Broken HX-40 parts

[Strick-9]

I had some spare time last night and finally decided to take apart my broken HX-40.



The first thing I noticed was the nut holding on the compressor wheel was finger tight. No wrench needed for removal!



Not sure how much that had to do with the failure or if it was a result of the failure.



I took two pictures of the damage to help describe my parts.



I tried to realign the broken shafts in the first picture to illustrate what it should look like.



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This is the first turbo I've ever disassembled, but why on earth is there an immediate step change in the shaft diameter. That's an engineering blunder for rotating shafts. My question is are all turbo shafts designed like this or is this an HX-40 trait. This design is just begging for a fatigue failure.



The second picture shows the end views of the two broken shafts. I'm not sure how well the pictures will turn out, but you can see the small grey region that was the last portion to snap off. It's a text book fatigue failure where a crack began in a sharp corner due to stress concentrations and slowly propagated its way to the center of the shaft. The relatively small size of the final fracture shows that it didn't fail due to a high tensile or torsional load. So, no barking or misuse involved. Just poor design.



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With a small fillet instead of the sharp step change in diameter, I'm certain my HX-40 would still be spinning today.



-Chris

 

[Bob Wagner]

great information

Chris, what would the shaft differntal be. 30% less diameter more or less?



Thanks for the pictures and post.

 

[Deezul1]

Hey Chris

How is the motor coming? Boy you get to get a whole bunch of new parts.

 

[KatDiesel]

My contribution - fished this out of the muffler

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Editing the pictures now to make them smaller... .....

 

[Strick-9]

Ah yes, the motor. It's been so long since I've seen it I've almost forgotten about it. I'm going to pick it up tomorrow in pieces and try to remember how they all fit back together.



While it's true I'm collecting a bunch of new parts, I'm also getting a huge bills to go with those shiny new parts.



I've now have 5 turbos and 3 P7100's. It's a shame I only have one block. (all in due time)



-Chris

 

[Jim Fulmer]

Chris I'm courious what you found out when you tore it down, clearences ect. what was the big problem other than that piston.



Jim

 

[HVAC]

Notice all the shafts break just behind the compressor wheel. As far off the map as we run the HX40 could it be surging? Surging causing the shaft to fail?

 

[Cummins Corvette]

Hey thanks for the pics Chris. That sudden decrease in diameter has me quite puzzled. What a POS design.