Heim joint failure (video)

[Johnny B]

http://www.youtube.com/watch?v=Zv_Yx...ature=youtu.be

After seeing this happen in one of my races at Mosport, I was wondering how often we should change the heim joints on my FM.

-John B

[mikey]

yowser! why was he "floating" out of the car? his head was above the roll bar when the car was in the air and then it looks like he slams back down into his seat when the car crash lands.

glad you did not get hit by that flying wheel

[Johnny B]

Forgot to add, everyone walked away, although his wallet is much lighter.

John B.

[glenn cooper]

Lee SHIP!
Damn that was close.
I think that car might just be the original F1000 car that originally belonged to Jeremy Hill.
It sure looks like a motorcycle engine in there and an early 90's VD F2000 car?

Anyway... Amazing no one was killed or maimed - surviving a wheel and suspension to the face might not be something you'd want to survive... Ewww

The rodends on that car are considerably smaller than most, if not all on an FM.
The FM's enjoy their "Tank-like" rep due to the robustness of the massive (1/2"?) rod ends for one.

Having said that it's a great habit to get into where you inspect them after each session, w/ a little tug on the corners to see if any slop has developed, and replace w/ new when you do find a loose one.

It's not uncommon to replace them all at a certain interval. I did all mine one time in a winter rebuild.

I was neverr much of a fan of the idea to have them NDI tested, as that only shows a broken, or close to broken one - it didn't seem to make sense to take them all off the car and then get a cert that basically says "Hey, these ___ yr old rod ends are still good", when you could set them up on a replacement/lifeing cycle.

[mikey]

upon closer inspection of the video, it appears his helmet visor flipped up during the jolt as he went airborne also .. this really could have been a lot worse for that guy..

[starfmguy]

My experience is that the 4 "camber rod ends" are usually the ones that fail. Those are the outer rod ends on the lower a-frame at each corner, where you set the wheel camber (1/2" x 1/2" - right hand thread).

Most of the rest of the rod ends seem pretty sturdy, but of course - check periodically for slop. This seems like one of the very few items on an FM that can just break with no notice. Other items may wear out, loosen up, get sloppy, whatever, but not cause a sudden problem like this.

Now days I am pretty conservative with safety items, so I replace all 4 of these "camber rod ends" each season (I run about 12 races a year), but if you don't run a lot or use the curbs a lot, maybe you could go every 2 years or more, but I would definitely change them on a routine basis that you are comfortable with. Not too costly (comparatively) and could save a lot of grief. This is just insurance (I started to say "cheap" ) There is no notice before they go...

Plus - if you have an incident or bang wheels hard, it is a good idea to change that one "just in case".

Also, be sure to use the best quality available, not any of the cheaper ones.

Moses has the correct ones, I think they are $68 each and you should do all 4.

Mel

[sflaten]

Moses Smith has suggested to replace rod ends each year if you run a full schedule. I run a bit less, so do one side each year.

[Johnny B]

Many thanks for the input. We've had our FM 3 yrs. now but run a very limited schedule ( driver is still a student ) However I don't know when the previous owner last changed them so I think I have a winter project ahead.

For Glen, the car was in our F-4 class which had a 750 cc. engine campaigned by Peter Barker ( RIP ) the new owner has upped it to 1000 cc. but is still working the bugs out.

John B.

[sprocketmensch]

So I had 2 different camber heims (himes, rod ends) fail this weekend leading to a ridiculous amount of damage and rebuild. Does anyone know if there is a STRONGER heim than the one that Moses sells? I am looking at the specs for FK, QA1, Aurora, etc. In theory QA1 has one that has a higher "ultimate radial static load." Has anyone had success with other brands or know of an aircraft or military spec replacement piece with better shear strength?
Doug

[sprocketmensch]

Having now spent many hours looking at Heims and manufacturers web sites, one idea occurs to me. The weak point of the camber heim is the threaded rod diameter. It seems like it would be fairly simple to use oversized heims and drill and tap the camber sleeve to accept the next size up. Many manufacturers make a 5/8 thread heim with a 1/2" bore. This looks to increase breaking strength by almost 50%. Seems like a no-brainer from a safety perspective. Would this be legal? It doesn't provide any racing advantage other than a little peace of mind and hopefully fewer wrecks.

[Eric Cruz]

I don't have an FM, but it sure sounds like a design feature similar to my old Zink Z-10 CF I raced years ago. There were two large dia. rods ends at the outboard end of the lower rear A-arm that were used to adjust rear toe/camber. They were the only ones I ever had fail of their own volition - without immediate overload being applied as a result of something I did on track. In my opinion, the design weakness is that the threaded shank is loaded in bending, and the thread root becomes a stress concentrator. If you look at my FE (or probably any semi-modern pushrod car) every heim is loaded axially, tension and/or compression, along the threaded shank. Bigger would be better as long as the arm can take the larger female threads without creating a weak point there, but I think as others have pointed out those should be subject to routine replacement for reliability (periodicity established by community experience), just like your trailer tires.

Best regards,
Eric

[sprocketmensch]

So it does not appear that the camber sleeve will accept being overdrilled and tapped to 5/8" as it is only 3/4" OD. So it seems the only solution is to get a very high strength heim or ask Moses to redesign for a lager sleeve and oversized heim.

[Darryl Wills]

I am changing all load bearing heims to 4340 body joints, PMX-T series. FK makes a race series with 4340 body and stainless race that is double the strength of a stainless body heim..reference https://www.mrosupply.com/mrosupply_...ng-catalog.pdf

[sprocketmensch]

Thanks Darryl,
I have decided to change the camber heims to Aurora PRM series. This is a near mil spec product (I think).
Had a conversation with MSR yesterday and on their radar is a change of the lower A-arms to accommodate an oversized thread for the camber heim. This will require a larger diameter tube and camber sleeve. I think all FM'ers should write or call Moses and voice support for this so they build them this year. The new Goodyear 255s are giving us higher speeds and causing more stress on this joint.
I was planning to strip the car down this winter and magnaflux the a-arms anyway. This would be a perfect time to swap out for a stronger unit.
Doug

[Darryl Wills]

I have never had a heim joint failure in 10 years and over 150 events of racing FMs. All of the load bearing heims get replaced each winter and all of the heims every other winter. I have replaced heims as a precautionary measure anytime a wheel or suspension part gets bent for whatever reason. Conversely, we did have one of our team cars break a rear lower heim at Texas Motor Speedway for no apparent reason. Was a fresh unit but Stuart did put wheels off several times at the preceding race...so maybe that weakened it...don't know.

[Darryl Wills]

The Aurora PRM series and the FK PMX series have the same load ratings and material composition...So I would suggest either. Roush Yates racing is selling the FK rod ends for $43 each for the 1/2 inchers

[Mike Devins]

Was he wearing a HANS or similar device?

A couple of points that I got from the Aurora engineers. When rod ends are being used as ball joint there is a bending load on the threaded portion unlike a tie rod that is only seeing a push/pull load. In the case of rod end being as ball joint it is very important the have proper torque on the jam nut and to be sure that the surface that the jam nut is locking against is perpendicular to center line of the threads.

[Darryl Wills]

Those pesky lock nuts do come loose. Make sure that ALL of the powder coat has been filed away from the mating surface of the nut. Caution to everyone about the front jam nut...You can over tighten that one and stretch the threads on the heim with a large wrench. Make it tight but not ridiculous tight.

[sprocketmensch]

Was he wearing a HANS or similar device?

A couple of points that I got from the Aurora engineers. When rod ends are being used as ball joint there is a bending load on the threaded portion unlike a tie rod that is only seeing a push/pull load. In the case of rod end being as ball joint it is very important the have proper torque on the jam nut and to be sure that the surface that the jam nut is locking against is perpendicular to center line of the threads.

This is an interesting point. My A-arms do have a slight radius at the point where the jam nut locks down (the outer surface). I think I will remove these and grind them down flat. This should help with any flex and hopefully eliminate these snapped rod ends.

That being said, I am still in favor of the oversized A-arm/camber heim combination. Why should the upper be 5/8" and the lower, which is more stressed, be only 1/2"
D

[stephen wilson]

I have also heard that overtightening the jam nut on rod ends can lead to failure. Maybe use some locktite, with reduced torque? IIRC NMB goldline/silverline are the strongest, but ery pricey.

[brownslane]

I have also heard that overtightening the jam nut on rod ends can lead to failure. Maybe use some locktite, with reduced torque? IIRC NMB goldline/silverline are the strongest, but ery pricey.

Overtightening rod end check nuts is probably the most common source of rod end failure next to impact damage. When you overtighten, you distort the threads between the jam nut and the threaded insert. This creates a stress riser which concentrates the stress loads. The result will be a failure.

A simple way to avoid overtightening is simple. Paint a dot of a bright colour paint at the intersection of the jam nut and the exposed threads of the rod end. Be sure the paint bridges the thread-to-nut area. Not need to constantly tighten the nut....just check the paint! If the paint is cracked, the jam nut has moved. If it is still bridged, no movement= no need to tighten. This will go a long way to saving rod ends.

The other major cause of failures is bending. If the car is designed correctly the rod end should not be subjected to bending loads. If it is, then coupon your rod ends and cycle them out. EVERY TIME you whack a curb, drop a wheel, or whack anything (that includes things like the trailer door, etc.....then you MUST check each rod end for bending.

Rod ends need to be treated as a wear item...like brake pads and tires. They wear with use. Proper replacement of them will save you a lot of time, effort and expense. Been there, done that!

Best, Tom

[old 59]

.

[brownslane]

Stephen you have now piqued my interest; what 3/8 rod end failed? What function was it performing?

In terms of what engine the car had in it, I was not the one who stated it was running a 1,000 cc engine. In terms of the side pod, I stand corrected.

[Johnny B]

No need to get twisted Stephen,
I know Mike has an abundance of bike engine parts. My mistake thinking he put his 1000 cc engine in it. I new he replaced the engine the car came with.
John B.

[old 59]

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[Rick Kirchner]

[Steve O'Hara]

Any old style FM owners need some very high quality 7/16 bore/7/16 male thread rod ends? I have some left over from my pro Mazda racing days.
I have three never used NMB stainless ART L 7 ECR that don't fit either of my Swifts so they are just sitting in a drawer.
These are as good as you can buy

Here's a link to some photos. https://dl.dropboxusercontent.com/u/...Rod%20ends.zip

These rod ends came from Baker... you can look here for the current price...

http://www.bakerprecision.com/nhbb1.htm

All three for $150 and I cover shipping.
Steve O'Hara

[Ted Idlof]

I see at least 2 references to slop in the camber heims (Coop said: "any slop has developed"). Whether or not they are talking about a loose camber nut or not, I have some slop on a tightened camber heim and I'm confused as to how that happens. I just discovered some slop on the LF.

I have tightened the bugger up, taken it apart to go thru my engineer SWAG analysis several times and still see about 1/64" slop. I have a spacer nut behind the jam nut as I always have had on all 4 corners. The other 3 are still as tight as can be.

What am I missing? How does slop happen on such a simple mechanical fastener.

[brownslane]

I see at least 2 references to slop in the camber heims (Coop said: "any slop has developed"). Whether or not they are talking about a loose camber nut or not, I have some slop on a tightened camber heim and I'm confused as to how that happens. I just discovered some slop on the LF.

I have tightened the bugger up, taken it apart to go thru my engineer SWAG analysis several times and still see about 1/64" slop. I have a spacer nut behind the jam nut as I always have had on all 4 corners. The other 3 are still as tight as can be.

What am I missing? How does slop happen on such a simple mechanical fastener.

Ted, can you identify where the slop is on the rod end itself? If it is in the ball, then the rod end has worn the liner and it needs replacement. If the rod end is moving in the threaded bushing at the end of the suspension arm then you need to check the threads on the insert and BE SURE that the insert is not breaking the welds holding into the tube. Powder coat can acutally remain over top of cracks in suspension arms and chassis....I have only seen it once, but I saw a weld-in insert crack its way off the end of an arm...

My guess is that the ball is a little loose on the rod end.

Best, Tom

[Darryl Wills]

Ted,
Are you referring to the camber sleeve that the heim threads into? If so, then the a-arm housing has been smashed 1/64". The best fix is to remove the sleeve and reduce the length of the sleeve until everything is snug once again.

[Ted Idlof]

Tom, It's not the ball.

Darryl, I agree it has to be the sleeve length although I have the same slop with a spare sleeve and had filed down the old one once already. But that's got to be it, so I'll look a little closer and probably file a bit more. Didn't think I had changed my camber that much but maybe I had and this is the result.

thanks guys.

[Todd TCE]

Don't pass through much any more but this issue has been around for 20yrs or so.

Damages aside etc here's a simple solution to a common problem. And it's easier on your forearm!

[dalz]

I for one have survived a genuine FM lower rear A-arm Hiem joint failure, at the Sebring pro race way back when. Happened in the right-hander before the final 180 turn onto the front stretch, no big deal there. One more turn, and it would have been much worse. My team at the time didn't account for the pounding that place gave the cars. Replacing them is part of the Jason's off-season yearly routine, because we ain't easy on them.

[rickb99]

Moses Smith has suggested to replace rod ends each year if you run a full schedule......

THIS used to be considered a 'routine maintenance' procedure every two years unless failure was noted earlier during inspections. But perhaps because of some improvement in materials and the continuing increasing costs in other areas of racing, it's gone out of focus for the average weekend racer.