Talk:Engine balance

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It is not my intent to be rude[edit]

It is not my intent to be rude to whoever wrote this article, but this article has so much wrong with it that I hardly know where to begin. Articles of this sort do more harm than good, and this article really should be removed. 1. The business of "primary" vs. "secondary" forces is useless nonsense. It is not a useful concept, and only serves to confound an intelligent consideration of the subject. 2. At the most fundamental level, this subject should be approached from the standpoint of conservation of momentum. An engine vibrates because it must in order that conservation of momentum not be violated. The law of conservation of momentum requires that the engine's aggregate mass not spontaneously move or rotate. Hence, whenever the aggregate center of mass of all the moving parts within the engine undergoes either linear displacement or rotation, the crankshaft and the engine block are required to move counter to that motion, in order that the aggregate center of mass of the engine not violate conservation of momentum. For example, in the case of a boxer twin that uses a crankshaft with two throws offset by 180 degrees, the motion of the pistons contains a rotational component, and the crankshaft and engine block rotate counter to that motion. While it is possible to perform the analysis from the standpoint of force and torque, anyone who attempts to do so without a clear and uncompromised understanding of the fact that ultimately it comes down the simple matter of compliance with the law of conservation of momentum, will almost certainly make a mess of it, just as whoever wrote this article has done. 3. "While these weights ... they cannot completely balance the motion of the piston, for two reasons. ... The second reason is that ... the smaller piston end of the connecting rod is closer to the larger crankshaft end of the connecting rod in mid-stroke than it is at the top or bottom of the stroke, because of the connecting-rod's angle. The piston therefore travels faster in the top half of the cylinder than it does in the bottom half" It is true that the piston speed is greater in the top half, but the explanation given here is one of the most preposterous explanations of anything that I have ever read. It is utter nonsense. The two ends of the connecting rod are always the same distance apart. Even if what this is supposed to mean is that the distance projected onto the vertical line, between the two ends of the rod is shorter in mid-stroke than at either extreme, this still does not, in any way shape or form, constitute a correct explanation of why the piston speed is greater when the piston is further from the crankshaft. There is only one way to explain that, and that is through the mathematical equation that relates the vertical displacement of the piston to the rotational displacement of the crankshaft throw. That formula, using T for the crankshaft throw, R for the connecting rod, and 'a' for the angular displacement of the crank, is: "D = R*sin(asin(T*sin(a)/R)-pi -a)/sin(a). 4. "Secondly, there is a vibration produced by the change in speed and therefore kinetic energy of the piston. The crankshaft will tend to slow down as the piston speeds up and absorbs energy, and to speed up again as the piston gives up energy in slowing down at the top and bottom of the stroke. This vibration has twice the frequency of the first vibration, and absorbing it is one function of the flywheel." The only sense in which it is correct to use the word "absorb" in connection with mechanical vibration is when the mechanical energy is converted to heat energy via damping. It makes no sense to say that the flywheel absorbs vibration. It does nothing of the sort. The kinetic energy of the piston certainly does change, and when the crankshaft is joined to the transmission via the clutch, changes in the rotaional speed of the crankshaft are accompanied by changes in the kinetic energy of the various parts of the drivetrain and even the kinetic energy of the vehicle's linear motion. Because that total kinetic energy is quite large in comparison with the kinetic energy of the pistions, there is very minimal change in velocity of any individual part, such as the crankshaft. This particular effect is therefore not a significant source of engine vibration except for when the engine is idling. 5. "Thirdly, there is a vibration produced by the fact that the engine is only producing power during the power stroke. ... This vibration is also absorbed by the flywheel." The only way that it would make sense to say that the flywheel absorbs the vibration associated with the power pulse, would be if all the energy of combustion were converted into heat energy within the flywheel.

This article simply needs to be removed. There isn't anything in it worth salvaging.

Princesscheetah (talk) 08:40, 8 April 2008 (UTC)

Fixed the main section for you. Incidentally you made at least one mistake above, so don't get too cocky. Greg Locock (talk) 20:57, 8 April 2008 (UTC)


I disagree with the definitions of "primary" and "secondary" balancing. My understanding is that "primary" refers to a vibration at a frequency equal to the speed of the engine. For example, a single cylinder engine would have a primary imbalance. "Secondary" refers to a vibration at a frequency equal to twice the engine speed. For example, the non-sinusoidal motion of the pistons in an inline-4 engine cause it to have a secondary imbalance. The idea of kinetic energy is useful in solving some problems but I don't think engine balancing is one of them. What we really care about are forces, not energies, and while the two are related, I think it makes more sense to talk about forces directly.

I would also suggest the following changes:

-introduce the concepts of static vs. dynamic balancing -mention firing frequency (and the general desire for it to be even for the engine) -discuss the difference between primary/secondary FORCES and MOMENTS -discuss the trade-off of crankshaft counterweights, particularly in engines with a small number of cylinders -delete the reference to carburetors, or at least change the wording. While some may refer to cross-cylinder fuel distribution as "balancing," it is wholly a different problem engine balancing in the common sense.

Unfortunately my library of engine books is currently at work, but I will retrieve them and work on completely reworking this article. In the mean time, anyone is free to implement any of these suggestions, or propose others.

I agree with this person who disagreed. Obviously some backwards thoughts written (yet again, in my pursuits at wikipedia- the coincidences are starting to bother me). Example from article: The undesired motion of a boxer four does not have an undesired motion. Primary balance correct has no secondary problems. A boxer four with 3 main bearings for example makes no use of harmonic balancers, like any counterbalanced engine would, unless the pistons themselves are doing the balancing for each other, they will be babbling about secondary.. The secondary comes from bad primary, allowing eengineers to "tinker" with this as secondary should be an international automotive standard crime. But the article has to stay friendly... just get the facts straight. Good luck to the above anonymous discusser and getting the job done.Even the definition has a terrible excuse for bad engineering. Unlike the boxer four, the only balanced engine on planet earth , and the universe as we know it.Writing defintions without facts is like an inline fours primary balance... and the straight 6, the 60 degree 6, the 5 main bearing boxer, the goofy shared rod pin of the last half century's v8, and on and on and on...anything but the 3 main bearing boxer.. Aside from my losing cool here, the article stinks, seriously.
~soob792~ 02:49, 9 February 2007 (UTC)
Well, don't just bitch us out, be bold and make it better! (But a hint: you may want to learn more about how Wikipedia uses punctuation, formatting, and markup first.)
Atlant 13:31, 9 February 2007 (UTC)

- Could someone tell me, where the heck comes the term "true" V-engine? The term keeps appearing time to time, but I have never found any legitimate claim that a V-engine is only V-engine when it has the twin crank arrangement (pistons of opposing banks sharing the same crank pin) in addition to its cylinder configuration. If there is a "true" V-engine, then there must be a "false" V-engine, which I have never heard of. As far as I know the twin crank configuration does not define wether or not an engine is V-engine, only the cylinder configuration does.

However to my knowlegde the term "true V-twin" is correct as V2 engine can have either Twin-crank or separate pin crank of which the latter would just be V2. AS I see it the problem with the term "twin" is that it is often used to describe only the numbr of cylinders while ignoring the crank arrangement. This is probably due to the fact that in practice it's nicer to speak V-twin engines rather than V-2 engines, thus the term V2 is seldom heard.

I hope someone would check the following line found in the midle of the chapter "Two cylinder engines": "A "true" V-twin, like all true V engines, has only one crank throw for each pair of cylinders, so the crankshaft is a simple one like that of a single cylinder engine, and unlike any other V engine no crankshaft offset is possible."

In my opinion the reference "like all true V engines," should be removed... —Preceding unsigned comment added by 80.220.135.173 (talk) 10:57, 12 October 2007 (UTC)

"People near the engine"?[edit]

From the opening paragraph: "... as well as reducing the stress on other machinery and people near the engine." People near the engine? Is that intentional? What is that supposed to mean? BK DC (talk) 02:44, 1 January 2009 (UTC)

Well, it might be a jke, or it might be someone expressing an important idea badly. Riders of single cylinder 2 stroke motorbikes would probably agree with that sentence. Greglocock (talk) 02:54, 1 January 2009 (UTC)

Engine mount[edit]

While in F1-cars, and many motor cycles the engine is a part of the frame, in cars for road usage the engine sits within its own suspension.

Source: Neuer Ottomotor mit Direkteinspritzung und Doppelaufladung von Volkswagen Teil 1: Konstruktive Gestaltung in MTZ 11/2005 Jahrgang 66

contents: Crankshaft housing weights: 29kg (for inline-4) Cylinder header: ? Crankshaft: ? Piston weight: 288 connecting rod: ?

That means: In a free floating engine with a single piston and 80 mm stroke the piston moves about 76mm and the engine block moves 4mm every stroke.


Source: Die Entwicklung von Massenausgleichseinrichtungen für Pkw-Motoren in MTZ 5/2003 Jahrgang 64

contents: says second order forces are 1/3 of first order forces (and moments for that matter). In an inline-3 engine the first cylinder moves 3mm up while the last cylinder moves down 3mm. In an inline-5 engine the first cylinder moves 1mm up while the last cylinder moves down 1mm.


Source: Baustein Grundlagen Motorentechnik by BMW

contents: Forces on piston due to pressure in cylinder: 68.000N  ! speed of piston: up to 32m/s at 700/6 Hz => 23457 m/s/s => 7000 N force on connecting rod


Porsche Boxster: Engine (flat-6) is mounted at three points

BMW on the topic why they do not built an V12 in the oil crisis: energy smoothness needs at least 6 cylinders


Sources needed:

  • Any friction in the mount reduces engine power / costs fuel.
  • V6 and V10 engine are mounted in a gimbal so that they can rotate freely.
  • The VW beetle has a flying arm in his flat-4 and the cross plane V8 compensate a lot of the imbalance at every crank, but in most engines the crankshaft is much too light to balance each crank individually and instead only the whole engine-block is balanced.

Arnero (talk) 11:41, 15 March 2009 (UTC)

Bugatti W16 (and other W and VR)[edit]

Looking at the firing order at their web page and comparing it with the 4 possible firing orders of the cross-plane 90° V8, it seems that the W16 is composed of two V8 (with different firing orders) rotated by 15° (with respect to each other) and shifted by half the cylinder pitch. And some swiss guy said, it has no first order imbalance. This may mean that the two cross-plane V8 compensate their first order imbalance and no heavy crankshaft is needed.

Thus in contrast to VR6, W8, W12 it has good balance. The VR8 by AlfaRomeo may also have a good balance. Do we mention inline-8 ? Arnero (talk) 12:02, 15 March 2009 (UTC)

Fork and blade ruins balance?[edit]

The statement "That corresponding cylinders do not lie in the same plane owing to the crankshaft design, a reciprocating torque also known as a rocking couple results. This can not be eliminated by the use of a fork and blade style conrods without ruining the balance completely" doesn't make any sense to me - it should presumably be removed. Any ideas? MalcolmMcDonald (talk) 10:00, 5 May 2009 (UTC)

I think there is the germ of an idea there, but yes, it makes no real sense as is. Fork and blade doesn't solve out of plane forces Greglocock (talk) 11:04, 5 May 2009 (UTC)
I removed two sentences, hope that was OK "This can not be eliminated by the use of a fork and blade style conrods without ruining the balance completely. The four-stroke boxer twin has an even firing pattern, but the kinetic energy is in imbalance, as both pistons accelerate and deccelerate together. " MalcolmMcDonald (talk) 15:21, 5 May 2009 (UTC)
There are three ways to arrange connecting rods for a V engine.
  • Out of plane cylinders, and simple rods sharing a crankpin. There's a rocking couple, but this is very minor.
  • Fork and blade rods, in plane. No rocking couple, no problems. Can be difficult or expensive to construct. In some cases this also gives trouble as the main bearing for the blade rod is now an oscillating bearing, rather than a rotating bearing, and so lubrication is a problem at the reversal of ddirection.
  • Articulated master-slave connecting rods. One rod runs on the crankpin, the other runs on an offset pin attached to the main rod. The problem here is that the strokes are now different (one crankpin being offset), and so the engine balance is all over the place. Some engines, infamously the Sunbeam Arab were so bad as to be almost unusable. A partial fix has sometimes been to alternate the master rod from bank to bank, trading rocking couples between cylinders for a better balance overall. Also has the oscillating bearing problem.
Andy Dingley (talk) 11:04, 31 October 2013 (UTC)

Confusion of subject gone too far.[edit]

I am reading this thread to get a better insight on engine balancing. As I have a engine that I would like to get balanced. The information that I have on my four cylinder engine stress the fact its got a Balanced crank shaft as standard. It is a peugeot ew12j4 petrol engine tuned to deliver its power as a deisel would. 80% Torque from 2000 rpm I was looking for an answer to the question " would having the pistons and conrods lightened and balanced futher would this cause further imbalance of the engine due to the crankshaft being specially balanced?" I not 100% sure Im allowed to asked these questios. If you dont ask you dont get. —Preceding unsigned comment added by S.phillips1988 (talkcontribs) 02:23, 24 May 2009 (UTC)

All first world car engines have balanced cranks as standard. Not many are balanced as running engines, as such, so so long as your pistons and conrods were still a balanced set you are unlikely to make things worse. By that I mean that all 4 pistons, should weigh the same, likewise the conrods. Normally when you balance a running engine you are correcting for the centring of the flywheel on the crank, nothing to do with the reciprocating components. Greglocock (talk) 04:15, 24 May 2009 (UTC)

Rotary engines[edit]

Nothing in this article about rotary engines (e.g. jet engine, turbine, wankle engine etc.) As article is titled 'Engine balance' I think types of engine other than just reciprocating ones should at least be mentioned. I'm not an expert enough on engines to start a new section, but know enough that these engines have some big advantages in terms of balancing. —Preceding unsigned comment added by 86.181.34.88 (talk) 15:31, 6 February 2010 (UTC)

Accuracy dispute / multiple issues[edit]

The statement that only straight six and flat six engines (and V12 which is two straight 6 ??) can be balanced seems very suspect - eg I see no difference between straight 6 and straight 4 in this respect, also what about boxer and opposed piston engines - it seems that if straight 6 can be balanced then all these other can be.. That is only my opinion + my unverified calculations.

To fix the facts (whatever they are) need to be checked, and referenced by truly reliable sources (ie those which mathematically demonstrate the truth of their statements).

The article also has issues with needing cleanup, references, and possibly containing WP:OR - which may also related to the claims about balance. It also omits other engine types ( see sections above - rotary etc)Imgaril (talk) 19:08, 29 August 2011 (UTC)

Single cylinder[edit]

http://en.wikipedia.org/w/index.php?title=Engine_balance&diff=496267331&oldid=496192903

(please ignore my previous garbled edit summary [1] if it doesn't help.

a. I attempted to simplify the textual description of the secondary (2nd harmonic) motions. Ultimately though it is nearly pointless - it needs diagrams and a mathematical derivation, (and a source). See also pt:Equilíbrio_de_motores_de_combustão_interna - this is part of what is needed here. This text shouldn't be in this section anyway - it should have all been explained in the earlier section Engine_balance#Primary_and_secondary_balance

b.the claim that "In general in a single cylinder engine it is not desirable to balance the weight of the piston and connecting rod 100% as large secondary vibrations are then produced. Often a "balance factor" of about 60 to 70 percent of the reciprocating mass will be chosen"

I'd like to see a reference for this. I understand that the in-cylinder-motion-axis vibrational motions cannot be 100% balanced by crankweights. I assume that the sentence refers to some attempt to minimise vibrations taking this into account. 60% sounds low to me. Needs WP:VERIFY.Oranjblud (talk) 12:59, 6 June 2012 (UTC)

I decided to totally remove this - reasons:
  • Adding balance weights does not cause any "secondary motions" - poorly written
  • Learn to walk before running. There article barely wipes it own arse. I will remove all the dubious parts. fed up of looking at poorly written unreference stuff that nobody is going to fix. Oranjblud (talk) 14:11, 6 June 2012 (UTC)


Rewrite 6/6/12[edit]

Looks good. I would like to see a mention of balance factor. "In general in a single cylinder engine it is not desirable to balance the weight of the piston and connecting rod 100% as large secondary vibrations are then produced. Often a "balance factor" of about 60 to 70 percent of the reciprocating mass will be chosen" is true enough, but all practical high speed conventional engines use the crank webs to compensate in important ways for the reciprocating masses. That 60% number is not too bad as a first stab. Greglocock (talk) 06:34, 7 June 2012 (UTC)

Massive rewrite October 2013[edit]

I am loathe to merely revert this, and yet there are many faults with it, of both style, as a wiki article, and content. Someof it is frankly nonsense, and some is misleading, and doubtless some is good. That being said the previous version was by no means a paragon. So, please could interested parties comment below as to whether to use the new rewrite as a basis for much further work, or should we try and improve the old version? Greglocock (talk) 05:25, 29 October 2013 (UTC)

Could you start by pointing out what parts are nonsense and what are misleading? That would form a basis for this discussion and would give me a chance to improve. Yiba (talk) 05:42, 29 October 2013 (UTC)
I'm not going to comment in detail on the new article since I suspect that there is an even chance that the old version is what we'll go back to. The question here is what do we use as a basis, not how do we improve whichever is used as a basis. Greglocock (talk) 05:55, 29 October 2013 (UTC)
Use the new rewrite as a basis for much further work. Abandon the old version. I'll go over both a few more times and add info from the old version, to this, as I see needed. I'm also going to add expansion needed tags to this new version. --Dana60Cummins (talk) 15:15, 29 October 2013 (UTC)
Fine by me, I suggest we leave it for two days, say end of October, just in case somebody comes up with a preference for the old one. Greglocock (talk) 22:30, 29 October 2013 (UTC)
Right and yes. I'll leave it alone until November to keep things simple. Although Yiba could edit.--Dana60Cummins (talk) 22:40, 29 October 2013 (UTC)
  • The big rewrite seemed to take an extremely broad view of "balance", broader than anything I've seen before under that title. I'd like to keep engine balance to the vibrational mechanics of the problem. A topic that is sorely needed by the encyclopedia. It should be fairly easy to write (there's plenty of sourcing and there's not much scope for creative flair), the main difficulty would seem to be producing the many drawings needed for such a topic.
Also writing that is readable by a lay audience! This is a hard topic and not generally well understood, even after reading most textbooks. We need an article that our readers can understand and learn something from: most of the standard texts fail this and are very hard going. Andy Dingley (talk) 11:10, 31 October 2013 (UTC)
What sticks out to me the most is the new Primary and secondary balance bit. As the old version really doesn't cover it like the new essay style here. In the event of a revert that bit will get shoehorned in the old. It is covered better than any of my books in college covered the subject.

The old version:

Secondary harmonics can be balanced in some multi-cylinder engines by appropriate selection of the phase of motion of individual cylinders. For example, flat-eight engines with an appropriate configuration can eliminate all primary and secondary balance problems, without the use of balancing shafts

Compare to the new one and the difference is obvious. I am alarmed that editors would blindly try to revert this.--Dana60Cummins (talk) 15:11, 31 October 2013 (UTC)

Massive removal of content[edit]

I'm flexible around WP:VERIFY and I'm not claiming that the verson https://en.wikipedia.org/w/index.php?title=Engine_balance&oldid=579588585 is fundamentally wrong - but it is "unuseable" - plus the issue of trusting and verifying content that can't be checked..

I find it practically unreadable - if the contributor can fix it to close to wiki standards then I will wait. But if not changes are made it has to go...

The article really needs referenced definitions of "what is meant by engine balance" and the basics of engine balance from reliable sources, preferably sources that include maths proofs of what is being talked about. I'm happy to wait a while, but if not fixed its gotta go or get a hell of a haircut.Prof.Haddock (talk) 09:42, 31 October 2013 (UTC)

I am very jealous of your username. My opinion is that the old version was pretty ordinary, and that the new essay style article might at least have some coherent structure. That being said if we agree to work on the new version the razor gang will be unleashed, as it has many faults. To my mind the question is which is the better basis, I find myself uninterested in that choice, except i'd like to see more people agreeing than not. FWIW nobody on the internet knows you are a dog, but I have defined the balance requirements for production engines for Corvettes and Falcons. So if anyone is defining themselves as an expert. well, so am I. I didn't just do it at uni. Greglocock (talk) 10:14, 31 October 2013 (UTC)
...Enjoy the name while you can - Don't know how long it will be before the joke gets lame ;)
Issues include :doesn't really state relative importance of factors - either qualitatively or quantitatively. My feeling is that Primary balance should be mentioned first, then secondary, then the other minor effects like mass flow of gases etc. Primary balance and secondary balance should have mathematical proofs or links to proofs eg as at https://pt.wikipedia.org/wiki/Equil%C3%ADbrio_de_motores_de_combust%C3%A3o_interna - I'm not saying it should be done as at the portuguese article which I think is over done - and too long.
I accept its a big ask for someone to do this for free..Prof.Haddock (talk) 17:00, 31 October 2013 (UTC)
I salvaged what I can from the old article and added a mathematical explanation on non-sinusoidal imbalance, although I don't believe the latter would add much to the value of the article. Relative importance of various kinds of imbalance is something I would have liked to present for the general audience, but since the order of importance changes drastically depending on the kind (e.g. F1 engine vs. Ocean freighter diesel, 2-stroke vs. 4-stroke) and the design (e.g. Long/short conrod, V8 vs. Straight-8) of an engine, I opted against including it. I'd probably include it if the article is about "Engine balance on 4-stroke 4 cylinder petrol engine for racing purpose with 2000cc displacement". I would like to have comments on what part is incorrect/misleading/stupid/missing etc., need expansion/simplification and such with some stated reasons. The insufficient proof/ref, I'd think, is common between the old and the new versions, so it might not be credible as a reason to revert. But I do admit the new version needs a lot of help in adding good refs. In my mind, the listing of things to be balanced (which I tried to be as concise as I can by using examples) is essential as a foundation of the article because so many of them are often ignored and not known in general, yet all are important elements. Yiba (talk) 18:59, 4 November 2013 (UTC)

How "ordinary" is the ordinary flat-four?[edit]

Subaru crankshaft, apparently not ordinary (right-left-left-right)

"'Ordinary' means left-right-left-right crank throws. Left-right-right-left boxer crankshaft is theoretically possible as noted above." - Note 7 in article.

The thing is, though, when I look at pictures of Volkswagen and Subaru crankshafts for flat-four engines, they all seem to be right-left-left-right. The article does not mention the balance in this case, but I think that, if the two biggest manufacturers of flat-four auto engines in the world use the configuration, it must have something going for it, beyond being "theoretically possible".

Sincerely, SamBlob (talk) 06:23, 29 December 2013 (UTC)

(P.S.: On another note entirely - "V4 engines come in vastly different configurations in terms of the 'V' angle and crankshaft shapes" must refer to motorcycle V4s. Only three car companies have made V4 engines for their cars: Lancia, with their narrow-angle V4 from the '20s to the '60s, Ford, with 4-cylinder versions of their Essex and Cologne V-6s, and Ukrainian manufacturer ZAZ. SAAB used Ford V4s in some of their cars. Sincerely, SamBlob (talk) 06:23, 29 December 2013 (UTC) )

Oops. Thanks for catching the error. Yes, the VW and Subaru crankshafts are the ordinary kind.
The Subaru competition crankshaft picture is a tricky one to look at. The crank throws are oriented right-left-left-right, and the conrods are oriented left-right-right-left in the picture. If you look carefully, bore spacing on the left is huge, and the spacing on the right side is so small that there is no space for two pistons to fit on the middle two conrods. This is because the picture was taken with wrong conrod orientations. The conrods should have been oriented left-right-left-right in this picture to show the correct positions in a Subaru engine, which has equal bore spacing on the left and the right sides.
The "theoretically possible configuration" is like the orientations shown in this misleading picture, except that the crankshaft is elongated in the middle so the middle two conrods would have enough space for the installation of two pistons. You can see such an arrangement will result in huge gap between the pistons on the first and the last conrod. (I have never seen such an engine built.)
The challenge in writing this article has been that the title is simply "engine balance" and not qualified with words like 2-stroke, 4-stroke, gasoline, diesel, automobile, motorcycle, airplane, ship, etc. So I opted to qualify it to a very narrow field in my mind at the beginning of the article (Balancing of structural and operational elements within a piston engine), and I hope you are not suggesting to limit it further to 4-stroke automobile petrol engines with the comment on V4. Yiba (talk) 15:14, 29 December 2013 (UTC)

Six cylinder engine[edit]

Six cylinder engine section was added by copying a part of Straight-six engine article with the statement "secondary imbalance is avoided because ....". This is particularly sad for me as I spent the entire Secondary (Non-sinusoidal) Balance section explaining what a secondary balance is, and how/why secondary imbalance cannot be avoided in ordinary single crankshaft piston engines. If someone has a better idea as to how to make the secondary imbalance concept more easily understood, I am all ears.
I was intending on adding 5, 6 and 8 cylinder sections, but the number of editors (who have spent considerable time and effort in creating/editing related articles) with incorrect understanding on the subject seems very large, and if this incident is representative of things to come, I would like to know how best to approach. Yiba (talk) 05:54, 4 February 2014 (UTC)

First of all, thanks for starting on this. Engine balance coverage on WP sucks and it has needed addressing for a long time. I've got the sources and background to do so, but I've long been unwilling to try eating that particular elephant myself.
As always with WP, two issues are ignored: clarity and accuracy, when instead it's so much easier to bitch about formatting style or editor conduct. As a result, we see the same WP:V blocks of nonsense circulating forever, in articles that no-one can understand and would be thoroughly misleading if anyone could! Complex topics like this require large, bold edits by single, competent editors who are prepared to stand up and go for it and they need to have an editorial narrative in mind behind them, not just to collate Google.
To defend a good change, it's necessary to phrase its defence in wiki terms. Sourcing is key to this. If a new and accurate section is provided, then if it also has sourcing that meets the rote standards of WP then it becomes harder for the policy-focussed but ignorant editor to revert it and replace it with some messy crud that would otherwise be preferred just because it has a ref with a URL to a bad coffee table book on the Google site that any idiot admin can verify the existence of. Ease of access in a source is all too often seen as equating to the quality of that source! This must be resisted.
As to concrete advice on you additions, I think SVG diagrams would be one of the next valuable steps. The Commons graphics workshop people are very helpful here - if you can supply a scrawled pencil sketch, there are graphics people there who can make it look slick. Andy Dingley (talk) 12:30, 4 February 2014 (UTC)
It's widely known, rightly or wrongly, that inline 6 engines are better balanced than v6 and even v8 engines, but there's nothing at all mentioned in the article. That's a strange gap. Even one unreferenced sentence would be better than this.GliderMaven (talk) 15:15, 4 February 2014 (UTC)
Yes that's a good point. Rather than rewriting the textbooks it might be a good idea to give a brief overview. And yes, I6 engines have very few nasty orders of vibration compared with most configurations, practically. Greglocock (talk) 22:18, 4 February 2014 (UTC)

Yiba please continue on with 5, 6 and 8 cylinder sections.--Dana60Cummins (talk) 18:24, 5 February 2014 (UTC)

Thank you all.
Andy, I read your comment of wisdom several times. I will think about illustrations and animations with new light, on which I had tended to consider the negative side of taking up space and making the long article longer.
GliderMaven, your point is well taken, and I agree I6 engines need to be discussed. Hope you like the 6 cylinder section when I re-wright it.
Greglocock, an overview seems like a good idea. I have always tried to make each section shorter for the ease of reading, but may be it's time to re-think about article organization.
Dana60Cummins, thanks always for your encouragement.
To all, for personal reasons, my progress going forward may be slow. Please bear with me. Yiba (talk) 23:31, 5 February 2014 (UTC)

Acceleration of change of position?[edit]

Is the text "acceleration of change in the position" in the article accurate? This reads as a third order derivative (i.e. jerk), when perhaps a second order one was intended? Should it actually read "acceleration of position", or simply "acceleration"?

"Acceleration of change in the position" is accurate. A position does/can not accelerate, so "acceleration of position" is incorrect. A simple "acceleration" does not describe what accelerates, so it is ambiguous. Please sign your comments, PerryTachett Yiba (talk | contribs) 01:49, 8 July 2014 (UTC)
Come to think of it, "Acceleration in speed of change of position" may be more accurate, but is bad English. If anyone can come up with a better alternative, I will be all ears. Yiba (talk | contribs) 01:56, 8 July 2014 (UTC)
So far as i can tell "Acceleration in speed of change of position" is d^2/dt^2 d/dt dx, which is d^3x/dt^3 which is jerk. I have not read the relevant part of the article, i doubt the 3rd derivative has much to do with balance. Greglocock (talk) 02:52, 8 July 2014 (UTC)
Are you PerryTachett, 178.128.192.226, or Greglocock? I'd appreciate if you could read the entire Secondary vibration and come back to me. Yiba (talk | contribs) 04:00, 8 July 2014 (UTC)
i am Greglocock (talk) 05:04, 8 July 2014 (UTC) . Sorry that section is confusing, wrong, lecturing and at first reading doesn't contain the phrase in question. For instance L/r secondary forces, as they are known in the automotive industry, can be represented as the sum of a Fourier series of which merely the first two dynamic components are E and 2E. In fact the series doesn't terminate. etc etc etc. Greglocock (talk) 05:04, 8 July 2014 (UTC)
I am open to suggestions on how to make the section less confusing, more correct, and less lecture-sounding. "Acceleration in speed of change in piston and smallend up/down position" can be expressed as d^2 x/dt^2 (see Piston motion equations#Acceleration 2). However, the equation I am using on this article just describes the "change in piston up/down position" part only, in order to make it simpler and easier to understand for people who are not familiar with methematical analysis. For those who are familiar, it might make it a bit confusing if it is taken to mean "Acceleration in speed of change in piston up/down position". But these people are exceptions, and they can normally see the difference between the two, and the reason for using the simpler equation that takes time domain out of the equation. I would appreciate any suggestion to improve the current article. Yiba (talk | contribs) 06:40, 8 July 2014 (UTC)
Thanks to Greglocock's comments, I re-examined the equation I used and realized I over-simplified it. So I made a correction. I considered adding the discussion on d^2 x/dt^2 (Acceleration in speed of change in smallend up/down position), however, I opted against it as it seems to add little for the understanding of this non-sinusoidal motion by people who are not used to methematical analysis. I owe this spotting the mistake to Greglocock. Thank you. Yiba (talk | contribs) 02:23, 15 July 2014 (UTC)

To 178.128.192.226[edit]

Thank you for your attention to this article. I reverted your three edits for the following reasons:

1. "apart from the first, only even numbered orders exist" in this case is wrong. The article talks about vibrations with frequencies of three, four and five times in a crank rotation, and when #1 and #2 cylinders in an inline six together have similar compression or combustion imbalance, it appears once in two rotation for each, or once in a rotation of crankshaft. If the spacing between #1 and #2 cylinders is 360 degrees, then it might result in a sinusoidal wave with the frequency of once in a rotation, but since the spacing is 120 degrees, this does not happen. Instead, one component of the resultant vibration ends up having the frequency of three times (360/120=3) in one crank rotation. So this is a totally different concept to the discussion of primary wave and secondary sub-waves of twice, 4 times, 8 times, 16 times, etc. frequencies.

2. I don't see why the statement "However, the piston pairs that move together tend to make secondary imbalance strong at high rpm, and the long length configuration can be a cause for crankshaft and camshaft torsional vibration, often requiring a torsional damper." is deemed inaccurate, or not necessary as you did not provide any reason. If you believe in deleting this part, please provide reasons.

3. Two stroke V6 engines with un-split shared crank pin normally has equally spaced firing when the bank angle is 60 or 120 degrees. I don't see any reason to support the deletion of "120 degrees" part in this. Yiba (talk | contribs) 04:00, 8 July 2014 (UTC)

Mecanique des moteurs alternatifs[edit]

Please to avoid misunderstanding refer to "Mecanique des moteurs alternatifs" by Bernard Swoboda TECHNIP editions, all dynamic behavior of balancing engines is covered. user talk:2.138.244.242 21 July 2014 (UTC)

The book likes good but it is in French: http://books.google.com.au/books?id=TsHRP4g0OakC&pg=PA1 . Which means it is useless to most of us and only a few people will have the neccessary understanding of the subject matter and of French in order to verify anything.  Stepho  talk  10:37, 21 July 2014 (UTC)
Thank you, 2.138.244.242. While I mostly agree with Stepho-wrs as a non-French speaker, I saw value (and no harm) in the book and added a reference to it as an information source. I wish if I can read French well. Thanks again. Yiba (talk | contribs) 11:30, 21 July 2014 (UTC)
Just for the record for future referencing, partial contents of the book can be viewed on:
http://books.google.fr/books/about/M%C3%A9canique_des_moteurs_alternatifs.html?id=TsHRP4g0OakC
and I didn't see any gross misunderstanding or wrong statements, and the general quality seems high, in what I could decipher from poor online translations. If someone can spot any discrepancy or contradiction, I would very much appreciate a brief comparison described in English. Yiba (talk | contribs) 12:17, 21 July 2014 (UTC)
Note that both of the above links are accessing the same data and just select slightly different options for the first page you see. The actual pages you can read are identical.  Stepho  talk  15:39, 21 July 2014 (UTC)
Stepho, you're right. It's just when I accessed the .au site, the preview pages were automatically selected and the message "Pages 14 to 131 are not shown in this preview." was displayed, while I wanted to see what's in that page range. The .fr site allowed me to select the page to start the preview, and then limits the number of pages I can see. It appears the underlying data are exactly the same, with different ways to whet reader appetite as you stated. Yiba (talk | contribs) 15:48, 22 July 2014 (UTC)

──────────────────────────────────────────────────────────────────────────────────────────────────── It's a pity you can´t read French, at the end of the book there is a summary of all forces and torques for in line engines (1,2,3,4,,5,6,8 cylinders 4 and 2 strokes) and for V engines (6,8(3 types of crankshafts),12,16 cylinders)up to harmonic nº6. I am sorry but I can't make a copy due to French copyright. user talk:2.138.244.242 22 July 2014

Thank you, 2.138.244.242. I checked on several formula (which I can read) used by the author in the book, and they appear to be correct. For example, the non-sinusoidal piston motion formula I used for explaining what a Secondary Vibration is:
\Delta x  = r \cos \Delta \alpha  + \sqrt{l^2 - r^2\sin^2 \Delta \alpha}
is described correctly on page 59 in a different format. So I can accept the correctness of the author's understandings in mathematical analysis. The challenge in editing this Wikipedia article have been to limit the use of technical terms and mathematical analysis to the minimum so that ordinary readers who are interested in "Engine Balance" could understand the basics without training him/herself in engineering theories and mathematical analysis. It looks to me that the book has a big value for those readers who are beyond the 'basics' stage, so I gladly added it as a reference source. If you spot any discrepancy between what's on this Wikipedia article and the text parts of the book, please let us know. Thank you again for introducing the book to us. Yiba (talk | contribs) 15:48, 22 July 2014 (UTC)