Eagle Forged Stroker Crank CRACKED
LOL at this thread. NONE of you have enough info to determine what caused the OP's breakage. NONE.
You don't know the alloy, you don't know the grain size, you don't know the damper condition, you don't know the material hardness, you don't know the material toughness. None of you can categorize the breakage as a fatigue fracture or an outright overload failure. You don't even know if the material is cast iron, cast steel, or Long Wang's House Of Secret Recipe's menu number 5. Any inclusions in the material? Don't know. Any corrosion? Don't know. Any casting flaws? Don't know. Any non-metallic alloying ingredients? Don't know. Post-production treatments? Don't know. Proper installation? Don't know. Proper handling during shipping? Don't know. Crank condition prior to install? Don't know.
You don't (in regards to the parts involved) know ****.
That is 100% NOT what 'those marks' are for. The forging is a piece of metal that's red hot, mashed into a crank shape by a massive hammer. The thick lines are flash (i.e. pieces of the original material that aren't going to be part of the crank. They are usually sawn off cold or cut off with a blade while still red hot. The forged crank is stronger because the material is 'worked' which strengthens it (for a variety of reasons). Think bending a paper clip or coat hanger; it's really hard to re-bend it in the same place, because the material has work-hardened in the bend. You don't usually see the flash lines on aftermarket cranks because they take great care to clean them up.
Maybe this will help:
The thin lines are where the two halves of the casting mold come together. It's thin because the two mold halves have to be a tight fit or the MOLTEN metal will just run out before it cools in the shape of a crank. The metal is not worked, which means it's strength as-cast is less than when it is forged. Please note that some processes can be used to change the properties of the material after it is cast, such as surface hardening, annealing, peening, etc.
A raw crankshaft casting. Note the thin parting lines, and that they are not all in-plane with one another.
That hole is CAST off center because Wang Dong didn't notice (or care) that the core was off when it was cast. It is impossible to 'manufacture in' a feature like this on a forging, so holes like this are machined after on forgings, but the surface conditions inside the hole and at the edge of the bore give it away; it is not machined and therefore the poorly-located feature was cast in place.
When you run a Chinese crankshaft, you don't know fuckall about what you just bought, other than that it's SUPPOSED to be what you wanted. I've see Chinese castings with gravel, bolts, broken end mills, and huge voids in them that you don't find until you machine them. There's ZERO accountability and ZERO U.S.-level Q.C until it gets here. After it gets here, VERY few people do material certs or anything else to verify it is what it's supposed to be. They take your money and they laugh all the way to the bank.
LOL at this thread. NONE of you have enough info to determine what caused the OP's breakage. NONE.
You don't know the alloy, you don't know the grain size, you don't know the damper condition, you don't know the material hardness, you don't know the material toughness. None of you can categorize the breakage as a fatigue fracture or an outright overload failure. You don't even know if the material is cast iron, cast steel, or Long Wang's House Of Secret Recipe's menu number 5. Any inclusions in the material? Don't know. Any corrosion? Don't know. Any casting flaws? Don't know. Any non-metallic alloying ingredients? Don't know. Post-production treatments? Don't know. Proper installation? Don't know. Proper handling during shipping? Don't know. Crank condition prior to install? Don't know.
You don't (in regards to the parts involved) know ****.
That is 100% NOT what 'those marks' are for. The forging is a piece of metal that's red hot, mashed into a crank shape by a massive hammer. The thick lines are flash (i.e. pieces of the original material that aren't going to be part of the crank. They are usually sawn off cold or cut off with a blade while still red hot. The forged crank is stronger because the material is 'worked' which strengthens it (for a variety of reasons). Think bending a paper clip or coat hanger; it's really hard to re-bend it in the same place, because the material has work-hardened in the bend. You don't usually see the flash lines on aftermarket cranks because they take great care to clean them up.
Maybe this will help:
The thin lines are where the two halves of the casting mold come together. It's thin because the two mold halves have to be a tight fit or the MOLTEN metal will just run out before it cools in the shape of a crank. The metal is not worked, which means it's strength as-cast is less than when it is forged. Please note that some processes can be used to change the properties of the material after it is cast, such as surface hardening, annealing, peening, etc.
A raw crankshaft casting. Note the thin parting lines, and that they are not all in-plane with one another.
That hole is CAST off center because Wang Dong didn't notice (or care) that the core was off when it was cast. It is impossible to 'manufacture in' a feature like this on a forging, so holes like this are machined after on forgings, but the surface conditions inside the hole and at the edge of the bore give it away; it is not machined and therefore the poorly-located feature was cast in place.
When you run a Chinese crankshaft, you don't know fuckall about what you just bought, other than that it's SUPPOSED to be what you wanted. I've see Chinese castings with gravel, bolts, broken end mills, and huge voids in them that you don't find until you machine them. There's ZERO accountability and ZERO U.S.-level Q.C until it gets here. After it gets here, VERY few people do material certs or anything else to verify it is what it's supposed to be. They take your money and they laugh all the way to the bank.