Calling all engineers and engine experts!

Scott_DeWitt · Aug 10, 2007

fryburner said:
So what can I do? If the crankshaft does have a crack in it, how much longer before it breaks? Is there anything I can do to prevent cracks and stop any cracks from getting bigger?

If your really worried about it, have your car torn down and have every bolt, nut and component xrayed, magnufluxed, and zyglo'd. Then replace any component that may look suspect. Now write a check for 300 million dollars for the NDT exam and another 40K for the teardown and buildup.

i think there are better things to worry about. In the 1 in 1000 trillion chance that you have a defect in a component and that defect causes a failure, spend the few hundred, or couple grand to get it fixed.

LurkerMike · Aug 10, 2007

Scott_DeWitt said:
If your really worried about it, have your car torn down and have every bolt, nut and component xrayed, magnufluxed, and zyglo'd. Then replace any component that may look suspect. Now write a check for 300 million dollars for the NDT exam and another 40K for the teardown and buildup.

i think there are better things to worry about. In the 1 in 1000 trillion chance that you have a defect in a component and that defect causes a failure, spend the few hundred, or couple grand to get it fixed.

Or he could just use Amsoil Euro, a non-VW certified oil recommended by Amsoil for VW 505.01 applications.

Then he should go read and post about this Amsoil AFL oil in the Fuels & Lubricants section where he will find hisself distracted by such a whirl with all the other "cracked crank" posters there that he will forget all about his own crank is about to break!

Smokerr · Aug 10, 2007

fryburner said:
Recently something rather unusual has been bothering me. I have been seriously worried about the crankshaft. After reading the article on wikipedia about metal fatigue and how a small microscopic crack can grow until the component fails, I thought about my crankshaft. Since the car has well over 100,000 miles on it and I have no idea how the previous owner drove it, there could be a crack in the crankshaft that I don't know about until the crack grows until suddenly as I'm driving along it snaps and I am left stranded, possibly in the way of oncoming traffic. The worst part is that this happens without warning but most of the time is happens when under load such as accelerating. And of course there is no way for me to know unless I remove the crankshaft and look at it under a microscope. And even if it were to have no cracks, that doesn't necessarily mean it will stay that way. The car is not a TDI by the way, it's a 2002 Audi A8 with the 4.2L V8. I also read that because of the compressive stress put on the shaft, it prevents cracks from forming, at the bearings at least where the compressive stress is. With 310hp and 307lb/ft, I would think there is plenty of power to break the crank. I am almost scared to drive it, especially because I go very long distances with it. I have actually lost sleep over this because I am so worried the crank will just snap when I least expect it, and when I really need power, like pulling out into traffic or merging onto the highway. If that wasn't bad enough, the frame is all aluminium and according the the wikipedia article, aluminium will fail after a time reagurdless of how little stress it is subjected to, unlike steel which has an "endurance limit" that gives it a theroetically infinite life if this stress limit is not exceeded (by the way, this limit is almost certainly exceeded by thr crankshaft). Wonderful, so now not only am I scared the engine will just break without warning, but now the frame could just fall apart too. I think my next vehicle will have pedals, oh wait that's made of metal and could snap in half without warning too!

So what can I do? If the crankshaft does have a crack in it, how much longer before it breaks? Is there anything I can do to prevent cracks and stop any cracks from getting bigger?

You have missed many key parts in your car that are going to fail

Lets see, pistons, probably aluminum, so they will burn thorough. Con rod is going to snap and pitch through the side of the block (or one of the end bearings will fail and do the same thing). The fuel pump will quit, the cam will break, and you will expereince that rare premature timing belt failure as well as an oil pump failure causing the engine to sezie.

Of course a meteoroid will hit you’re your house soon as well (see Wikipedia on Near Earth Objects).

What you have is compulsive obsessive problem, which is focused on a non issue, help is just a phone call away.

Vipervnm · Aug 13, 2007

LurkerMike said:
http://en.wikipedia.org/wiki/Aloha_Flight_243

Wow, 1988. That was 20 years ago. Times have changed, man. I'm surprised you didn't post a link from wikipedia about why planes don't have square windows anymore

. I know there's a more recent reference than that. An engine fell off a plane when the break away dowel...broke away, but it was during takeoff and that is never good. The design of the pin was changed after an investigation found the cause. There was also a plane that had a roof panel tear off, but it landed without crashing. Still, it is the vast majority of flights, well over 99%, where this isn't a problem AT ALL.

thermopylaetech · Aug 13, 2007

fryburner said:
If that wasn't bad enough, the frame is all aluminium and according the the wikipedia article, aluminium will fail after a time reagurdless of how little stress it is subjected to, unlike steel which has an "endurance limit" that gives it a theroetically infinite life if this stress limit is not exceeded (by the way, this limit is almost certainly exceeded by thr crankshaft).

Do you by chance know what the elastic modulus and ultimate tensile strengths of the crank material are? Temper and post treat requirements? Has the issue of elastic versus plastic deformation or the "2%" number ever really been a hot one at your dinner table?

I'd stop relying on wiki to learn you some materials engineering and start doing some real reading. The two books I'd recomend are

"Strength of Materials" J.P. Den Hartog ISBN- 0-486-60755-0
Dover Publications 1977
"The New Science of Strong Materials, subtitled 'Why We Don't Fall Through The Floor'" J. E. Gordon ISBN 0-691-12548-1
Princeton Science Library 2006

Those two will help you grasp how things like your crank and frame are built and how they are stressed and how on a molecular level they are both strong and weak and how engineering balance these competing instances.

Material science is a big big big world on it's own. Alcoa and Audi spent tens of millions developing the new era of aluminum pre-stressed frames that make your car so light and so strong yet so able to absorb an impact. And it's not just because I'm working for Alcoa that I say this, it's becasue it's fact.

I'm sure you will have a lot of question on a lot of topics so ask away but for the love of god do not rely on wiki to learns you sum injun'eering.

nortones2 · Aug 13, 2007

Fryburner: promise never to buy a BMW (or Ford) as the makers break the con-rods before assembly, the swine! You'll never sleep at night if you do, thinking of the tinkling of con-rods, and bearings flying around the crankcase. http://tinyurl.com/23o8fz:D

DPM · Aug 13, 2007

Don't PDs use this technique too?

thermopylaetech · Aug 13, 2007

Thermal fracture is too daunting an issue to discuss in the open here. We might be overheard and then the fear will be what if it gets cold out and my hot engine... oh lawdy no!

nortones2 · Aug 14, 2007

DPM said:
Don't PDs use this technique too?

So they do: but I didn't want to cause alarm

Actually, I didn't know, but this link lists the engines with this technique: http://en.wikipedia.org/wiki/List_of_Volkswagen_engines

In so far as it is reliable.....

nortones2 · Aug 14, 2007

From JE Gordons other well-known book "Structures, or why things don't fall down" In his "A chapter of accidents" "There is however, the story about two cleaners at London Airport. These ladies finished sweeping out the cabins of an empty airliner late one night. They shut the door and went down the steps on to the tarmac.

'You've forgotten to switch off the light in the toilet Mary'
'How do you know?'
'Can't you see it, shining through the crack in the fuselage?'

Thermopylaetech: thanks for reminding me of the texts by Gordon, yellowing with age now though, in my editions!

thermopylaetech · Aug 15, 2007

I do love his style. He's telling you a story about dynamics and what not which beats the pants off of a technical tome. God do I have some dry ones on metallurgy. Damn things are almost unreadable.

LurkerMike · Aug 17, 2007

Vipervnm said:
An engine fell off a plane when the break away dowel...broke away, but it was during takeoff and that is never good. The design of the pin was changed after an investigation found the cause.

I used to know the guy's name who cracked that pin. He is a pariah in the US airline business. At the time he was an overhaul Foreman at American. He ordered the factory engine installation procedure be ignored and a short cut taken with a forklift to lift the engine in place which cracked the pin as McDonald Douglass said it could. The following wiki excerpt is too kind to him as it infers that what he did was an official "procedure". It was not. It was this one dude ordering A&P mechanics to specifically NOT follow the OEM procedure on the cards that caused that DC-10 to crash and burn!

http://en.wikipedia.org/wiki/McDonnell_Douglas_DC-10
"Engine pylons
Although the design of the engine pylons was adequate, it was not designed to facilitate easy maintenance; the original procedure for an engine change was to detach the engine from the pylon first which was tedious and time consuming due to tight tolerances. To save time and costs, American Airlines started to use a faster procedure, instructing their mechanics to remove the engine with pylon as one unit using forklift trucks. McDonnell-Douglas advised against this procedure.[5] This procedure was extremely difficult to execute successfully and led to damage which was the principal cause of the crash of American Airlines Flight 191. In November 1979, the FAA fined American Airlines $500,000 for using this faulty maintenance procedure. Continental Airlines was fined $100,000 on a similar charge.[6][5]"

This dude moved around from one airline to another over the years but was always considered a "valuable management asset" everywhere he was employed by the company executives. Most union and craft workers under him considered him a blundering fool and a murderer, which is probably why upper management thought he was so good.

http://www.airdisaster.com/investigations/aacrash.shtml
"On recovery of the engine/pylon assembly, it was discovered that there was a 10 inch fracture on the rear bulkhead on the pylon. 8 weeks before the accident, the aircraft went through a major check and the self aligning bearings on the bulkhead to wing attachment joints were changed. Normal procedures would involve removing the engine and pylon from the wing separately, by use of a special cradle to lower the engine, but to save on time, a new idea was adapted using a forklift truck to take the whole assembly off as one unit. This did not prove to be a good idea because of down travel on the forks. When the assembly was being put back on to the wing, a disagreement occurred between the mechanic and the forklift driver, and a sound like a gun shot was heard, which resulted in the flange on the pylon bulkhead fracturing. Unknown to the mechanics, the aircraft was put back into service with a weakened pylon assembly that seemed to be OK until that fateful afternoon when it failed under normal load conditions."

http://lessons.air.mmac.faa.gov/l2/Am191/
http://lessons.air.mmac.faa.gov/l2/Am191/sum1
"Accident Summary - continued
Strut failure was determined to have been caused by unintended structural damage which occurred during engine/pylon reinstallation using a forklift. The engine/pylon change was being conducted to implement two DC-10 Service Bulletins, one of which (54-48) called for replacement of the aft attach spherical bearings on engines 1 and 3, and the other (54-59) called for lubrication/replacement of the forward attach monoball bearings for engines 1 and 3. If you select these links a second browser window will open. Close the window to return to the lesson. Note these files may take a moment to load.

Service Bulletin 54-48 superseded, but did not cancel an earlier Service Bulletin (54-45), which required inspection/replacement of the aft attach bearing. Both Service Bulletins 54-48 and 54-59 required that the pylons be removed, and recommended that this be accomplished when the engines were removed. The Service Bulletin instructions assumed that engines and pylons would be removed separately, and did not provide instructions to remove the engine and pylon as a unit, nor was removal as a unit an approved Maintenance Manual procedure.

Since the Maintenance Manual did not provide instructions for removal of the engine and pylon as an integral unit, American Airlines developed a procedure using a forklift to remove, support, and replace the engine/pylon assembly.

AAL's engine change procedure removed the engine and pylon as a unit. A forklift was used to support the engine while the forward and rear pylon/wing mount bolts were removed. Select here to view a Flash animation illustrating how the lack of precision associated with use of the forklift to accomplish the engine change resulted in damage to the aft pylon attach fitting.

American Airlines developed the forklift procedure for removing the engine without acceptance from McDonnell Douglas. AAL's procedure resulted, upon engine replacement, in damage to the same part that had just been inspected.

The figure below shows a side view of the DC-10 engine and strut assembly showing the attachment points. Select here to view a Flash animation showing the engine separation."

http://lessons.air.mmac.faa.gov/l2/Am191/sum1a/

The 3 page NTSB report:
http://lessons.air.mmac.faa.gov/l2/Am191/find/

See pages 26, 27, 29, 30 for a little more accurate description of what went wrong in the hanger bay:
http://amelia.db.erau.edu/reports/ntsb/aar/AAR79-17.pdf

If you study the engineer's on record remarks you will see how evident it is that AA engineering did NOT develop this procedure. They were called in after the fact to document and "legitimize" what was already decided on as being the "Company Procedure" by a high order of management.

If anyone has some other interpretation, I would be glad to hear it. Meanwhile I'll ask around and see if I can get you the arsehole's name who thought this was a great idea despite nearly all of the A&P's that worked for him thinking otherwise but being intimidated into following his personal instructions that lead directly to 273 deaths. Can you say, "Oooops"? Sure you can.

thermopylaetech · Aug 17, 2007

Umm... so forklifts == bad?

LurkerMike · Aug 17, 2007

Forklifts being used to do a job that was never intended to be done that way = very bad when peoples lives depend on the quality of the work being done.

The pylon reattachment alignment with the engine still attached required precision movement of the engine on the order of say .050" or "fifty thousandths". And it required the forklift maintain this tolerance in all directions during the whole procedure no matter how many days it might span for even unrelated reasons. The downward stability alone was horrendous as a creep down rate of at least .5" per hour is normal for a load over 10,000 pounds like the engine and pylon was.

Even of the forklift were capable of such precision movement, it would be a tenuous task with several spotters required (who would do better to have remote control of the forklift from their positions next to the wing and pylon than to be shouting orders down to a dude sitting on the lift who could not see the critical alignment points at all).

What happened was simple. They did brain surgery with forklift forks hoisted 20' up in the air with like a 13,000 pound load on them. Would you be comfortable allowing them to work on your brain like that?

Always they put significant abnormal loading forces and stresses on the anchoring hardware that it would never otherwise see and therefore was not engineered to sustain without damage. It would be no different than me rebuilding your engine with only the following tools and no more:

Several rusty old pairs of ViceGrips in various sizes.
A claw hammer and a cold chisel.
A hacksaw and a large knife.
A couple of dull and rounded off screwdrivers.

I could get your engine apart with the tools, install new rings and bearings and more or less cobble it back together for ya. But would you want to drive it like that? Well that maintenance Foreman thought it was just a dandy way to save some $$$ on a procedure and let the public bet their lives on it.

thermopylaetech · Aug 18, 2007

Well I can tell you from personal experiance forklifts == bad. Thirty 5 pieces of implanted hardware later, if I'm not the operating the equipment, I refuse to work with it. Period.

Fifty thou' and they are using a lift truck? That's like using some old channel locks for dental work.

LurkerMike · Sep 3, 2007

"Forklift Joe" Leonard, was the AA maintenance head that copied the flawed DC-10 forklift engine changing technique from Continental Airlines and ordered it be adopted by American Airlines. Oppps! That didn't work out so well... but now were is Forklift Joe? He's the CEO of AirTran!!! No worries there, he contracts out all the serious maintenance to places like SabreTech. You remember second-rate el-discount aviation maintenance subcontractor SabreTech don't you? Here's a refresher and an why cheaper is not always better when it comes to servicing aircraft:

http://en.wikipedia.org/wiki/ValuJet_Flight_592

More about Forklift Joe:
http://www.forbes.com/finance/mktguideapps/personinfo/FromPersonIdPersonTearsheet.jhtml?passedPersonId=938017

Joseph B Leonard

CEO/Chairman of the Board/Director at
AirTran Holdings, Incorporated
Orlando, Florida
SERVICES / REGIONAL AIRLINES
Officer since January 1999
Director since January 1999
Joseph B. Leonard joined us in January 1999 as our chairman of the board, president and chief executive officer, but relinquished his title of president in January 2001. Mr. Leonard continues to serve as our chairman of the board and chief executive officer. From 1993 to 1998, Mr. Leonard served in various executive capacities for AlliedSignal, Inc. and its Aerospace division, last serving as the president and chief executive officer of marketing, sales and service of AlliedSignal Aerospace and senior vice president of AlliedSignal, Inc. during 1998. From 1991 to 1993, Mr. Leonard served as executive vice president of Northwest Airlines. Prior to that, Mr. Leonard served in various executive positions for Eastern Airlines from 1984 to 1990, as assistant vice president, aircraft maintenance for American Airlines from 1982 to 1984 and in various maintenance and quality control positions for Northwest Airlines from 1969 to 1982. Mr. Leonard was elected to our board of directors pursuant to the terms of his employment agreement. Mr. Leonard also serves on the board of directors of Walter Industries, Inc. (since 2005) and Mueller Water Products, Inc. (since 2006). Mr. Leonard is a Class I director whose term expires in 2009.

http://www.prnewswire.com/airtran/bios/joe_leonard.shtml

http://www.usaviation.com/forums/lofiversion/index.php/t22390.html

http://www.usaviation.com/forums/index.php?showtopic=7695&st=0&p=85073&#entry85073

http://www.airliners.net/discussions/general_aviation/read.main/2207440/

Good old Forklift Joe...

TurbinePower · Sep 4, 2007

Crap like this is why I'm afraid to fly...

LurkerMike · Sep 4, 2007

When it is your day to die, there is little that you can do to stop it.

Trying to extending our time here is probably not a good idea really IMHO. The bible speaks of God granting a few years for a certain King who begged God to live longer past his time, but during that time he fathered and evil son who brought much harm unto his people. Probably something that most of us would not have wanted to do had we known the consequences.

But I suppose you can cut your days shorter here than they were scheduled. I would stick to a well run airline like... well like... ummmm... dang, they all seem to not be what they were years ago... the discount carriers have served to lower the safety and quality standards of the whole industry. When you get on a plane and the interior is nasty and shoddy looking, what does that say about the pride of the maintenance workers? It tells me the bottom line comes first, before all other criteria. When you can't see out the window because the outer glass or inner plexi is so scratched up, it is a sign of an airline that doesn't give a darn.

It is another case of "deregulation" NOT working in the consumer's favor.

At least we have our somewhat fuel efficient TDI's to do long hauls in as an option to flying commercial.

Honeydew · Sep 5, 2007

The poor OP has been so thoroughly dogged for his question that it was his last post on the forums!

nicklockard · Sep 5, 2007

Honeydew said:
The poor OP has been so thoroughly dogged for his question that it was his last post on the forums!

No kidding. Poor guy.

gulfbear · Sep 9, 2007

One word.... Lycoming.

Just saw this thread.... but his question is not entirely unfounded..... there are flaws (dislocations) in all crystalline metallic structures. All steps in the manufacture of materials will have an effect upon the final macroscopic properties, eg. heat treating, nitriding, cold work, hot work, annealing...etc. Polymers are extremely sensitive.

The upshot, well, it could happen. Lycoming recently replaced the crankshafts on a series of engines due to just such a failure as the OP fears. Dislocations pile up, stresses build microscopically and what you call a crack appears... the stress multiplication at the edge of the crack will allow stresses well below the theoretical yield limit applied to the material as a whole to ultimately lead to rapid crack growth and part failure..... unless..... but that is a whole series of topics.

The good news: Don't worry about it with a stock engine or stock power output. If a manufacturing problem led to a series of failures, then you will hear about it. Let the engineering safety factor handle the rest... and he should get some rest.

Yes, I do have a graduate level degree in Materials Science and Engineering. I also fly airplanes for a living. I must be one conflicted individual! I am, however, betting that all those cracks in those airplanes are below their critical limits.

Oh, LurkerMike.... those guys at AA sure took that lesson to heart, especially there in Chicago ... I used to know the director of Maintenance there back in the late '80s. The fork lift method included jamming it up to the point of contact... resulting in said damage.

By the way, the head tech at Sabretech (can't remember his name...but he went by "Mad Dog" or "Mad Max" as his nickname) that signed off on that load of O2 generators still sits in jail to this day. The procedure regarding O2 generators changed from one paragraph to 12 pages (or was it 14... something like that) in the wake of that accident.

..... and Joe Reynolds is CEO of a US airline.... priceless.

maverick06 · Sep 20, 2007

for what its worth Metal fatigue is a serious issue. I work on stuff that we do worry about metal fatigue. Millions of cycles on pieces of equipment will eventually result in failure. Tiny defects fractions of an inch thick can ruin massive components. However, detecting them is nearly impossible for guys like us, unless you want to perform a magnetic particle or liquid penetrant test on a component.

But what can youy do about it? Nothing, if it is in the engine you assume that good old german engineering is more than satisfactory to prevent this from occuring during the operational lifespan of this stuff.

This used to be a big problem for train axles.

Pretty neat concept, dont worry about it. I suggest the beer remedy to the problem (above mentioned)

Pat Dolan · Sep 22, 2007

Gulfbear:

I was trying diligently to avoid doing any work and stumbled on this thread as well. I was about to throw IO 540 cranks into the pot, and raise you bid IO 520 crankcases (that was a while ago). They were built by a sub-contractor and found (the hard way) to be horribly crack sensitive. There was a re-design (not very successful) but TCM elected to use all of the existing really, REALLY bad parts before bothering to bring manufacturing inhouse. Won't even bother to mention B-18 spar attach fitting failures, early V33 wing failures, B95 (and derrivatives) milk-bottle bolt SCC failures, or anything else like that, or nobody will want to fly anymore (certainly not from Beechcraft).

I suppose we could tell the OP (if he is anywhere to be found) how torque reversals make 4 (and under) cylinder engines SO much more fatigue sensitive, but he is probably walking now anyhow.

thermopylaetech · Sep 23, 2007

Well to be honest, work embrittlement and various other "crack" related issues are of massive import when you design something like the crank and rods of a highly stressed IC Diesel engine... hence why they are so thoroughly investigated and studied. Its not like VAG or MB or BMW via Styer-Puch are building engine components out of hot poor pot metal; what does this look like; china?

Calling all engineers and engine experts!

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