How to detect a cracked Crankshaft - Video

[maxracesoftware]

i previously Posted this similar method on Speed-Talk
but here's a Video :
i just wish the Guy would have hit all the different Counterweights on each Crank

i hit all the Counterweights , then flip the crank on its snout , then hit all the Counterweights again ,
listening for distinct sound a cracked crank makes = it does not ring very long at all, almost 100% of time its dull thud

the Guy hung the Cranks in mid air ... pretty good method as well

How to detect a cracked Crankshaft - Video
https://www.youtube.com/watch?v=GGe56QKtrnE
or
https://youtu.be/GGe56QKtrnE

[maxracesoftware]

Re-Post from old Link :

viewtopic.php?f=1&t=62171&p=877417

Craig's Record setting A/ND and B/ND engines use just a solid Hub
reason : no way to run a real Damper because of all the front-driven drives Magneto,etc
Craig wants to run a ATI Damper , but can't fit it in

One time , on my SF-901 with the old 1000 Lbs Brake/Absorber
we made 4 or 5 Dyno tests ...everything was great ... then next Dyno test ,
the 2 bolts that hold the Strain-Gauge started backing out from engine vibrations + HP was down too
i told Craig , the Crank might have just cracked
i'd go back after each Pull and retighten those 2 bolts ... made 4 or 5 more pulls , bolts kept loosening + HP was down a little
Craig decided to run it in Houston ... 2nd or 3rd Run it killed all the main bearings

Craig brought me the Crank after he had it magnufluxed ... said it didn't look cracked ??
i stood the Crank on it end ... hit the top counterweights with a Hammer ... very dull thud ... no ringing
flip it over on its snout ... hit the other counterweights with a Hammer ... again , very dull thud ... no ringing

i went get my stock GM OEM steel 3.480" crank i ran in my 355cid 725HP @9000 RPM 10000 RPM thru MPH lights
i hit counterweights with Hammer ... beautifull long ringing tone

i told Craig , next time try hitting counterweight to verify crank is cracked + the magnafluxing

[dannobee]

Crank grinding was about the only shop machining process that I've never done. I left it to the "old timers" at a different shop. I was always amazed that no matter what I oddball crap I dragged out of the back of the truck, the one guy could rattle off what kind of crank it was from what seemed to be 50 feet away. And he was good enough that no matter what my request, it would always come back perfect, within a tenth. He too, would drop every crank from about a half an inch off of the ground and listen for the ring before wasting anymore time on a cracked piece. I have crazy mad respect for those type of guys.

[panic]

From my "Chevrolet Stovebolt" book ( http://victorylibrary.com/235BK.htm ):
" An unknown clean crankshaft can be crudely tested for cracks (but not wear) by this method: suspend it vertically with a strong piece of wire or rope through a flange hole. Strike it smartly with a light brass or lead hammer on a non-structural surface, such as a counterweight. The hammer should be metal, but softer than the crankshaft.
If the grain structure is continuous and uninterrupted the crankshaft will ring since the impact wave will travel through it as if it were a bathtub full of Jell-O. It’s a large and malformed tuning fork.
If a crack is large enough, its sides will abrade and chafe each other when excited and the vibration will be damped by this friction, as it will with anything attached that is not contiguous (carbon and debris in the oil passages, old bearing material, broken flywheel bolt, Mallory metal, welding, threaded oil galley plugs, &c.). The tuning fork is now grounded, and the resonance is suppressed at the point of contact, and also damped by the natural frequency of the grounding material.
The noise will be a dull “clunk!” rather than a sharp and semi-musical “bong!”. This can also be used to test connecting rods, but remove the cap and any fasteners first.
If the crack is very shallow the internal friction will be very low, and no audible change may be detectable. If the crack is open all the way down (viz. its sides are separated by .0001” even when excited) the ring tone may be only minimally disturbed. A ring can never be an absolute test, but in general comparative testing of the subject against a known-to-be-good crankshaft for tone will tell you when to be nervous."

Please do not copy or re-post.

[maxracesoftware]

He too, would drop every crank from about a half an inch off of the ground and listen for the ring before wasting anymore time on a cracked piece.
I have crazy mad respect for those type of guys.

before i started Meaux Racing Heads / Machine Shop , i worked at NAPA Store/Machine Shop in Abbeville , LA
and they had a brand new Crankshaft Grinder in that Shop on a cement island because there was a 4-Lane HWY in front the Store
i was told the cement island was more than 4 Feet thick .

The previous Machinist quit , i was bymyself , no help to learn the Crankshaft Grinder ,
so reading thru the Manual , i came across this : that you should strike the Crank Grinder's very large Stones ,
and if it does not ring , its cracked internally , do not use it , it can come apart !

_____________________________________________________________

a little more Info getting back to Crankshafts on the Dyno .....
the 1000 Lbs Torque SF833 Absorber's Strain Gage had 2 bolts on it ,
i kept them finger tight ... if the Crank was good + Engine balanced too ... it never loosen anyone of those 2 bolts

if the Crank assembly was not balanced well ... it vibrated one or both bolts loose backing out about 1/2 to 1 turn out

for "Cracked Cranks" .... if the Crank cracked just happened to crack on the Dyno after a few Pulls
it started backing out these 2 Bolts , when before it cracked, it never backed them out .

Likewise , if the Engine wan't Balanced well from the get go ... it would loosen those bolts during each Dyno test
i had a Dyno Customer / Machine Shop Owner dyno test a Big Block Chevy Engine ,
the Strain Gauge bolts were loosening on each Dyno test ,
i told him his Crank is not balanced that great , he said "How do you know that ??? "
then he tells me , you're right , i had trouble with the front half balancing it , its good as i could get it without using a Heavy Metal slug "

that was one very good and useful thing about the Strain Gauge setup on the SF-833 1000 TQ Absorber
but since i upgraded my SF901 to SF871 2000 TQ Absorber , i can't tell if a Crank cracks , or is cracked , or if Engine is out of Balance

[In-Tech]

40 years ago my balance dude, Johnny O, grabbed my bs steel 427 crank and gave it a ring. It made me curious so I asked. He rang a good steel crank, a good cast crank and one of each that were cracked and I could hear the difference. Also explained to have them wet magged even if they pass the "ring test". Pretty awesome knowledge to learn at 14 years old and of course still true to this day

[Dave Koehler]

before i started Meaux Racing Heads / Machine Shop , i worked at NAPA Store/Machine Shop in Abbeville , LA
and they had a brand new Crankshaft Grinder in that Shop on a cement island because there was a 4-Lane HWY in front the Store
i was told the cement island was more than 4 Feet thick .

The previous Machinist quit , i was bymyself , no help to learn the Crankshaft Grinder ,
so reading thru the Manual , i came across this : that you should strike the Crank Grinder's very large Stones ,
and if it does not ring , its cracked internally , do not use it , it can come apart !

True Dat.

_____________________________________________________________

a little more Info getting back to Crankshafts on the Dyno .....
the 1000 Lbs Torque SF833 Absorber's Strain Gage had 2 bolts on it ,
i kept them finger tight ... if the Crank was good + Engine balanced too ... it never loosen anyone of those 2 bolts

if the Crank assembly was not balanced well ... it vibrated one or both bolts loose backing out about 1/2 to 1 turn out

for "Cracked Cranks" .... if the Crank cracked just happened to crack on the Dyno after a few Pulls
it started backing out these 2 Bolts , when before it cracked, it never backed them out .

Likewise , if the Engine wan't Balanced well from the get go ... it would loosen those bolts during each Dyno test
i had a Dyno Customer / Machine Shop Owner dyno test a Big Block Chevy Engine ,
the Strain Gauge bolts were loosening on each Dyno test ,
i told him his Crank is not balanced that great , he said "How do you know that ??? "
then he tells me , you're right , i had trouble with the front half balancing it , its good as i could get it without using a Heavy Metal slug "

that was one very good and useful thing about the Strain Gauge setup on the SF-833 1000 TQ Absorber
but since i upgraded my SF901 to SF871 2000 TQ Absorber , i can't tell if a Crank cracks , or is cracked , or if Engine is out of Balance

Concerning the strain gauge vibe test. Would they loosen up on something with normal shake like a 4 cyl with a good crank?
Could a poor man's strain gauge or knock sensor be attached to the dyno to indicate the crack?

Crank Chimes
I was thinking that if the guy in the video had 2 hammers and some drumming experience he could crank out some new wave crack rock.