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Post by finiteparts on Aug 25, 2021 20:29:03 GMT -5
Hi Patty, It looks to me like your exducer tips took a significant rub...due to the amount of smeared metal and rub marks. Is the dark area around the "hole" heat staining or is it more material that has flaked out? It is hard to see from the photo.
Are those two different blades or is it the same blade?
Also, can you add another photo that gives an idea of where it is relative to the backface and the scallops? - Chris
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Post by madpatty on Aug 25, 2021 21:03:26 GMT -5
Hi Chris. Those two pics are of the same blade. The stains are some oil leaking past the seal and getting on the hot wheel post run. Here are some more pictures. Thanks
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Post by madpatty on Aug 25, 2021 21:07:01 GMT -5
Hi Patty If there was a bearing failure the resulting gyrations will result in extra tensile loads being placed on the blades above the usual ones from temps and rpm , it might have exacerbated an already "weak spot" in the wheel . I've had a wheel "expand" during a bearing failure and had to cut the tips off the wheel with the oxy torch so as to disassemble the engine Cheers John Hi Racket. There wasn’t any bearing failure at all. Engine was started and shutdown a couple of times. Total time on this turbine wheel is about 30 minutes. Thanks
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Post by racket on Aug 25, 2021 23:26:26 GMT -5
Hi Patty
In that case it was a faulty wheel made from inferior material, 30 minutes with temperatures within design along with rpm , shouldn't result in a wheel suffering creep to that extent
Cheers John
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Post by finiteparts on Aug 26, 2021 7:06:54 GMT -5
Is that a crack in the first photo or is it just scraped on line from maybe cleaning it?
I am wondering if your rub caused a fatigue crack. Rubs can put alot of heat into the impeller and they may have vibrated the blade tips due to the imposed one per rev (at minimum) forcing input.
The hole does appear to be inline with the rub radius and as such, maybe it was at the line of flexure and this took a sufficient alternating stress. Just food for thought.
The idea of a bad casting is feasible, but I thought you had previously said this was a Holset wheel and I would be surprised if they made such a poor quality wheel.
-Chris
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Post by madpatty on Aug 26, 2021 9:46:06 GMT -5
Hi Racket and Chris. Its just a scrapped off line from my pocket screwdriver in the first picture. The crack is just a pinhole. Well it’s an aftermarket turbine wheel not an original Holset one. racket. Creep has happened otherwise how do you explain the dimensional increase of 2mm Chris I don’t understand what you mean by “The hole does appear to be inline with the rub radius and as such, maybe it was at the line of flexure and this took a sufficient alternating stress.” I have used turbine wheel from the same supplier before and have never experienced anything like this. Thanks
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Post by turboron on Aug 26, 2021 14:41:40 GMT -5
Patty, chris said "I am wondering if your rub caused a fatigue crack. Rubs can put alot of heat into the impeller and they may have vibrated the blade tips due to the imposed one per rev (at minimum) forcing input."
My experience is this type of airfoil strike from excessive radial growth or insufficient clearance can "ring the bell" exciting the airfoil's natural frequency. This type of strike can result in a fatigue failure. I have seen this a few times on axial turbines.
Thanks, Ron
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Post by racket on Aug 26, 2021 17:59:28 GMT -5
Hi Patty
Yep , creep has occured , as would happen from an "overspeed" increasing tensile loads beyond the strength of the material , any gyrations will impose additional loads to those just from rotation , this combined with any abberant heating or vibration will surely stress even the best material .
Just throw the wheel away and get a new one , thats what I did with my FM-1 engines wheels after each failure .
Cheers John
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Post by wannabebuilderuk on Aug 27, 2021 3:24:48 GMT -5
Hi Patty Yep , creep has occured , as would happen from an "overspeed" increasing tensile loads beyond the strength of the material , any gyrations will impose additional loads to those just from rotation , this combined with any abberant heating or vibration will surely stress even the best material . Just throw the wheel away and get a new one , thats what I did with my FM-1 engines wheels after each failure . Cheers John Patty the next day 😁
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Post by racket on Aug 27, 2021 3:27:27 GMT -5
LOL........I've felt like that a few times
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Post by madpatty on Aug 27, 2021 7:15:26 GMT -5
Hi Patty Yep , creep has occured , as would happen from an "overspeed" increasing tensile loads beyond the strength of the material , any gyrations will impose additional loads to those just from rotation , this combined with any abberant heating or vibration will surely stress even the best material . Just throw the wheel away and get a new one , thats what I did with my FM-1 engines wheels after each failure . Cheers John Patty the next day 😁 😂😂😂 This is an expensive hobby for sure. Cheers
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Post by wannabebuilderuk on Aug 27, 2021 10:21:10 GMT -5
racket is the wheel not even usable as a freepower for a smaller engine?
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Post by racket on Aug 27, 2021 16:33:57 GMT -5
Only if the rpm are kept very low , like with a direct chain drive
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Post by madpatty on Aug 31, 2021 19:19:01 GMT -5
Shoutout to the fun days when the world was still free of the 🦠
cheers. Patty
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