Aluminum PHB vs. Steel PHB

[CCS86]

Can you take out that picture? It screws up the page sizing.

 

[CCS86]

P-delta effect is a pain in the ass.

Bingo :beer:

 

[dirtyd88]

Bingo :beer:

The whole reason I didn't go into structural building design and work with utility/transmission poles. :lol1:

Anyways, I spoke a little bit with Tad at Freedom Racing Tool and Die earlier through email. He basically said that for any cars putting down 500+ HP to the wheels, he personally recommends going with a steel PHB. For a daily driven street car, you can go either route, just a matter if you feel the lost weight is enough for little bit of added cost.

 

[me32]

The whole reason I didn't go into structural building design and work with utility/transmission poles. :lol1:

Anyways, I spoke a little bit with Tad at Freedom Racing Tool and Die earlier through email. He basically said that for any cars putting down 500+ HP to the wheels, he personally recommends going with a steel PHB. For a daily driven street car, you can go either route, just a matter if you feel the lost weight is enough for little bit of added cost.

i would like to know how having more power would change which PHB to get.

 

[Tob]

CCS86, I'll address each item in your response as soon as I'm home.

 

[dirtyd88]

i would like to know how having more power would change which PHB to get.

Somewhere, somehow, I'm sure the fact you are applying more power and therefore more torque, through the rear end of the car, you can be susceptible to greater cyclic loading, thus increasing the fatigue seen by the PHB. If that doesn't make sense, someone please correct me. I won't get mad. LOL :beer:

 

[Radar Doc]

I volunteer to be the official svtperformance.com aluminum panhard bar test dummy. If you don't see me post at least once per week, you can just assume my aluminum panhard bar broke and I crashed.

 

[dirtyd88]

I volunteer to be the official svtperformance.com aluminum panhard bar test dummy. If you don't see me post at least once per week, you can just assume my aluminum panhard bar broke and I crashed.

:lol:

 

[CCS86]

Hahaha

 

[Radar Doc]

I just installed my aluminum bar a few weeks ago and made a short post about it. The bar I have has high-durometer rubber bushings vs the poly/rod-ends talked about in this thread. I'm 100% confident with it for my use, which includes highway driving, twisty roads on my way to work and the dragstrip every six months or so.

 

[dirtyd88]

I just installed my aluminum bar a few weeks ago and made a short post about it. The bar I have has high-durometer rubber bushings vs the poly/rod-ends talked about in this thread. I'm 100% confident with it for my use, which includes highway driving, twisty roads on my way to work and the dragstrip every six months or so.

This is me. Good to know it will suit me after I ordered it last night. :lol1:

 

[Tob]

It will.

You missed my point. The bushing will destroy itself (poly or factory rubber). The torque applied at the pivot, in this case the bushing, will overcome (in short order) the excess friction within the joint. Better yet, cite me an example of an S197 chassis aluminum panhard bar failure due to a bound joint.

Spherical bearing and heim joint are the same thing Tob.

And three rights make a left. The only way I'd have given you props were you to also include 'rose joint' in your lesson plan.

Yet again...

There's always an out.

I think that in concert with any discussion such as this, should be the inclusion of bushing choice. I agree with your earlier comment "If I ran an aluminum bar, I would never use one with double poly. One or both ends would be a del-sphere joint or spherical bearing" (less the del-sphere mention, anyway). If choosing aluminum over steel has more to do with weight loss than near OE levels of durability then one is likely willing to sacrifice at least some NVH in the name of performance. To use an aluminum bar with polyurethane bushings would be counterproductive in my book. Hence heims (or sphericals or roses:-D). At that point I see no performance benefit in utilizing a poly bushing at one end. Thus, heims at each end.

Bind gone. Problem solved.

 

[dirtyd88]

You missed my point. The bushing will destroy itself (poly or factory rubber). The torque applied at the pivot, in this case the bushing, will overcome (in short order) the excess friction within the joint. Better yet, cite me an example of an S197 chassis aluminum panhard bar failure due to a bound joint.



And three rights make a left. The only way I'd have given you props were you to also include 'rose joint' in your lesson plan.



There's always an out.

I think that in concert with any discussion such as this, should be the inclusion of bushing choice. I agree with your earlier comment "If I ran an aluminum bar, I would never use one with double poly. One or both ends would be a del-sphere joint or spherical bearing" (less the del-sphere mention, anyway). If choosing aluminum over steel has more to do with weight loss than near OE levels of durability then one is likely willing to sacrifice at least some NVH in the name of performance. To use an aluminum bar with polyurethane bushings would be counterproductive in my book. Hence heims (or sphericals or roses:-D). At that point I see no performance benefit in utilizing a poly bushing at one end. Thus, heims at each end.

Bind gone. Problem solved.

Well I ended up ordering heim (axle) and poly (chassis) bushing on my Aluminum PHB, and the fact that my car is a daily driven car, hardly ever pushed through corners hard, at all, I should be fine in regard to strength and durability, correct? I've read that the above setup of bushings I mentioned provide the least amount of increased NVH over stock.

 

[CCS86]

I don't understand you Tob.

You attempt to pick my posts apart and debate them, yet you haven't actually disagreed with anything I've said. At best, you've just twisted my words into something I never implied, then argued that fictional point. Every time I reply, you just side-step.

It's not about having "an out". This is an open discussion about the pros and cons of an aluminum panhard bar. I mentioned some entirely valid points (which you have yet to actually refute), but in no way said aluminum is just a bad idea, just that you must take extra precautions in design.

I don't know what your background is, but you seem to dodge the technical points. I have been fabricating, machining, and welding for over 7 years, then went back to school and was at the top of my Mechanical Engineering class at UT Austin.

 

[CCS86]

At that point I see no performance benefit in utilizing a poly bushing at one end. Thus, heims at each end.

The "performance benefit" of running one heim, one poly; is to alleviate some of the NVH. One heim will accommodate all of the angular misalignment.

 

[dirtyd88]

I have been fabricating, machining, and welding for over 7 years, then went back to school and was at the top of my Mechanical Engineering class at UT Austin.

This is hard to disagree with....

 

[jayman33]

Derek, I've sent out the PHB so you should be getting it Wed. If you have any trouble with the heim joint, let me know. They do create higher NVH so if the extra noise becomes an annoyance just let me know.

 

[dirtyd88]

Derek, I've sent out the PHB so you should be getting it Wed. If you have any trouble with the heim joint, let me know. They do create higher NVH so if the extra noise becomes an annoyance just let me know.

Thanks, Jason. I'm sure it won't be much of a problem. I plan on sound deadening the trunk when I do my audio install, and plan to do the rear seat area as well.

 

[Tob]

I don't understand you Tob.

You attempt to pick my posts apart and debate them, yet you haven't actually disagreed with anything I've said.

I'm not attempting to debate your posts. I am debating certain positions you have proffered as well as implied, whether you choose to recognize them or not. If you haven't sensed or read any disagreement in any of my statements then I'd suggest that your comprehension skills are lacking a bit. Don't take it personal, and by all means, lets hash the subject matter out. Go back and reread the counter to your position - its all there.

At best, you've just twisted my words into something I never implied, then argued that fictional point. Every time I reply, you just side-step.

Do I really have to go back and address the points you have missed? Fictional points? Here...

If one of the bushings starts to bind, it will put a bending moment through the bar. This could weaken it quite a bit. Fatigue issues could come into play too.

I went steel.

You started with If and backed it up with could (twice). So you began with a condition or constraint and used that constraint in support of an open ended conclusion. Immediately thereafter, you declared that you went with steel.

I addressed your supposition directly with no "side-step" as you put it, with the following statement.

If a bushing were to bind? The lever arm acting through an 'S197 chassis length' panhard bar wouldn't be stopped by a polyurethane or rubber bushing. It would instantaneously tear or shred it, were it unable to rotate about the sleeve.

I also added...

Regarding fatigue 'issues', did you model them as well?

I wanted to see your response because I was curious as to what geometrical conditions you were plotting. I don't know how far you've gone with it (roll center height, etc) but I'd have liked to see what 'loads' you were imparting. Again, I don't know how far you went with it.

It's not about having "an out". This is an open discussion about the pros and cons of an aluminum panhard bar. I mentioned some entirely valid points (which you have yet to actually refute), but in no way said aluminum is just a bad idea, just that you must take extra precautions in design.

My point was that it appeared as though your argument initially supported steel only (the conditions of which I mentioned above) but then 'covered your bases' when you stated...

Is it possible to design an aluminum panhard that has a high safety factor (even with a binding bushing), and will outlive the vehicle? Absolutely. But...

Then I saw the word absolutely, followed immediately with 'but'. Don't take it the wrong way, but that kind of wording is an attempt to allow freedom within an argument. Plain and simple and I don't fault you for that - at all.

Regarding refutation, of course I did. Ry even summarized it for you when he said...

what Tob is saying as that a rubber/poly bushing is made of material that is significantly weaker than aluminum. the effect of a seized bushing on the strength/durability of an aluminum panhard bar would be negligible at best.

Here's a YouTube link that illustrates my argument, albeit a different /component/material/vehicle. Yet kinematically, very near the condition (or a portion thereof) you hypothesized in that original post.

Jeep JK Trackbar Movement - YouTube

The lever arm will not be stopped the bushing. Yes, you stated that you never claimed that the bushing would stop the suspension from moving but that it could weaken the bar.

You further refined your position with a bent straw under compression example.

Now push only half that hard, but use the other hand to put a very small force downwards in the middle. It fails.

That response was after you quoted Ry's summary of my statements, regarding an aluminum bar. Hence, and in contrast to your statement that you "went steel" I posted the humongous photo of a steel bar failure. The conditions of which aren't well documented but it would appear that at some point the factory panhard was bent (if it wasn't - wow) and then cycled enough to fracture and ultimately fail. The relevant thread is here.

I don't know what your background is, but you seem to dodge the technical points. I have been fabricating, machining, and welding for over 7 years, then went back to school and was at the top of my Mechanical Engineering class at UT Austin.

I've dodged nothing. I asked you specifically...

...cite me an example of an S197 chassis aluminum panhard bar failure due to a bound joint.

...and have waited patiently. If you can find one, you're a better man than I. 'Cause I can't.

And regarding your background - kudos to you. I'm sure those around you are as proud of your accomplishments as you are. I've been welding and fabricating since Ronald Reagan's second term along with machine work at hydro, nuclear, and cogeneration plants. I'm a journeyman carpenter and millwright that has a BS degree in economics as well as a MS in education. Blah, blah.;-)

 

[CCS86]

This is getting boring and I'm not interested in arguing in circles or nit picking wording. I stand behind everything I've said, and there is nothing wishy-washy about it. I understand that you have a background in mechanical things, but you are trying to debate engineering concepts that you don't have knowledge of. Your "compliment" of my education comes off backhanded and snarky.

Facts:

-Steel alloys are stronger than any aluminum alloy.

-Aluminum has a finite fatigue life, while steel is infinite and will not fatigue all the way to failure

-Aluminum also precipitation (age) hardens, making it more prone to failure.

-It is absolutely possible to engineer an aluminum panhard bar that will outlive the vehicle.

-You can not be sure of this without a comprehensive analysis.

-Just because a shop builds an aluminum bar and slaps their sticker on it, does not mean they have done so.

-Friction at one or both bushings is capable of geometrically deforming the bar. This deformation WILL change the loading scenario drastically when under compression in a way that seriously weakens the bar. If you still refuse to accept this fact, I'm not sure what to tell you.