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+--- Thread: Ring-a-ding crankshaft (/showthread.php?tid=2024)
Ring-a-ding crankshaft - cardiffrob - 18-11-2018
Would any kind soul be able to post a brief video that demonstrates the sort of sound one might find trying to make a crankshaft ring after being hit? Not exactly NDT Science but I have several old cranks here and I noticed they all sound the same with neither a Crystal Wineglass ring nor a dull thud. All cracked or all good? Dinggggg, Dangg or Donk? I have an excess of old blocks and crankcases that I need to sort through and am not sure if anything is really worth hanging onto.
Thanks.
Rob
RE: Ring-a-ding crankshaft - Martin Prior - 18-11-2018
Hmmm.....I'd go for "Denggggg". Definitely not "Donk".
RE: Ring-a-ding crankshaft - Chris KC - 18-11-2018
Rob, you are looking for a clear ring, which you are only likely to get if the shaft is suspended e.g. from a bit of string.
But...it's not a reliable test, and consider what's at stake (at best, you throw away a perfectly good crankshaft; at worst, you blow your engine to bits).
Buy a dye penetrant crack test kit, which will set you back 25 quid or so, follow the instructions.
If it flags up any clear cracks then you know what to do.
If you are unsure of the result, try it again.
Any that pass, or that you're still not sure about, take them to a specialist and get them crack tested by magnetic particle inspection (MPI).
DP is most effective at finding surface cracks. MPI can pick up cracks just below the surface where DP won't see them.
If a shaft passes both tests you can proceed with reasonable confidence.
RE: Ring-a-ding crankshaft - Robert Leigh - 18-11-2018
(18-11-2018, 04:07 PM)cardiffrob Wrote: Would any kind soul be able to post a brief video that demonstrates the sort of sound one might find trying to make a crankshaft ring after being hit? Not exactly NDT Science but I have several old cranks here and I noticed they all sound the same with neither a Crystal Wineglass ring nor a dull thud. All cracked or all good? Dinggggg, Dangg or Donk? I have an excess of old blocks and crankcases that I need to sort through and am not sure if anything is really worth hanging onto.I'm no good at posting pictures of anything, but for the ding etc test I suspend from a loosely fitted flywheel nut, which gives a handy attachment point for Chris's piece of string. If any give a dull thud at that stage it's probably not worth a scientific test. I checked 2 3-bearing shafts recently and the difference was instantly recognisable. One is definitely a dud.
Thanks.
Rob
Robert Leigh
RE: Ring-a-ding crankshaft - Chris KC - 18-11-2018
It may also be worth saying that while crack test kits are good for drawing your attention to areas of interest, they sometimes highlight tool marks etc. which are not cracks, so the test must be followed up by careful inspection with a magnifying glass. If you don't have a crack test kit it is perfectly possible to find surface cracks - the larger ones at least - by optical means. None of these methods is infallible so they are best used in concert with each other.
RE: Ring-a-ding crankshaft - Bob Culver - 18-11-2018
The ringing test works on crockery but based on a pile of cracked Seven cranks, useless. If reduced to a donk very seriously cracked. Have to be free of any other dampening factor; grease etc.
I have timed the ring on apparently good Jowett cranks and varies greatly (although these do come with various heat treatments)
I purchased a gallon of black not ultra violet fluid 45 years ago ago " for use with a Benault portable detector". A bit of a fiddle for an amateur to use, but only use a few drops at a time. .I supect it is just fine iron dust in kero.If such a basic product still available a Club may be able to purchase and dispense in small (shielded) bottles. Might be able to make with fine emery paper!
RE: Ring-a-ding crankshaft - Howard Wright - 18-11-2018
Hi Rob
I found a local machine shop that tested a crank and a steering arm for 10 quid. Worth it!!!
Howard
RE: Ring-a-ding crankshaft - Alan - 18-11-2018
The ring of an uncracked crank is unmistakable and it goes on for ages. Equally unmistakable is the donk of a badly cracked crank. It’s the bit between that’s difficult. Having said that I wouldn’t waste time deciding. If I’m building an engine it gets a new crank. End of.
RE: Ring-a-ding crankshaft - Viteran - 18-11-2018
Hi Howard
Useful,
Is “Local” anywhere near South Yorkshire ( tho I travel to Brum a lot ) ?
Ian
RE: Ring-a-ding crankshaft - Howard Wright - 19-11-2018
(18-11-2018, 09:09 PM)Viteran Wrote: Hi Howard
Useful,
Is “Local” anywhere near South Yorkshire ( tho I travel to Brum a lot ) ?
Ian
Hmmm
Not exactly, I'm in sunny mid Wales. But if I can find a friendly machine shop here I'm sure you can find one in (sunny?) South Yorkshire (did my degree in Sheffield!)
Cheers
Howard