How bolt rod end on frame

[Big Pablo]

Hi, just finished to read a bunch of discussions about rod end Vs. spherical bearing on suspension arms.

I got that rod end in the inboard location and spherical bearing in the outside, is definitelly the way to go.

No question about it, but I would like to know more about the better way to bolt the rod ends to the frame brakets. I've seen many cars have they fitted with bolt going through it horizzontally while vertically on others.

What are the pro and cons of the two solution ?

[Big Pablo]

Hi, just finished to read a bunch of discussions about rod end Vs. spherical bearing on suspension arms.

I got that rod end in the inboard location and spherical bearing in the outside, is definitelly the way to go.

No question about it, but I would like to know more about the better way to bolt the rod ends to the frame brakets. I've seen many cars have they fitted with bolt going through it horizzontally while vertically on others.

What are the pro and cons of the two solution ?

[Chris Craig]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Big Pablo:

I got that rod end in the inboard location and spherical bearing in the outside, is definitelly the way to go.

</div></BLOCKQUOTE>

We have never used rod ends inboard, and i dont plan on it in the future either. Also looking at other teams, you will find a mix of rod ends and sphericals inboard.

You need to quantify why it is the way to go. And i'm pretty sure there is no straight answer, everyone has a different opinion.

Once again horizontal of vertical is down to team choice, attachment method etc.

We placed them horizontal at the front for extra clearance and easier jigging due to their angles however they were vertical at the rear due to our rear plate.

[murpia]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Big Pablo:
What are the pro and cons of the two solution ? </div></BLOCKQUOTE>
1) the differences in the load ratings axially vs. radially
2) friction

Both are valid whether you consider sphericals or rod ends.

You need to know all your suspension link loads to work it all out, for all relevent load cases for your car.

Regards, Ian

[RollingCamel]

Pat had a good input about it in his column.

[Simon Dingle]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by murpia:
1) the differences in the load ratings axially vs. radially
</div></BLOCKQUOTE>

Really? Surely since the wishbone arms are always in compression or tension (this is a bit of an assumption since I've never bothered to test it) as long as the axial centreline of the bearing is perpendicular to the axial centreline of the wishbone arm, then the bearing is always loaded radially regardless of whether the bolt hole is horizontal or vertical.

I would suggest that the only difference is the range of movement that the wishbone arm has before the wishbone interferes with the clevise.

Simon

[BrendonD]

I see lots of teams mounting them horizontally (bolt is vertical through tabs and bearings) because they have multiple holes in the tabs for adjusting castor angles. If you don't need that there's really not a difference as far as the bearing is concerned.

[Big Pablo]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by BrendonD:
I see lots of teams mounting them horizontally (bolt is vertical through tabs and bearings) because they have multiple holes in the tabs for adjusting castor angles. If you don't need that there's really not a difference as far as the bearing is concerned. </div></BLOCKQUOTE>

if I mount it so, the control arm will have less excursion due to the limitation of rod bearing angle. Right ?

I guess this it not a problem due the lenght of the arm and the relative low excursion it needs in a FSAE car.

[murpia]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Simon Dingle:
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by murpia:
1) the differences in the load ratings axially vs. radially
</div></BLOCKQUOTE>

Really? Surely since the wishbone arms are always in compression or tension (this is a bit of an assumption since I've never bothered to test it) as long as the axial centreline of the bearing is perpendicular to the axial centreline of the wishbone arm, then the bearing is always loaded radially regardless of whether the bolt hole is horizontal or vertical. </div></BLOCKQUOTE>
Factor in the friction of the bearing and the wishbone arms can start to transmit bending moments. Especially if there is any misalignment during assembly. Also, any time the bearing takes up an angle, that must resolve into a combination of axial and radial loads. I think (someone could test it?) friction is higher for an axial loading.

Low friction solutions such as flexures and Fafner bearings are often used when loads are high. This helps dampers to do their job. Also, evaluating a roll centre height with joint friction is pretty tricky...

Regards, Ian

[BrendonD]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Big Pablo:
if I mount it so, the control arm will have less excursion due to the limitation of rod bearing angle. Right ?

I guess this it not a problem due the lenght of the arm and the relative low excursion it needs in a FSAE car. </div></BLOCKQUOTE>

A combination of your suspension points and how much travel you're building into the system should tell you what sort of misalignments you need for your bearings.

[RobbyObby]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Simon Dingle:

Really? Surely since the wishbone arms are always in compression or tension (this is a bit of an assumption since I've never bothered to test it) as long as the axial centreline of the bearing is perpendicular to the axial centreline of the wishbone arm, then the bearing is always loaded radially regardless of whether the bolt hole is horizontal or vertical.

Simon </div></BLOCKQUOTE>

I'm sure Pat would love to say otherwise. http://fsae.com/groupee_common/emoticons/icon_wink.gif
Especially with some of the newer teams.

[Big Mo]

The type of load on the rod end depends on how the joint is mounted and the constraint on the control arm. In theory, a (frictionless) rod end on the inboard side of the control arm that does not mount the push/pull rod or toe arm will be a 2-force member in 2D or a 3-force member in 3D. Statically, this will have all load transmitted down the member centerline, and will have all of its loads resolved as axial load on the threads and a radial load on the ball (either compression or tension on the race).

But we all know how theory ends up working out in the real world: kinda sorta.

Friction, three dimensions, constraints, misalignment, manufacturing errors, installment bending preload (ugh), additional interfering loads like a Z-arm (ugh again) all can change this assumption.

TL;DR: Read Pat's Corner.

[Big Pablo]

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

A combination of your suspension points and how much travel you're building into the system should tell you what sort of misalignments you need for your bearings. </div></BLOCKQUOTE>

Hom much travel a typical FSAE car front suspension ?

[murpia]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by murpia:
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Simon Dingle:
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by murpia:
1) the differences in the load ratings axially vs. radially
</div></BLOCKQUOTE>

Really? Surely since the wishbone arms are always in compression or tension (this is a bit of an assumption since I've never bothered to test it) as long as the axial centreline of the bearing is perpendicular to the axial centreline of the wishbone arm, then the bearing is always loaded radially regardless of whether the bolt hole is horizontal or vertical. </div></BLOCKQUOTE>
Factor in the friction of the bearing and the wishbone arms can start to transmit bending moments. Especially if there is any misalignment during assembly. Also, any time the bearing takes up an angle, that must resolve into a combination of axial and radial loads. I think (someone could test it?) friction is higher for an axial loading.

Low friction solutions such as flexures and Fafner bearings are often used when loads are high. This helps dampers to do their job. Also, evaluating a roll centre height with joint friction is pretty tricky...

Regards, Ian </div></BLOCKQUOTE>
I forgot to add, most designs have the push / pullrod picking up off a wishbone. That adds additional bending moment.

Regards, Ian

[Barky]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Big Pablo:
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by BrendonD:

A combination of your suspension points and how much travel you're building into the system should tell you what sort of misalignments you need for your bearings. </div></BLOCKQUOTE>

Hom much travel a typical FSAE car front suspension ? </div></BLOCKQUOTE>

a couple feet, give or take.

[Drew Price]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Big Pablo:

Hom much travel a typical FSAE car front suspension ? </div></BLOCKQUOTE>


How far from comp is your school?



Drew

[Goost]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Simon Dingle:
the bearing is always loaded radially regardless of whether the bolt hole is horizontal or vertical. </div></BLOCKQUOTE>

That's true, for inboard points. Good to note though that since we're mostly talking about double a-arm suspensions one of the outboard bearings will be loaded differently: there has to be a push/pull rod somewhere...

[moose]

<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 far from comp is your school?



Drew </div></BLOCKQUOTE>

http://fsae.com/groupee_common/emoticons/icon_biggrin.gif