motorbikes, although it would still remain clearly understood.
  • "Tandem" is obscure and rarely used. It is somewhat ambiguous as it is perhaps most commonly used for multiple engines (mostly in drag bikes) where they still have transverse crankshafts.

There is no unambiguous term available for the 360° four strokes specifically.

The scope of the two articles is now completely confused. Is straight-two engine about (broad) two cylinder non-Vs, or (narrow) about transverse engines only? Similarly is inline-twin about broad or narrow scope?

  • If both are broad (as the general use of their names suggests), they overlap.
  • If both are narrow, then we've lost a general article on two cylinder engines and these two articles have really become motorbike-only.
  • If straight- is broad and inline- narrow, then the name is doubly confusing for an article that's only on an obscure motorbike layout. It doesn't explain what it does cover, it misleads as to what the name suggests it does. Non-motorbike layouts would be covered by a broad straight-two.
  • If straight- is narrow and inline- broad, then the articles are completely about-face from where they were to begin with. Straight-two would also need to be renamed as "transverse twin motorcycle engine".

Andy Dingley (talk) 15:35, 3 July 2012 (UTC)

There is actually almost as much ambiguity as to whether V or boxer twins should be called transverse or longitudinal, depending on whether you're thinking of the crankshaft or the line of the cylinders. Darwin Holmstrom, for example, used the terms in both senses in different books, and Moto-Guzzi habitually calls their configuration "transverse", even though the majority of sources are clear that it's the crankshaft that counts, so Guzzis and traditional BMW boxers are really longitudinal. Sorry to bring all that up, it's well discussed at Talk:V-twin_engine#Transverse_vs_Longitudinal. The only solution is to say "longitudinal crankshaft" or "transverse cylinders", and never assume the reader knows what you mean by longitudinal or transverse. The terms are skunked and require clarification at all times.

Parallel, inline, and straight are skunked too. So it goes.

My point -- the one I always make because I think it's a big deal -- is that these terms are not well defined. We can't impose order where there is disorder. It's one of the reasons we don't see dictionaries clearing this up for us. It's inherently unclear, because the experts use the terms in all sorts of different ways. So be it. Just give the reader examples of each different usage, and don't try to rationalize it. It's like English-language spelling reform. A great idea to fix the confusion, but it's not Wikipedia's role to do that.

Wikipedia:Article size says that perhaps at 6,000 to 10,000 words, spwawning sub-articles per Wikipedia:Summary style is in order. Currently it's only 945 words 1/10th, or perhaps 2/10ths as much as the rough maxim. So splitting should be off the table. When the article grows to at least five, even ten times, it's current size, then we can talk about splitting it up. --Dennis Bratland (talk) 15:55, 3 July 2012 (UTC)

I'd not heard of "skunked" before, but would agree that this is just what has happened here.
Given the current articles, I'd prefer to see them merged into one. Clearly we will always need something that sits at the top level of "Engines with two cylinders that aren't Vs".
I'm not against other articles, but this is on scope for readers, not for size. Transverse twin motorcycle engines has a sensible scope and target readership, and could make quite a good stand-alone article. Also 360° four stroke twins is a narrow, but interesting niche. Both would be there because there's need for that article specifically (and so they'd probably be written from scratch), not just to split off content from a larger parent. Andy Dingley (talk) 16:09, 3 July 2012 (UTC)
Are there any ISO, JIS, SAE, EN, or DIN glossaries or vocabularies on engine configurations from which a convention can be established? Sincerely, SamBlob (talk) 16:22, 3 July 2012 (UTC)
The trouble is, there are probably several. Nor would a clear source for these engines being called "stereo pairs" in one unimpeachable source remove the situation that they're also called by the problem terms in other sources. Andy Dingley (talk) 16:33, 3 July 2012 (UTC)
I am sorry but straight two is contentious. No one uses it. Twin or two cylinder, yes; two, no.
The bottomline is,
a) there just isn't the weight of references to support "straight two" or "transverse twin motorcycle engine" and policy states "Recognizable, Natural, Precise, Concise and Consistent". The industry and authors have gone with parallel twin. Even if an engineering institute had their own, it would not pass the first two.
b) if we go back to the original establishment of this topic [9], it does not exactly reek of inspiring competence, does it?
Lastly, I'd really like to know just how the jump in the engine configuration template codification some anonymous editor made, here from here and where it came from? In English, common use has always been twin, triple, inline-four, straight-six and eight (from the Daimlers), never twos. --Bridge Boy (talk) 21:52, 3 July 2012 (UTC)
Actually, straight two is used. Here is the DK cite again:
  • Car: The Definitive Visual History of the Automobile. p. 156. "Origin Germany/Australia Engine 392 cc, straight-two Top speed 65mph (105km/h)" and 17 other instances.
  • I cited Mark Tuttle in Rider above to show that parallel and inline are used interchangeably. Mick Walker, too, uses them interchangeably.
  • The OED says: straight eight n. Mech. (a motor vehicle having) an internal combustion engine with eight cylinders arranged in a straight line; freq. attrib.; similarly straight four, straight six; (cf. in-line adj. 1a). (citation: straight, adj., n., and adv. Second edition, 1989; online version June 2012. accessed 03 July 2012. Earlier version first published in New English Dictionary, 1917.)
  • Under inline the OED says:

a. Applied to internal-combustion engines in which the cylinders are arranged in one or more rows (in contrast to radial engines); usu. restricted to those in which the cylinders are vertical (so excluding V engines). Also ellipt. or as n.

  • 1929 V. W. Pagé Mod. Aviation Engines II. xlvi. 1886 Engines of the in-line type and both static and rotary radial two cycle forms continue to receive attention.
  • 1934 Discovery Dec. 353/1 The tendency..is to develop..the large in-line engine.. composed of four banks of cylinders forming an H, and the corresponding radial engines with two circles of cylinders one immediately behind the other.
  • 1949 I. Katz Princ. Aircraft Propulsion Machinery i. 13 The principal cylinder arrangements are: 1. Inline—Single crankshaft, one cylinder bank, one piston per crankpin. 2. Inline-inverted—Inverted version of inline to ease problems of installation and facilitate larger propeller swing in small aircraft. 3. Opposed-cylinder... 4. V... 5. V-inverted [etc.].
  • 1958 R. D. Blacker Basic Aeronaut. Sci. ix. 145/2 In-line engines consist of one or more lines of cylinders placed one behind the other. The rows of cylinders may be arranged in an ‘X’ or ‘V’, as well as in a single line.
  • 1961 J. Mackerle Air-cooled Motor Engines x. 200 Twin cylinder engines are arranged in in-line parallel twins, V engines or horizontally opposed.
  • 1969 K. Munson Pioneer Aircraft 1903–14 22 Wright Flyer III, ca. summer/autumn 1905. Engine: one 20 h.p. (approx.) Wright 4-cylinder water-cooled in-line.
  • 1970 Commercial Motor 25 Sept. 56/2 A 370 bhp version of the Cummins 335/350 bhp six-cylinder in-line was in production.
  • 1971 P. J. McMahon Aircraft Propulsion xi. 312 By the early 1930s..the inline vee..was beginning to offer strong opposition.
  • 1971 P. J. McMahon Aircraft Propulsion xi. 312 Even though the radial made a comeback..the inline always had this fundamental advantage of a lower frontal area.
The cite for that is: in-line, n. and adj. Second edition, 1989; online version June 2012. accessed 03 July 2012. First published in A Supplement to the OED II, 1976.

The OED says nothing about engines under parallel. They only mention straight and in-line.

Nice try, but no. Sorry, no.--Dennis Bratland (talk) 22:27, 3 July 2012 (UTC)
You state again that "Mick Walker, too, uses them interchangeably" but I have shown you above how, in the references you gave, Mick Walker is using "inline" for an inline-twin engine, e.g. the Rota 256 or Kawasaki KR250. Both are inline-twin engine.
In the discussion above, I have evidence that the world's leading major manufacturers refer to transversely mounted two-cylinder engines as "parallel".
If we go one step further, and we look at how Mick Walker describes the Kawakasaki KR1, he calls it a "parallel twin",[10]. You can see am image of the engine configuration, here [11] or here [12].
You will notice that the KR250 street bike and racers [13], which Walker describes as "inline" have cylinders arranged front and rear; whereas the KR1s, which Walker described as "parallel" have the cylinders mounted side by side.
Perhaps you can explain to us how they are the same?
For the sake of non-technically minded editors, these are images of the two different engine configurations.
  • Comparison of two separate engine designs
  • Parallel twin - side by side
    Parallel twin - side by side
  • Inline twin - for and aft
    Inline twin - for and aft
  • Parallel twin - side by side
    Parallel twin - side by side
  • Inline twin - for and aft
    Inline twin - for and aft

(I am limited by the choice of available images on the Wikipedia)

--Bridge Boy (talk) 08:57, 4 July 2012 (UTC)

360 vs. 180 vs. 270: What do the thumbnails illustrate?

In the section titled "Motorcycle use" there are thumbnails showing a Norton Commando as an example of a 360° engine, a Honda CB450 as an example of a 180° engine, and a Yamaha TRX850 as an example of a 270° engine.

What are these thumbnails supposed to illustrate? The difference between the engines cannot be seen in static photographs of fully assembled engines, let alone fully assembled motorcycles.

I suggest these "examples" of different crankshaft configurations be replaced with one photograph of a motorcycle with a straight twin mounted across the frame. The Commando photo might be good enough for this purpose to be retained, but if a better picture of a motorcycle with a transverse straight twin is in Commons it should be used instead.

Sincerely, SamBlob (talk) 15:50, 23 September 2012 (UTC)

Good point. OK with me. --Biker Biker (talk) 16:26, 23 September 2012 (UTC)

Missing archive

Talk:Straight-two engine/Archive 1 I knew the page had been archived, but I couldn't find the link in the header. Sincerely, SamBlob (talk) 08:02, 16 December 2012 (UTC)

Fixed - the bot was archiving to the wrong place. I moved the archive and tweaked the bot instructions. You can now see Bridge Boy's bollocks in all its glory. --Biker Biker (talk) 08:17, 16 December 2012 (UTC)
And I just did a manual archive to Archive 2 for good measure as one hadn't bee done since July. --Biker Biker (talk) 08:22, 16 December 2012 (UTC)
Thank you. I am also thankful that what you have described is not literally so; I'd rather not see those. Sincerely, SamBlob (talk) 11:05, 16 December 2012 (UTC)

Proposed change of thumbnail in the "Automobile use"

Straight-twin engine mounted in a Subaru Sambar

Proposed thumbnail:

  • More compact
  • Clearly shows two plug leads
Longitudinal straight-twin engine at the rear of a Fiat 500

Existing thumbnail:

  • Shows engine relative to car
  • Two branches of the exhaust manifold can be seen, although one is obscured by shadow
An alternative pic of the Fiat 500 engine

Another alternative:

  • Shows context
  • Fewer shadows, clearer view of the engine

Please give your opinion on this proposed change of thumbnail.

Sincerely, SamBlob (talk) 02:45, 20 May 2013 (UTC)

  • support The old Fiat 500 engine is one of the canonical examples of this rare use, older engines look less like smooth square boxes and this image does show the detail features as you describe. Andy Dingley (talk) 08:51, 20 May 2013 (UTC)
Based on your statement, I am not sure whether you support the change (replacing the Fiat image with the Subaru image) or you support keeping the existing thumbnail (i.e. keeping the Fiat image). Sincerely, SamBlob (talk) 13:42, 20 May 2013 (UTC)
Oh, opppose then. I can't imagine, other than simple WP:RECENTISM, why anyone would want to remove the Fiat image in favour of some anonymous box. Andy Dingley (talk) 17:12, 20 May 2013 (UTC)
Because the "anonymous box" has two plug leads coming in to show that the engine has two cylinders side by side while it's very hard to see any indication that the engine in the Fiat is a straight-twin. Sincerely, SamBlob (talk) 18:01, 20 May 2013 (UTC)
When you said "two visible plug leads" I assumed you meant the Fiat. Andy Dingley (talk) 19:28, 20 May 2013 (UTC)
No, I did not mean those long cables in the original Fiat picture where one can't tell where they come from or where they go. Sincerely, SamBlob (talk) 09:40, 21 May 2013 (UTC)
I don't think that picture is "slightly better"; I think it's much better. Sincerely, SamBlob (talk) 09:40, 21 May 2013 (UTC)

Parallel twins & V-twins compared.

Re: SamBlob's edit of 00:04, 18 January 2014‎ "It depends on one's point of view": The parallel twin is lighter than a V-twin and narrower when viewed along the crankshaft, allowing a lighter frame and shorter wheelbase if placed across the frame, or a narrower frame if placed in line with the frame. I accept all that you say, but I feel it is perhaps unnecessary. First "than a V-twin" is superfluous, since all the bullet points in this paragraph compare parallel-twins to V-twins. Secondly, apart from the Sunbeam S7 & S8 and some racing two-strokes, there are so few examples of parallel-twin engines in-line with the frame that perhaps they should be in a post-script, since this paragraph essentially compares the conventional V-twin and the across-the-frame parallel-twin. I've done a rewrite that I hope covers your view. Arrivisto (talk) 12:35, 18 January 2014 (UTC)

First of all, when one looks at an engine, what is "width" and what is "length"? As far as I understand, "width" is the distance across the crankshaft while "length" is the distance along the crankshaft. Therefore, a V-twin will always be wider than a straight twin but can, depending on design, be a lot shorter.
Secondly, I had thought that the list included flat-twins as well, and I still think it should. The original subheading was "Advantages in motorcycle use" and meant advantages over both V-twins and flat-twins. This might best be dealt with using a table.
That's all I can think of saying right now. There might be other objections but they haven't come to mind yet.
Sincerely, SamBlob (talk) 16:42, 18 January 2014 (UTC)
There's a lot of work gone into the new table, so bravo! But I do miss the straight V-twin / transverse parallel-twin comparison, as they are competing layouts. In the 1950s, the majority of British big bikes (BSA, Triumph, AJS, Matchless, Norton, etc) were parallel twins, but in recent times V-twins seem to have become regarded as the optimum layout. The parallel Yamaha TRX850 (my favourite bike) has a following, but it didn't sell well. I'm not biased against V-twins, having had five (two Ducatis, an Aprilia, a Guzzi and a Hesketh); but the fact that the new Norton Commando and the big Triumph Thunderbird are both 270° parallel twins shows there's life yet in that format. Arrivisto (talk) 19:15, 19 January 2014 (UTC)

Parallel twins & Straight-twins

I'm happy with the name "Straight-twin engine" for the page as a whole, but wouldn't it be better to use "parallel-twin" in the motorcycle section? In the UK, "parallel twin" is the standard term, and I personally have never heard anyone use "straight-twin" in respect of motorbikes. Is it an American usage? Arrivisto (talk) 19:12, 19 January 2014 (UTC)

There is disagreement as to whether the term "parallel twin" refers to all straight-twins in motorcycles or whether they only refer to straight-twins running across the frame (i.e. transversely mounted straight-twins). Sincerely, SamBlob (talk) 22:59, 19 January 2014 (UTC)
As I understand it, UK usage is that "parallel-twin" does indeed apply only to transversely mounted engines; the others are "inline twins". Arrivisto (talk) 01:25, 20 January 2014 (UTC)
Longitudinal inline engines (of any number) are so rare for motorbikes that there's no credible claim that one term is used in preference to another. "Inline" is probably the most common for longitudinal engines in cars and "straight" is certainly used too.
In the UK, "parallel twin" still has a use, IMHO a majority use, to indicate the 360º four stroke twin, whether transverse (all those I can think of) or possibly a longitudinal layout for them. Andy Dingley (talk) 02:10, 20 January 2014 (UTC)
I'd really, really like to find some way to put these semantic issues to rest. There's no dispute that 360° and 180° engines exist. Transverse and longitudinal crankshaft engines exist. The physical traits that distinguish them are not in dispute. But we keep seeing debate over what we must call them. Isn't it enough that we inform readers what the various uses of the terminology are, as we do in Straight-twin engine#Terminology? What more needs to be done? To what purpose? --Dennis Bratland (talk) 02:43, 20 January 2014 (UTC)
Agreed, Straight-twin engine#Terminology does indeed cover the points. Probably no more needs to be done, now that the headings of the new "Comparison of twins in motorcycle use" table have been made clearer. Arrivisto (talk) 11:29, 20 January 2014 (UTC)

Lead sentence

The lead says a straight-twin has "its pistons connected to a common crankshaft". Does this mean anything? Surely it can be described rather better? Arrivisto (talk) 10:52, 18 April 2014 (UTC)

It differentiates the straight-twin from the tandem twin, the latter of which is basically two singles with their crankshafts geared or otherwise linked together. Sincerely, SamBlob (talk) 14:37, 18 April 2014 (UTC)
Why, in the introduction to a common type, is it necessary to distinguish it from an obscure type that's barely mentioned in the whole article? Andy Dingley (talk) 15:24, 18 April 2014 (UTC)
From WP:BEGIN: "If its subject is definable, then the first sentence should give a concise definition..." Isn't the common crankshaft part of the definition of a straight-twin? Sincerely, SamBlob (talk) 17:15, 18 April 2014 (UTC)
Also, if we ask why it's necessary to distinguish it from an obscure type, I'd ask, "why even have a whole article about straight twins?" If we accept the premise that there needs to be a whole article delineating all the frankly obscure minutiae that defines a straight twin, why arbitrarily draw the line at any defining characteristic? From the point of view of a car-centric world, straight twins themselves are not at all common anyway. It's basically recentism as well; many of the engine configurations we consider common are only common in recent times; in earlier times (as well as other vehicle types, like airplanes, or watercraft) other engine configurations were more common. --Dennis Bratland (talk) 17:43, 18 April 2014 (UTC)
In response to: ""why even have a whole article about straight twins?"", I suggest, "because it serves a useful purpose". The page has existed for more than a decade, and numerous editors have considered it worth their time to add their halfpennyworth. "From the point of view of a car-centric world, straight twins themselves are not at all common anyway." Perhaps, but why not look at it from the point of view of, say, motorcycles? To allege recentism smacks of semantics. The significant Edward Turner engine came about almost 80 years ago; that's just about half of the history of the internal combustion engine in motor vehicles! Hardly recent! Maybe there should be more material on "airplanes & watercraft". Arrivisto (talk) 15:25, 19 April 2014 (UTC)
"Because it's useful" is considered begging the question by Wikipedia's standards; you must still give reasons why it's useful. In contrast, recentism, as well as other kinds of systemic bias are valid arguments. In any case, my point is that it is arbitrary to say on the one hand you like being able to give all these details about straight twins, but then for no clear reason you want to prune out a meaningful part of how straight twins are defined. If it's useful, if readers come to this article because they want to understand exactly what a straight twin engine is, because they didn't get enough detail from Multi-cylinder engine, then we shouldn't hold back. Not without a clear reason. Give them the complete definition, not just a selected piece of the definition right in the lead. It goes all the way back to WP:OBVIOUS: tell the reader exactly, not just approximately, what the subject of the article is, right up front. --Dennis Bratland (talk) 19:39, 19 April 2014 (UTC)

Yes. Elinetom (talk) 15:09, 2 March 2016 (UTC)

Comparison of twins in motorcycle use

The table "Comparison of twins in motorcycle use" may be a good idea, but there are some issues. First, there are no references, although perhaps that isn't a major problem as most of the "facts" are common-sense observations. Secondly, however, some of these observations are questionable. For example: (i) BMW-type flat twins are said to have a high cost, whilst Guzzi-type twins have a medium cost. Surely their costings are near identical (both high)? (ii) BMW-type flat twins and Guzzi-type twin hare both said to have a CofG "Limited by need for cornering clearance for wide engine". True for the BMW, but NOT for the Guzzi; I doubt if anyone has ever grounded a Guzzi's cylinder head without crashing! (iii) The parallel twin has this claim "Narrow engine gives short wheelbase". This is not true, as narrowness is immaterial to wheelbase. (iv) The Harley-type V-twin is said to have the possibility of "one block" rather than two cylinders. The included angle would have to be tiny, say 10°. Are there any such engines with a single block? (v) There is no mention of the relative ease of siting of carbs, ancillaries and exhausts. --- I propose to leave these point for talk discussion, and if there is an agreeable response (or a nul response) I will make appropriate changes. Arrivisto (talk) 16:06, 12 April 2014 (UTC)

1. Ah, but Honda CX engines weren't that high-cost, were they? However, I see your point and I have changed these from "Medium" to "Medium to high" for V-twins.
2. Perhaps, as a Guzzi is probably better in this regard than a four-across-the-frame UJM. However, the problem would increase with V-angle; the Honda CX engine actually had an 80° angle to reduce the risk of grounding. A wide-angle V would have a greater problem with this.
3. If an engine is placed in a motorcycle frame with its crankshaft transverse to the frame, it is the width of the engine (i.e. the maximum distance across the line of the crankshaft) that becomes a limiting factor for the wheelbase, not the length of the engine (i.e. the maximum distance along the line of the crankshaft). A narrow engine placed sideways in a bike will allow a short wheelbase.
4. I see where this would cause confusion and have changed "one block" to "one casting" in these instances. This is where the money would be saved on a V-twin or straight-twin; the use of a single casting for the engine block, whether with one bank or two. This is generally not done with flat engines, which have at least two blocks with a central, built-up crankcase.
5. Feel free to make any additions regarding relative ease of siting of carburettors, ancillaries, and exhausts.
Sincerely, SamBlob (talk) 21:48, 12 April 2014 (UTC)
"Ah, but Honda CX engines weren't that high-cost, were they?" Apples & oranges! If BMW made a Guzzi-type V-twin, it would be just as expensive; and vice-versa (if Guzzi made a flat-twin).
"Honda CX engine actually had an 80° angle to reduce the risk of grounding". Not so. First, there is absolutely no way to ground a CX's cylinder heads without crashing, especially as (with the transmission beneath the engine) the cylinders were higher than, say, on a 500cc Guzzi. The 80° was chosen over the more usual 90° to keep the engine & carburretors from interfering with the rider's legs; the heads were twisted for the same reason.
"(I) have changed "one block" to "one casting"". I repeat, "Are there any bike V-twin engines with a single block? " I know of none.
I accept your other points. Arrivisto (talk) 18:33, 13 April 2014 (UTC)
Is there one single citation to support any of these claims abut what is an expensive or inexpensive engine to build? It looks like pure original research. Why don't we delete the entire table, per WP:V and WP:NOR. I find it patently absurd to compare the costs of a massive, diverse multinational like Honda with a tiny boutique operation like Moto Guzzi. Or even BMW Motorrad, much smaller than Honda but much larger than Guzzi. The comparisons almost make sense if you restrict only comparing Honda with Honda, but even then I want to see sources first. I bet Kevin Cameron's columns would be a good place to start. Move the table in the Draft namespace, or here on the talk page. We can always put it back if good sources are found later. --Dennis Bratland (talk) 19:04, 13 April 2014 (UTC)
As you are probably aware, there was (in January 2014) a paragraph named "Parallel-twins and V-twins compared". This was deleted and the more comprehensive table of comparisons was constructed. I'm not sure that was necessarily a good thing, but most of its contents appeared reasonably sensible. But as I observed in the first line of this section, there is indeed an absence of references. I'm not sure that matters much if one is saying "the bleeding obvious"; but some of the items in the table are contentious and probably should be referenced or deleted. Arrivisto (talk) 20:03, 13 April 2014 (UTC)
In response to these comments, I have removed the "Cost of construction" row from the table. I have also added citations for most of the statements made about flat-twin motorcycles and those made about air cooling of V-twins. They weren't hard to find; they were already in their respective articles. I will look for more references, particularly on the Zündapp KS601 wide-angle V-twin. Sincerely, SamBlob (talk) 14:43, 14 April 2014 (UTC)

Surely most would regard the Zundapp as an unusual variant of a boxer twin? See: http://www.motorcycleclassics.com/classic-german-motorcycles/1942-zundapp-ks750.aspx#axzz2zLkm0cZK It seems to be stretching a point to call it a "wide-angle V-twin." Arrivisto (talk) 16:29, 19 April 2014 (UTC)

For whatever reason, the Motorcycle Classics site does not seem to be available at this time. I remember reading their description of the engine as a flat-twin with each bank raised upward by five degrees for better ground clearance.
On the other hand, there is this quote: "The Zundapp (sic) was powered by an air-cooled 170-degree V-twin that was very similar in design that was very similar in design to the BMW boxer twins" - Gantriis, Peter; Von Wartenberg, Henry (2008). The Art of BMW: 85 Years of Motorcycling Excellence. MotorBooks International. p. 80. ISBN 978-0-76033-315-0.
This opens a lot of questions: Does a boxer have to be 180 degrees? Is a 170-degree engine a flat-twin or a V-twin? What are the limits of a flat-twin, or of a boxer?
Then there's the biggest question of all: What do the reliable sources say? I am not sure there's a source that includes "more or less" in defining the flatness of a flat engine.
Sincerely, SamBlob (talk) 21:54, 19 April 2014 (UTC)

< Are there any such engines with a single block? > Matchless Silver Arrow 86.130.154.30 (talk) 14:10, 4 October 2018 (UTC)

Parallel twin

I started to try to correct the damage done by the Norwegian IP, then looked at the Indian website that gives a definition of parallel twin as where the pistons on a 360 degree crank move in unison. Alleluia! For 55 years I have been under the impression it was the cylinder centrelines that were parallel to each other. Thank goodness for the unregulated internet for putting me right - it's the crank throws that are on the same centreline. If it's published - with a copyright footer - it's good enough for WP. I give up, off my watchlist. Come back Bridge Boy... don't think so - 69 years old and just bought into a new business after a few years of semi-retirement.--Rocknrollmancer (talk) 02:16, 22 January 2020 (UTC)

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