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How does the crank sound when you tap the counterweight with a hammer? I'm curious because I've seen cracked cranks before, pretty sure they were cast, and when you tapped it with a hammer, there was no ring. It was a bit of a dull sound, not the type you have to grab the counterweight to make it go away.
just so everybody knows, those 3 pictures are 3 different journals. all 4 rod throws have cracks, i just didn't photograph the last one.
if someone were to base whether or not this crankshaft was any good based on how it rings, they'd think it was perfectly fine. on three of those journals the cracks run more than half way around the journal. basically it's a failure waiting to happen.
i wanted to post these pictures for a couple of reasons so i'm glad you asked about how it sounds, or whether it rings or not. sometimes a cracked crank will have a dull ring, but other times it'll still have a nice clear ring like this one.
another reason i posted this is because i don't think i've ever seen anyone post pictures of Zyglow under UV lighting. i think a lot of people don't really know much about the process or what their machinist is actually doing or looking at to qualify whether or not their crankshaft is fit for service. it's not like this is high tech or anything like that, but it's a great, cost effective method with crystal clear results.
just as a side note, every now and then what appears to be a crack isn't a crack at all, but perhaps a grease line or some other annomoly that appears as such. often times a little bit of very light sanding and those will disappear. actual cracks won't disappear when you do that since the particles will remain in the crack below the surface.
machine shop owner and engine builder
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