T-BAR VS. U-BAR ARBs
T-BAR VS. U-BAR ARBs
(OP)
First, thanks to all who responded to this newbies very first thread last week.
Having set aside geometry for awhile, here's my next query.
I'm intrigued by the use of T-bar ARB's on some cars (there a beautiful pic of one on the Radical SR9). Nobody seems to talk much about this, but it's function with respect to the opposite wheel seems to be fundamentally different to the conventional U-bar.
Is the simplest terms, roll induced compression on the outside wheel is tranlated as a downward force on the inside wheel, rather than an upward force in the U-bar version.
Rotation torque is still referred to the chassis by the torsional compliance of the bar, although the bar is now 90 deg. from the the U-bar version.
The load transfer to the inside wheel would seem to be highly advantageous. Why isn't this used more..or at least talked about more?
As an aside, it seems to function much the same the oh-so-trendy "monoshock" configuration of a few years back, but without the potential binding and friction problems in that design.
Is there an Achilles heel that I'm missing here?
Having set aside geometry for awhile, here's my next query.
I'm intrigued by the use of T-bar ARB's on some cars (there a beautiful pic of one on the Radical SR9). Nobody seems to talk much about this, but it's function with respect to the opposite wheel seems to be fundamentally different to the conventional U-bar.
Is the simplest terms, roll induced compression on the outside wheel is tranlated as a downward force on the inside wheel, rather than an upward force in the U-bar version.
Rotation torque is still referred to the chassis by the torsional compliance of the bar, although the bar is now 90 deg. from the the U-bar version.
The load transfer to the inside wheel would seem to be highly advantageous. Why isn't this used more..or at least talked about more?
As an aside, it seems to function much the same the oh-so-trendy "monoshock" configuration of a few years back, but without the potential binding and friction problems in that design.
Is there an Achilles heel that I'm missing here?





RE: T-BAR VS. U-BAR ARBs
You wouldn't use it on a road car, it's only really practical if you are going to do lots of maintenance, and adjustability just isn't a requirement for road cars.
The vast mass of suspension theory and practice is aimed at roadcars, racers deal with much smaller wheel velocities and have a simpler task. They also have fewer resources of course.
Here's a MBS simulation of a Lola 3 spring setup http://greglocock.webs.com/
So far as tuning them goes you can do things like adding inerters and also jounce and rebound stops in roll, which is cute.
FSAE kids like them, personally if I am ever a design judge for FSAE again then I will be marking them down unless they can give a good reason why they are being used.
"The load transfer to the inside wheel would seem to be highly advantageous."
Don't agree.
Cheers
Greg Locock
SIG:Please see FAQ731-376: Eng-Tips.com Forum Policies for tips on how to make the best use of Eng-Tips.
RE: T-BAR VS. U-BAR ARBs
The Matthews Lola dwg, by the way, does a beautiful job of showing how this setup separates differential and common mode movements into two orthogonal movements: differential being the transverse Belleville arrangement, and common mode bump via the longitudinal bump stop.
RE: T-BAR VS. U-BAR ARBs
Yes, Tony's drawing is rather good, he's a clever bloke.
Cheers
Greg Locock
SIG:Please see FAQ731-376: Eng-Tips.com Forum Policies for tips on how to make the best use of Eng-Tips.
RE: T-BAR VS. U-BAR ARBs
RE: T-BAR VS. U-BAR ARBs
If it is ground effect aero then this is a bigger concern as the ride heights also need to be controlled as well.
Cheers
Greg Locock
SIG:Please see FAQ731-376: Eng-Tips.com Forum Policies for tips on how to make the best use of Eng-Tips.
RE: T-BAR VS. U-BAR ARBs
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It does not work any differently than the conventional U-shaped ARB. It pushes (or pulls) the other wheel in the same direction.
The T-bar is a torsion bar. See the square end? It is twisted when the car rolls. It is free to move fore-aft with the vertical motion of the suspension. There is another tee on the other end of it that is hidden in the monocoque that is has ball bearings on the ends. The "T" (or the horizontal "H" to be exact) can rock freely, but it takes an effort to twist it. It is the same Anti-roll bar, not a pro-roll bar.
RE: T-BAR VS. U-BAR ARBs
There seems to be some contention here: In one of the submissions above, it is suggested that a T-bar functions exactly the same as a Z-bar (commonly used as an anti-jacking devive in VWs and swing-axle Corvairs).
Its application in a high downforce racecar makes perfect sense, given the very stiff anti pitch springing required, which would otherwise suppress individual wheel motion in bump.
RE: T-BAR VS. U-BAR ARBs
RE: T-BAR VS. U-BAR ARBs
Cheers
Greg Locock
SIG:Please see FAQ731-376: Eng-Tips.com Forum Policies for tips on how to make the best use of Eng-Tips.
RE: T-BAR VS. U-BAR ARBs