Turbo shaft failure - what do you think?

[Levigarrett76]

7.3 powerstroke with T4 S366 w/ Turbonator VGT/VNT On friends truck posted on fte.

whats yalls opinions of failure mode?

 

[pvkj454]

Caused by turbo bark?

 

[Donk]

Sticking VNT leading to turbo chatter (or whatever the correct term is) and eventual failure as a result.

Edit: compressor surge.

 

[Levigarrett76]

Correction, s366
Hes swapping to a 472

Link to video of it before the shaft broke
https://www.ford-trucks.com/forums/1628232-ftns-t4-sxe-build-conversion-thread-42.html

and then post 642
https://www.ford-trucks.com/forums/1628232-ftns-t4-sxe-build-conversion-thread-43.html

 

[Elwenil]

It's broken.

 

[70 tp]

Surge

he said shaft

 

[Levigarrett76]

View attachment download.jfif

 

[Donk]

Correction, s366
Hes swapping to a 472

Link to video of it before the shaft broke
https://www.ford-trucks.com/forums/1628232-ftns-t4-sxe-build-conversion-thread-42.html

and then post 642
https://www.ford-trucks.com/forums/1628232-ftns-t4-sxe-build-conversion-thread-43.html

Looks, like a big compressor surge when he steps off the gas at around the 35 sec mark. I'd like to see graphs of the MAP vs the exhaust pressure. On the other pulls he seems to ease off the gas rather than step off which gives the VNT more of a chance to respond. Also if he'd been making a lot of smoke previously that can clog up the VNT again making it slower to respond.

 

[Eric]

Fatigue fracture. Stress reversals and thermal cycling created micro cracks that slowly propagated over time until strength was reduced enough to cause failure.

 

[Baconator]

Had it been balanced?

 

[ExWrench]

 

[DMG]

Boots were on too tight.

 

[[486]]

his stretched tires and leveling kit broke it

 

[Ted_Kaczynski]

He forgot to wear his white sunglasses

 

[TrikeKid]

7.3 Rejecting his attempt to make more than 200hp?

 

[sdmuleman]

Obvious signs of fatigue cracking, which looks to have initiated at about 7 o'clock in the picture on the outside of the shaft. The progression and origin is consistent with primarily bending load, as is the final failure plane (perpendicular to shaft).

What I'm less sure of is what caused that loading - imbalance is the most likely source of bending load to me, but the only cyclic change is in magnitude and that only with change in compressor shaft speed, which means relatively few cycles of fairly low magnitude - for that to cause failure it would probably have to be significant imbalance and/or significantly higher than design speed. That being said, I am not sure what compressor surging looks like in term of shaft load - I would expect vibration and torsional loading, but I'm not sure if you get enough pressure imbalance across the wheel to cause significant bending load, and with rapid enough change to cause cyclic loading. Also, I would be surprised to see enough load to cause shaft fatigue without also having visible compressor blade damage.

 

[Levigarrett76]

thanks for the input guys