Talk:Flat-twin engine/Archive 1

Archive 1

Archive 2

Why are they called "boxer"?

Why the hell are they called "boxer" Litch 22:23, 23 September 2006 (UTC)

Because they are on the same line and their movements against each other simultaneously are reminiscent of boxing. 91.127.249.121 (talk) 09:38, 2 March 2010 (UTC)

Transverse vs Longitudinal

All this talk of "transverse" and "longitudinal" reads badly. The "Boxer" BMW uses a longitudinal crankshaft, but the engine is fitted across-the-frame (ie transverse). If we're to carry on calling it "longitudinal" (and it's a bit late to change the terminology now) then we need to make it clear that it's the crankshaft that is "in-line".

The better alternative (since almost nobody these days ever sees the inside of an engine, let alone splits big-ends) might be to call the "Boxer" an "across-the-frame" design and the over-heating experiments "fore-and-aft". That might appear not to solve the problem, since we have nothing left to describe the UJM (*). But we (wrongly!) call those "in-line fours" anyway, which is a relatively easy concept for modern peoples to understand.

• UJM - Universal Japanese Motorcycle. TomRawlinson 09:30, 23 April 2007 (UTC)

Citroën 2CV

The production of the Citroën 2CV started in the late 1940's. It was introduced to the customers in 1948. Its development started in the 1930's. The early prototypes used a BMW flat twin. Later a own developed flat-twin was used. —Preceding unsigned comment added by 213.84.254.212 (talk) 18:50, 15 March 2008 (UTC)

Air Cooled versus Water Cooled

"Advocates of these air-cooled engines[who?] remind us of the large number of car break-downs directly caused by failures of the water-cooling, and also the big penalty in weight."

The sales literature for the Citroën 2CV certainly made this point, so the answer would be Citroën. I don;t have a copy to make a citation though. —Preceding unsigned comment added by 213.48.150.168 (talk) 09:06, 8 October 2008 (UTC)

Can the opinion of a document that exists to sell a product really be trusted? Respectfully, SamBlob (talk) 03:35, 3 November 2008 (UTC)

Yes, when the details are as obvious and straight-forward as this. Air-cooled engines are indeed lighter and have less to go wrong - and they don't heat the inside of the car very well. It's questionable how much space we give to the air-cooling connection (and how much mention we can/should make of flat-fours), but there's no problem with the information itself. TomRawlinson (talk) 23:18, 23 December 2008 (UTC)

There are a couple old VW ads for the original air cooled Beetle that claims improved reliability over larger water cooled vehicles by showing a VW Beetle. In one of these commercials a man with an overflowing radiator hitches a ride with a passerby driving a VW Beetle.

Balance and Smoothness

In line with the templatse of other engine configurations this page should have a section on Balance and Smoothness 213.48.150.168 (talk) 09:11, 8 October 2008 (UTC)

Rewrite and reasons

The best known example of the flat-twin engine is the 'traditional' BMW motorcycle. - If this is true, then it should not be difficult to find a credible source stating this. Since none is stated, this is gone.

This geometry gives (uniquely, among twin cylinder engines) virtually perfect horizontal and vertical balance. There remains a vibrating torque reaction which is noticeable at low engine revolutions, and a torque reaction when, for instance, changing gear. - Not only is this rather badly formatted, but also, once again, no citation is stated for this. Since this is a technical matter and not one of being "well-known", it might be more difficult finding a credible source to back this up. Actually it might be impossible, since the least complicated engine without primary or secondary unbalanced forces or moments is the straight-6 engine, and the torque reaction is largely due to the longitudinal engine and the shaft drive rather than anything inherent in the flat-twin engine. I'll give it seven days anyway. Good luck.

(BMW has supplied police motorcycles all over the world since the 1950s - in the last two decades some forces have moved away from this traditional "Boxer" layout, but it remains popular in the leisure market and many authority markets). - This has no real bearing on the merits or demirits of the flat-twin engine, as the move away from traditional BMW bikes may be for other reasons.

"Automotive use" has been reduced to a partial list of flat-twin cars. If any of those advantages and disadvantages can be backed up with reliable sources, put them back in and cite the sources.

Respectfully, SamBlob (talk) 03:34, 3 November 2008 (UTC)

I've edited this again, before noticing that you've commented. I agree there was excessive mention of the BMW, but I still feel that this is the most accessible example to the reader. (Actually, there are better photos available and already used in other articles).

I can cite numerous motorcycle magazines that discuss the odd characteristics of a flat twin mounted in a motorcycle engine, but there seems little point in getting these things out of the loft in order to do so. Both the tick-over and torque effects are significant and very, very well-known.

I'd struggle to find references for the "mechanical noise" and "lousy heating" associated with the use of flat-twins in cars (ie pre-war and early post-war European) but there's nothing the smallest bit contentious about that information. TomRawlinson (talk) 22:25, 5 November 2008 (UTC)

The BMW boxer may be the most accessible example to the reader (more so than a Citroen 2CV, I would suspect), but when one sees superlatives in articles one expects some source to back them up. Just because neither you nor I know a more famous example of a flat twin engine doesn't mean there isn't one. There must be some source to back that statement up, and the one I used does not state that and should have been removed along with the statement it actually verified.

The statement about "virtually perfect horizontal and vertical balance" is in even greater need of citation because, not only is it an unsourced statement, it is a statement I personally do not believe. I was taught at university that the least complicated engine without primary or secondary unbalanced forces or moments is the straight-6 engine. For this one I really need to see a citation to an iron-clad reference.

Further, I am really not seeing the relevance of the police use of BMW boxer bikes to the subject of flat twin engines any more than I see the relevance of the British police use of Velocette LEs to the subject of water-cooled engines. (Interestingly enough, though, Velocette LEs were also flat twin bikes with shaft drive.)

I think I shall request a peer review so that people more qualified than me can tell you how bad this article is and what is needed to improve it.

What I will do quite immediately, though, is replace the weasel words tag that I removed after I rewrote the article the first time. The "Many motorcyclists appreciate..." line is a classic use of weasel words and, until there is a cited reference stating who these "many motorcyclists" are and what they actually appreciate, it has no place in a Wikipedia article.

Respectfully, SamBlob (talk) 23:08, 5 November 2008 (UTC)

I did, and got, MechEng at UC Cardiff - and engine balancing was mentioned in passing. However my source for saying "flat twin almost perfect primary and secondary balance" comes from motorcycle magazines. But you can immediately figure that the flat-twin has got to be better than even the straight-6, since the reciprocating parts are in (almost) perfect alignment. The torque reactions (tick-over wobble, gear-changing twist) may be less obvious, but every road-test of a flat-twin (ie BMW in modern conditions) motorcycle mentions them. And it's intrinsic to the layout.

As regards the police motorcycle thing, that needs writing to anything you consider fit. I'd argue it's the most accessible, but it's no longer general, so an outside review may be order. TomRawlinson (talk) 21:23, 8 November 2008 (UTC)

An analysis of the balance of a boxer twin: http://www.timberwoof.com/motorcycle/Flat-TWIN-7.html

Flat-twins and flat-fours have unbalanced moments that rock the engine. Properly-designed straight-sixes and flat-sixes do not, and they also do not have unbalanced forces.

However, if you have the magazines around that make those statements, then by all means cite them as sources.

BTW, my BSc. Mech. Eng. was from UWI St. Augustine.

Respectfully, SamBlob (talk) 02:16, 22 November 2008 (UTC)

I have added citations and rewritten the text to match the information (but not the actual wording) stated in the cited sources. Based on this, I can remove the weasel words tag and maybe the citations tag (although there are still uncited statements in the article), but I won't, at least not until I am fairly sure that the changes are stable and the weasel words won't come back. I've been stung like that before on this article. Respectfully, SamBlob (talk) 01:54, 22 December 2008 (UTC)

Obvious? If so, someone should have mentioned it somewhere...

The trouble with most folks ain't so much their ignorance, as knowing so many things that ain't so. - Josh Billings

The good Mr. Rawlinson likes to throw the term "obvious" around as a reason for deleting citation request tags. Perhaps he should take a look at one of the statements he considers "obvious" and beyond the necessity of citation:

The layout lends itself particularly well to air-cooling, either natural or forced (common in motorcycles and cars respectively).

If by this he means the layout of the flat-twin engine itself, then there is evidence in the article itself that shows this not necessarily to be the case. The flat-twin engine that allegedly "lends itself particularly well to air cooling, either natural or forced," did not do so in the Helios motorcycle and may also have been troublesome in the Douglas and Harley-Davidson motorcycles with similar positioning of their flat-twin engines.

Holding truths to be self-evident may work in political documents, but encyclopedias require sources. Respectfully, SamBlob (talk) 00:56, 24 December 2008 (UTC)

The worth and readability of this article is not greatly enhanced by slapping it with tags. Especially regarding article fundamentals so self-evident that few regular authors will ever have bothered to state them, taking the intelligence of their audience for granted. The flat twin lends itself particularly well to air-cooling - the fact you can also make a flat-twin that is not properly cooled is a piece of synthesis, as we're specifically told to avoid. Raising such an objection will make people wonder what other harm poor reasoning skills can do to articles. Respectfully, TomRawlinson (talk) 12:11, 24 December 2008 (UTC)

We want to include sourced facts, not reasoning skilled or otherwise. I own four air-cooled vehicles. Three front-engined ones have excellent cabin heating, only the rear-engined VW has a problem - conversely the VW cabin is extremely quiet, since the engine, if noisy, is well behind it. Are my poor reasoning skills keeping me warm? The article won't be slapped with tags for long - unless those statements are sourced soon, they're coming out. -- Ian Dalziel (talk) 16:23, 24 December 2008 (UTC)

Torque reaction

There remains a vibration which is noticeable at low engine revolutions, and a torque reaction when changing gear.

Is this torque reaction due to the motorcycle being powered by a flat-twin, or is it due to the shaft drive? Don't the Moto Guzzi V-twins and the Honda ST1100/1300 V-Fours have this problem as well? Respectfully, SamBlob (talk) 19:20, 3 January 2009 (UTC)

Longitudinal crankshaft. There is a tendency for the crankshaft to remain fixed in place and the engine to revolve (rotate? I always get those two confused) around it. So yes as to the Guzzis and the Hondas, but unless we have a control specimen that is a longitudinal-crankshaft chain-drive layout, we can't lay them blame at the door of the drive shaft. That said, there would also be a tendency for the drive shaft to stay fixed in place and the vehicle to revolve (see above) about it. But I believe the experimenter can easily straddle a BMW flat twin in neutral and blip the throttle. Note that some bikes (Gold Wing for a start IIRC) deliberately had some counter-rotating components such as the alternator to null out the torque reaction.

What used to ping my weirdometer when I first rode my R65 back in 1983 was that the rear end tended to climb under acceleration. That was the shaft drive in operation - specifically, trying to climb up the rear bevel. Odd sensation the first few times, and then the brain just filtered it out. Captain Pedant (talk) 12:24, 14 May 2012 (UTC)

Temperature difference vs. temperature value.

User:TimTay changed the written conversion in the text to the "convert" template, resulting in this: "100 °F (38 °C)"

I shall now demonstrate why this does not work for temperature differences, as the phrase "...maintained an oil temperature 100°F cooler than..." implies.

Let us assume that the hotter temperature is 200°F. Using the template will give us 200 °F (93 °C)

Then let us assume that the cooler temperature is "100°F cooler than" that, or 100°F. Using the template will give us 100 °F (38 °C)

Subtracting the cooler temperature from the hotter, we get a temperature difference of 100°F, but the difference between the conversions is 55°C. Using decimal places in rounding would give a value closer to the 55.55555... that the difference in °C would actually be.

This is because the conversion of temperature value is Value in degrees Fahrenheit = ((5/9) * Value in degrees Celsius) + 32, while the conversion of temperature difference is Difference in degrees Fahrenheit = (5/9) * Difference in degrees Celsius.

I hope I have made my point clearly.

Respectfully, SamBlob (talk) 12:50, 8 January 2009 (UTC)

Good point. I'll change the same item in History of BMW motorcycles if you haven't already. If only everyone in the world would use proper temperatures then this wouldn't happen! --TimTay (talk) 14:48, 8 January 2009 (UTC)

I fail to understand why anyone would want to use the "convert" function. It puts an unnecessary extra load on the server, it confuses the next editor - and now we discover it doesn't work reliably anyway! 86.135.5.35 (talk) 19:13, 30 March 2009 (UTC)

The convert function is great because it gives a way to get accurate values without relying on humans to perform bad math. The server load is very light- computers are GREAT at math, after all. tedder (talk) 19:20, 30 March 2009 (UTC)

Additional citations tag

The "additional citations" tag, or "refimprove" tag, has been up since September 2007. Since that time, the article has been greatly revised. The "Motorcycle use" section has only two statements for which citations are needed. the "Automotive use" section is unreferenced, but consists mainly of a list of cars with flat-twin engines with links to the cars' articles. The "Other uses" section has one sentence with two citations.

I suggest that the article is quite well cited at present and might not need the "refimprove" tag at the top, as the inline tags (and maybe a "refimprove" tag for the "Automotive use" section) might suffice.

Should we remove the "refimprove" tag from the top of the article?

Respectfully, SamBlob (talk) 17:06, 21 January 2009 (UTC)

Works for me (removing the refimprove tag). tedder (talk) 17:56, 21 January 2009 (UTC)

I think both tags can go. Article is wikified/clean(ish) and has reasonable number of references --TimTay (talk) 18:05, 21 January 2009 (UTC)

Tags removed. Respectfully, SamBlob (talk) 23:19, 26 January 2009 (UTC)

My reasons won't fit in the edit summary

This is to explain this edit (http://en.wikipedia.org/w/index.php?title=Flat-twin&diff=284816537&oldid=284788789), as all the issues I have won't fit in the edit summary:

• Please do not change sourced information from what the source says. If you have a more credible published source from a third party that says otherwise, please include that information along with your source.
• Please do not remove citation requests from uncited statements. If you have a credible published source from a third party that either confirms or contradicts what is said in the uncited statement, then rewrite it to reflect what the source says and cite the source. If you disagree with the statement or with the inclusion of unsourced statements, remove it. But don't remove the citation request without removing the statement and don't replace one uncited statement with another, especially if the initial statement has a citation request tag and the equally uncited replacement doesn't.
• How do you know that the layout is inconveniently long? Common sense (which I know isn't enough, hence the citation requests) tells me that putting a long engine along a frame will make the frame long, but how would either you or I know that the frame will be inconveniently long as a result? Again, this is where cited sources of information come in. (While I know I didn't cite my sources in this instance, I am fairly sure that sources exist somewhere and I intend to find at least one of them, although I would be grateful if someone else who has access to such a source would cite it.)
• Not everyone knows what CoG means. Either write out "centre of gravity (CoG)" the first time and "CoG" thereafter or write "centre of gravity" each time.
• The Honda GoldWing never had a flat-twin engine. I don't know of any Honda motorcycle that had a flat-twin engine, but I do know that the GoldWing never had one. Therefore, statements regarding the GoldWing's features are irrelevant to an article on the flat-twin and would be more relevant to the flat-4 (early GoldWings), flat-6 (later GoldWings), or flat engine articles. However, editorial commentary based on these statements are not welcome in the text of any article, much less in articles where the reference itself doesn't belong.
• If you naturally write phrases like "Honda do something similar in the Gold Wing..." and "Honda then gain more benefit by lowering the fuel tank...", then I suggest that you keep a textbook of English grammar by your computer at all times and refer to it whenever editing Wikipidia, or, for that matter, whenever writing business correspondence. Respectfully, SamBlob (talk) 15:18, 19 April 2009 (UTC)

1) Tell us what's actually in the source, in context. Does it really use the word "heavily" for the cooling of the front cylinder?

2) Are you challenging statements such as "the flat-twin has a low centre of gravity? If not, then there's no need for it to have{{cn}.

3) We know the "along-the-frame" flat twin is inconveniently long, because that's what the article already said, in a clumsy (and uncited) way. Much of the statement as it stood is simply wrong - a longer wheelbase has very little benefit (which would explain why it's not used in any modern motorcycle).

4) Anyone not knowing the meaning of "CoG" will be reading up knitting patterns, not technical descriptions of engine layouts. The full "Centre of Gravity" was already in that passage - we can repeat if you insist.

5) My apologies for applying a description of the considerable thought (and design and construction) that's been applied to one form of flat engine to the pared down version of the same thing. What I've written is highly relevant to this article, but should be transfered to Flat engine and linked from there.

6) And I apologise for not speaking English English the way you do, but I take some comfort in speaking British English, as this article is written in. Please answer the two questions I'm asking at the beginning. MalcolmMcDonald (talk) 20:33, 19 April 2009 (UTC)

1. Right then, the exact quote first of all:

"Politely but firmly, Friz suggested that the best thing Popp could do was to dump it in the nearest lake. Specifically, Friz felt his engine shouldn't have been mounted with the crankshaft in the transverse plane, because this left one cylinder with plenty of cooling and the other with very little. Of course, the Helios had it this way in order to simplify the gearbox for use with the usual chain drive." - BMW - Bavaria's Driving Machines, Norbye, Jan P., Beekman House New York, NY, USA 1984 ISBN 0-517-42464-9 "The Origins of BMW: From Flying Machines to Driving Machines" page 15

2. Yes I am, despite writing it myself. I believe it to be true, but I do not have a published source to verify it as yet. Apparently you don't either, or can't be bothered to look it up, because you haven't supplied a source.

3. I wrote it like that *precisely* because I did not know whether it would be inconveniently long. Would it be longer, for instance, than having a straight-4 mounted with the crankshaft along the frame... as BMW did with their K-series bikes until the 21st century? I had it there for it to be confirmed or denied by a contributor with a credible source to alter it to what the source had to say and to cite the source. Besides which, rather many modern motorcycles have long wheelbases. They're called cruisers.

4. It might come as a surprise to you, but people read encyclopedias to be informed. People who have come to be informed might not know our jargon, and might not appreciate being confused by unexplained terminology when they have come to be enlightened.

5. I still fail to see how a flat-4 or flat-6 design becomes relevant to a flat-twin article except by conjecture, especially since conjecture is not really welcome in Wikipedia articles anyway.

6. If using the present tense and first person in reporting what someone else did in the past typifies British English, then I shall throw away all my Oxford dictionaries and replace them with Webster's. Speak whatever English you like, if any at all, but please use proper grammar in editing the articles.

Respectfully, SamBlob (talk) 00:30, 20 April 2009 (UTC)

1) Thank you for the quote - now compare it with WP:RS and you'll discover no compliance, either of the source itself, nor of the use thereof. (Interestingly, your source has what I wanted to put in about the drive-train - except I'd use something technical. I'd definitely eschew a translated and imaginative paraphrase of 1,000 conversations held 4,000 miles away. Thankyou for bringing to my notice that Helios is not a valid alternative company, so the alleged conversation is actually BMW's own designer-to-be knocking a copy he made of the 1904 or 1907 work of a British company, the nation to whom they've just lost a war and ordered their top aircraft engine designer to cease this activity. No wonder he was rude about it, desperate to turn his hand back to the only thing he knows - so?)

2) Check WP:V, first principles are in the headline. "This page in a nutshell: Material challenged or likely to be challenged, and all quotations, must be attributed to a reliable, published source". Now find me anyone who would challenge the descriptor "Low Centre of Gravity" for the flat twin fitted in a motorcycle.

3) This gets worse and worse. You're now admitting adding "The length of the engine required the motorcycle to have a long wheelbase" when you don't know if that's true (and the photograph rather tends to disprove it, the motor by no means fills the space).

4) You'll startle me claiming "C of G" is "unexplained terminology" needing explanation in a technical article. This in a paragraph wherein "Centre of Gravity" has already been used. Furthermore, if I changed something like that (and I'd be very loath to do this to another editor) I'd hardly want a battle over it.

5) Now you worry me. Are you really claiming that the weight-distribution principles of the flat-engine don't apply to the flat-twin? (I should not have apologised for bringing in the flat-four/six because although it might be a bit confusing, my word-use is in fact perfectly proper).

6) Saying "Honda do" and "Honda gain" about a company and machine in current production is almost certainly the correct thing to do. Well, in the English we're enjoined to use in motorcycle articles, anyway. I'm sure you'll bring me up to speed if I'm wrong, just as I'll help you with WP rules if you trash them. On the other hand, I might just decide you're really challenging me to a show-down to see which of us has most authority, most friends and most time to waste. MalcolmMcDonald (talk) 07:37, 20 April 2009 (UTC)

Resetting the indent

• 1. The Helios was initially made by Bayerisch Flugzeugwerke (BFW) using engines purchased from BMW. When BFW was merged into BMW, Popp asked Friz to assess how the Helios could be improved. Friz gave his assessment as stated above. Popp, with too much inventory to take Friz's initial advice, then asked Friz to make whatever short term design changes he could to the Helios and to design a new motorcyle, which ultimately resulted in the R32. And I would more believe a book published by Jan P. Norbye than anything you or I pull out of thin air.
• 2. If someone did, could you defend it without relying on original research?
• 3. Indeed, and I shall now remove it, along with all the other uncited statements in the section.
• 4. Since you are such a believer in the rules, here's one for you: WP:PCR, and within that: WP:OBVIOUS
• 5. Weight distribution principles that apply to flat engines are relevant to all flat engines and may be placed in flat engine. Specific examples that have not been applied to flat-twin engines are not relevant to the flat-twin. After all, Wikipedia is not a technical journal.
• 6. For your information, what has already been done is in the past, and what has been done by someone other than you or me is done by a third person. The third-person past tense of "do" is "did" (in fact, past tense in *any* person would be "did") and of "gain" is "gained". Those who call themselves journalists should know that. Those who call themselves journalists and do not know that are probably not called journalists by anyone else.
• 7. I have brought your hidden statements out into the open so that I could answer them openly. I have also converted them to italics so that I can tell the open remarks from the hidden ones. A difference check will show that I have not altered them otherwise in any way. However, I answer here something you had not hidden:
  • I do not presume to have any more authority than those provided by the rules, which you seem to know well and honour greatly in the breach with your speculations and editorial commentary.
  • I neither have nor want any friends.
  • I shall do with my time as I see fit, as you do with yours.

Respectfully, SamBlob (talk) 16:12, 20 April 2009 (UTC)

Further correction: Friz was not BMW's "engineer to be". He had joined Rapp Motorenwerke in 1916 before it became BMW GmbH in July 1917. The Helios was brought into BMW when BFW was merged into it in 1922. Respectfully, SamBlob (talk) 16:20, 20 April 2009 (UTC)

I simply cannot be bothered with any of this wiki-lawyering. Statements about the natural low CoG of flat engines are good enough at flat engine without references - why are they not good enough at flat twins? Actually I can see an entire paragraph at "flat engine", telling us a second time that flat engines have low CoG - but saying nothing else that's useful or true. I'd immediately scrub that bit if it didn't threaten to set off an edit-war. Why aren't you doing something useful? MalcolmMcDonald (talk) 18:25, 2 May 2009 (UTC)

Book reference confusion and non-technical

Can someone check reference number 2? It currently says "^ a b c d e f Wilson, Hugo (1995). "The A-Z of Motorcycles" (in UK English). The Encyclopedia of the Motorcycle. London: Dorling Kindersley. pp. 26-32, 51. ISBN 0 7513 0206 6." The cite is to two books - by two different people! Roland Brown published in 1997 and re-published in paperback "The A-Z of Motorcycles" in 1999 and 2001 (it gets no Amazon reviews). Wilson's book "Encyclopedia of the Motorcycle" came out in 1995 and gets 3 fairly decent reviews (but was never re-published).

Perhaps more seriously, neither book is technical and one of the six seven claims taken from this so-called reference "disadvantage of this layout is that it exposes the cylinders to collision damage" is so misleading as to be wrong.

Unless someone currently editing now has either or both of these books and can check, it would be better to remove this reference completely. In addition, general books like these two (especially books specialising in photographs!) regularly peddle technical misconceptions. MalcolmMcDonald (talk) 08:36, 23 April 2009 (UTC)

It doesn't take much to go into the edit window and extract this: cite book|last=Wilson|first=Hugo|title=The Encyclopedia of the Motorcycle|year=1995|publisher=Dorling Kindersley|location=London|language=UK English|isbn=0 7513 0206 6|pages=26-32, 51|chapter=The A-Z of Motorcycles

From this, you see that the author of the book is Hugo Wilson, the title of the book is The Encyclopedia of the Motorcycle, and the title of the chapter is "The A-Z of Motorcycles".

If you have a more "acceptable" source that makes a contrary statement, then by all means change the article to reflect your source, and cite your source. If not, however, please leave it alone.

Respectfully, SamBlob (talk) 13:08, 23 April 2009 (UTC)

"Less informed commentators..." like the editor of Classic Bike?

In removing sourced information and replacing it with unsourced statements, User:MalcolmMcDonald states the following as his edit summary.

Less-informed commentators on flat-twin motorcycles sometimes assume that the cylinders are vulnerable to impact, when in fact they are extremely strong.

It is interesting to note that the cited source of the information that MalcolmMcDonald contradicted is a book written by Hugo Wilson, editor of Classic Bike magazine. I would like to know what credentials MalcolmMcDonald can present to show that he is more or better informed about the vulnerability of flat-twin engines with their cylinders across the frame than Hugo Wilson. If MalcolmMcDonald cannot present such credentials, then he should state the source of his information. If, as I believe, the information comes from the top of his head, then he should apologize for his unconstructive edits and endeavour not to make any more of the same. Sincerely, SamBlob (talk) 21:52, 4 September 2010 (UTC)

Motorcycling says "Start" while Automotive says "C"

It is interesting to note that Wikipedia:WikiProject Automobiles gave this article a "C" rating on the quality scale on 1 October 2008. Since then, the article has been extensively edited, unsourced statements and weasel words have been uprooted, most of the article is now cited, and the article has been divided into sections. Much of this was done before 11 August 2009, when Wikipedia:WikiProject Motorcycling gave this article a "Start" rating on the quality scale. I guess either WikiProject Automobiles overrated it or WikiProject Motorcycling underrated it.

Would it be possible to get an editor to review the quality of the article, and to include the reasoning of his/her assessment on the talk page?

Sincerely, SamBlob (talk) 15:29, 9 September 2010 (UTC)

Done- gladly. It's certainly in C territory. tedder (talk) 02:39, 10 September 2010 (UTC)

Thank you. Sincerely, SamBlob (talk) 13:09, 10 September 2010 (UTC)

Maytag Washing machines

Back in the days when a lot of people didn't have electricity at home or any experience of high-pressure, foot-in-the-door salesmanship, it would seem that some people out in the boondocks must have been sold a washing machine that, almost incredibly, was powered by an internal combustion engine. The article on Maytag (a company no longer in existence) doesn't mention it but we have to accept it's true because one (two?) personal web-sites tells us that "... pictures are of our Maytag wringer washer. We purchased it at the SIAM show in June, 2000. We already had the engine. These were sold by the Maytag Company to rural areas where there was no electricity. They were sold until the early 1950's. The motor is of Maytag's own design. It is a single cylinder two-stroke engine. Called a "Model 92" The motor we have was manufactured in March of 1934. We also have a two-cylinder Maytag which is called a "Model 72" and, very oddly, we're to be persuaded that the latter machine was in fact a flat-twin. Then we have another personal web-site that proves Maytag carried on producing engines until 1952 (but we don't know what models they were or what use they were put to).

Would it be reasonable to suggest that this information is unreliable triviality of the first order and we can take it out of the article on Flat-twin engines? MalcolmMcDonald (talk) 19:47, 27 December 2010 (UTC)

Since I an not going to buy a copy of the August 1992 issue of Gas Engine Magazine just to incorporate the information from that into this article, I shall have to continue my search for more references online. This search has found another source since the above appeal to limit the article to motorcycling and automotive uses was written. The schematic on page 11 might convince Mr. McDonald that the engine is actually a flat twin, or it might not, depending on how entrenched his obduracy is.

I cannot understand why a section pointing out that flat-twin engines were used to power machines other than motorcycles or automobiles would be considered offensive. I, for one, welcome any evidence that they have powered pumps or generators, as they appear to be quite suitable for such use.

By the way, the motorcycle manufacturer Douglas has been out of business for a lot longer than Maytag has. Should reference to Douglas motorcycles also be removed?

Sincerely, SamBlob (talk) 00:20, 28 December 2010 (UTC)

Congratulations, you've now actually found evidence that Maytag once made a flat-twin. Though not, that I can see, that it was called the Model 72 nor that it was ever used to run washing machines. Since (if we trust people's personal web-pages) they stopped making any engines almost 60 years ago and their known washing machines engines were single cylinders of 80 years ago, this flat-twin usage remains unreliable trivia of the first order. MalcolmMcDonald (talk) 09:29, 28 December 2010 (UTC)

Although I'm not familiar with a twin Maytag, they certainly had IC washing machines. If you try Usenet (of all places!), easily accessible through http://groups.google.co.uk and the newsgroup uk.re.engines.stationary I'm sure you'll find people who know chapter and verse on Maytags, and certainly Douglas twins. Andy Dingley (talk) 09:43, 28 December 2010 (UTC)

Good - when there is information on this use (and if it adds anything to the article) then we should include it. For the moment, a flat-twin powered washing machine is in the same class as Jeremy Clarkson's V8 powered food-mixer - except we have proof of the existence of the latter and video of it running! MalcolmMcDonald (talk) 10:48, 28 December 2010 (UTC)

Did you say you wanted video of it running? (YouTube video, Flash required)

Another difference is that, unlike Clarkson's beef blender that wasn't sealed properly and was dismantled to make a device to rock rocking chairs, the washing machines were put into production and sold to the public for several years.

Sincerely, SamBlob (talk) 12:29, 28 December 2010 (UTC)

Congratulations on finding someone's personal video that might be a 73 year old Maytag running - but there is still nothing to link any part of it to a flat-twin engine. Furthermore, now we've seen it in operation, it's even less likely that a horizontally-opposed twin is suitable for the space available.

Incidentally, "back in the civilised world" (his words, not mine) Clarkson indeed dismantled the V8 food blender - he built a stair lift that would propel granny towards the loo in 0.01seconds. Should I add that to the article on the V8 engine too or does this nonsense stop now? MalcolmMcDonald (talk) 17:10, 28 December 2010 (UTC)

Oh? And how many years was that stair lift in production? Oh, I forgot, it didn't work, unlike the Maytag 72 washing machine engine which, according to a magazine article now being used as a source, was being sold from 1937 to 1960, although production might have ended before 1960.

Why is it so important to you that uses other than in motorcycles or in cars be ignored in this article? It is interesting how much you scoff at the engine-powered washing machines that allowed rural households without electricity to use these powered appliances. I would think they were rather more significant to humanity in general than the two hundred or so Peel microcars powered by moped engines.

The only nonsense I can see is your continued rant, which you may stop at any time.

Sincerely, SamBlob (talk) 20:54, 28 December 2010 (UTC)

Whatever we decide about the Maytag, makers such as Douglas and Norman produced a great many flat twins as generator sets that were important during WW2, and afterwards as surplus. Andy Dingley (talk) 23:49, 28 December 2010 (UTC)

Thank-you, I would like permission to remove poorly referenced trivia, with not a single photograph to be found anywhere, from this article, but tips like yours are perhaps more valuable.

You don't think this is a sort of urban-myth, do you? One can see how the story might be handed down, but it hardly makes any sense. The last thing a washing machine needs is less vibration! Even if Maytag decided they wanted more power (why, when they were only using a small single-cylinder?) a flat-twin is the worst possible shape for the space available - see the YouTube video of a different version running. The motor fits underneath a square tub. MalcolmMcDonald (talk) 10:10, 29 December 2010 (UTC)

The "poor references" of this "trivia" now include the following:

• a magazine article: Shelton, Charles L. (1999). "Maytag Twins or 'Look-a-Likes'?" (aspx). Gas Engine Magazine. Topeka, Kansas, United States: Ogden Publications. Retrieved 2010-12-28. The twin, or 72 as it was commonly referred to, was used primarily as a source of power for the Maytag washing machines. Even as late as the early '30s, some brands of washers were hand operated; thus a ready power source such as the twin had a great deal of influence on Americans' work habits. {{cite journal}}: Cite has empty unknown parameter: |separator= (help); Unknown parameter |month= ignored (help)
• a service manual for both the singles and the twin: "Maytag Service Instructions" (pdf). {{cite web}}: Cite has empty unknown parameter: |separator= (help)

As to "not a single photograph to be found anywhere", there are four photographs in the photo gallery of the magazine reference. There are several videos of the engine on YouTube. There is at least one video, linked earlier in this thread, of the engine installed in and powering a washing machine: in fact the same video, showing the flat-twin (note the spark plug at each end) in use in a washing machine, is linked to by the editor who suggests that it is an urban myth. There may not be any photos in WikiMedia Commons. There are also no photos of Excelsior Super X motorcycles from the 1920s in WikiMedia Commons. Does that make the Schwinn-era Excelsior Super X a myth?

Although this should be enough evidence to convince a rational man, I will look for more later. Somehow, however, I doubt that even an article from The Sunday Times or National Geographic will suffice as a reliable enough source.

Sincerely, SamBlob (talk) 12:41, 29 December 2010 (UTC)

I'm going to step in with my admin hat. Please follow Wikipedia's guidelines on civility. That means to discuss the article, not the contributor. Any messages including content not following this guideline will be removed and warnings placed. Now play nice, okay? tedder (talk) 01:55, 29 December 2010 (UTC)

By your command. Sincerely, SamBlob (talk) 02:07, 29 December 2010 (UTC)

I confess I was engrossed in trying to improve the article. Can we be allowed to use our common sense and strike the very poorly referenced Maytag business? While the single-cylinder business (to my astonishment!) is well attested, we're not even offered a photo of the flat-twin arrangement. I think we have every reason to suspect a hoax. MalcolmMcDonald (talk) 10:10, 29 December 2010 (UTC)

It is very obvious that Maytag sold a twin, the model 72, for some time. It is unhelpful to still be using terms like "hoax".

We have, I think, one question remaining. Is the use of twin cylinder washing machines sufficiently relevant to an article on flat-twin engines? Anything underlying this is now established well enough for the purposes of immediate debate, even if we might still improve those descriptions for the purpose of making a better article.

Petrol-engined domestic washing machines are, I would suggest, clearly noteworthy for articles in both domestic appliances and petrol engines (at a broad level, or at the level of small engines). This is because they were common enough (i.e. sold by a well-known manufacturer) to be beyond a Rube Goldberg lash-up, but equally they're at a level of obscurity that makes them novel and interesting, beyond that for electric motors (i.e. it's not worth adding to electric motor).

Is it still noteworthy for flat twins, above and beyond that for singles. Clearly less obviously so, but I'd suggest that it still is. There are much fewer flat twins, particularly in small engines, so individual uses are more important. Also there's the question of why pay for two expensive cylinders for what is still such a small power application? Was it for doubling the capacity with existing components, or for smoother balance when running or easier starting? Andy Dingley (talk) 13:43, 29 December 2010 (UTC)

ABC engine

I'm entirely new to this and apologise if I do this wrong! Here goes ..........

The now almost forgotten All British Engine Company (ABC) used this cylinder configuration for around twenty years from 1929 to the early 1950’s. They made a series of Auxiliary Power Units (APU’s) for a variety of aircraft but the great majority were used in Short’s sea planes, the most obvious being the Sunderland Flying Boat. The units were controllable from the cockpit by a number of cabled clutches and had electric start.

Obviously, it was most important that the engines were as vibration free as possible and this was achieved by designing a crankshaft where the pistons were opposite each other, thus doing away with the rocking couple that is the source of vibration in this type of engine. The vertically-split crankcase carried the ingenious three-throw nickel-chrome steel crankshaft in large diameter ball and white metal bearings that were fitted to the crank after it was inserted into place. It featured thin section, all machined cylinders with heat-treated bores. On one piston, the Duralumin connecting rods supported the ends of the gudgeon pin outside the piston lands whilst the other single rod ran inside the other piston in conventional fashion. in such a way as to eliminate the rocking couple which plagues more mundane horizontally opposed twins.

The Mark 1 as it was known was compact, lightweight and able to supply a surprisingly varied number of services. Going into quantity production in 1932, it was an 115cc water-cooled, side valve flat twin of all aluminium construction. A dry sump engine, it was mounted on a cast aluminium oil tank that usually carried two separate chambers, one for engine & the other for gearbox oil.

Following the end of WW2, ABC’s examined various styles of engine looking for a more powerful unit to follow on from their successful range of flat twins. It is worth bearing in mind that at the time, there were several flat four motorcycle engines either produced immediately pre war like the Brough Superior Golden Dream or post war like the Wooler. Neither were ever produced in anything other than prototype numbers & some never got past drawings and the smoke from a well filled pipe! However, Granville Bradshaw was always interested in the use in motorcycles of engines produced for Government contracts in other modes of use. It seems to this author that it is not unlikely that in the atmosphere in which he worked, it seemed that another opportunity was about to present itself to turn an honest penny!

Designated the Mark Ten, a flat four APU driving a 24 Volt generator was planned and Lord Ridley was heavily involved in the design as he had been in the earlier light alloy flat twins. Smooth running, high power output and compactness were important features and aluminium and magnesium were used wherever possible, even the cylinder heads being cast in magnesium. To start with, 20 – 25bhp was considered sufficient, but as things went along, more power was expected from the design & 30 + bhp at 4,200rpm was expected.

The vertically split crankcase carried a three piece bolted up crank carrying four Duralumin connecting rods of the fork-and-blade type. These operated upon a hardened steel bush on the crankpin & the rods had Vandervell thin shell bearing caps. The case hardened gudgeon pins were retained by circlips and floated in the rod eye. The aluminium slipper pistons had three compression rings & one scraper, all above the gudgeon pin. The skirt was left thick enough to allow an extra ring to be fitted but it was never used. Looking at the sole remaining example in the Aviation Hall in the London Science Museum brings it home with something of a shock that things are not always how they appear. The cylinder blocks are in line as you’d expect, but because the pushrod tubes are so staggered, it gives the engine a curiously unbalanced appearance and might lead one to expect the cylinders to be similarly asymmetric. If you are going to look at it, it is behind Sir Roy Fedden’s post war flat six prototype engine & not especially easy to find.

The question of balance was dealt with in typical ABC fashion! In its simple form, such a design has an important couple due to the mass acceleration of the pistons that would lead to damaging vibration. Balance shafts are common practice nowadays, but were unusual to say the least - although not unknown - in 1948. By having a separate means of dealing with out of balance forces, the engine could be designed to have cylinder axies unconventionally far apart

The timing gear train included a shaft lying parallel with the crankshaft and rotating in the opposite direction to it. Out of balance masses were attached to the end of the shaft and to the crankshaft in such a way that a couple is created rising to its maximum value in the horizontal plane and falling to zero in the vertical plane. This couple was made equal in value but opposite in phase to the piston acceleration couple, which was thereby cancelled. Although the principle remains the same, this arrangement entailed the use of three shafts including the crankshaft. The out-of-balance couple resulting from the rotating parts of the crankshaft and connecting rods were constant, and were balanced by masses attached to the two outer crankshaft webs. These balance weights were increased by an amount sufficient to create a couple equal to half the maximum value of the piston couple. Steel weights were incorporated in the ends of each intermediate drive shaft to the two camshafts and were such that each of these shafts generated a couple equal to one quarter of the maximum value of the piston couple. The balance weights of the crankshaft and intermediate shafts were in phase in the horizontal plane, but since the two intermediate shafts rotated in the opposite direction to the crankshaft, the vertical plane couple was thus reduced to zero.

Such an arrangement deals only with the primary piston couple, but as the cylinders were exactly opposite each other, no secondary or higher order forces and couples were generated. The engine would therefore have been effectively vibrationless as it was in perfect dynamic balance. Like the other Ridley Engines, (as the post 1931 APU’s & GPU’s were known) a series of elegant solutions were applied to simple problems that others may have ignored or managed in a cruder way.

Perhaps too complex for its own good, this engine never advanced beyond the prototype stage & the sole remaining unit can be seen tucked away in a corner of the Aviation Hall at the Science Museum in London, a gift from Lord Ridley himself in the 1970’s.

~~32cj~~ — Preceding unsigned comment added by 32cj (talk • contribs) 21:01, 29 December 2010 (UTC)

Welcome aboard, 32cj! I hope you don't mind that I've moved your addition to the talk page to the bottom and put it in a new section. The page history will show that the text itself was not altered. As you are new to the project, you probably don't yet know that new discussions on a talk page are supposed to be placed at the bottom of the page.

Thank you for your effort. You seem to be particularly well informed about the ABC flat-twin auxiliary power unit. Unfortunately, most of what you included isn't directly relevant to an article on flat-twin engines, and none of it was verified.

If you have reliable sources for this information, you could probably use it to expand the ABC Motors article, or, if the unit itself meets the notability guidelines, perhaps you could write an article about it.

Sincerely, SamBlob (talk) 01:33, 30 December 2010 (UTC)

Briggs & Stratton

Someone should add the Briggs and Stratton 42 Cid and 46 Cid opposed twin engines. I think it could easily fit into the "Others" section of the page. —Preceding unsigned comment added by 71.184.255.19 (talk) 02:03, 2 March 2011 (UTC)

I've found a few sources of information on Briggs & Stratton flat twins, but most of them are advertisements and YouTube videos, and I don't know if they can be considered reliable sources. Sincerely, SamBlob (talk) 02:12, 18 March 2011 (UTC)

Two-cylinder engine as parent page

The following discussion is closed. Please do not modify it. Subsequent comments should be made in a new section. A summary of the conclusions reached follows.

The result of this discussion was No merge of this article is being considered.

---

Hi,

I put a "portion to be merged" tag at this top of the page as it seemed to be the closest tag to use for the job.

The intention here is to resolve a problem that has arisen relating to the three main groups of 'non-V' or 'non-flat' twins, i.e. transverse or parallel twins, inline or longitudinal twins, and tandem twins.

At present all three are being shoehorned into a single article called "Straight-two engine", which I argue is a far more obscure and minor terminology for some engine configurations, and not used widely by manufacturers. The previously unreferenced topic was started by a non-native English speaker, sometime ago. The preponderance of references suggests this does not meet Wikipedia naming conventions, as per WP:NAME; Recognizability, Naturalness, Precision, Conciseness, Consistency, English language use etc.

No changes to Flat-twin engine are being suggested whatsoever. Only a short introductory paragraph and, perhaps, image gallery relating to the configuration be included at Two-cylinder engine "master page" for all configurations.

Discussion, here: Talk:Straight-two_engine#Merger proposal

Thank you. --Bridge Boy (talk) 18:49, 14 July 2012 (UTC)

There being "no changes...being suggested whatsoever" to this article, I shall remove the "partial merge to" tag, which was mistakenly misused by the proposer. Sincerely, SamBlob (talk) 17:07, 15 July 2012 (UTC)

The discussion above is closed. Please do not modify it. Subsequent comments should be made on the appropriate discussion page. No further edits should be made to this discussion.

Deletion

You recently deleted my edit that stated that not all flat twin engines are boxer engines, but that there are two distinct types of which the boxer is one of them. Why do you think the Briggs engines are called "180 degree opposed twin" instead of "boxer"? There were many engines made that way in the past, not least some of the primitive motorcycle engines of which some are shown in this page. If you wasnt aware of that such engines existed, so that you want a "verifiable source" I should say you are unfit for editing such an article. Its the kind of thing that anyone that are into engines just know. http://en.wikipedia.org/wiki/Boxer_engine

83.178.226.183 (talk) 23:38, 1 April 2013 (UTC)

My fitness as an editor, or lack thereof, doesn't change WP:V or WP:OR. Sincerely, SamBlob (talk) 00:52, 2 April 2013 (UTC)

Furthermore, there are three motorcycle engines shown in the article, and at least two of them (BMW R50/2 and Harley-Davidson XA) are boxer engines. Do you have any proof that the Douglas engine is not a boxer engine? Sincerely, SamBlob (talk) 02:55, 2 April 2013 (UTC)

Well thats the point, such verifications are very hard to find... Yet its still there. I know for sure that some big old stationary engines was made that way, but cant find any on the net. And as for motorcycle engines.. There are 200 PAGES of defunct motorcycle manufacturers only from the UK.(dont ask me where to find, I know I saw it once.) And mind you, if it can be done, it has been done. Inventing a new type of piston engine or a such with a feature never seen before is near impossible.

Just for returning your question, how would you verify that the early Douglas twin indeed IS a boxer? Or the Harley XA? On sources I read it says its a copy of a BMW, but how can you know for sure they didnt choose a simpler crank, so it would for instance be interchangeable from a V-twin for simplifying logistics? Can you even find verification for that a BMW twin is a true boxer? Perhaps you can, but why should you when everyone knows it is anyway? Its just pure logic. If there is two ways of doing something, both has been done many times. Shouldnt need any verifivation.

--83.191.149.152 (talk) 16:55, 3 April 2013 (UTC)

And mind you, if it can be done, it has been done. Inventing a new type of piston engine or a such with a feature never seen before is near impossible.

Why, therefore, do you assume that there are only two possible layouts for a flat-twin? Are you sure there hasn't been a flat-twin with a 90°/270° crankshaft, or with a 120°/240° crankshaft? Sincerely, SamBlob (talk) 23:38, 3 April 2013 (UTC)

Just for returning your question, how would you verify that the early Douglas twin indeed IS a boxer?

The same way I would verify anything else: I would find a source and I would cite it.

I haven't verified that that the Douglas engine is a boxer, but, looking back at the aritcle as I had edited it, I see that I hadn't claimed that it is one. You have said the following: "There were many engines made that way in the past, not least some of the primitive motorcycle engines of which some are shown in this page." The onus is on you to prove your statement.

Or the Harley XA? On sources I read it says its a copy of a BMW, but how can you know for sure they didnt choose a simpler crank, so it would for instance be interchangeable from a V-twin for simplifying logistics?

Since you reject the many sources that call it a copy of a BMW, all I have is a bit of synthesis, which isn't allowed in articles, but I haven't made the statement in the article either, so here goes:

The XA was a flat twin with opposed cylinders across the frame and was also a system in perfect primary balance. – Girdler, Allan (2002) [1997]. "Chapter Fifteen – The 841 and The Model XA: Shot Down by Friendly Fire". The Harley-Davidson and Indian Wars. St. Paul, MN US: MBI Publishing. p. 132. ISBN 0-7603-1353-9. {{cite book}}: Cite has empty unknown parameter: |chapterurl= (help)

This works in conjunction with the next quote, which will establish excellent primary balance as a characteristic of a boxer twin.

Can you even find verification for that a BMW twin is a true boxer?

Yes, I can:

The 180° crankshaft means that the two pistons always move in opposite directions and the cylinders are by necessity positioned out of line. The design offers excellent primary balance, compromised only by the imbalance caused by the out-of-line pistons attempting to create a rocking motion on the crankshaft." – From the entry BMW R32 in: Wilson, Hugo (1995). "The A–Z of Motorcycles". The Encyclopedia of the Motorcycle (in UK English). London: Dorling Kindersley. p. 27. ISBN 0-7513-0206-6. {{cite book}}: More than one of |at= and |page= specified (help)CS1 maint: unrecognized language (link)

Perhaps you can, but why should you when everyone knows it is anyway?

I have given three reasons: WP:V, WP:OR, and WP:ONUS. We are on Wikipedia, we are to follow Wikipedia's guidelines. Besides which, if "everyone knows it is" then why should it be in an encyclopedia?

If there is two ways of doing something, both has been done many times. Shouldnt need any verifivation.

Hole #1: Are there only two ways of doing it? How do you know that there hasn't been a flat-twin with a 90°/270° crankshaft or a 120°/240° crankshaft?

Hole #2: There's a large amount of documentation of one of them. I haven't seen any documentation of the other and you haven't produced any. How do I know that the other "has been done many times"? If it has been done so many times, someone must have documented it. Why should I believe you when you say it has been done many times? You could be a prankster, or a lunatic. So could I. That's why WP:V, WP:OR, and WP:ONUS exist, and that's why we should follow them. Sincerely, SamBlob (talk) 23:38, 3 April 2013 (UTC)

There could be many ways of doing it if you see it that way, but they would be illogical. Why produce a complicated engine that is out of balance anyway? The 180 degree non boxer twin has a point in that the crankshaft is simpler, and therefore also sturdier. Why the flat layout in a such case could perhaps be explained by the advantage of low center of gravity in a motorcycle. In case of a stationary engine its easy to imagine why, double power from an already existing engine without changing the construction too much. The reason why there is little information on this type of engine is that we are talking of very old examples here, mostly out of production before WW1. This means any infomation on the net is rare and comes mostly from younger enthusiasts of older machinery, which also is a rare breed in themselves. I'm working on it, but dont expect any result too soon. Regarding the Douglas engine I didnt refer to that specifically, I believe I said "some of the primitive motorcycle engines of which some(other?) are shown in this page". I cant prove it, but I bet its not a boxer. A way of finding out would be to find an enthusiast, or a such motorcycle for sale and dismantle it. But if I did, it would be "original research", wouldnt it? If Ifound a verifiable source, how could I be sure this also wasnt "original research"? How would you verify for instance that the Grey Fergie tractor is started with the gear lever? It will surely be stated somewhere on the net, but the person that wrote it will surely be an original researcher. Its a dilemma if you ask me.

--83.178.226.241 (talk) 13:30, 4 April 2013 (UTC)

Just because something isn't immediately logical doesn't mean it hasn't been done.

Information doesn't have to come from the Internet. There are books, magazines, libraries, and museums. Granted, you might have the same problems accessing the libraries and museums with access to this info as I do, but that's why this is a collaborative project; you can ask someone with better access.

Only three motorcycle engines were "shown" (i.e. had photos depicting them) on the page: the Douglas, the BMW R50/2, and the Harley-Davidson XA. BMWs have been generally established as being boxers, and the XA has been established as being a BMW clone. This left the Douglas.

How much are you willing to bet? If it's up to US$1.50 (one and a half United States dollars) I'll take you up on it!

I am certain that a description or cutaway drawing from a book, magazine, or document from a museum exhibit can be found. If the document meets the requirements of WP:RS, then voila! You have verification!

OBTW, although these are primary sources, I found some diagrams of crankshafts for Briggs and Stratton flat twins:

• List of model numbers for twin-cylinder B&S engines
• Crankshafts for 400400, 401400, 402400, and 404400
• Crankshafts for 421400 and 422400
• Crankshafts for 400700, 401700, 402700, and 404700

I don't know, but those look like 180° crankshafts to me. If they are, then those engines would be boxers. Why would they call them "'180 degree opposed twin' instead of 'boxer'"? Because people buying lawn mowers probably neither know nor care what a "boxer" is, so they just describe what the engine looks like.

Sincerely, SamBlob (talk) 15:58, 4 April 2013 (UTC)

As for the spurious guff about whether Douglas have horizontally-opposed twin engines, here's a picture of the crankshaft. To be honest I think it's time to stop feeding the troll. He/she clearly doesn't stand a whelk in a supernova's chance of getting consensus on this. It's Bridge Boy all over again t.b.h. --Biker Biker (talk) 16:57, 4 April 2013 (UTC)

http://media.caranddriver.com/images/10q4/370718/lanchester-twin-crank-twin-schematic-photo-370766-s-1280x782.jpg

This is the only one I found so far. Its a Lanchester from the early days of automobiling. But perhaps it doesnt count, since it has two cranks?

--Rolling Phantom (talk) 17:03, 6 April 2013 (UTC)

Definitely a link to remember, as is the article it came from. Could and probably should be mentioned in the article, although it didn't last beyond 1904 or so. Sincerely, SamBlob (talk) 02:42, 7 April 2013 (UTC)

Uncredited copyvio of Commons:File:Knight sleeve-valve engine (Autocar Handbook, Ninth edition).jpg there too, along with a fair misunderstanding of the Commer TS3 and forgetting that the Panhard twin was also stacked to make a successful flat 12 armoured car engine for the EBR. Andy Dingley (talk) 08:23, 7 April 2013 (UTC)

I don't see how it's a copyvio if, as the Commons link says, the image is in the public domain.

Is that Panhard flat twelve a boxer, or did it have shared crankpins? I know most flat-twelves are not boxers, not even the Ferrari Berlinetta Boxer.

Sincerely, SamBlob (talk) 13:43, 7 April 2013 (UTC)