Oddjob

Anyone have good success with checking spindles and hubs for fatique/stress cracking?

Mag testing the steel spindles and die penetrant or x-raying the cast alum hubs?

Worthwhile or waste of time.

Geo

I'm surprised more people don't do this with common failure components. I know the front aluminum control arms on the 944 are a known problem, yet I never hear of anyone getting them tested. For PCA that is a non-issue generally because as I understand it, alternative components are allowed, but in series where they are not, NDT would be the order of the day IMHO.

Cory M

pretty cool non-destructive testing chart here:

http://www.insight-ndt.com/ndt-methods.html

Geo

Cool chart. We use NDT on almost everything we produce at work. I know there are some tests that are similar to Magnaflux that can be used on non-ferrous materials. I think 944 control arms are a MUST for NDT on a regular basis.

GUMBALL

I agree with GEO, I am sometimes surprised that more people don't avail themselves of this service. On CART Indycars and IRL cars, NDT of wheels and specific suspension parts is mandatory. Many of these pieces lend themselves very well to proper non destructive testing.

I would also have the rear hubs done also - either dye or flourescent magnetic particle.
And you might want to have the wheel centers radiographed as well.

Look in the yellow pages under X-ray, Industrial...or NDT.

Oddjob

I have a set of 944 TS/M030 spindles and hubs that I wanted checked. Brought them in and the shop did mag. particle testing on the spindles, but they said the hubs were too corroded/dirty to use dye penetrant (and I had put quite a bit of time into cleaning them already).

To get testing done on the hubs, I may have to get them chemically etched to clean them, as any sort of mechanical cleaning (sanding, sand blasting, etc) can actually fill/deposit material into small cracks and hide them from exposure by the dye method. Another good/better option is x-ray, and I have not got a quote on that, but I assume its much more expensive.

At some point, it may be more cost effective to go buy the Racers Edge billet replacement hubs - especially if I end up spending a couple hundred bucks on cleaning and testing, and they end up finding a problem with the hubs.

George, I dont believe the alum control arms are a common failure item. Especially the 87+ arms (which are beefier than the 85.5-86 arms). As with any model year 944, the "control arm" failures are most often the balljoints. And I believe that the balljoint failures are most often a shear or bending failure due to an impact or extreme suspension travel (worn balljoint bushings and control arms sockets allow slop in the joint and make them much more prone to failure) - I dont think the common pins failures are from fatigue, so there really isnt a way to test for an impending shear failure . It sure wouldnt hurt to test them, but Im not sure if it would help in most cases (?). Maybe x-ray, to look for inclusions or porous areas to determine if the casting is good or not. Thoughts?

Geo

Jim, I agree 100% about the failures due to too much suspension travel. I think that's easy when modifying the suspension with aftermarket performance and race struts.

Since I am in a position with the SCCA to influence the rules, and I have a 944, I get a lot of feedback about failure of the aluminum control arms. In addition, I've tried to read all the accounts I could of the failures. I think there are some fatigue failures occurring, but I can't prove it. I do think most failures are due to the reasons you mentioned. Still, if I were running them I think I would have them tested at least annually.

GUMBALL

Some configurations (cylindrical - such as hubs and shafts) do not lend themselves well to x-ray technique. I would suggest instead flourescent mag particle. Also, with this technique, mechanical cleaning in much less of an issue.


Properly done, x-ray on aluminum parts will show a great deal. In addition to inclusions of various types, it should show a grain structure change that you would get from fatigue or from an impact bend.

.

ngoldrich

FWIW -

I too am amazed...

On my old CanAm and GTP car I used to pull every suspension component after each race and have it x-rayed by a local aircraft company.

It was amazing the number of internal cracks on splines we found in axles and stub axles. Many were not visible o the human eye...

On my GT2 i give very low life time to all components and proactively replace everything (nuts, bolts, uprights, axles, arms, bearings, turbos, engine components... by hour...)

It helps to be **** retentive LOL...

Norm

leif997

NG...you are being too kind on yourself....we all have seen your bolt/change time index charts...it is rumored that your entire car changes all bolts and suspension components at least 2X per season if not sooner....what base-line do you use for this and do you use alternative sources for parts other than the factory?....could you e-mail me a copy of your change out schedule? No one can touch your preparedness when it comes to this type of maintainance...

ngoldrich

Norm

LOL ur funny...

Main parts are all factory or Motorsport.

Some hardware comes from my aircraft suppliers, Turbos come from Garrett, etc....

I can pm you the high level proactive change schedule if you like.

The detailed scheduling is handled by my database system.

When i get a chance I will put it together and pm you...

Norm