Chris Harris drives the Deltawing

http://www.youtube.com/watch?v=c_INdbXMqsw&feature=g-user-u

Pretty sweet!

Jaynen wrote: http://www.youtube.com/watch?v=c_INdbXMqsw&feature=g-user-u Pretty sweet!

No, it's new & different and we don't DO new & different here on GRM.

That was a really good piece . . .

I like the 417 kilo weight.

That was pretty cool. The talk with Bowlby was very interesting.

I still think it's hideous, and I don't like the idea of driving something with that much width to keep track of behind me, but those are all things that could change with time and practice. I think most of my misgivings are really my own problem, but I am curious about what it would be like to have three of those things dicing with all that width variation...

It was interesting to hear about their focus on damping in roll, which when it comes up on normal vehicles generally gets filed under "if you've got enough heave damping, you'll be fine in roll". Which may be true, but it does seem interesting that antisway bars of such varying sizes are fitted with dampers still tuned based mostly on spring (as I understand it)...

I wish they'd have had better pics of the rear end because I liked what he had to say about the 2:1 ratio on the bar to dampen roll but not heave, but I have no idea how they actually did it.

The rear braking bias makes more sense now too.

Ooh... I like the rear suspension bit.

Cool car, cool piece.

I want that guy's job.

Very cool. Given the recent turmoil that has engulfed IndyCar lately, one has to think, "what if?" when you look at the Deltawing.

Not that the Deltawing could have saved IndyCar, it likely would have made them a laughing stock (imagine an entire field of those things and the jokes write themselves), but it might have reduced costs and garnered enough sponsors enough to forestall the ousting of Bernhard. (More info on the mess that is IndyCar now)

Oh well, at least he ALMS/Grand-Am merger isn't nearly the mess that CART/ChampCar/IndyCar/IRL, etc is currently. Hopefully the Deltawing can find a place within the new ruleset to be a competitive option for some teams wanting to get into prototype-style racing.

carguy123 wrote: I wish they'd have had better pics of the rear end because I liked what he had to say about the 2:1 ratio on the bar to dampen roll but not heave, but I have no idea how they actually did it. The rear braking bias makes more sense now too.

I think I've figured it out. You know how high-end race cars with double wishbone pushrod suspension have a springloaded piece that links the two bell cranks that acts as an anti-roll bar? Pretty much the same setup, but it sounds like they have an unusually high amount of leverage on the anti-roll piece (2:1 ratio, so the links to the anti-roll are twice as far out on the bellcrank as where the coilovers mount) and it has a shock absorber on it as well to slow the roll motion.

Chris Harris drove that car really well and the suspension and handling dynamic explanations from Bowlby were clear and understandable. I still think they should paint it in the old AutoUnion silver so it's a bit more visible and expressive. I bet John Fitch would've enjoyed discussing this car with Bowlby. Well-done piece of thinking and driving.

So I have a odd question. Why don't we setup brake bias for the rear of a car like they do. Normally you have more tire in the rear, and its not like you are steering with them.

He explains that near the end. This car has way more weight and traction on the rear than the front, it's running a lot of rear brake bias but it's not disproportionate. If you run monster slicks in the back with skinnies in the front and have almost all the weight on the back axle, you could do the same thing.

Also even on a regular car with more tire in the rear like a Corvette, it will have a fairly even or possibly forward-biased weight and when you hit the brakes hard, the rear will have way less weight on it than the front. On this car when you hit the brakes, the weight distribution is probably still slightly rear-biased.

wearymicrobe wrote: So I have a odd question. Why don't we setup brake bias for the rear of a car like they do. Normally you have more tire in the rear, and its not like you are steering with them.

Drive down a deserted road and suddenly pull your e-brake.

After you've pulled the car out of ditch and cleaned your shorts, do it a few more times (cause its freakin fun!)

Now realize that too much rear brake bias is not good, mkay?

Not to say that you couldn't balance it a bit more than the factory does, but there is a balancing point due to the front heavy nature of most cars and the simple physics involved with braking. It also varies depending on any number of variables involved (picked up some groceries? or a couple of friends? Or did you just drop them off?)

BTW, the majority of factory brake bias solution tend to favor the front to induce understeer as it is safer and makes use of the maximum amount of weight transfer. ABS improves upon this.

I know here at Acura, our cars have a bit more rear bias than most. This also means the rear brakes are typically the first to go... And on some cars (like the tsx) you do 2 rear brake jobs to one front. But... When you stab the brakes the front bumper does NOT hit the ground like half the other cars out there.

Thank you for the link!
Very cool video, lots of want involved with that car.

Thanks for sharing this. Very cool explanation of some of the finer points of the car. I loved how a human can pickup the front end of the car.

turboswede wrote:

wearymicrobe wrote: So I have a odd question. Why don't we setup brake bias for the rear of a car like they do. Normally you have more tire in the rear, and its not like you are steering with them.

Drive down a deserted road and suddenly pull your e-brake. After you've pulled the car out of ditch and cleaned your shorts, do it a few more times (cause its freakin fun!)

Brake bias is something that I could never wrap my head around. So....

Maybe I am just thinking about this wrong but on a track. I pull the rear brake while going straight and its going to stop straight. In a turn its is going to pull you into under/over steer, provided you don't lock them up depending on chassis balance.

But the front tires are going to yank you back to the direction you want to go eventually. That is provided you have grip and the delta wing has very little grip up front.

Its a little odd to think about this as I normally don't run around slamming on only my rear brakes only in a turn or straight at full steam.

In my world, just pondering.

I have ~1600lb's of down force in the rear and 350lb's or so up front, but a lot more of the weight biased toward the front. If I moved more of my braking to the rear I should be able to brake harder as the car would be more balanced. Until I move so much bias to the rear that I start locking them up before the fronts and cause all kinds of havoc as the brakes overcome downforce and traction.

BTW, Heir Schumacher would adjust brake bias between corners while racing in F1.

turboswede wrote: BTW, Heir Schumacher would adjust brake bias between corners while racing in F1.

A lot of them do, mind you its not corner to corner but driven by fuel load and to save tires.

turboswede wrote: BTW, Heir Schumacher would adjust brake bias between corners while racing in F1.

McLaren actually put an extra pedal in their F1 cars back in the late 90's. pretty ingenious if you ask me and amazing that drivers could use it so effectively.

http://www.f1fanatic.co.uk/2007/05/24/banned-mclarens-rear-brake-pedal/

wearymicrobe wrote:

turboswede wrote: BTW, Heir Schumacher would adjust brake bias between corners while racing in F1.

A lot of them do, mind you its not corner to corner but driven by fuel load and to save tires.

Yes, I'm aware of that. The fact that the Shumacher was doing it between corners was the amazing bit considering how busy they are in the cockpits. Adjusting BIAS, sway bars and trackbar/roll centers based on fuel load and tire selection is common in many professional racing series (V8 super cars does this as do other endurance series)

It's not that amazing - I do the same thing Sure freaks out passengers, though.

To give Harris the full experience, someone should have driven into him That car needs to be neon green and electric orange. As for driving it with the wider rear - lots of cars are built like that, but maybe not as extreme. A set of long curb feelers might help some drivers.

Brake bias is easy enough to understand. Basically, your braking ability at each end is determined by how much load is on each end. Braking transfers load from the rear wheels to the front wheels, so the fronts will gain traction while the rears lose traction. On a car with a massive static rear weight bias, you may still end up with more traction at the rear so you can run more rear bias.

As for why it's unstable to lock the rear tires but not the fronts, remember that a locked tire doesn't give as much grip as a rolling tire. If you lock the rears, you've got a car that's trying to slow the fronts but not the rears, so the rears will try to pass the fronts. It could also be explained in full-on engineering terms, but that'll probably help you wrap your mind around the concept even if it is a bit inaccurate.

If you've got a lot of static front weight bias but a lot of aerodynamic rear downforce like wearymicrobe, you'll never get the braking balanced well. The ideal brake balance will change fairly dramatically with speed. I've experienced a similar thing when doing wing testing. Good luck getting that sorted out! I'd try to get some downforce on the front of the car first.

Note that f/r brake bias does not affect nose dive.

I thought one key point that Bowlby made with regard to brake bias was that with the DW's heavy rear brake bias, the fronts are doing very little, so when you do lock a rear, you don't have the front trying to slow down and the rear trying to pass it.

EDIT: Keith totally had this in the midst of his summary...

You still want the fronts to lock first, but with all the extra grip in the rear of the DW compared to a normal car, you'll have a lot more rear bias.

You might find some of this entertaining: http://www.flyinmiata.com/pdf/HPMM_sample_chapter.pdf