Premature Slop In Spherical Bearings

[Scalesy]

Hey guys, I'm suspecting I know the cause of this but I wanted to hear some opinions.

Our car has pull rods all around, and 3 out of 4 upper ball joints on the upright have developed some axial play after only a few hours of testing....this happened last year too. The lower ball joints where no rod is connected have been fine for 2 years.

We ran really stiff springs last year, and this year so far we've had stiffer springs than I'd like (softer ones on the way from Risse, supposedly).

My thought is the excessive impact (i.e. spring not absorbing enough of it) is causing the ball in the spherical joint to gradually come loose. Any other thoughts as to why this would happen prematurely? I'm confident that the installation is correct (pressed in, lip machined on one side of the housing, retaining loctite).

Thanks

[Scalesy]

Hey guys, I'm suspecting I know the cause of this but I wanted to hear some opinions.

Our car has pull rods all around, and 3 out of 4 upper ball joints on the upright have developed some axial play after only a few hours of testing....this happened last year too. The lower ball joints where no rod is connected have been fine for 2 years.

We ran really stiff springs last year, and this year so far we've had stiffer springs than I'd like (softer ones on the way from Risse, supposedly).

My thought is the excessive impact (i.e. spring not absorbing enough of it) is causing the ball in the spherical joint to gradually come loose. Any other thoughts as to why this would happen prematurely? I'm confident that the installation is correct (pressed in, lip machined on one side of the housing, retaining loctite).

Thanks

[The AFX Master]

The same with us!

Are you using aurora?.. we are having the very same problem but with rod ends. Last year's car rod ends never suffered from that issue

[Mark TMV]

+1 for Aurora RAM rod ends developing play after a few hours of running.

[Drew Price]

How much play are we talking?



I have never had this happen on any of our bearings (last year's car has ~50 hours testing and a competition on them). BUT, my bearings are a little oversized, -5 bearings all around and -4 for steering components, rather than the 1/4" bearings most people are using for hardpoints these days.

Make sure you're not accidentally misaligning them too much, the -4 COM bearings can only take ~13 degrees misalignment, and if your bushings / spacers are larger O.D. where they seat on the flat on the bore of the ball you will quickly bind up the race and cause issues, look for chew marks around where the spacers sit on the ball where they have misaligned too far.


Best,
Drew

[Scalesy]

We're using FK HIN6T sphericals...they are rated for an alignment of 23 degrees and since our a-arms are pretty close to straight out, I'm going to rule that out. I thought after last year that maybe tightening them down a little more might help but it hasn't prevented it.

+1 to the 1/4" rod ends too...this usually takes a bit longer to happen though

Any thoughts as to how much slop in a spherical or rod end will cause the ball to pop out? We ran last years car for a substantial amount of time AFTER I discovered the problem and still have yet to see one fail.

But I suppose this is part of the reason we believe in double shear http://fsae.com/groupee_common/emoticons/icon_wink.gif

[Scalesy]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Drew Price:
How much play are we talking?
</div></BLOCKQUOTE>

I'd say in the .050" range

[fixitmattman]

FWIW I run teflon lined Aurora's on my street car. Was 3 years of harsh Canadian winter road salt and sand before they needed replacement due to excessive play. They had their fair share of wheel eating potholes.

[Luniz]

The fact that the Sphericals on the upper a-arms wear more rapidly because of the pullrods being attached there is pretty usual. Sphericals can take a pretty high load in radial direction, but not axially. In attaching the pullrod to the a-arm, you add a strong axial load to the bearing which causes it to wear more quickly.

[woodsy96]

We too have had this happen a couple of times, but mainly on the lower rear wishbone sphericals. (We run pushrod in the rear). But when this happens, it appears to be because the lining (I think it is teflon) becomes dislodged/ damaged. As our callipers were mounted at the bottom, I had put this down to excess brake fluid getting into the spherical and damaging it. But now I am inclined to think that Luniz is right.

We run Aurora over FK, as we found that when we used FK they developed a little slop quickly in all areas, whereas the Auroras, although having more stiction, have less compliance in general until 'instantaneous' slop.

Has anyone else found this?

[Rob Klyver]

At Jim Russell we have run Aurora for at least 11 years. Aurora has worked 100% per spec on the Formula Fords, Formula Mitsubishi, Formula Russell (Mazda) and now the FJR50 Lola F3 that we started running last season.
In a pinch we have run NHBB, FK and others. I'll take Aurora hands down...when spec'ed correctly.
If you have a spec question call Aurora they actually answer you! Also look at this page full of tech info Aurora (http://www.aurorabearing.com/technical-resources/articles/default.html)

[Drew Price]

Rob, good info there, thanks for adding.

As an aside, I don't remember where I saw this (probably the Aurora catalogue) but you should only be putting at max around 10% the rated radial load into the sphericals in the axial (bolt direction), which means it's pretty easy to overload some of the small bearings if you are testing somewhere that's not particularly smooth and the car is crashing around over rough surfaces and access grates and things like that.

Remember that the spherical raceways are staked / pressed into the housing. Enough load will pretty them right back out!



And 0.050" play is DANGEROUS, get those replaced in a hurry. You don't want anything coming loose and crunching an upright or a suspension link this close to comp, things you might not be able to re-fabricate on this short notice.

Best,
Drew

[Pennyman]

Stop grounding your welder to your A-arms while welding your chassis!....Wait that isn't your problem its ours...

Ever seen a rod end race melt before?

[Scalesy]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Pennyman:
Stop grounding your welder to your A-arms while welding your chassis!....Wait that isn't your problem its ours...

Ever seen a rod end race melt before? </div></BLOCKQUOTE>

haha i have a set of crappy rubber lined rod ends we use to mock up with...it smelled great...really healthy too...

on another note, in response to above, our parking lot at the shop is REALLY rough...My thought is that the combination of that and over-stiff springs is overloading in the axial direction...

the sphericals we use have an ultimate static radial load of 16, 983lbs...10% of that is about 1700 lbs. The pullrod is also at an angle so the loading due to the rod is combined radial and axial. Now the question becomes, does impact at the wheel exceed this?

[Rob Klyver]

This from the lead racing product tech at Aurora



"If you want to post that I’m always available to discuss such issues, I’d be ok with that."

Best regards,
John McCrory
Product Manager at Aurora Bearing Company
970 West Lake Street Suite 1
Aurora, IL 60506-5954
jmccrory@aurorabearing.com

[Scalesy]

thanks for the input guys...the springs have been softened up, and I actually was able to get the play out of the sphericals without replacing them. An old timer told me to get two sockets the size of the race of the spherical, and press on the race from both sides (i.e with a big vice, or press), in effect tightening the race around the ball.

I was a bit skeptical but it actually worked great, and the slop has yet to come back. I'd imagine this could be an quick fix for a loose rod end too...I'd give it a try if you didn't know about this...definitely saves the hassle of replacement.