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Detecting invisible faulty/crack in 4WD steel rims?

Submitted: Wednesday, May 01, 2002 at 00:00

Guy

An invisible faulty / weak / cracked rim is detected easely by weight balancing.
If the total weight (inside-outside) exceed 130 grams the c hance of having something wrong
with the wheel is great ----
But if you have to re-balance your wheel every 2000 kms or more and if the weight
varies by more than 30 grams the rim is cracked or weak at one spot.
It took me 20000 kms to detect a brand new steel rim which had an invisble crack.
What alerted me was the constant wheel alignement I had to do as it was getting worse.
The crack was 70 mm long under the paint.
Guy
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AnswerID: 3255   Submitted: Wednesday, May 01, 2002 at 00:00

Will replied:

Guy,
What sort of wheel was this?
What car?

Will
Reply 1 of 2
FollowupID: 1313   Submitted: Wednesday, May 01, 2002 at 00:00

Guy posted:

It was a steel rim 16 inches which comes with the car as new.
The car is Nissan Patrol GU 2.8 litres Diesel.
Guy
FollowUp 1 of 2
FollowupID: 1314   Submitted: Wednesday, May 01, 2002 at 00:00

Will posted:

Guy,
That is exactly the reason why I asked, GU Patrol Rims are now known for cracking, however Nissan Claims it only happens to the utes (such as used by Telstra etc) which are heavily loaded.
In my optinion this is a highly dangerous scenario.

Will
FollowUp 2 of 2
AnswerID: 3256   Submitted: Wednesday, May 01, 2002 at 00:00

Gordon replied:

Guy
For future reference, it is possible to detect cracks in steel rims using the magnetic particle method. This is a non-destructive testing method in which very small magnetic particles (often in a liquid mixture) are spread in the areas of concern. When a magnetic field is applied to the part, the particles allign in unusual patterns around any cracks. This method, unlike the dye penetrant method can be used to detect cracks underneath painted surfaces without stripping the paint.
Reply 2 of 2
FollowupID: 1323   Submitted: Thursday, May 02, 2002 at 00:00

Guy posted:

Gordon - - - Have you got any more informations on this process - - -
I have electrical magnets at home, where would you buy the magentic particles? - -
actually I remebered doing a "magnetic liduid" by adding steel filing particles in some Johnson Baby oil found in any supremarkets.
That should work- - - Last time I did this I wiped one of my credit card but it was fun to do - - - Gordon how would you set the experiment yourself?
Guy

FollowUp 1 of 2
FollowupID: 1327   Submitted: Thursday, May 02, 2002 at 00:00

Gordon posted:

Guy, I have been out of the engineering world for a few years now. Both dye penetrant and mag particle methods should be in common usage in workshops that re-build engines (particularly high performance) and should be available from suppliers to that industry. Dye penetrant is more common than mag particle but if you start with this line of enquiry you should get there. If you don't want to buy the proper gear yourself there are companies that provide engineering inspection and testing services - look under Inspection and Testing Services in the Yellow Pages. One I used to deal with in Brisbane is ETRS - now at Riverview. If you are near a university try their mechanical engineering workshop. You might get some sort of result by making up a very thin liquid solution in the manner you describe and using two magnets - one each side of the suspect area. It should work best with a low viscosity fluid with evenly dispersed iron powder (rather than filings) and strong magnets. Good luck. (Let me know how you go by posting another follow-up under my original reply.)
FollowUp 2 of 2