3126 CAT needs replacement!

Yes, this is the postwar Navy standard. German's military forces were completely reformed according to the Marshall plan and are part of the NATO forces today directly supporting the US and other Western allies in Afganistan. They are also still the closest US ally in the Western world behind England.

I fear this post is going in a direction I don't want to take it or see it go, so I am going to recluse myself from any more comments on this matter. It really does not belong here. Sorry I did not mean it to go this way. It was all meant in the spirit of fun and jokes.
 
Actually... I remember the flag because something similar was in the movie "Independence Day" towards the end of the movie when the coordinated attack happened against the aliens...

How's that for stupid crap to remember. Want to sing the theme to Gilligan's Island?
 
Hey, I have been out of town for a few days.....whatever happened to the broken diesel engine? I understand the shaft issue but I still don't get what really failed on the diesel and the internal damage that resulted.

-John
 
I have an appointment tomorrow morning with a second diesel mechanic to go and look a the engine and try to determine the cause of the failure, and the best course of action for its repair, or replacement.

I will post results on Friday....will be out of town until then.
 
Well... I think the coordinated alien attack brought more tears to people's eyes.
 
Back to fatigue... and btw, I'm very rarely offended, have thick skin, so don't worry! And I'm glad I can finally give a little back...

A beachmark, striation, is one cycle. With good material property data, you can theoretically correlate the stress intensity factor to the distance between striations. As the net section is reduced, the stress will naturally increase, so you'll see the striations get longer. But if you were to hammer on it, then not so much and then hammer on it, you'd see the variation. More likely, while you're not hammering on it, the crack might not grow at all, making it harder to determine when the incident happened.

If you remember that strength of materials lab that you probably had to take, the surface of a torsional failure is grossly different from tensile or bending failure (I really should find pictures and post them)... and as such, the striations will grow differently depending on what is causing the cyclic loading. Most likely, it is shaft flex, so the nucleation point would be on the outer surface and the striations will be slightly curved growing toward the center of the shaft. Now to count them, remember that one cycle is a striation and that occurs every time the shaft goes around. Often, something will damage a part and it will take sometime before the crack initiates... this is actually the definition between fatigue and fracture mechanics... once you have a detectable crack, it's a fracture mechanics problem... but I digress.

So, if this is a well behaved fatigue problem from normal wear and tear, we'd expect it to take sometime to happen. If the engine is running 2k RPM and the reduction is 2:1, we're talking a 1000 cycles every minute, 60,000 every hour! How big can the striation be to fit that on about half of the shaft diameter (remember, it is going to fail quickly in the end and it will need probably half it's material). This is why we would need the electron microscope because if I can see them with my naked eye or a loupe, it means something happened and a minute later it failed. I'd still have striations, but that's certainly not from wear and tear or neglect.

I hope that's clear to those that care... and those that don't, oh well... it was more informative than reading something like the NY Times! :p
 
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Here are some photos of the shaft:
 

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Here are a few more photos the shaft.

I got a price of $26K for a brand new replacement engine. If you add in labor, it will be in the range of $35K.

I am meeting with my attorney regarding the insurance claim, and am exploring less expensive options.
 

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I'd have to say it does look like a fatigue failure. The beach marks are evident from the pictures. It appears as though the shaft imperfection may have been in the keyway since it appears as though the beach marks are propogating from that area.

Doug
 
I speculated ( and am still speculating) in the original thread about the broken shaft that it could have come from an improperly seated keyway. The props were removed, then replaced by the OP shorty before the shaft failure.

I believe it is far more likely that the failure was due to this, rather than there just happening to be a "shaft imperfection" right at the keyway- not very likely IMO.

Shaft failures would more typically occur just aft of the strut- not midway along the keyway.
 
tobnpr said:
I speculated ( and am still speculating) in the original thread about the broken shaft that it could have come from an improperly seated keyway. The props were removed, then replaced by the OP shorty before the shaft failure.

I believe it is far more likely that the failure was due to this, rather than there just happening to be a "shaft imperfection" right at the keyway- not very likely IMO.

Shaft failures would more typically occur just aft of the strut- not midway along the keyway.
Click to expand...

Could be that as well. I was purely speculating myself. Either way it 'appears' as though the problem originated from the keyway side.

Doug
 
The surface is pretty heavily damaged. The dark areas are most likely oxidation. Usually, oxidation will take some time to set up, but salt water on a fresh fracture face can oxidize fairly quickly.

Yes, there are striations, and they even appear to shift a bit indicating what was the dominate stress (shaft flexure versus shaft torsion). What's much more interesting to me is the color shift and texture of the area near the keyway. It's hard to know without more significant tests, but it is possible that crack initiation and initial crack propagation may have been from stress corrosion cracking. That would say that only after this damage occurred did the fatigue take over, and then cleavage (fast fracture). This isn't all that unusual of a failure scenario.

I don't know the buildup of parts on the shaft, or the load path as it all gets assembled, but if you've got a good tensile field there, it's possible. Then it would come down to seeing if the alloy is off, the preload (assembly load) was too high or some other spec that was missed.

It all depends on how far you want to take it, but I would doubt at this point anyone knows the root cause.
 
fc3 said:
You mean they were involved with the mass murder of several million men, women, and children?
Click to expand...

This is a really bad and wrong (joke).
You can go to far, this kind of remarks don't belong here.

I hope that Wes takes the only right decision and delete this.

Thanks Peter.
 
Well, I am finally ready to close the loop on my engine issue. Sorry it took so long.

After the insurance company denied my claim for the broken shaft, I hired a marine attorney to handle all correspondance with the insurance carrier.

He submitted a claim for the engine damage. By the time he got involved, the surveyor had already seen the boat, and concluded that the bent push rod in the engine was as result of the broken shaft. The yard and the surveyor agreed that the engine over-reved when the shaft broke, causing the "floating of the fuel injector" and ultimately, the failure of the injector caused the push rod to bend.

The insurance company agreed to pay for replacing the engine with a brand new engine (estimated cost for parts and labor of $40K). They would not pay for the broken shaft (estimated cost for parts and labor of $8k). It was their position that the shaft broke due to normal wear, and that the failure of the shaft caused the engine to fail. They would not pay for the cause (the shaft), but they would pay for the result (the engine). I decided not to argue with a man who was writing me a check for $40K.

In the mean time, the yard was able to locate a brand new 3126 engine. Apparently, these engines are no longer in production, and are extremely difficult to find in brand new condition. Most of these engines, at this point, if you can find one, are already re-built. However, the engine they found was rated for the higher horsepower (420 HP, I believe). This now requires that they replace the bell housing on the new engine, with the old bell housing from my old engine, and adjust the fuel flow, to "de-tune" the engine down to 350 HP. This work will begin in January, after the yard gets back from "shut-down".

Once the work is complete, I will try to sell the old engine. I believe it can be rebuilt.
 
Glad it worked out, hope you didn't have to waste too much $$ on the attorney.
Curious, though- doesn't the insurance carrier now own the damaged engine?
 
Glad it worked out as well. I'm curious if your rates will increase so the insurance company can recoup some cost?

Doug
 
I just read through the pages and I feel for you here. Its a big expense to incur and I am glad somebody stepped up to the plate for you!

Have you given any though to upgrading the other motor to 420 hp? You would have a rocket ship on your hands!
 
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