Oh no, we've thrown a rod.

1988RedT2 wrote: Can you get it back up and running this afternoon?

If this were a LeMons car, I'd have drilled, pinned, and welded the counterweight back on, wrapped a belt around the crank journal and metal-banded it in place, hammered the porthole back into shape, and fired her back up.

And probably won some sort of trophy.

Fueled by Caffeine wrote: Does that engine have engine journal temp sensing?

No, and when I was going back through the datalogger everything seemed perfectly normal leading up to the failure. Other than the cliff-like drop-off of the oil pressure immediately following the rod separation, there's not much to indicate why this would have happened. We have other engines of the same type running in the same application, so it'd be nice to figure out why it happened so we could possibly prevent it in the others.

Sorry I'm being purposely vague about the engine type and application, but I really don't want to go into any more detail for privacy's sake. I will post more pics, though.

That's what you get for using a GM motor I remember some of the damage we were getting on the GE AC4400 motors before they changed the cam gear metallurgy and they were getting ripped up on a regular basis.

It's amazing how bad some of that damage can look. :)

Yikes. I just know that won't be cheap to fix. Of course, if it's a critical application then I'm sure you have back-ups/redundancy in the system.

Saw something similar when I was witnessing a factory test of a customers genset. Big bang, lots of smoke but I'm not allowed to share pictures.

We also got to do a postmortem on a 2.5mw generator that had the front bearing fail on the generator shaft. The armature ate through the housing and walked around the room a bit. Not much left that was recognizable.

Nice carnage. Due to the lack of bearing discoloration and what appears to be a dark area in the casting of the counterweight that broke, I'm guessing the CW came off due to metal fatigue (the boss won't like hearing that!) and then broke the rod. Ouchie.

Curmudgeon wrote: Nice carnage. Due to the lack of bearing discoloration and what appears to be a dark area in the casting of the counterweight that broke, I'm guessing the CW came off due to metal fatigue (the boss won't like hearing that!) and then broke the rod. Ouchie.

That's the hypothesis right now. The counterweight (and the crank area it used to be attached to) have a smooth area that looks like fatigue, and then striations interspersed in a brittle failure region. Luckily these surfaces didn't get beat up in the metal-flying-around after party of the failure. The engine's been in service for 4 years, so it's neither in the infant mortality stage nor the million hours worn out stage.

I have the counterweight in my car and we're going to section it and do some microscopic inspection this week.

The thing that gets me, though, is that big end bearing. Man is it beat up- and the mating surface on the rod matches. The bearing didn't spin (dowel locating holes and dowel were in tact) but it sure looks bad.

Only a SWAG on my part: if the CW got 'trapped' between the rod and the block, it could have acted as a crude press, causing everything there to get squashed. As that happened and the metal of the rod cap split, it would 'press' those split lines into the back of the bearing insert.

Lack of heat damage (no brown, blue or black discoloration) of the bearing or what I take to be the crank journal points to a sudden failure, not lubrication related, or at least that's my take.

I wonder what the engineering/design reason was for having that counterweight out there on a 'stalk' from the crank like it seems to be? It looks to me like that would be much more prone to having it vibrate, sort of like a tuning fork, in response to crank harmonics. Which to me would seem more likely to concentrate twist/bend forces in the small area of that 'stalk'.

Wow that is a mess. Almost seems like the chicken and the egg problem, did the counterweight cause the failure of the bearing/rod or did the bearing/rod cause failure of the counterweight. The parts look like they have been mechanically beat to hell like something came loose in the engine, got in the way of the moving bits and basically wreaked havoc. Keep us unwashed masses informed as to what happened.

Counterweight on a stick: Pendulous harmonic damping?

edwardh80 wrote: Not to sound like a gratuitous violence/vandal type, but I love seeing industrial carnage like this. More info and pics please!

I've had nights like that before.

Is this in continuous use or does it start/stop? You said 4 years of use is it 4 years old or accumulated four years of hours.

My what a big rod you have!

In reply to The_Jed:

That's what she said!

nocones wrote: Is this in continuous use or does it start/stop? You said 4 years of use is it 4 years old or accumulated four years of hours.

4 years time-wise, not 4 years of hours, shutdown maybe once every other week or so. And they have a system to prelube the engine (spin the oil pump) prior to putting any revolutions on the engine.

Based on the rest of the bearing surfaces we've looked at, lubrication does not seem to be an issue. As many have rightly pointed out, there was almost no indication of heat-related damage (bluing, etc) other than a few places where there was metal-on-metal (presumably after the failure, when chunks were flying around).

Hauled the crank damper into my office today- man that was fun lugging that up from the parking garage. Going to get some NDT set up for it and the crank, we'll see if it tells us anything. Thanks for all the good insights and theories. I agree, this pendulum on a stick thing seems like it might have been a weak feature of the design. My guess: casting imperfection.

Sounds like LCF, which probably means that you can find the crack origination.

170 liters?! Did you forget a decimal point in there, or is that number correct?

That's either a big honkin' engine, or a big honkin' engine.

Yup. One Hundred and Seventy Litres.

10,370 cubic inches. I guess around 4000BHP? That will generate a LOT of electricity. Or pump a lot of water, or.....