Is there anyway to get a closer picture of the broken part of the bolt?
almost looks like to me that there is some issues with how the bolt is formed but i need a better picture to tell.
Since the threads arent polished and the bolt isnt necked down i would say that it probably didnt get overloaded, maybe there was some quenching cracks in the threads, or some sort of inclusion in the base metal to begin with.
:whs: need better pictures but it looks like there is an inclusion in both of them. The fact that two of them failed in the same way and same location imo either says that there is a manufacturing process problem or that area of the bolt is exposed to more/extreem heat cycles. What did they come out of?
I will post better pics on Monday when I get back to the shop.
Those are 2 of the Flex plate to crankshaft bolts, all of them were like that.
We had made several passes at the track and were on the way home when I got into a race with a twin turbo 6.7 Cummins(while on a stretch of closed hi way sanctioned for hi speed racing) at any rate after several 70-100 mph hits and not being able to get away from said Cummins, I hit it one last time and stayed in the throttle till I saw 3800rpm on the tach at which point said Cummins was several truck lengths behind. All was good till we exited the freeway at which point I heard a rattle and pulled into a parking lot. Long story short pulled the trans and this was what we found.
Bolts are produced on a machine called a cold header. They are made from a spool of wire that is drawn through a die to achieve roundness and shank diameter. The wire is fed into the header where is is fractured to length and forced into dies where the head and shank are formed in multiple hits and transfers. The boltmaker style cold headers usually include flat die thread roll forming positions. Inclusions in the steel usually result in cracks that run along the axis of the cylindrical body of the bolt. Heat treatment follows on most fasteners after the heading process. Boltmakers will knock out a ballpark of 3000 bolts per hour with this size bolt, and the lot sizes are generally in the hundreds of thousands. Best way to test short of paying a lab to analyze the bolt is buy new bolts that are made by another company, and beware of rebranding, and see if the failure continues.
I would guess they backed out too. The threads close to the shoulder look slightly shiny.
I would think the loctite is a good idea. I would also use loctite primer, helps to get full holding strength out of the loctite. Spray threaded hole and bolt. Let sit and dry or blow out with compressed air.
well based of my Mechanics of Materisals class, that would be torsional shear. Just like if you take a piece of chalk and twist it in half, it goes at a 45 degree angle that look EXACTLY like the bolts where they are broken. Same thought process here, most materials do that because max shear is at 45 degrees from horizontal. That bolt has to much force on it. And well the force on the bolt is hard to tell because its on a rotating flywheel, but im sure its pretty high. Its just over working the bolt
I dont get how you guys thing that it can be on a torsional plane, i mean i see what your getting at and i know alot of times stuff breaks at a spiriling 45 degree angle, but the pictures do not give enough evidence of that, there could also be a loaded shear cliff that is caused from when a hard bolt becomes corroded near the outside of the bolt, too many variables and not nearly good enough pictures at this poing to come up with anything...
i understand what you are saying but i dont understand how you feel that is what happened based on the crappy pictures that were given to us.
Remember whats posted on ARPs site is the more Common failures...
FWIW im not saying your wrong, im just saying you cant make a good educated call with that crappy ass picture
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