RR98ITR

...then I may as well do it right. Thanks to Brian Slames of PCI for demonstrating that it can be done.

Scott, who is really enjoying making progress...however slow it is...

descartesfool

Teaser!

TunerN00b

Wow. Bar size?

RR98ITR

My scientific calculations indicate that 3/4 inch or 19mm if you prefer is the correct complement to my front spring rate (900 lbs). Of course I could be wrong about that. Or perhaps right and wrong don't strictly apply. I can go as high as one inch on the bar, though I'm unlikely to do that since it would put me above 40% for the contribution of the bar. The lever arm is around 5.5 inches, and a couple of hole sets would give a useful range of adjustment - by useful I mean quicker than making a camber adjustment and toe correction. I had intended to do an adjustable blade arm on the right side, but am tending towards not. I could change my mind about that again.

Scott, who can still remember when he passed the point of no return...well, the last one anyway...on to the next!

azian21485

Why do you not want the swaybar to contribute more than 40% of roll stiffness?

dirty19

iTrader: (1)

Very interesting.
40% is alot... Im listening.

descartesfool

That would make it rather difficult to tune the dampers properly. For pitch, squat and heave when driving in a straight line the anti-roll bars are not in play. So if you tune the dampers for stability in those situations, going over bumps and swales etc., they would be way off if in roll the damper has to control 40% more springiness when the bar adds in parallel to the springs. Then if you had decided to tune the dampers just right for roll handling, they would likely be much too stiff in the straight line stuff. Good compromise is 20% according to Olley. That way bar can be used to tune balance, rather than to dominate the roll stiffness. But whatever makes the laptime faster works too.

Way to go is blade adjustable with cockpit adjuster, even if it has to be out of reach of the driver. I would so much like to have that on my car. Genesis has a nice one from HRP. And Realtime uses them on all their cars, so it must be good. I know, I know, Realtime this, Realtime that.....

get RIGHT

Can't wait to see the finished product.

914Racer

Of course then you have yet another undamped spring in the system. But it is probably the best option.

RR98ITR

I cannot believe nobody is going to step up and do their pedantic duty...

No - not "another undamped spring". The blade is in series with the bar, so the result is a bar/blade system with a lower resultant rate. That's it. And it's no more damped or undamped than the main spring(s). It's a system (the car that is - don't get locked into looking at a corner in isolation) and it operates in modes (heave, pitch, roll, warp, and whatever else happens in other dimensions that are undetectable by current corporeal earth technologies), which is what Claude was alluding to.

In fact if you think about it (in the incorrect way but less incorrectly), the bar with the blade is apt (ie at less than full stiff) to be more rather than less damped, and so contrary to the idea that you've added another undamped spring to the system, you have in fact reduced the amount of undamped spring in the system. In fact, if you think about That some more you can't help but suspect that in the crunch George Costanza wouldn't make a half bad race car engineer.

Scott, who is rotating toward full stiff with regard to running a blade but hasn't locked the detent on his thinking yet...my detent lock is persnickety and not to be relied upon...

vinuneuro

I talked to Lee Grimes a couple weeks ago and he mentioned that Koni doesn't take sway-bars into consideration because they're not used during transient phases which doesn't really make sense to me. Bilstein doesn't use sway-bar rates for valving either so there's something off with our(my) understanding of how ARB's factor in.

OT: how do ARB's oscillating characteristics compare to coil springs? Are they self-damping to any extent?

descartesfool

They are certainly wrong about the bar not being active in the transient phase. That does not make sense to me. Car rolls, bars are bending, and transferring weight. Tire doesn't know if wheel rate came from the spring or bar. Rate at the wheel depends on bar, spring, and damper. Springs are active at all times the suspension is moving, bars during cornering only (actually when wheels at one axle move un-evenly), and dampers only in transients.

I would think they don't consider the bars because on most cars the wheel rate contribution from the bars is low enough compared to the contribution from the springs, so you can ignore the bars and tune the damper rates based on the springs alone. But if you go to 40% wheel rate from the bars, then I think one needs to consider the bars. That is the reason bars are not typically contributing above 20% of the total rate.

Think of it this way. Take out the bars, and drive the car into and out of a corner. Say it rolls 2 degrees, starting at 0 then transitioning to 2 degrees and then transitioning back to 0 degrees. Now add some stiff bars, increasing roll resistance, and at the same g's car rolls less, say from 0 to 1.5 degrees and then back to 0. Of course the bars are active in the transient phase, as well as at maximum roll, which is theoretically not transient. They are simply not active before the car starts cornering or after, except for movement over uneven pavement. Perhaps there is something I'm missing?

solo-x

My sway bar is connected to two dampers. How exactly is it "un-damped" again?

solo-x

Think of a spring as a sway bar twisted into a helix. Or, think of a sway bar as a spring that has been untwisted.

descartesfool

Here are some nice rear blade adjustable anti-roll bar pics, along with the other end of the bar with multiple holes to get the bar rate in the right range for adjustment with the blade, just for inspiration (note how the suspension has caught rodenditis disease):

914Racer

AS I understand it the blade will flex independently of the rest of the sway bar. According to Smith, the blade type while being the best solution also has problems all its own.

RR98ITR

Caroll Smith is not a God...merely a Demigod...now ascended. Sometimes he said some things - not that often. Other times people misunderstand him - much more often.

No, not "independently". It is an individual object. But it's not doing anything unless it's attached to a bar, and to a load. And that load see's the system comprised of the the arms and the bar (and any compliance in the mountings). The resulting spring rate is the inverse of the sum of the inverses of the component rates. The chassis mounts and the control arm mounts don't even know there's a blade. Let's say the blade could and did flex "independently", which it couldn't and didn't, but lets say it did, but not so loud that too many could hear and giggle at us like japanese girls, when would it stop flexing independently, and by independently you mean while the bar not since what else could you mean, and so cognitively, but wrongly and again only for the sake of conversation, and the giggling etc, but that when the blade had flexed all it could then the bar would start to flex.

No.

Scott, who does not know where Demigods go when they die...but hopes it's like Spa only better...

PS - Claude..."What, you camera only take picture of Realtime kaa?"...

descartesfool

Scott, I had to look hard, but I did fine some pics my camera took not of Realtime

So first up is Randy Pobst's Mazda rear bar with some trick adjustable length arm. As I recall, he drove that little Mazda pretty quick.

Some guys even ran a non-orange&white Acura, actually a green Acura. You might know of them.

and then, there are other fine pics I found at the American Le Mans in Sebring;-)

Fastom

Hey Scott and Claude. How about some linkage that would connect to the sway bar ends and a damper. Sort of like a backwards momo-spring or third spring linkage that would damp the sway bar only in roll ?

Tom - Who likes Claude's non-Realtime photos !

TheMidasTouch

iTrader: (2)

Weird they would alter the link pivots on the right and not left. Accounting for weight placement lining up CG's with roll centers? They do carry ballast from time to time... Anyone else want to enlighten a fool?





Sorry for the thread jack Scott, looks fantastic. Great idea!

RR98ITR

No need to apologize...I hadn't noticed that right/left discrepancy. Hmmmm - I can't think of a reason....Hmmmmm...Who could I ask about Realtime?.....Hmmmmm....Who do I know that's really up on Realtime?...Hmmmmmm.

Could be pics of two different cars...one adjusto, the other not? (*Yeah, pretty sure, I've got a copy of the pic of a rear subframe/fuel cell assembly removed and both sides are adjustable).

Scott, who is in no position to enlighten a fool...there ain't even enough light for me!

spAdam

iTrader: (1)

I think its two different cars. Look at the pic of the removed subframe assembly, the left arm is round like the right arm in that one.

descartesfool

Well we don't need to fret about those old-school Realtime designs, circa 2005-2007. Here are some pics of the 2010 blade adjustable anti-roll bar design as shown in pictures I took at Mosport. Definitely same car. Race cars evolve, never ceasing to chase those last few tenths.

They do so, so much work on their rear suspension, and some people think those rear tires are just along for the ride.

And imagine adjusting camber by just loosening two bolts on the upper A-arm and stuffing in a pre-determined thickness shim. And changing rear roll rate by pulling on a pin and rotating the blade and then pushing the pin back into one of several pre-calibrated holes. Nice.

spAdam

iTrader: (1)

So badass. Thanks for those pictures. I was so disappointed when I found out that World Challenge wouldn't be at Sebring this year

I'm often kind of shocked with how common that attitude is, even amongst some people who otherwise have a pretty strong understanding of suspension design.

RR98ITR

This again (as if I actually believe it could ever end)? Do the rear tires do the steering? Do they transmit power? Do they do much braking?

How many tiimes have you heard a front wheel drive racer complain that the car was working really well untill the REAR tires got hot and greasy and the car developed so much oversteer that it was almost impossible to drive? I can't be the only one who doesn't hear this.

Hmmmm - why would Realtime, or any, front wheel drive racing effort spend a bunch of time and money on the rear of the car if it were just along for the ride? What kind of question is that? A bunch of heims, a bar, even an adjustable one, and a more convenient way to adjust camber...That's a big deal that proves how critical it is to "maximize" Rear grip? That's a pretty good leap of logic there. The size of the bar on the RTR car kinda makes that argument untenable, since it would obviously develop more grip with a smaller bar right?

Scott, whose rear tires are just along for the ride, but that doesn't mean I haven't had to expend some effort to ensure that they don't cause mischief...