Broken Crank

[LMTC]

If there's any question about the possiblity of cobbled together parts, I'd be curious as to the origin of the machine. Have you spoken with the seller? How long did you have it before the first crank broke?

 

[CAT793]

G'day gents,
Are there any pictures of the fractured crank ??? There is a lot to gained from the failed iron. The crank will most likely be a forging, forging created flow lines (steel grain) parallel to the fillet and journal surfaces resulting in a stronger crankshaft.

There are quite a few different failure modes associated with crank failure . Basically the crank will see two types of load , Bending ( During combustion) and torsion ( caused by the resistance to crankshaft rotation by flywheels, pulleys, transmissions etc.)

I'll list a few types of failure that we look at.

Slow failure ( over time)
Bending Fatigue
Torsional Fatigue

Quick failure (can happen at anytime)
Contamination
Misalignment
Heat
Grinder cracking
Straightening cracks
Welding
Inclusions
Flaking
Forging burns
Quench cracks

I could keep going on but that should do. If any photos are available can we see them.

Your first crank could have failed from Fatigue, second cranks unless it was used would not have failed from fatigue, but more than likely from one of the others on the list above. There is a lot that goes into a crank shaft it is a very involved process, a problem during the manufacturing process if not caught will cause a low hour failure. I usually work with engines from 100hp to 3500 hp but the same principals apply to a small engine.

The iron will tell you what happened if you know what to look for. Let me know if I can be of any more help.

Cheer's
Pete

 

[LMTC]

For those of you--like me--whose technical level was just exceeded by light years in this last post, Pete is an engineer with Caterpillar. And that accent in his typing (G'day gents).....he's from that island where they all say "G'day", thus eliminating the totally useless and time wasting double "O".

And you should see some of the stuff he gets to play with. Machines bigger than my house.....

 

[phatgemi]

For those of you--like me--whose technical level was just exceeded by light years in this last post, Pete is an engineer with Caterpillar. And that accent in his typing (G'day gents).....he's from that island where they all say "G'day", thus eliminating the totally useless and time wasting double "O".

And you should see some of the stuff he gets to play with. Machines bigger than my house.....

Yep, it sure sounds like he knows his stuff. There could be one reason missing from his list however. But we can't be sure........

- Improper VN rebuild!

Would be interesting to learn the orgin of this tractor........

 

[RJYork]

Thanks again for the input. I will try to post a picture of the crank before I send it back to Hoye Tractor.

New information:
The crank has broken on both sides of the engine. First in front, latest in back.
Mechanic says there is no misalignment or any sign of a misalignment.
He is taking the flywheel to a racing shop to test that component.
He had the injectors tested and found them in good condition. He had the same thought as some of you. Good guess, but no cigar on that one.

Yes, I really want to find out what is happening before I put it back together. That is why I am having it checked thoroughly.

I ran the unit for two years before first break. But hardly any time before the second break. I will let ya’ll know as things progress along.

 

[CAT793]

Mate,
Make sure the photos are very good quality close-ups we really need to see what happened , need to see both side of the fracture ........... if the size exceed what's allowed on the forum , you can email them to me direct and I can have a look at them for you.

We all want to see the iron..............

Let us know how you get on.

Cheer's
Pete

 

[RJYork]

I just got off the phone with my mechanic. He was installing the new crank, from Hoye, when the light hit the new crank just right. He discovered a crack in the brand new crank. He was able to put a knife blade into the crevice. The location of the crack? Glad you asked. Same place as the break in the crank being replaced, which was also purchased from Hoye. I asked Hoye to contact the mechanic and let me get out of the middle. I will send both cranks back to Hoye for their analysis. Stay tuned for the next installment.

 

[mark777]

Incredible!

If Aaron at Hoye has two bad cranks form their supplier, wonder how many, and from what source are on the shelves.

I'd bet my next paycheck We'll hear from Hoye and let us know what actually happened. Obviously nobody is safe from faulty manufacture regardless of how big (or small) the volume of your business is.

I'm sure I would Zy-glow AND magna-flux any crank shafts from that, or any particular supplier.

Good luck,

Mark

 

[kenmac]

If I were Aaron, I would check the rest of my stock. Not just these cranks , all my cranks

 

[MJPetersen]

Incredible!! I for one would still like to see those pics up close and personable for the first second and third cranks. If at all possible.

Mike in Warsaw