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Magnaflux and why we recommend it.
#1258412
06/27/12 06:59 PM
06/27/12 06:59 PM
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Joined: Jul 2010
Posts: 2,091
Delray beach, Florida
Performance Only
OP
top fuel
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OP
top fuel
Joined: Jul 2010
Posts: 2,091
Delray beach, Florida
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here's some pictures of a crankshaft a customer brought in to have us modify for his application. we almost always recommend magnetic particle testing on crankshafts.
had we not found this now, i'm sure the owner would've found it in short order the hard way.
machine shop owner and engine builder
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Re: Magnaflux and why we recommend it.
[Re: Moparnut426]
#1258418
06/27/12 07:34 PM
06/27/12 07:34 PM
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Joined: Jan 2003
Posts: 1,420
FastOne
pro stock
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pro stock
Joined: Jan 2003
Posts: 1,420
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Re: Magnaflux and why we recommend it.
[Re: Moparnut426]
#1258420
06/27/12 09:12 PM
06/27/12 09:12 PM
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Joined: Jul 2006
Posts: 382
Roseville MN
72swgnr
enthusiast
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enthusiast
Joined: Jul 2006
Posts: 382
Roseville MN
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Quote:
And unless ya have it radiographed you wont know how deep it is.
I cant imagine too many engine shops have an x ray machine at their disposal.
They can also use ultrasonics to find the depth of the indication. I've been working on a 1,000,000 HP/1 billion dollar steam turbine that self destructed for the past 3 weeks 
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Re: Magnaflux and why we recommend it.
[Re: dodgeboy11]
#1258422
06/27/12 11:59 PM
06/27/12 11:59 PM
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Joined: Jul 2010
Posts: 2,091
Delray beach, Florida
Performance Only
OP
top fuel
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OP
top fuel
Joined: Jul 2010
Posts: 2,091
Delray beach, Florida
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Quote:
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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Re: Magnaflux and why we recommend it.
[Re: Performance Only]
#1258423
06/28/12 01:03 AM
06/28/12 01:03 AM
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Anonymous
Unregistered
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Anonymous
Unregistered
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Wow, I sure hope that isn't my crank. 
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Re: Magnaflux and why we recommend it.
[Re: BIGSPEED]
#1258430
06/29/12 03:53 AM
06/29/12 03:53 AM
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Joined: Jan 2004
Posts: 13,247
Mt. Vernon, Ohio
dartman366
I Live Here
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I Live Here
Joined: Jan 2004
Posts: 13,247
Mt. Vernon, Ohio
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Dan, I take it that you used the Magnaflux Zyglo process, we used to use that process to inspect turbine blades and turbo shafts, also used the magnaflux spot check system but zyglo will go where most anything else won't.oh by the way,,nice catch.
Light travels faster than the speed of sound,,,this is why some people seem bright untill you hear them speak.
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