A-arm rod ends

[Jon_Dal]

Can anyone shed some light on suspension rod end selection? We're a first year team and I've designed our suspension to use threaded rod ends like this:
C:\Documents and Settings\Sir Jon\Desktop\Formula SAE\temp\rod_end_thread.gif

However, I see that many teams use ball joint swivel type bearings mounted in a tube or some such thing like these:
C:\Documents and Settings\Sir Jon\Desktop\Formula SAE\temp\swivel.gif

My thoughts are that threaded rod ends would be much better given that you can adjust the lengths to account for slight build errors. Also this provides a simple way to adjust camber. How do these teams using the non threaded variety adjust camber?

We are using a-arm mounted pullrods in the front and a-arm mounted pushrods in the back. I realize this can make for some pretty nasty thrust forces on the rod end.

Any thoughts, suggestions, or words of warning would be appreciated. Thanks

[Jon_Dal]

Can anyone shed some light on suspension rod end selection? We're a first year team and I've designed our suspension to use threaded rod ends like this:
C:\Documents and Settings\Sir Jon\Desktop\Formula SAE\temp\rod_end_thread.gif

However, I see that many teams use ball joint swivel type bearings mounted in a tube or some such thing like these:
C:\Documents and Settings\Sir Jon\Desktop\Formula SAE\temp\swivel.gif

My thoughts are that threaded rod ends would be much better given that you can adjust the lengths to account for slight build errors. Also this provides a simple way to adjust camber. How do these teams using the non threaded variety adjust camber?

We are using a-arm mounted pullrods in the front and a-arm mounted pushrods in the back. I realize this can make for some pretty nasty thrust forces on the rod end.

Any thoughts, suggestions, or words of warning would be appreciated. Thanks

[Jon_Dal]

Well....my images didn't seem to post.
http://www.me.dal.ca/fsae/images/temp/rod_end_thread.gif

http://www.me.dal.ca/fsae/images/temp/swivel.gif

[LU-Bolton]

Hey Jon. Most of the top tier teams generally use spehericals(your second picture) both inboard and outboard. I would suggest against the use of rodends(your first picture) outboard. The reason for this is the high bending loads seen outboard on our suspensions can cause the rodend shank to shear right off. Inboard it is not as big of an issue. The reason top tier teams use sphericals both inboard and outboard is because the spherical joint is generally both a stronger and a lighter joint.
With sphericals outboard, camber adjustment becomes a concern. An easy way is to design an upright which uses shims to change the camber as opposed to actually changing the length of your a-arm. Type in "upright" into the search box or search some other teams' websites and i'm sure you'll be able to find an example of what i'm talking about. Good luck.

[mtg]

If you adjust camber by changing the length of the control arms via rod ends, keep in mind that you are also changing the kinematics of the suspension- which can be quite significant.

[Jon_Dal]

The kinematics are changed by shimming as well though. Shimming the upright should change your kingpin angle where a rod end would not.

[kwancho]

Good question. The most common name for the second picture is spherical bearings. If you do a search, there's a TON of relevant threads, one especially, called "Spherical Bearings in A-arms".

[Korey Morris]

We broke one TODAY. Watch yourself....

Our failure came after dropping the car from about 3 feet, but I think we're going to look into something different. I'm not incredibly impressed with our descision to take the easy(er) way out.

[drivetrainUW-Platt]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Korey Morris:
We broke one TODAY. Watch yourself....

Our failure came after dropping the car from about 3 feet, but I think we're going to look into something different. I'm not incredibly impressed with our descision to take the easy(er) way out. </div></BLOCKQUOTE>

racing against the Baja team were ya?

[-Peter-]

Shimming upright side will keep the same kingpin angle as the LBJ and UBJ points have not changed. Our adjustments are on the LBJ of the upright. A larger shim will push the tire center out, creating a larger scrub radius with the given kingpin angle. The movement in the contact patch associated with the camber change will likely offset this. Shimming A-arm side would keep the scrub radius relative to the tire center the same but the contact patch will move and change actual behavior. It is a matter of convenience what method you use.

As far as bearings go, we will run spherical bearings as opposed to rod ends at every joint. Just my opinion, but get some midline metal contact sphericals and make your own stake tool. No sense in $25 teflon lined wonders and $180 stake tools when $7 metal contacts and free homemade stake tools will do.

[Korey Morris]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by drivetrainUW-Platt:
racing against the Baja team were ya? </div></BLOCKQUOTE>

Hey we'll race anyone we can...

No really, our shop has no large door, only a set of 2 28" double doors. To get the car out we pick it up, and carry it trough sideways. Do it three or four times on a sunday, and you be pissed too. Oversight in judgment on dropping the car. At least we found out in our own parking lot vs. in the middle of a bunch of people...