A-Arm bearing question-Help Needed!

[LafayetteFSAE]

Another question..On both of our previous cars, we have been using spherical rod ends/pressed in spherical bearings which have worked fine. The major drawback with our design is the spacers that we have in there to allow the travel from the bearings. Pics are below.

http://i149.photobucket.com/albums/s58/bluestang2002/Formula%20Car%2007-08/DSC00132.jpg

From walking around and checking out cars from VIR last year, I know there is a much easier way to do this, since assembling this with the spacers is a pain, and not good engineering IMO. Any help would be appreciated for a fairly new and inexperienced team!

Thanks,

Will

[Mike Macie]

Look into "high misalignment" rod ends. They should give you the travel you want and you will not have to run those spacers.

http://aurora.thomasnet.com/vi...series-male-rod-ends (http://aurora.thomasnet.com/viewitems/ll-products-commercial-male-rod-ends-english-units/am-t-hxab-t-high-misalignment-series-male-rod-ends)

[rjwoods77]

Aurora HAB-4tg bearings are perfect for every join in a suspension.

If you do continue with spacers there is a easy solution. Buy the correct OD and length dowel pins(super cheap) and insert the dowel in the rod end and spacer setup, insert into suspension mount, then push the bolt you are using through the mount pushing the dowel out the other end. I like the high misalignment rod end setup better but it adds about 10-15 bucks per joint when using them.

[RacingManiac]

we have spacers for our spherical joints too, just that they are jig welded into our bolt-on clevice blocks...

You can sorta see it in this pic, circa 2007
http://www.fsae.utoronto.ca/20...uction/Rolling05.JPG (http://www.fsae.utoronto.ca/2007/pictures/2007%20Construction/Rolling05.JPG)

I believe they revised the design on the rear of the car these days for other purpose....also note that we use staked spherical instead of rod ends.

[Chris Lane]

Originally posted by LafayetteFSAE:
Another question..On both of our previous cars, we have been using spherical rod ends/pressed in spherical bearings which have worked fine. The major drawback with our design is the spacers that we have in there to allow the travel from the bearings. Pics are below.
From walking around and checking out cars from VIR last year, I know there is a much easier way to do this, since assembling this with the spacers is a pain, and not good engineering IMO. Any help would be appreciated for a fairly new and inexperienced team!


Why is it bad engineering? If you do it properly, it is fine. The Spacers need to extend into the bearing (a little under halfway from both sides), and a bolt straight through everything. However, if your tolerances are not looked after, you will end up with a lot of compliance in your joints.

Have a look at 'Prepare to Win' by Carroll Smith. This book details this in depth.

This practice is widely used and is not considered 'bad' engineering. I would be more concerned about your rod ends in bending....

[MalcolmG]

are you sure that rod end is in bending? Looks like a toe control arm to me, and you can't see the outboard joint on the UCA (or is there a rod end in bending I can't see?)

We use spacers and they're definitely a bit annoying at times, and there's a reasonable amount of machining involved in making enough for the entire car + spares, will give more though to using those high-misalignment rod-ends/sphericals...

[STRETCH]

I agree its not great engineering to have such a fiddly assembly, and component count. But there is definitely one way this assembly can be made easy, instead of machining up spacers, machine up a tophat shaped part that also acts as the washer. Just means a bigger hole where the bolts go through, and reduces 5 parts to 3. Plus its a doddle to assemble as only have to line up the spherical!

[Chris Lane]

Originally posted by MalcolmG:
are you sure that rod end is in bending? Looks like a toe control arm to me, and you can't see the outboard joint on the UCA (or is there a rod end in bending I can't see?)

Looks like the same rod end is used for both the toe control and rear link for the upper wishbone.

[LafayetteFSAE]

Originally posted by Chris Lane:


I would be more concerned about your rod ends in bending....

If you are talking about the bearing on the Upper A-arm, it is not a rod end therefore not in bending...It is set up the same way as the Lower a-arm


Thanks for the help guys, keep the suggestions coming, and if you have any pics that would be a great help as well

[swong46]

What is the angle of misalignment rating to those rod ends?

I picked out some with 14 deg for our arms and I think we will have to run those spacers as well.

[Ben K]

Originally posted by swong46:
What is the angle of misalignment rating to those rod ends?

I picked out some with 14 deg for our arms and I think we will have to run those spacers as well.

Aurora Bearing's catalog has all the info you need. I thin a HAB-4T has 16 degrees of misalignment at least.

[BilletB]

Originally posted by STRETCH:
I agree its not great engineering to have such a fiddly assembly, and component count. But there is definitely one way this assembly can be made easy, instead of machining up spacers, machine up a tophat shaped part that also acts as the washer. Just means a bigger hole where the bolts go through, and reduces 5 parts to 3. Plus its a doddle to assemble as only have to line up the spherical!

This is a bad idea and poor engineering. You've turned your bolted connection into a pin joint. Wear is accelerated and slop creeps in quickly since your entire load is bearing stress on your mount holes. I found our old cars had this style of "bolted connections" which explained the excessively sloppy suspension. This was not allowed on my year's car and things tightened up nicely.

High misalignment bearings are the only option, but they are expensive and unnecessary. Using the necessary spacers is proper and justifiable engineering. The performance of your suspension joints and their connections is much more important than worrying about eliminating a $0.02 spacer.

[Canuck Racing]

Originally posted by BilletB:

This is a bad idea and poor engineering. You've turned your bolted connection into a pin joint. Wear is accelerated and slop creeps in quickly since your entire load is bearing stress on your mount holes. I found our old cars had this style of "bolted connections" which explained the excessively sloppy suspension. This was not allowed on my year's car and things tightened up nicely.

High misalignment bearings are the only option, but they are expensive and unnecessary. Using the necessary spacers is proper and justifiable engineering. The performance of your suspension joints and their connections is much more important than worrying about eliminating a $0.02 spacer.

I might be missing your point here but how does a high misalignment bearing not put the load on the bolt holes? We have used this setup on our cars for several years and it is quite frequently used in the motorsports industry. Yes it does require competent machining of the "top-hats" which not everyone is capable of, but that doesn't mean the rest of us can't make it work.

[Ben K]

Originally posted by Canuck Racing:
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by BilletB:

This is a bad idea and poor engineering. You've turned your bolted connection into a pin joint. Wear is accelerated and slop creeps in quickly since your entire load is bearing stress on your mount holes. I found our old cars had this style of "bolted connections" which explained the excessively sloppy suspension. This was not allowed on my year's car and things tightened up nicely.

High misalignment bearings are the only option, but they are expensive and unnecessary. Using the necessary spacers is proper and justifiable engineering. The performance of your suspension joints and their connections is much more important than worrying about eliminating a $0.02 spacer.

I might be missing your point here but how does a high misalignment bearing not put the load on the bolt holes? We have used this setup on our cars for several years and it is quite frequently used in the motorsports industry. Yes it does require competent machining of the "top-hats" which not everyone is capable of, but that doesn't mean the rest of us can't make it work. </div></BLOCKQUOTE>

Carroll Smith's "Nuts, Bolts, and Fasteners" would disagree with your statement, BilletB.

Ben

[The AFX Master]

That top hat idea works great indeed... IF and only if, the bearing surface on the top hat is a little bit shorter than the thickness of the sheet metal the clevis made from. That means that when you tighten everything properly, you have 4 faces in shear (each face on clevis plates).

Properly done, you could transmit almost all load as double shear on each clevis plate, and little or no load as direct contact bearing pressure between the top hat and the clevis hole.

[Jay Lawrence]

We used to use spacers, but they are a pain in the butt to make and get right and are easily lost/damaged. Top hats are a fantastic solution, as we have found. Ideally they are welded then reamed in steel and pressed into ally components. Seems to work quite well provided you get your top hat shank lengths right (as AFX said). Aurora even sell them for their bearings! Makes the job much easier and guaranteed to be accurate/fit properly.