Debate about Mark Langford's 3rd crank failure

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Dan Thomas

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Most of the Lycomings have a pilot thread insert so the prop only goes on one way.
The fat insert in the Lycoming's prop flange is for locating the flywheel with its timing marks. It doesn't index the prop. The large diameter of that insert stops just under the surface of the flywheel and the rest of it, the part that goes into the prop, is the same diameter as the other five inserts.

Dan
 

Dan Thomas

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If one compares the weights of the Continental 200 with the Rotax 212, there is not that much difference. The drawback of the Continental, ( apart from not being able to obtain one, which is a severe drawback - ) is that it is out-of-date in several respects, amongst which are:

A. Not able to function on Mogas - owing to bearings not being sufficiently robust to withstand the less smooth firing - valve seats being too soft, not able to withstand the pounding of valve to seat without lead particles to soften the blows which unleaded delivers -
B. Lack of FADEC facility ( this is just stone-age, all modern automobiles have this )
C. Lack of watertight, breakerless electronic ignition timing -
D. lack of an heating element around the venturi to render icing impossible - a simple solution, very cheap - yet one reads about venturi icing all the time.
Are people mad, or what ?
1. The O-200 is still being manufactured.

2. The O-200 is STC'd for Mogas. It doesn't particularly care for it, but it's legal. 87-octane Mogas burns just fine in an engine designed to run on 80. Auto Fuel STC Approved Engines and Airframes

3. Yes, it doesn't have FADEC. That way it's still sort of affordable.

4. For a homebuilt, one can forget the magnetos and buy E-Mags. Breakerless electronic self-powered ignition that will soon be certified. Ignition for Continental O-200

5. "Carb ice" forms in the venturi, on the fuel nozzle, on the throttle plate, and can form farther up in the induction piping. It's certainly not limited to the venturi. The evaporation of the fuel and the pressure drop in the venturi can lower the temperature of the incoming air by as much as 70°F. Multiply that drop by the volume of air passing through and one gets some idea of the amount of heat needed to prevent ice. A simple heating element able to keep up would be rather bulky and consume a lot of power. Exhaust heat is waste heat anyway, there's an awful lot of it and it's easy to manage, so it makes far more sense. That's why we use it. You read about venturi icing because pilots are poorly trained, by poorly-trained instructors, and they simply don't understand it nor the conditions in which to expect it. Many, for example, think it's only a wintertime thing. Pouring electricity into a heated carb 100% of the time just to cover their ignorance is a waste, and it also costs not only the HP to generate the juice, but it heats the charge and reduces its density all the time, costing more HP all the time instead of just when the heat is necessary. And an electrical failure is much more likely than an exhaust heat failure.

6-11-formation-carburetor-ice.jpg

Both Continental and Lycoming are working on FADEC systems, and Lyc's is available for sale. Right now. It's up to date. We just have to buy them.
http://www.lycoming.com/news-and-events/pdfs/iE2_Engine.pdf

Dan
 

Max Torque

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Re: O-200 - What Dan said. No sense posting what would be, basically, a duplicate of Dan's reply.
Tom

PS - https://www.homebuiltairplanes.com/forums/members/bberson.htmlBBerson,
Interesting that prop indexing is new to you. (Not berating you.) I'll have to make it a point from here on out to teach my junior A&Ps about it to ensure they are aware of its existence.
 

rv6ejguy

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Pops

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Dan -- On my 1835 cc VW engine, I was getting carb ice at the drop of a hat with my Zenith carb. I built a hot oil box around the intake tube at the flange of the carb. I run oil from the engine to the hot oil box then to the oil cooler, to the filter and then back to the engine. The hot oil box also cools the oil 20 degs. Not only did it stop the carb ice problem but the engine runs smoother and stronger. The charge in the intake was condensing in the long intakes and forming droplets and the cylinders were running lean and then rich when the droplet would run in at the same time. I still use my Exhaust carb heat on landing as usual but I have never had any carb ice since installing. Sort of what Lyc did on their engines by mounding the carb on the bottom of the oil slump and running the intakes inside the oil slump. Pops ( another Dan).





1. The O-200 is still being manufactured.

2. The O-200 is STC'd for Mogas. It doesn't particularly care for it, but it's legal. 87-octane Mogas burns just fine in an engine designed to run on 80. Auto Fuel STC Approved Engines and Airframes

3. Yes, it doesn't have FADEC. That way it's still sort of affordable.

4. For a homebuilt, one can forget the magnetos and buy E-Mags. Breakerless electronic self-powered ignition that will soon be certified. Ignition for Continental O-200

5. "Carb ice" forms in the venturi, on the fuel nozzle, on the throttle plate, and can form farther up in the induction piping. It's certainly not limited to the venturi. The evaporation of the fuel and the pressure drop in the venturi can lower the temperature of the incoming air by as much as 70°F. Multiply that drop by the volume of air passing through and one gets some idea of the amount of heat needed to prevent ice. A simple heating element able to keep up would be rather bulky and consume a lot of power. Exhaust heat is waste heat anyway, there's an awful lot of it and it's easy to manage, so it makes far more sense. That's why we use it. You read about venturi icing because pilots are poorly trained, by poorly-trained instructors, and they simply don't understand it nor the conditions in which to expect it. Many, for example, think it's only a wintertime thing. Pouring electricity into a heated carb 100% of the time just to cover their ignorance is a waste, and it also costs not only the HP to generate the juice, but it heats the charge and reduces its density all the time, costing more HP all the time instead of just when the heat is necessary. And an electrical failure is much more likely than an exhaust heat failure.

View attachment 21840

Both Continental and Lycoming are working on FADEC systems, and Lyc's is available for sale. Right now. It's up to date. We just have to buy them.
http://www.lycoming.com/news-and-events/pdfs/iE2_Engine.pdf

Dan
 

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Max Torque

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Pops! Thanks for jogging the memory. Years ago I remember reading about a homebuilder who heated his intake tubes with hot oil in a similar manner - wish I could remember who/what engine/airplane - he spiral wrapped the intake tubes with oil lines. Seemed like an idea with merit. Would still want to combine it with exhaust carb heat as you did, though. Interesting...
 

BBerson

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Interesting that prop indexing is new to you. (Not berating you.) I'll have to make it a point from here on out to teach my junior A&Ps about it to ensure they are aware of its existence.
I have always known that the prop needs to be set to the proper position for proper hand propping. (Yes, my use of all those props in that sentence was intentional) Sure, the Cessna manual explains how to set the prop to trail 30°, as Dan said in post #46. I always thought this was for hand propping and so it stops more or less horizontal. The Cessna manual doesn't explain the reason for this or say why this would be important or even use the word "indexed". Nor is there any FAA approved warning anywhere that mentions crank breakage caused by prop position, as far as I know.

And as Dan already said, the 30° is not the 90° that John Affleck insists is required.
The topic here is crank breakage. I just searched several sources and found nothing to support Johns "clocking theory" to prevent crank breakage.
So maybe you can teach all of us.
 

Max Torque

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BBerson,

Please enlighten me - Just exaclty where in my posts have I ever stated that indexing a prop has anything to do with crank breakage?

My statement was about teaching my mechs to be aware of prop indexing and that it may be required for certain aircarft/engine/propller combinations.


I don't know where you're coming from with your sarcasm in your last post - I stated that I wasn't berating you - , but the fact that you "never really heard of 'indexing' a prop on any certificated GAairplane I owned or worked with in past three decades." speaks volumes (and makes me wonder if my mechs are cognizant of it). Sorry if it offended you.
 
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Dan,
the thinking on a venturi heater is that that is the spot where carb ice forms first - so instead of heating the air, you heat the surface.
In Uk it has been found to work.
Allan
 

Max Torque

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Thanks for the post, Mark.

You're crank break experiences are examples that illustrate an engine failure in flight doesn't necessarily mean a catastrophic outcome, although it certainly could mean that. Obviously you possess some great flying skills!

Looking forward to your getting your KR back in the air.

Tom
 

Pops

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Very common used on the 1/2 VW's with the long intake runs. It's a twofer :) takes care of the carb ice problem and makes a more consistent mixture to the cylinders by preventing the condensing of the charge before it gets into the heads, resulting in a smoother running engine with more power. Pops



Pops! Thanks for jogging the memory. Years ago I remember reading about a homebuilder who heated his intake tubes with hot oil in a similar manner - wish I could remember who/what engine/airplane - he spiral wrapped the intake tubes with oil lines. Seemed like an idea with merit. Would still want to combine it with exhaust carb heat as you did, though. Interesting...
 

stol

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I was notified that there was a thread that might be of interest to me on this forum. After reading Mr. Affleck's rather caustic comments gleaned during his "extensive communication" with me, I posted some comments on that to my webpage, at From: John Affleck. I hope this is the last word on the subject, but suspect it won't be. Sorry about that. I'm too busy getting my KR back in the air to spend any more time clarifying this, so I'm done arguing the point. I think his correspondence says it all.

Just to throw out a real-world data point on the machined billet 4130 crank's apparent suitability for aircraft use, GPASC has been using them in conjunction with their "Force One" bearing for many years, and will tell you that not one of them has broken when used with a wooden prop. No, it's not better than a forged crank with huge radius rolled journals, but it's apparently good enough. Having a brand new crank with large radii is a huge step in the right direction. I applaud Dan Weseman for stepping up to the plate with these new cranks. I have one on order for my Corvair engine...

Mark...... I went to your site and read the emails from Jack, or John, or whatever his name is..

All I can say is WOW... just .......WOW.......

Don't ya just LOVE engineers..:speechles

Ps.. He has been on this site, trying to set them straight too... Big Engine Videos - SmokStak

What a piece of work...
 

BBerson

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Max,
You defended Mr. Afflecks rant right from the start with posts to me like this:
Re: Debate about Mark Langford's 3rd crank failure
It appears John is rather frustrated and he seems to be venting his frustration in his post. Granted his grammar, etc. isn’t the best, but he gets his point across. I’ve worked with brilliant engineers – geniuses, really – and way too many English is their first language college grads whose writings were terrible. (Probably why TinBender is having to do so much tech writing in school.) I can remember some of them - engineers, not college grads - going on a rant or two due to frustration because people weren’t listening. (I remember that most of the time they were right too.)


BBerson, I’m not an engineer and I'm unfamiliar with “torsional bending”, please enlighten me. (I recall torsion, shear, twist, and bending but not torsional bending.) Thanks.

Then you take me to task for not being familiar with "indexing" ( even Affleck didn't use the word indexing, I first saw that on Marks web page) WW doesn't mention the word either.
Then you imply I am a "junior mechanic" because I don't recall discussion of indexing. As I said, 40 years ago we just set the prop for good hand propping, nobody called it indexing.
If you have information from the certificated world that can support Afflecks claims, please enlighten us.
Otherwise I am done here.
 

Max Torque

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Gang,

I certainly apologize for "defending" Mr. Affleck's rant. I also apologize for not being an engineer and for including in my posts sincere questions such as what is torsional bending while trying to learn something. My previous post, as was referenced by BBerson, was simply an attempt to offer a possible explanation for Mr. Affleck's rant from the way it appeared to me. I admit I related anecdotal instances from past experience with other engineers, i.e. engineers who are not John Affleck. Re-reading it, I can see where my statement: "(I remember that most of the time they were right too.) " could cause confusion; "too" in this case was meant as "indeed" not "also". Sorry about that. I don't agree or disagree with Mr. Affleck. I have no idea who is right or wrong or what is causing the crankshaft breaks, but I am, however, trying to learn something from this discussion, and, unlike some others on this site, I don't post with intentional condescension and animosity.

With regards to prop indexing ("clocking"): It's pretty basic stuff for an A&P....or at least it should be....and, while not all mechanics read them, it is mentioned in various ACs (Advisory Circulars), SIs (Service Instructions), maintenance manuals, etc.. Lycoming even has a SI that addresses the bushings in the prop flange that, if installed in the wrong places, will index the propeller incorrectly and may introduce excessive stresses into the prop.

Tom
 

revkev6

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let me preface this post with; I am one of those armchair engineers.

given that, I have several years worth of experience pushing VW's to their limits in automobile racing. I have built, broken and rebuilt lots of engines. granted they are not a corvair, or a six cylinder but some of the practical experience does transfer.


apples to apples, a forged crank will be stronger than a billet crank. when same material is used. most aftermarket companies use the same 4340 material for a forging as they do for a billet crank. given the choice between a good forged or a good billet, I would choose the forged every time.

I haven't looked at the pictures of break #1 or break #2 but from what I have heard, in an automotive application breaks of this nature are almost always caused by a problem with the harmonic balancer. broken key ways as well. undamped harmonics. is there a way to check for this??

the machine work on that factory crank is TERRIBLE! I wouldn't put that in a car. With the time and effort that it appears Mark has put into his corvair conversion I'm utterly astounded that he let this go. Especially after two previous crank failures! This engine should be built to race spec, not factory. You have to find a machinist to blueprint your engine not remanufacture it. fatigue resistance is in the little details!
 

stol

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