Adjustable Blade Anti-Sway Arms ???

[442 Ragtop]

Sorry; Hi, all! I've been lurking so long I didn't even realize I've never posted here. As my alias indicates, I have a 442 convertible, it's a 68, and basically stock right now. W/ plans to upgrade. ;-)

[Norm Peterson]

How about other mechanical ways of making a sb adjustable?

I can think of a few:

1. An arrangement that lets the arms slide horizontally on the torsion bar. Put them close together, and you effectively have a stiffer arm; move them apart, and its looser.
2. An arrangement that lengthens or shortens the arms. Short arms effectively stiffens the bar.
3. End links with springs in them, with an arrangement to lock out coils of the spring. Lock out all the coils, and you have a stiff bar; lock out just a few and it's looser.

I like 3. the best, since it would work w/ a bar that fits in the stock location.

I think years ago there was a commercial offering that used method #3, but I have no idea how well it fared. This approach has a built-in limitation in that you cannot make the bar any stiffer than OE, and even that value is with all of the coils stacked completely solid.

Method #2 is readily do-able, although you might want to be able to move the bar's frame mounts slightly to avoid excessive endlink angularity. Bar stiffness is somewhere between a square and cube function of arm length, so it doesn't take much change in the effective arm length to make a fairly large difference in overall stiffness, and this can easily be made greater than the bar's as-stock-installed value. I know of at least one individual (an engineer & amateur fabricator) who has done precisely this mod for the rear bar on a 4th gen Camaro.

Norm

[David Pozzi]

The method #2 was done a lot with push pull cables on race cars until the blade type came out. Some of the IMSA and Trans-Am cars of the 70's used it. Often they used a slider on a greased anti-roll bar arm.

Adjustable arms with clamps are still in use, the trick is to use long end links which allow more adjustment on the arm without much angularity change. On my vintage Lola, the rear end links are 16" long.

[chicane67]

I believe ATS is coming out with just what is being talked about here. I wonder if Shane or Tyler would like to pop in and show off a little. In fact, I'd be interested in one for my '77 Camaro. Hell, I may just do it with a stock car bar.

Uhm... not at this time. The boyz are a little busy with what they have on their plates already.

[TT402LS1]

OK, this is what I want to run on my 71 Chevelle. A anti roll bar from www.wolferacecraft.com . I was told it would be too stiff for the street and cause a understeer problem. This is about the same thing you guys are talking about, except adjustable, right? Could this me made to work on the street? I see them in the jegs catalog, and it says race or street.

Also, seen a pic of a 05 Mustang rear suspension. It uses a panhard bar and a sway bar that is mounted to the LCA w/ links to the frame. I have a stock 4 link in my Chevelle. If I was to make adj. links that go from the sway bar to the frame, how well would that work? (I want it to handle, and hook up 750hp)

Thanks - Ron

[wendell]

Ron,
The Wolfcraft sway bar is a sway bar in name only. It's designed for dedicated 10.5 drag racing. It's made to keep cars launching straight and lets you adjust preload on the rear tires to maximize traction. It's so stiff that as the car leaves the line and weight is transfered rearward, it is distributed evenly side to side. The result is a rear suspension that in side view functions like a piano hinge. Not the hot ticket for a road car.

[Norm Peterson]

OK, this is what I want to run on my 71 Chevelle. A anti roll bar from www.wolferacecraft.com . I was told it would be too stiff for the street and cause a understeer problem.

The issue for such a huge rear sta-bar is oversteer, not understeer. Those things are marginally streetable in any car; less so in a PT type of car with relatively much better front grip than a skinnies/drag radials strip car. You CAN drive around with it (or any of the similar offerings from other makers), but don't expect much warning when the rear end comes unstuck in a turn taken with any enthusiasm.

As regards the '05 Mustang arrangement, changing the method of attachment of a bar changes its effectiveness, and details other than bar diameter and arm length also matter a great deal.

Norm

[rabieng]

Hi guys,

Well, as promised I am back with some pics of the designs I did in that ARB assignment using some of the ideas and information which was presented here. I have just been very busy with work and hadn't had the time to post sooner.
The first two pics show the assembly of the ARB Design 1. The Blade is fitted in a T-shaped Joint/Clamp (no bolts shown). There is The Joint itself is fitted to the ARB Tube using splines and locked in place with a bolt groove fixing on splined part of joint. A splined fixture has been chosen to provide the possibility of replacing or using another gauged tube. The blades can be adjusted by loosening the clamp bolts, turning the blades say 90° and then re-tightening the bolts. The ARB is bearing mounted in brackets and the bearing also faces off on the ends of the Joints providing a "frictionless" mounting. This design may work but is rather complex from a design/manufacturing point of view. Also depending on space/application the length of ARB may cause problems.
The alternate joint shown in the third drawing is a simpler design (I think). The Blades are mounted above the Torsion Tube and snug fit in the hole in Joint Block. This time a transverse bolt goes through the slot in the side of the Joint (as shown) and screwed into the Blade root which tightens up against Joint Hole. This locks Blade in either hard or soft position. The joint is bolted to the end of the tube by means of a welded (or even brazed) threaded tube end fixture. Since the Blades are mounted above the Torsion Tube it makes for a more compact design in length.
I haven't added an assembly drawing of second design for obvious reasons but hope to get your imagination going. Well I hope you will be able to see the pics as this is the first time I am trying the attachment feature. Any comments or suggestions would be welcome.

[pav8427]

Give Hoerr Racing Products(Peoria, Il.) a call and get a catalog.
They have one that looks like it would be easy to reverse engineer or atleast use cfor a model.
The pics of installed unit and sub-assemblies for anything they offer are very good.

[trackrat79]

Have you decidedon a material for the blades. What Kind of adjustment range are you hoping to get.

[rabieng]

Hey pav,
I saw that adjustable blade kit from HRP the thing that I have noticed with it is that they put the Blade Roots (the round ends) in bearings. I would think that those bearings would introduce some "play" in the whole system and eventually affect the overall handling of the car in "tight" situations. Haven't spoken with anyone who has actually used these bearing mounted Blades but would interest me to know if it is actually how I think it is.

trackrat
As for the materials. It all depends on the type of application and the length of blades and bars that one uses. Of course it also depends on budget (hehe). For this assignment, I was given certain specs about the length of bar and blades and that is what I had to work with. So depending on the kind of spring rate (just talking about ARB rate here) required the type of material chosen could vary. My specs required me to get a spring rate of 90lb/in to 250lb/in, from a SOFT/SOFT to HARD/HARD position and max. deflection of ARB of 80mm (just over 3 inches). I had to develop a spreadsheet which would give me the max. stresses in the blades and tube. Needed something strong for the given spec. blades so chose a nice 300M HS which was just about suitable working within certain safety limits. A british spec T45 steel was used for the tube. This type of material is used on some Lotus, roll cage, bike frame and aircraft applications. Other possible materials Cr Mo, aircraft spec steel.

[pav8427]

If done with a tapered roller bearing(think spindles)there would be little, if any, slop and very free movement. And these would take a hell of a load with zero affect to the whole system.

[phaseshift]

I am harping in late here as usual, but I have a couple of opinions-

Wow, this is a very interesting project; it is full of challenges and variables.
The idea of the adjustable bar is cool, but one of the main things that I see as a problem is material selection. The designer needs unobtanium which is blessed with ideal properties in stiffness, ultimate strength and weight. It would also need to be ultimately damped to not be part of the spring system adding a variable to the shock damping.
For instance, yield strength (if you use aluminum or even a good alloy) will be an issue if you are running significantly lengths on the arms. This becomes a bigger issue if the bar is in the "soft" position; it will be very easy to get into a condition where you have a force into one wheel that will result in the bar going past critical in yield strength. In a turn, hit a bump and the link is done (bent, but may still work... more adjustment? crash?)

Connection to the LCA and actual motion in the real world environment- Unless the blade is dead on above the LCA, you will have a complex angle of inclination between the sway bar arm and the LCA. IN a typical car, this is dealt with using very heavy arms or good centering or a compromise of both. If you are not well centered, the link will push the bar to one side or the other during compression and tend to be pushed back by the restoring force of the bar. In the case of the adjustable bar, you may find that the mechanics of the adjuster system are significantly stressed at times, perhaps beyond their yield limits.

It may be interesting to look at other shapes as well, especially if you have access to some good FEA rigs. For instance, diamond or oval shaped bar may work out a few of the problems, but introduce some new complexities such as a more limited range of adjustment. If you can do this design in a typical parametric 3D software package like Pro E or SW, you can use one of the FEA suites to really get a good look at the load and stress / yield limits and variables.

I have given no answers here and I hope I have not re-hashed too much. This is a very interesting discussion and I just wanted to throw a couple more variables into the pot. I do a great deal of kinematics and load based design work and I find this sort of discussion very interesting. I hope my comments will be a positive contribution to this thread.

[cagedruss]

Use the adjustable blades for tuning your bar. One is only need to get results. Math has to be only close, change the angle with a cable adjuster or by hand.

We use this type in GT cars and the driver can make changes for varying track conditions.

http://www.raetech.com/Suspension/Blades.php

[Mean 69]

Hoerr Racing is another excellent source for blade adjust components. Good folks to work with, lots of knowledge, very courteous.


www.hrpworld.com

Mark

[formula]

out of curiosity--Why aren't these more popular? Just because they're overkill for the vast majority of cars out there? I guess cost would be a major issue, too.

Awesome ideas, though. Very ingenious.

[Norm Peterson]

Cost would definitely be an issue, especially if the assembly is held to tolerances close enough to eliminate virtually all "free play". Not much point in having the capability to adjust to within 10 lb/in wheel rate if the amount of "slop" (aka a dead spot around zero bar loading) that gives away the first 50 lbs of force.

It's also another periodic-maintenance item, being in most street-driven cars down there underneath most everything except the water, dust, dirt, slush, etc.

I'd think that it's a rather narrow-focus product, with at best a relatively small portion of the aftermarket sta-bar customer base having a really good grasp of what's going on.

Re: leaving the adjustability to one arm only - I'm not at all convinced that a one-sided adjustment wouldn't introduce a couple of side effects due to the asymmetry (coupling between roll and two wheel bump, and the jacking of some weight around as the car rises and falls in pure 'heave'). Something like that might work for a circle track setup given some extra test'n'tune time, though. Or possibly in a car with very stiff springs and only a small bar for fine-tuning.


Norm

[forzaferrari]

Hi everybody I am a frech student in mechanical engineering and I am new on this forum.
Is there anybody who could explain me the following equation in the sheet posted by David Pozzi on the first page:

dv= 1.2 Pl / G b (H-h) * ln(H/h)

Thank you very much and excuse me for my poor english...

[Norm Peterson]

[Force P] * [Length l] / {[Shear Modulus G] * [Section Width b] * [Section Height H,h function]}

looks like an equation for estimating shear deflection in arms of non-uniform depth.

Generally this is only a minor effect with the possible exception being in very specific situations where the arms are deep (large H & h) and short (small l ) and the central torsional section is short.

Most of the time, center-section torsion and arm bending account for at least 95% of the total bar deformation (making them primarily responsible for its overall rate).


Norm

[Bryce]

i know this is an old conversation, but what about a linear actuator instead of the sway bar arms. Obviously the actuator would need to be strong enough to support the loads. Just simple beam theory. Then you have your adjustment in a neat package with all the cool factor.