TheV6jerk

The other thing I will note that is good about the Hollow bars is the arms are also stiffer from flex than the solid bars (*NOTICE*now I am saying this even thought I own Spohn Solid chromemoly bars)

Tube stock is less likely to bend under small forces than solid tube stock. Why? because the inner and outer walls make the bar dirvert stress loads different than solid stock. One side goes under compression and the other side exerts an opposing force under tension so it will not bend as easily as a solid bar. However, once enough force is exerted on the tube bar it will catasthrophically fail far sooner than the solid bar would.

Now take the point I listed above about finding a "new" hollow bar. If you can not, chances are very great that most of you are running around with an older corroded hollow bar. Now combine that with upgrading to stiffer poly endlinks or even rodended hiem joints to minimise stess absorbtion so the bar is more seat-of-the-pants feel and this can and gerenally will lead to the bar breaking from age, corrision, and cycling.

I built a designated street car that I intended to maximise strength and minimise manitenace on over the years hence why I opted for the stronger solid Spohn chromemoly bars for years of trouble free very hard use

Lo-tec

I'm assuming your comparison is of two different sized bars, like the 32mm solid and the 34mm hollow as listed before. A solid bar deflects just like a hollow one, with one side going under compression and the other tension. The reason it doesn't deflect as much is because the moment of inertia of the 34mm hollow is higher (the bar is stiffer) than the 32mm solid. The link you posted before does show a good picture of the higher stress in the hollow bar. Now if they were the same size, that would be a different story.

TheV6jerk

Lo-tec, thats not to what I am refering to.

From what I have studied about hollow tubing compared to solid tube of the same diameter, the hollow tube will not flex as easy as the solid tube. We are talking bending, NOT twisting forces) That is why I was refering to the arms. On the front swaybar you have the straight section that of course mounts to the chassis (this part twists under load) and then the two side arms that lead to the control arm links (these arms are under bend force, not twist). The hollow bar arms will not flex as easy as the solid bar but will break and/or perminantly kink bend and fail fat sooner than a solid core bar will.

When ever you have seen anyone post pictures of broken swaybars on this site it has always been broken in the arm sections and not the twist sections of the hollow bars.

Tubing of the same diameter is much less prone to flex if it is hollow rather than solid even though the solid has more mass.
The reason I have read is because the hollow void in the tube allows for the force exerted on bending to render tension on the top half and compression on the bottom half keeping the bar more ridgid from flex (But not strongerrfor overall load).

I'll give an example of what I have researched-

take for instance two bars both 36mm dia tubing that are both 4 feet long. Solid mount on side of each tube and then hang weight on the other side (say a hypothetical example of 500lbs). The hollow tube may only bend an 1/8" where as the solid tube may bend 1/4". NOW put 1000lbs on the end of each and the hollow tube will fold in half failing from the load exerted on it and colasping the tube where as the solid may bend to 1/2". Take the weight off and the solid goes back to normal (like sping quality material is intended to do), the hollow is broken.

*Note* this is why younever see coilsprings made out of hollow tubing stock. They are always solid wire bar.

-----------------

Now the link I posted up above in my first post shows the forces exerted on the hollow and solid tubes from "twist" and the example tell that they use arms that are using separte link arms spanning back to the suspension that do not flex.

We do not have 3 piece swaybars with nonflexing arms, we have 1pc swaybars and the arms. This bar area flexs and bends under load.

The arms sections of the 36mm hollow bars is much less prone to flex than the arm sections of the 34mm solid bars, thus making the 36mm bar stiffer in these arm areas- but weaker when it comes to how much maximum load they can handle.

Lo-tec

I was talking about bending, not twisting. Take a look at this formula:

http://www.engineersedge.com/beam_be...m_bending9.htm

Total deflection is inversely proportional to the moment of inertia. The higher the moment (stiffer) the less deflection. Again, there is compression and tension in a solid bar just like a hollow one.

Try this. Let's assume your 36mm hollow bar has a 6mm wall thickness. The hole would then be 24mm in diameter. Hang a 500 lb weight off the hollow bar and measure how much it bends. Now, stick a 24mm solid bar inside the hollow bar, effectively making this new bar a "solid" bar. Put your 500 lb weight on it again, and it will bend less due to the extra support of the 24mm bar that is now jammed in it. Show me on paper how the hollow bar converted to "solid" bar will bend more with the extra bar inside of it.

Any ME's out there feel free to lend me a hand.

TheV6jerk

This is wheree we respectfully disagree. Take a look at this report I have read from retired process engineer where he discusses the difference between a 2" solid and 2" hollow bars in bending.
http://www.madsci.org/posts/archives...2595.Eg.r.html

Lo-tec

Look down at the bottom of my link:

Deflection at the unsupported end:

Wl^3 divided by 3EI

where I is the moment of inertia. The greater the # for I, the less deflection.

Think of this. When the solid bar bends, the top of the bar must be in tension because it is now longer than unloaded. The bottom must be in compression because, low and behold, it is now shorter than it was before. As far as your link, show me a formula that either proves or disproves what I am posting. For Mr. Bob Gibilisco, Staff, Process Engineering, Retired, I see now why he is retired.

ME Leigh

A solid bar will always deflect less and be stronger in torsion and bending than a hollow bar when made of the same material. This is simply because the solid bar has a larger cross-sectional area, meaning higher moment of inertia.

But as discussed earlier the solid bar has some major drawbacks.

ME Leigh

Also a solid bar will have a longer fatigue life. Because they is lesss surface, stress and strain and the crack has to grow through a much larger area.

TheV6jerk

Ican not find anything yet to back this but I strongly feel it is to do with the laws of radius' and how they distribute load. A hollow tube has both an outer and and inner radius whereas the solid has only the outer with solid mass in the center holding the sidewalls together.

Best way I can explain it is like a straw. It will not bend, it will simply kink once enough force is applied. Since there is no center mass holding on the side walls, the side walls can exert outward in an oblong shape and this tension forces them back inward giving the tube more strength against flex along the inner radius' bending under compression on the inner sides and tension on the inner top and bottom radius'.

Soild bar stock simply exerts stress pulling of the mass molecules of the steel (elasticity) but has not strucural arch or radius to ditribute load agaisnt flex. The molecule solid mass of a bar allows the solid structure to have more surface area stregth against tearing (molecular structure of the steel breaking apart) so it will elastically bend more yet not break as easy as the less mass hoollow struture of the same diameter.

I can not prove this theory from any factual links other than the speculation link I posted a few post ago. It is an educated guess on my part and I will continue to research for any proofs.


In conclusion- I will resort back to my statement that coil springs can NOT be made of tubular material because it is too stiff and will break rather than flex and elastically spring back. If you disprute this, Please explain to me why springs are all solid wire steel and not tube steel construction? Fact is, swaybars are springs.

JPrevost

You're right, he's wrong. I'd post up a simple FEA but I'm afriad some people would discredit my knowledge of the software .
What do you want, you've already stated the obvious. The only thing left to consider is gravity .

JPrevost

No, the straw will bend, just not much before failure! The material has a lot to do with it too. Plastic, white metals, cast finishes, tempered, etc. They all have special properties so comparing a plastic straw to metal tube is like apples to oranges.

JPrevost

My 36mm bar also has the vents on the top. Here's a picture I took today.

CaysE

Wait, hold on a sec... swaybars aren't springs. If they were, they wouldn't keep a car level as it turns; they'd just bend uselessly and allow body roll. They do flex slightly when hitting bumps on one side of the car, but not nearly as much as the springs themselves. Correct me if I'm wrong.

83 Crossfire TA

iTrader: (2)

Why? You’re right and you’ve stated correct reasons why… what more do you need?

Yes, the solid bar can bend more then the hollow one before it yealds, but it will also take much more force. The straw example is flawed. First, a straw will bend a little before it kinks, second, if you had a solid rod made out of “straw plastic” it would bend less with the same amount of force on it.

As far as the rest of this… it’s just dean talking for dean’s sake… doesn't matter if it's right, wrong, or just plain stupid, he'll keep going and never admit he's wrong.

FWIW, both 36mm hollow bars that I have sitting in the garage have the holes on the bottom and I’m too lazy to go out and look at what the one on my formula has right now, but I seem to remember seeing them which since you usually see the bar from the bottom I would be surprised if it was on the top.

ME Leigh

A hollow bar sees much higher stresses because there is less cross-sectional area for the same amount of load.

A swaybar is a spring, it is just a different type of spring, a torsional spring.

You could make a coil spring out of hollow stock, but the diameter would have to be large, so the stresses would be low enough for the spring to live.

83 Crossfire TA

iTrader: (2)

Your own quote disagrees:
“In final analysis, the resistance to bending prior to failure depends upon
the mass of the member and the weight applied.”

ME Leigh

Also i went and looked at my 36mm hollow swaybar and the holes are on the bottom. I wonder if i put it on upside down. But then again it would make absolutely no sense to have the hole on the top. The arch in the middle of the bar curves down. How are yours?

ME Leigh

Stress distribution. As you can see the hollow bar has much higher maxium stresses.

TheV6jerk

ME liegh, that applies to twist forces, not bending forces

Crossfire- takes a stupid person to call another person stupid. How about answering my question on the spring wire question about it not being made out of tube wire instead of the solid wire like they are.

Cayse, 1 pc swaybars are springs. They are designed to built and release tension using spring type elasticity of the steel. Only they work more on twist elasticity (torsion) rather than bending elasticity. However, they do have some bend elasticity in the arms unlike a more rigid designed 3pc swaybar arm.

ME Leigh

I know thats for torsion, swaybars are pretty much only in torsion. Thats how they work. But the same will hold true for bending and shear. A hollow bar loaded the same will have higher levels of stress.

83 Crossfire TA

iTrader: (2)

curves down… I’m not sure that it makes any sense to have the hole at either end at all… for that matter, just heat them 150* or so and seal them without any holes, or a single hole in the middle…

83 Crossfire TA

iTrader: (2)

We’ve long since established that I believe that you’re a complete, flaming moron with a massive, undeserved ego. Not sure where the debate is or why this needs to be debated. You’re not going to convince me otherwise at least until well after you stop stating opinions and misinformation as fact.

it’s a simple packaging issue. Cross section, alternatively weight, determine cycle life, so you’d have to use a much stiffer, larger diameter, “wire” (tube) wound for many more and larger coils to end up with something that will give you a reasonable life, durability and useable range. Conveniently, you’d have to do the same to manufacture the thing at anything resembling a reasonable cost since a tight coil of a tube with a large enough diameter would be difficult if not impossible to make. The end result is that you’d need to find room to package an enormous spring which would weigh the same if not more then a conventional spring.

Of course, for some bizarre reason yet unexplained by science or engineering you still believe that spring frequency is determined by free coils (as opposed to the reality that the rest of us live in: spring rate), which if this would be the case you’d also end up with a spring that would have an enormously low frequency at any useful spring rate causing race car drivers everywhere to suffer from sea sickness…

JPrevost

Am I dead? Can anybody see my posts?
83 Crossfire TA, it's as if you didn't even see my 3 posts.
Did you not see the picture? It couldn't be more clear that there are at least 2 36mm hollow bars out there with the holes on the top.
Oh, and stop being my echo in this thread . 1 smart *** is enough

RBob

iTrader: (1)

As installed center of bar has a belly. These bars are easily made with the holes up or down. Top or bottom I can't see where they are really drain holes. Any water will collect at the lowest point, the belly of the center of the bar. In order to dump out any water some serious corning is required.

I too have thought of adding a single hole in the bottom of the center. Just didn't like the idea of adding a stress point, so haven't done it.

RBob.

soulbounder

Has anyone actually changed out the sway bars either way and noticed a difference? I'd be surprised to find out that you could tell the difference between the two on the street, granted you had enough spring rate to utilize them.

83 Crossfire TA

iTrader: (2)

Yes, and I stated that 2 of mine are on the bottom and I woudn't be suprised if the ones on my 3rd one were on the bottom also...

So, you've got one with them on the top... it's a pretty picture also... what do you want me to do about it? I'm sorry if it offends you that mine are on the bottom...

83 Crossfire TA

iTrader: (2)

Like I said earlier, I think that my 36mm hollow bar on the formula now is too stiff and I perfer the 32mm solid, which should be abou the same difference in stiffness. You actually notice it more on the street. On the track you don't notice the difference in stiffness but you do notice changes in balance.

soulbounder

The question was not geared towards you. I remember reading that in your earlier post. I know you know more about suspensions than I ever will so I have a question.

A sway bar is a tuning device correct? Are there ways to tune something like this without going to the track?

Lo-tec

I changed mine from a 32mm solid to a 34mm hollow and cannot tell the difference. That is probably because according to my back of the envelope calculations earlier in the thread, they are about the same stiffness. The only way to tune this would be to change to a weaker or stiffer bar and see the difference in how your car handles after the change.

JPrevost

You said, and I quote, "I would be surprised if it was on the top." That makes me think that you're doubting me, my picture, and RBob. It also makes you look stupid for assuming something you haven't looked is one way or the other RIGHT after somebody posts a picture saying there's a good possibility that it's holes are on the top .

I did a search and found 2 pictures of hollow 36mm bars where one had holes on top, other on bottom. That makes the evidence so far (in my book) so random that they were made both ways, not one way more than the other. If you've got proof that we're freaks to have the holes on the top than please do post it. As for me, I think it would be a good idea to run a poll question on this. It would be interesting to get a general consensus don't you think?


Soulbounder, yes a sway bar is a tuning device. There are ways to tune this without going to the track but they're expensive and only a few places in the world have the machines... GoodYear in Ohio has one that can be rented out for a pretty penny.
Also, when talking about tuning you need to have a goal. Is the goal to tune the car for the street comfort or best track times? Depending on the goal, it wouldn't make much sense to tune for best track time without actually testing it on the track... that's like trying to predict 60' times on the street where traction is completely different. Just makes more sense to go and tune it where it needs to be tuned.

RBob and the rest of the hollow bar guys, have you seen the previous posts where the bars have broken at the ends of the bar right before the frame bushing? It looks like rust can be a problem with these bars. I'd like to remove the rust but am not sure how I would go about doing it. I don't have enough naval jelly so what other options are there? As for drilling a small hole in the bar, I wouldn't do it but I would seal up the bar so no more mosture could get in. A little bit of WD-40 and tap, teflon tape the holes after you remove the majority of rust.

83 Crossfire TA

iTrader: (2)

Dude, please call your mother over to the computer and have her help you.


Without reposting everything, in a nutshell, I said I have 2 hanging on the wall in the garage that have the holes on the bottom, and considering that I remember seeing the holes in the one that is on the car and usually when you see the bar on the car you’re looking at it from the bottom I would be surprised if my 3rd bar that is on the car doesn’t have them on the bottom also.

I DIDN’T SAY ANYTHING ABOUT YOUR BAR OR RBOB’S in the original post. Please learn to read before calling someone else stupid.

JPrevost

lol, that was pathetic.
Why, if you weren't conjecturing with me, did you even have to say that you would be suprised if the bar on the car had the holes on the top? Sounds like you were stating a point that you wouldn't even need to get up off your "lazy" *** to go check. If you're not going to check, don't go assuming when it makes it look like you're arguing that those that have the holes on top are idiots. Or we don't know how the bar goes on the car. That's how I read into your post.
As for learning to read, I do know how to read thank you but it would help if you learned how to type and follow a thought. When I say learn how to type, it's not just spelling and punctuation. It's also timing and implication. You implied with your words that you would be suprised that a bar you can barely remember, would have the holes on the top. It was rather insulting.

83 Crossfire TA

iTrader: (2)

It’s a matter of approach, but in my mind:

- pick the wheels/tires you want to run, bigger tires need a stiffer suspension to control them properly, if you want to run bigger rear tires you’ll need more rear roll stiffness. A heavier rear axle will have much the same effect.
- Pick springs/spring rates that give you the ride height that you need and are basically as soft as you can go and still support the car under the conditions that you intend to use it under. The faster you go and the less travel you have (on these cars lower ride height dramatically decreases travel) the higher your spring rates will have to be. I hate progressive rate springs, they belong on luxury cars and pickups.
- Get your suspension geometry right/as optimized as you can get it, you don’t want to find yourself trying to fix a problem caused by geometry/alignment with hard parts…
- Shocks and struts are next… they need to dampen enough for the spring rates that you end up with, and then you can fine tune characteristics like corner entry/exit by slightly changing bump/rebound. Of course, you don’t even come close to having that ability with most of the shocks that people run on these cars and would have to have the budget for something like Penskie’s to really do this. That being the case, I consider this a lost cause unless you have way too much money to spend and I like koni yellows on all 4’s when optimizing for road race type speeds and koni’s on the front and a generic “performance” shock in the rear for autox speeds (I’ve used gabriel gas riders), or a softer Koni like the rear shock for a t-bird which will bolt into an f-body.
- At this point you can optimize your overall balance, whether the car over steers or under steers, using sway bars. I personally usually prefer stiff enough, specific rate springs (to a large extent to get around the little if any antidive built into the front suspension on these cars) that the typical 36mm/24mm “good” bars are too stiff. If it was a no comprise handling deal the big bars are usually a good choice but I think that with the stiff springs they’re too obnoxious on the street with potholes… I also like slightly stiffer then normal rear springs (in proportion to the front), so I do not like the 24mm rear bar with the 36 front unless I’m running much bigger rear tires. With the same size tires on all 4 I end up stepping down a size in the rear to control over steer.
- I get things exactly where I want them by using combinations of rubber and poly sway bar bushings… in most cases if I’m running a factory matched pair of sway bars I end up with all poly in the front and all or mostly rubber in the back. Finally, when this is close you can do a final quick tweak with slight changes in tire pressure (but do not take them out of the range where the tread is properly supported)

How’s that for a long winded answer

TheV6jerk

And my car will kick the sh*t out of yours any day of the week on an autox course ********

soulbounder

83 Crossfire TA, thanks for posting your approach. I will most definitely follow that with my current buildup.

Dean, we realize that your car will kick the crap out of our cars on the track. You really do contribute a lot to the boards although your methods are sometimes questionable. You have real world experience which is every bit as valuable as technical background.

In short, stop getting banned! I'm tired of keeping track of your screennames!

kalel21

Im still waiting for the rest of the suspension kit. Also slp headers 1 3/4 w/air and front rebuild kit. Will post more pics when there here.