WhiteDiamond

For those of you with the background and education in this area, what would be the major problem for GM to put the aluminum frame(assuming it is coming for the Z06, at least I think that would be an excellent weight reducer) into the coupe and convertible at some point in C6 production? I am guessing a weight change of 100 to 250lbs(depending on what thread you read) would have serious effects on the handling of the vehicle and require suspension changes. What else may prevent GM from doing this?

Todd

Timmy's C5

Expand please.

RichieRich

Somebody page SWCDuke. He undoubtedly has the best answer for this.

For anyone who's picked up some of the suspension pieces in the C5, you know - the stuff is VERY light. Someone showed me one of the control arms once - it looks about 3 times as heavy as it is. A hydroformed aluminum frame would be a massive breakthrough in automotive engineering/manufacturing.

LongTimer

Soon to be appearing at a C6 Z06 dealer near YOU!!!

Weight reductions not only improve performance, for lesser cars they allow engines to work less hard to maintain accepted levels of performance and help reduce emissions. Weight is the enemy of everything. In ten - twelve years GM will have a dozen cars with significant light weight materials content. Sooner if congress starts to move on Truck emissions and economy.

Scissors

I do expect an aluminum frame in the Z06, but I do not expect it in the Coupe and 'Vert. Why? Because I doubt GM would pay all of the money for the steel frame tooling, only to use it for a year or three.

SWCDuke

We've had this discussion a number of times. The key points are as follows:

1. The primary consideration in Corvette chassis design is global STIFFNESS, not strength, except for crash performance, where inelastic (deformation) characteristics and ultimate strength come into play particularly in the "crush zones" fore and aft of the cockpit.

2. Though aluminum is one-third the density of steel it is also ONLY ONE-THIRD AS STIFF!!!

3. Thus, in order to substitute aluminum for steel in the side rails and achieve the same global chassis stiffness both the section size and wall thickness must be substantially increased, which negates much of aluminum's weight advantage.

Because of the above issues and the Corvette's tightly packaged design, in order to incorporate aluminum side rails (which would not save as much lweight as most people think), the entire vehicle would have to be redesigned.

Consider that the NSX is an all aluminum structure and is no more than 100 pounds lighter than the current Z06. I believe the F360 is all aluminum, and it weighs about the same as the current Z06.

Aluminum is NOT the holy grail of structures, and where stiffness is a primarly consideration steel is very competitive in finished weight and a lot cheaper to implement.

Duke

WhiteDiamond

Duke,

Thank you for the info. I believe there where some discussions in the general C6 forum many months ago when it was though the aluminum frame may still be possible for all C6 Vette's. In the information that was posted back then, there where several comments that the aluminum frame may save nearly 200lbs. If aluminum is 1/3 as stiff as steel, what is the general quideline on how achieve equal stiffness in the aluminum frame? I believe it does not take 3x the material to get this just becuase it is 1/3 as stiff. Interesting material, as I do believe GM is going to put an aluminum frame under the Z06. Guess we will know that next year.

Todd

WhiteDiamond

Tim,

My logic for that statement comes from GM's continued tuning of the Corvette's suspension. If one where to mearly unload 100 to 200 lbs of weight the reaction of the suspesion would change. I believe GM would end up having to recalibrate spring and shock rates to keep the feel they engineered in. Then again, it may not be a big enough weight change.

Todd

SWCDuke

I don't think there is a general guideline. It's to dependent on the specific geometry of the part and the entire structure. I appears to me that some think you can just substitute aluminum for steel and save 2/3s the weight, but this is not the case. Likewise you will not have to use three times the material with a good design, so there should be some weight saving.

Given the fact that the example aluminum structure cars I cited are not significantly lighter than a Corvette, there may not be a big savings in weight with an aluminum structure over the current steel backbone/siderail architecture.

Duke

LTC Z06

In the 80's and early 90's we thought aluminum and carbon fiber would be the save all, but there have been great advances in steel (like hydroforming), and carbon fiber is still expensive. Even those all carbon fiber, mega expensive cars are not far from the Z06 weight, and when comparing price, forget about it.

Admit it, we really want this stuff just for the cool factor :yesnod: :)
Double over head cams, turbos, aluminum and carbon fiber seem more sexy than steel, pushrods, and fiber glass. (It's that dang ***/German advertising again) :lolg:

WhiteDiamond

Well, I was thinking that the aluminum frame could give GM a lot of weight savings for the Z06 model, but possibly not. I wonder what other tricks Dave Hill is looking at to get the weight of the Z06 down? Maybe the Z06 won't be much lighter, if at all, then todays version. It sounds like the lexan windows are also coming in the future, but I'm not sure that technology is quite ready as well. That may be 20 to 40lbs if they did the rear and side windows. Those ceramic brakes would be neat ;)

Todd

sebastienaubouin

--------------------------------------------------
Admit it, we really want this stuff just for the cool factor
Double over head cams, turbos, aluminum and carbon fiber seem more sexy than steel, pushrods, and fiber glass. (It's that dang ***/German advertising again)

----------------------------------------------------------------------------
:iagree:

Curb weight of 360 Modena 3,064
Acura NSX 3,163 (with a V6)
Ford GT40 3,4xxlbs
Viper 3,4xxlbs
911 Turbo 3,505 Tiptronic 3,594

Aluminum would also be more costly to produce then steel. Do you want to drive up the cost of the Vette? You might as well buy one of the above mentioned cars then.

WhiteDiamond

Sebastien and CptZ06,

I am very happy with my pushrod LS series motors and could care less about the cool factor. 99.5% of the people on the road only see the body and decide if it is cool or not. I get to drive it and performance is what I like. When a 50K American Icon competes with the best the world has to offer, I am very curious if there are a couple of things GM can do to easily drive the performance another notch. The aluminum frame has a tremendous amount of rumor and speculation about it posted on this forum. If weight drops 100 or 200lbs, that is that much more we get in performance.
Besides, I have never been asked, "Hey, what is the frame made of?" at the local gas station ;)

Todd

need-for-speed

Maybe they'll remove the A/C like they did on the earlier 1LE Camaros......boy that will **** everyone off :lol:

SoCal

I disagree that the more expensive cars utilizing carbon fiber extensively are about the same weight as the ZO6. Example: My own favorite "exotic", because it uses the Corvette LS engine, is the Mosler MT900. This car was completely designed on a very technical computer program, and has been very successful.

The structure uses very advanced aircraft-like technology, such as a laminated honeycomb monocoque body, with chrome-moly 4130 subframes.
The suspension is essentially Corvette.

This whole package weighs only 2450 in street form, and under 2000, I believe, for racing. The older 345hp LS1 engine took this car to 60 in 3.5 sec. I'm sure they're using the LS2 now, so the performance is even better.

This is the technology, the aesthetics and the performance I'm hoping for in the next generation Corvette. Everything about it appeals to me, and I can still say that after sitting in it, which isn't as comfortable as my C5.

LongTimer

Duke,

I know you're the engineer and you know much more about the tech stuff than I ever will, but I think the vette boys have designed the C6 to accept Al HF rails. Take a look at the Door sills of the C6 vs those of the C5. To me, they look wider - perhaps wider than required for the Steel HF rails. Maybe they are having problems with the AL HF rails and they will end up staying with steel for the Z06 - but maybe not. Maybe, as Scissors says, the Z06 will get them exclusively. Hill said there will more and bugger differences between the [coupe / vert] and the Z06. ... and maybe I am completely wrong and will be disappointed in a 3118 lb, 500 HP Z06. MMMM, no I guess we all win either way!

TTRotary

On the contrary (in my view) packaging of the AL frame becomes much tougher in the C6, given its width is 1 in less with the mandate to preserve interior dimensions including the footwell area.

We have beat the AL topic pretty hard in the thread entitled "Aluminum Frame ?????" in the C6 Z06 section , for those wanting more info on it.

Runga Kutta has put up some great information there. Most of it points to a 100lb maximum savings, for the reasons explained by Duke. This comes at significant expense, making for a tough business case for the Z06. From a performance perspective, GM can achieve the same result with a 12HP increase. I can see AL frame being released on a test basis within a C6R/Blue Devil/Caddy race car homologuation program, as a test-bed for future GM-wide applications. In particular, mass-saving has future merit in SUV/truck frames where mass reduction becomes an important consideration for several reasons including CAFE and accidents involving SUVs vs cars. But I don't think we'll see it on the C6 Z06, even though would be nice.

I consider the BMW Z8, Acura NSX, and Audi A8 perfect examples of why all-aluminum cars do not work well in the real world. Each of these cars gets an F in the bang-for-the-buck category because they are prohibitively expensive and deliver meager performance for the price. That is because they are expensive to build and not particularly light, in the end.


[Modified by TTRotary, 7:40 PM 1/27/2004]

Iboomalot

hell use ti instead it just as strong and stiff as steel and weights 57% of steel.

on the AL topic if memory servers me correctly Alum comes in different stiffnesses due to being an alloy 1053 vs T6 alum very different properties. Also when you double a wall thickness you quadruple strength/stiffness. So 33% less wieght double thickness = stiffer and only 66% of the weight of steel. of course this assumes the 1/3rd stiffness ratio.

hell, cost no factor carbon fiber or magnesium :D

TTRotary

Well there are two factors that need to be adressed: tensile strength and total frame stiffness. As shown by Runge Kutta's info, tensile strength of annealed 5754 or similar hydroformable AL is 25% that of HSLA steel. This must be adressed either by increasing thickness within the frame rail by a factor of 150%, increasing mass to within 10% of that of a steel frame, or by increasing the size of the box section, which is required anyway to preserve the stiffness of the frame. In fact, a combination of the two is required to achieve the 100lb weight savings cited above while maintaining strength and stiffness comparable to the present steel frame.

The problem arises is the larger box sections. I believe the requirement is 33% larger volume, which potentially poses packaging problems given the already sizeable dimensions of the steel sections. Aside from the packaging issues (read reduced interior space - a big no-no) these requirements imply a total redesign of the components appertinent to the frame, as others have indicated. That potentially includes engine accessories, the balsa/steel floor pan sections, and so on.

I just don't see it.

SWCDuke

Well, maybe you're right, but I'm not holding out hope for aluminum side rails. I think the last couple of posts by TTrotary summarize the issues in understandable terms - cost and structural. There are probably better ways to take 100 pounds out of the car, but I don't think it's aluminum side rails or carbon fiber body panels. The CF hood on the Z06 Commenorative Edition seems to be a production nightmare (achieving an acceptable finish without the grain showing through), and it's a pretty expensive way to save 10 pounds!

Regarding the potential weight savings of aluminum side rails, the first thing to understand is what the current steel side rails weigh. I have never seen it quoted, but I don't think its as much as some may think. I think they start out at 3" diameter tubes, about 13' long. If I knew the wall thickness of the stock I could compute the weight.

Only thing I have to add is that aluminum's and steel's stiffness is not a function of alloy or heat treatment. These affect the yield and ultimate strengths of both materials, but stiffness, as expressed by Young's modulus, is about 10,000,000 psi for AL and 30,000,000 psi for FE in the elastic (no permanent deformation) range. You can view this as a "spring rate". If "strain" (local material deflection due to load) is given as inches/per inch, then multiplying by Young's modulus yields material stress is psi.

Duke