It's possibly only where confined environments require short arms, which cannot be made thin enough for the required flexure without compromising integrity. If you are requiring that much softening of the ARB it suggests the full stiff setting is too high, and a softer bar should be used anyway. Otherwise there is very little logic in having two blades unless you like extravagance!
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Martin Cutting
aka Keeper of "The Teutonic Kitten"
It's not better than sex, but it runs it a close second. -
Making the adjustable rollbar for our cars isn't that hard. However making them in a way that they perform well is another story. I think our best solution is to fabricate several blades, with a minimal amount of 3, with various thicknesses. Then put them on a "control" car. Then consecutive track test all the versions. this way there is a benchmark in blade thickness and effect on the handling. I know it's a very primitive way of testing. However there are so many variables in an ARB that IMHO only real world sircumstances will tell what works or not....Comment
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I would agree with the above. All designs, no matter how well thought out and designed, should be track tested anyway. Pure theory only gets you so far...Comment
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Absolutely ...testing is the way to find the solution given any other limitations. Getting an educated theoretical thickness for a given arm length and then making at least one thicker and one thinner version. Bear in mind this will only allow you to go to a maximum of the stiffness of the torsion element and that may also need to be manufactured in more than one size. I have looked into this before and 4130 tube is more than adequate for ARB applications.Martin Cutting
aka Keeper of "The Teutonic Kitten"
It's not better than sex, but it runs it a close second.Comment
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I've fitted Sellholm ARB's with adjustable blades, in front 320mm blades, rear 280mm and 30x3 crmo pipes. Rear is connected to shocks, front to control arms.
As i'm using AIM MXL Pista for dataloging, on track you can see every detail (even just adjusting arb blades) and how it effects speeds, over/understeer, cornering G. Anyway you don't need stiff in front, because you will have a lot understeer.
If it's track car and you can log the difference - not feel then adjustable blade arb's is OK, otherway you will spend 2x+ more money than to buy for example H&R or whatever..Comment
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997 gt3 cup car rear anti roll bar, other side is as normal, this side has the blade adjustment
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Don't like the way they have the adjustable blade bush overhanging but that's probably to get blade length and to keep within the rules about suspension mountings being stock location.Martin Cutting
aka Keeper of "The Teutonic Kitten"
It's not better than sex, but it runs it a close second.Comment
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how else would you mount it so that the blade is inline with the rotation centre point? as well as making it seconds to adjust between a wet and dry setting? we can change from wet to dry settings in the collecting area - minutes before the race starts!!
this is porsche standard equipment, all the cars in the carrera cup are exactly the same and this is heavly scrutanisedComment
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I know - it's rules driven. Ideally the bush would be directly on the end of the torsion element and the bar mounted accordingly, but the rules dictate standard location points. I investigated GT cars when we were originally asked to build a GT2 TT back in 98.Martin Cutting
aka Keeper of "The Teutonic Kitten"
It's not better than sex, but it runs it a close second.Comment
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(I think you were missing the point slightly Will - the bush on this bar isn't even connected to the end of the bar, it's on an overhanging gussetted piece, which I wouldn't personally choose to do!)Martin Cutting
aka Keeper of "The Teutonic Kitten"
It's not better than sex, but it runs it a close second.Comment
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Yes, like to see your setup aswell.
I agree with the fact that a single blade will do the job, can't figure it out myself why bothering to use 2 blades. Couldn't be the difference in unsprung weight...
But if you use a single blade, the strip on the other side has to be torsion-stiff.
This has to function properly if the bar is easy to rotate under load, i.e. low friction between bar and mount. The OEM ARB takes a bit of bending with the additional torsion, certainly no pure torsion! Theoreticly i'd like a perfect distribution of body-roll forces in the entire assembly.
I did some CFD calculations on a 175mm blade with a 0, 15, 75, 90 degree angle to get some idea of the difference in displacement due to the load applied.
I'm still trying to figure out what the max. load of the ARB is. Vehicle dynamics isn't that easy, you have to take in account that the spring/damper combination is influencing the entire load distribution.
To get an idea of what the blade flexes in a couple of different conditions:
Max. stress on the biggest displacement is under 350MPa. A CrMo alloy like 4130 will do the job.
Like already said, ultimately the set has to be track-tested. Calculations might be wrong due to the dynamic situation.Comment
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dont really know a massive amount about anti-roll bars but just thinking out loud, would it be worth having two bars per axle, that way you could pre-load them agains each other, that way they would take effect instantly during cornering rather than waiting to be loaded....or would the fact that you'd be unloading the other counteract the pre-loading of the other.....if that all makes sence??? trying to think about the forces in my head but not feeling to well today so brain cant work....
Ant91' Coupe quattro 20v - project
KW V2s and other goodies
now gone
03' BMW 330CI - Sold
08' A5 Coupe 3.0l tdi quattro - Sold
57' BMW 525d M Sport TouringComment
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I think the thing to remember is that the torsion element is a spring - and two springs acting against each other will broadly behave like one spring of a different rate.Martin Cutting
aka Keeper of "The Teutonic Kitten"
It's not better than sex, but it runs it a close second.Comment
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Did anything come of this?ChefComment
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