Rod end failures everywhere!

[Frank]

Bryan P

After:

A heaps of statics (maths)
B using strain gauges and a DA box built specifically for the job
C using a tensile machine to test a few different rod ends
D designing 4 SAE cars (the last two were ok, perhaps ask a few judges)

I have come to the following conclusions:

A 1/4" heat treated rod ends are in most cases the best choice for:
inboard a-arm joints, push (or pull) rods, and toe links

I would not use "non heat treated" 1/4" rod ends for these applications

Smaller heat treated rod ends (such as 10/32 or 6mm) might be OK for these applications, depending upon the surface encountered, the mass of the car, and the specific suspension geometry (which of course will effect the load, on each member). I'd be very careful for a while, and probably do some fluro magnetic particle testing on these units.

Rod ends used (deliberately) in bending such as is the practice on rustic racecars
((at the outboard end of an a-arm, to enable camber adjustment))
would certainly need a rod end larger than 1/4".

Personally, I don't like the outboard rod end design too much, but that's a long sordid argument....

As for your comments about roll hoops, HANS devices, and go-karts...

well, I ask again, what are you on about? We are talking about rod ends on FSAE cars, are we not?

This is what I call "going down in flames".

This is the last time I post on these forums. I've had enough.

Kind Regards to all the helpful people over the last few years..

Special Thanks to:

Charlie Ping
Denny Trimble
Micheal Jones
Scott Wordley
Big Bird
Handles
James Waltman
Vin Honda
Kevin Hayward
and of course Pat Clark

(IMO search these people's posts, you'll get the best answers)

Frank
www.uq.edu.au/fsae

[Denny Trimble]

Cheers Frank, it's been good talking with you, and I appreciate your contributions.

You'll have to make up another account so you can come back now and then to give us all hell...

That's 1000 posts for me, I guess I'll have a beer

[cdkrishen]

hello all,

just to clarify any discussion about the team that lost both front wheels at the recent compeition, here are some pictures i snagged just as it happened. i did have to poke my camera between people's legs, which was rather awkward...

i am by no means a suspension guy...but i can see sheered rod ends and a ball joint that failed at the weld. also its amazing how their break lines poppped right off too.

http://home.cwru.edu/~cdk5/images/fsae/DSC01090.jpg

http://home.cwru.edu/~cdk5/images/fsae/DSC01091.jpg

http://home.cwru.edu/~cdk5/images/fsae/DSC01092.jpg

http://home.cwru.edu/~cdk5/images/fsae/DSC01094.jpg

[Denny Trimble]

How's this for a failure sequence:
1) Upper balljoint (aluminum rodend in bending from brake torque) failed
2) Brakes locked wheels to uprights, and the kinetic energy of the 60mph wheels was transferred to the upright assembly with no upper restraint. This spun the upright/wheel around the lower balljoint and tore the LBJ (spherical bearing) out of the a-arm
3) Tierod outer joint (aluminum rodend) and brake lines failed from the wind-up.

[Tony K]

Speaking of failures... did anyone catch the European Grand Prix and see the suspension failure on Kimi's car? Now that was impressive. I've never seen a flat-spotted tire cause that much vibration, yet, it was a rather large flat-spot. Add in a litte braking force, and you've got yourself some nice carbon shards where your suspension used to be.

[James Waltman]

Frank,
Thanks for hanging out here for the last few years

We have learned a lot from you too

I'll miss your choppy writing style


----------------
Calvin,
Check your PMs


.

[sprintcar8]

Marshall, I never said not to tighen the jam nut, I said not to overtighten. Also, be careful when talking about steering angle as compared to suspension travel and wheel geometry as I am refering to. Try an experiment as to what Im saying. Use a bar with a rod end and see which direction you have the most travel. Simply insert a bolt and then move the bar in the vertical and then horizontal motions with the rod end in each different position. Let me know what you find or if Ive confused you more. we need to make sure that we all learn from the mistakes made by others this year.

[syoung]

Thanks Calvin, they're... 'interesting' photos!

Re: the Grand Prix, I'm interested to see if anybody thinks McLaren should have pitted Kimi? I know I wouldn't have changed tyres if I was the driver or race engineer.

[vinHonda]

Re: Kimi's failure.

As his race engineer, I would have yelled at him over the radio for flat spotting the tire in the first place trying to pass a BACKMARKER Villeneuve....

Then when he gets out of the car, whip a steering at his helmut.

I am a big Kimi fan and believe he's got talent..but if u want to win a championship, you have to put on your noggin and realize a tire with a flat spot on it isn't a fast tire.

Cheers,

[SD]

Has anyone heard of inboard 1/4-28 threaded 1/4 eye rod ends failing?

As others have mentioned and as I have found out the calculated loads indicate these should be more than sufficient.

Thanks,
Spencer