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Certified engine <30 hours run time making metal

mechmike

Member
Not in an RV. This is my new engine in a certified C2 Skimmer (Lake amphibian pusher) that was making some aluminum.
Was making some aluminum starting at first oil change at 2 hours, then at 4, then 6 then 15 and at about 28hrs enough was enough and pulled the engine.

This is a freshly rebuilt certified case (and rebuilt engine). Just sorting out what on earth to do now.

For your viewing pleasure, hopefully this works out well and we can all learn from it:

https://youtu.be/JIP8Lh8EjdY

Mike
 
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That looks horrible. Were some critical components missing to allow the crankshaft to rub against the crankcase? Seems like whoever put that engine together has some explaining to do.
 
I would not immediately jump to that area as the source of metal. The fwd face of the #1 journal rides against the case and acts as a thrust surface in tractor configurations. It would be really odd for a case overhauler to mess that up. In a pusher config, all the force is aft and the oil slinger hits the case in it's cavity and acts as the thrust bearing. Can't see that area with the case halves together.

Just because you see shinny AL doesn't mean it is wearing there. The case overhauler would have dressed this area as part of the machining process and not surprising that they ate into a bit of new casting area on the outside. That face of the case will wear, as IT is the thrust bearing. The case shop has to machine it back to flat and that means taking away some material. If it meets axial play spec, all good. If not, they weld on new material an machine again. In your case, it looks like they just machined it down and have to assume it still meets the thrust play tolerance. Just stick a feeler gauge in there to confirm.

Several areas of the engine can make AL shavings. I would keep looking. Does it have AL pin plugs? Those would be my first look. I had one that made metal for 100 hours after overhaul until l pulled them out. Wear on the plugs was less than I expected for the amount of metal found. The silicon bronze caps that make shavings can also be confused for alum, as they are still shinny and non-magnetic. Size is so small that you can't really see the unique color of bronze.

Larry
 
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That looks horrible. Were some critical components missing to allow the crankshaft to rub against the crankcase? Seems like whoever put that engine together has some explaining to do.

The crank is supposed to rub against the case in that area. It is what prevents the crankshaft from pulling out of the case. Every engine has thrust surfaces to deal with axial movement of the crank. Most use thrust bearings, but the lyc just rubs the crank against the case.

Larry
 
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Oil Pump

Disassemble the oil pump and see what it looks like. Just another source for metal.
 
.... Does it have AL pin plugs? Those would be my first look. ....
Larry

I have the cylinders are off to hopefully have found a pin plug shaved down. They were all good.

That I'm looking at here is it looks like the crank is wearing into one side of the case and the other side has a space.

Crank end play is ~.017 so within the huge spec they give.

More inside photos coming

Mike
 
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That I'm looking at here is it looks like the crank is wearing into one side of the case and the other side has a space.

Mike

Yes, the fwd end of the crank is rubbing against the case. This is normal and the engineered behavior. The question then is it just rubbing or making metal. Without a microscope, they can look the same. Remember, this area is flooded with oil from the main journal. What leads you to believe those two rubbing surfaces are making metal? Your engine has numerous metal on metal rubbing surfaces that aren't throwing metal.
 
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Yes, the fwd end of the crank is rubbing against the case. This is normal and the engineered behavior. The question then is it rubbing or making metal. Without a microscope, they can look the same. What leads you to believe those two rubbing surfaces are making metal?

I can see a curl of aluminum that isn't visible in the video

Mike
 
Not in an RV. This is my new engine in a certified C2 Skimmer (Lake amphibian pusher) that was making some aluminum.
Was making some aluminum starting at first oil change at 2 hours, then at 4, then 6 then 15 and at about 28hrs enough was enough and pulled the engine.

This is a freshly rebuilt certified case (and rebuilt engine). Just sorting out what on earth to do now.

For your viewing pleasure, hopefully this works out well and we can all learn from it:

https://youtu.be/JIP8Lh8EjdY

Mike
Mike, please post when you get the case split, it is not clear what has happened. We can see the curled aluminum, but is the thrust face recessed?

Thanks for posting - - hope you get satisfaction on this.
 
I can see a curl of aluminum that isn't visible in the video

Mike

If the shavings are curled, that means large pieces. Split the case and look at the thrust surface. If it is making curled shavings any wear should be visible to the naked eye. You also need to examine the thrust surface in the oil slinger recess, as this will take the most abuse in a pusher config. In a pusher, the thrust contact at the #1 journal should be minimal.
 
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Ouch! What does the crank surface look like that is touching those thrust surfaces on the case? Have you figured out what is causing that gouging? Odd that you are getting damage on both the fore and aft thrust surfaces. Something definitely not right.

Larry
 
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Misaligned Cases

Ouch! What does the crank surface look like that is touching those thrust surfaces on the case? Have you figured out what is causing that gouging? Odd that you are getting damage on both the fore and aft thrust surfaces. Something definitely not right.

Larry

I’m with Larry on this one. I would send the case back to DIVCO and have them explain the misalignment. Good chance this case goes to the dumpster. At this point another case seems the prudent move. I know the case shops can do amazing jobs of welding and remachining but with these issues it’s best to start clean.
Duff
 
I’m with Larry on this one. I would send the case back to DIVCO and have them explain the misalignment. Good chance this case goes to the dumpster. At this point another case seems the prudent move. I know the case shops can do amazing jobs of welding and remachining but with these issues it’s best to start clean.
Duff

And what is interesting is it does not look like misalignment that is causing the damage, though it does appear to be misaligned. If that were the case. the wear surfaces would be relatively flat and clean, just offset a bit; WIth everything right, I doubt you could even see uneven wear at 30 hours. something is tearing chunks out of the case surface. Can't be smooth metal rubbing doing that type of damage, especially with all the oil coming out of the journal area. Something sharp is literally tearing the Aluminum off the surface (curled metal shavings, just like a lathe). Please post pics of the crank in the mating areas. Curious if there a machining flaw there.

Larry
 
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This video about overhauling a Lycoming engine shows the clearance checking before the two halves of the cases are mated and the crankshaft end play is checked, about the location where the pictures show the parts rubbed together. The time is about 10min 10 secs

https://youtu.be/n-26eqLc4pQ?t=609
 
The mismatch at the rear journal being offset at the back of the engine isn't unusual. The areas with the damage are lubricated from oil that is pushed out of the nose bearing. It looks to me that either the supply of oil to the nose bearing was limited or the clearance at the nose bearing bore was too small or the nose bearing was defective. That would cause the clearance between the crank and the bearing to be too small which in turn would limit the oil supply to the thrust surfaces. When I was working we always made the nose bore at max new limits, thus making the bearing clearance at maximum to combat this issue. On our experimental engines, we drilled extra holes/ passages to help provide extra lubrication to the thrust surface. Time will tell the actual cause upon further investigation. Crankshaft likely has heat check cracks at the thrust surfaces and is ruined.
Good Luck,
Mahlon
 
Methinks I would be looking for warranty coverage.

+1 ohhh yeah - you betcha!! The thrust surface "could not support hydrodynamic lubrication due to poor geometry from the machined surface"

Well, Mahlon has spoken, I defer.
 
This is what I think:

.... The thrust surface "could not support hydrodynamic lubrication due to poor geometry from the machined surface".....

A thrust bearing cant work if it's only half way around the piece bearing against it. The oil film wouldn't make the trip around the circle if there's no circle. (

To me the telling part is this photo, there's no good reason that the crank hasn't touched all the way around. Even if you ran it with no oil in it, it would contact the thrust all the way around:
 

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This is what I think:



A thrust bearing cant work if it's only half way around the piece bearing against it. The oil film wouldn't make the trip around the circle if there's no circle. (

To me the telling part is this photo, there's no good reason that the crank hasn't touched all the way around. Even if you ran it with no oil in it, it would contact the thrust all the way around:

I see gouging marks all the way around. Granted, they are MUCH smaller on one side, but definately there. You can even see pock marks in the flat areas. Pretty easy to put a machinist square in the bore and see if the worn area is perpendicular to the bore. While it would appear from the damage pattern that one side was higher than the other, until you know what was eating it apart, it is hard to say that one side has more damage due to an uneven surface or some other factor. Oil should be pouring out of the bearing clearance, so no need to carry a film around the area; It should be constantly flooded with oil, assuming the correct bearing to journal clearance exists. Have you got a bore gauge inside the bearing to get a clearance measurement? Does your case have alignment dowels. If it does, that makes poor machining less likely, as it would be a royal screw up by the case shop.

I still see concentric grooving patterns which would seem to point to something tearing out those trenches vs two flat surfaces wearing each other down. Then again I don't have a great deal of failure analysis experience, so could be barking up the wrong tree.

Larry
 
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This is what I think:



A thrust bearing cant work if it's only half way around the piece bearing against it. The oil film wouldn't make the trip around the circle if there's no circle. (

To me the telling part is this photo, there's no good reason that the crank hasn't touched all the way around. Even if you ran it with no oil in it, it would contact the thrust all the way around:

Mike, valid observation. Hydrodynamic lubrication (oil) requires that the surface finish of the mating parts be sufficiently smooth so that the oil film is greater than the finish, else the tips (asperities) will touch and fail. Interesting that the "untouched" part of the case is not smooth. Now, I don't know what the surface finishes specification of the thrust faces are, but it is very important. This is why cranks are like mirrors. Micron range surface finishes. The untouched case portion does not look shiny.

The finish may be more important than the case offset even if it only carries 1/2 the load as a full circumference.

Do let us know what they say as it appears this engine was somehow not built right. Many possibilities for this, squareness relative to the bore, surface finish of the crank, and case, original axial clearance, and installation of the bearing to provide sufficient oil for this surface. Do check Mahlons comment on lubrication.
 
Engine shop says the crank is still great and they sent some photos.
It's very clear to them that the case halves at the thrusts have not been machined off when the main bearing bore was line bored.

Case is getting sent back to the Case shop that, 30 hrs ago, put the dowels in it, bored it and sold them the certified case.

Case rebuilder will give their failure analysis and course of action once they get their hands back on it.

Mike
 

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Continental Prime crankcase thrust surface

The crank is supposed to rub against the case in that area. It is what prevents the crankshaft from pulling out of the case. Every engine has thrust surfaces to deal with axial movement of the crank. Most use thrust bearings, but the lyc just rubs the crank against the case.

Larry

Just for general information, Continental's crankcases that are used in Titan engines have steel thrust washers installed. It's one of the improvements that ECi added having been a crankcase repair shop. Continental bought ECi and carries on the product line.
 
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