Topic: Front brace types comparison, cross-bay, ladder, DDM, Werks, LatinVenom

[Dave@DDMworks]

In order for Dave to do an FEA (finite elemental analysis) he is going to have to have a pretty complete CAD model of the car.  Which I doubt anyone outside of GM has taken the time to draw. Your talking hundreds if not thousands of hours of time to draw.

We have been able to a lot of the CAD files from the GM for the Solstice/Sky and have created large assemblies in CAD to do the FEA with. The biggest problem is that with really large assemblies even my I7 machine with 6gb of RAM takes quite a while to crunch it all down and spit out some results. Here is a picture of what I was using when designing the front cross bay brace. It has the frame rails, the upper shock mounts, engine, and lower "U" that the engine mounts to.




Dave

[snaponbob]

This is starting to sound like dyno racing on a Cobalt forum !!!!!!!!!!!!!!!!!

Frankly, all of this is subjective. It is not debatable that the Kappa platform flexes. GM quietly confirmed this when they developed and sold the rear chassis cross piece for the GXP. Then the ProBeam and Rebar hit the market, and all improved the characteristics of the rear end of the car. The Backbone further stiffened the chassis. Doubts? The Corvette C5 and C6 Z06's have the same type stiffener from the factory while the non-Z06's do not have them. Along come the DDM front cross brace, Werks has theirs, and LV comes up with one. All three will further stiffen the chassis, but differently. The Werks and LV units seem to add an additional rung to a ladder while the DDM "boxes" the chassis. If legality within a racing sanctioning body is not a consideration, any of them will help. How much is a matter of "how many angels can fit on the head of a pin".

First hand observations on chassis stiffness issues and other stuff--
1) The SCCA ruke set will not allow me to use a Backbone (or I would have one). The car needs it.
2) With spring rates 2-3 times the stock rates, tighter than stock shocks, a ProBeam, and 315 A6s on 11" rims, my car gets a lot of loads induced to the chassis and body. And I am not racing on billiard tables, rather on mostly concrete that is not smooth. How do I know about how much flex I am getting? A) I can see the windshield jiggle, and b) the windshield has a stress fracture.
3) I have a DDM cross brace installed (a prototype, not the finished one with the extra supports in the cross bar itself). The handling differences are subtle, but real. But, the cowl shake IS reduced substantially.
4) If I find that the DDM brace starts to "slip", it will be welded up. But so far, NO movement at all. Evidence? If it WAS slipping at the eight points where it is bolted together there would be paint rub. And there is none. I've checked, and will continue to.
5) If the rules allowed it, I WOULD have a BackBone installed, AND I would ADD either the LV or Werks brace. The stiffer the platform, the better the handling. The extra few pounds would be worth it.

[NormSky]

The C5 Corvette in hardtop, coupe, convertible, and later Z06 hardtop used a tunnel plate or brace from the factory.

http://forums.corvetteforum.com/c5-z06-discussion/1966099-tunnel-plate-theory-a-myth.html

My '00 coupe flexed allot without it's removable roof in. With just B&G springs my 07 SKY is very tight from the factory.

The big question is does the upper shock mounts flex on the Kappa?  Sounds like SOB has experienced some movement or quiver of the front end but that could be the driver ballast. 

Remember too that the C5/C6 Corvette uses an aluminum sub frame that is held on with four (4) long bolts going through the hydro-formed rail vertically.  On the front of the Kappa it is steel and welded.  Also remember that the Corvette uses a composite monoleaf spring that attaches to the underside of the frame rail out to the lower control arm where the Kappa has a coil over spring.

...The Backbone further stiffened the chassis. Doubts? The Corvette C5 and C6 Z06's have the same type stiffener from the factory while the non-Z06's do not have them...

[LatinVenom]

My Brace and Weks are quite different.
His goes about 1" below the upper part of the rails, goes forward and then up.
I am attaching a sketch of my Kappa Front Chassis Brace.
With mine the main bar is  7/8" above the rail, with the rest just below the edge.
It is also a straight tube no bends, welded to a sideways T.

[Graywolf]

Great subject that will not resolved unless comparitive testing is done by an outside source. Can the car become too stiff ?  Snapon if you have a roll bar attached @ 4 points you will not need a backbone. Also would like to know how the bars are affecting oversteer /understeer, corner drifting ect. Have these devices improved your autocross /track times? Maybe Viagra can sponsor a study.

[Treeman]

Maybe Viagra can sponsor a study.

 

[snaponbob]

Great subject that will not resolved unless comparitive testing is done by an outside source. Can the car become too stiff ?  Snapon if you have a roll bar attached @ 4 points you will not need a backbone. Also would like to know how the bars are affecting oversteer /understeer, corner drifting ect. Have these devices improved your autocross /track times? Maybe Viagra can sponsor a study.

The British use Viagra below their noses. Hence, their expression - "stiff upper lip".

Now, onto the serious subject at hand. (Absolutely NO connection to the last sentence.  ) Apparently a car can NOT be too stiff. EVERY manufacturer continues to make more rigid frames  and/or unibodies. A four point roll cage would certainly stiffen the body.  again. But, it would a) nearly destroy the car doing it, and b) add a bunch of weight. As for "bars", are you referring to sway bars, or the various stiffeners.  some more.

[Treeman]

You never know what will pop up in these threads.