Runge_Kutta

I thought I'd summarize information on a possible hydroformed aluminum frame.
Is the Z06 or Blue Devil going to get one? You decide!!

Primary links:
==============
http://media.gm.com/division/2004_pr...droforming.pdf
http://patft.uspto.gov/netacgi/nph-P...4&RS=6,732,434
http://www.climaxresearch.com/papers.htm
http://msl1.mit.edu/msl/meeting_0419...onstantine.pdf
( http://aluminium.matter.org.uk/aluse...asp?alloyid=20 )
( http://aluminium.matter.org.uk/aluse...asp?alloyid=34 )
( http://aluminium.matter.org.uk/aluse...asp?alloyid=23 )
http://www.sae.org/servlets/productD...D=1999-01-3180
http://www.afsa.co.za/media/news/march03article3.html
http://www.sae.org/news/aluminum-suv.htm
http://www.sae.org/servlets/productD...D=2003-01-0572


Here are some other relevant links:
====================================
http://www.secat.net/tech%20adv%20te...h%20121302.php
http://nsmwww.eng.ohio-state.edu/Alt...the_Future.pdf
http://www.hydroforming.net/hydro/ho...rder=0&thold=0
http://natt.pnl.gov/tech/extrusion.pdf
http://www.autoaluminum.org/corpub.pdf
http://www.autoaluminum.org/reppub.pdf
http://www.autoaluminum.org/frame.htm
http://www.efunda.com/materials/allo...num/temper.cfm
http://www.metalcenternews.com/2001/...f2autobody.htm
http://www.thefabricator.com/xp/Fabr...icle266_p1.xml

Relevant GM patent applications:
================================
20030196307 Joining and forming of tubular members
20030192160 PROCESS FOR FORMING ALUMNINUM HYDROFORMS
20030164255 Modular chassis with simplified body-attachment interface
20030102668 Method of hydroforming articles and the articles formed thereby
( http://appft1.uspto.gov/netahtml/PTO/search-bool.html )

Relevant GM patents:
================================
6,739,166 Method of forming tubular member with flange
6,305,201 Method and apparatus for forming unobstructed holes in
__________hollow hydroformed metal parts
6,183,013 Hydroformed side rail for a vehicle frame and method of manufacture
5,557,961 Hydroformed structural member with varied wall thickness
5,445,001 Method and apparatus for forming and cutting tubing
5,431,326 Method of forming a tubular member with separate flange
5,333,775 Hydroforming of compound tubes
( http://patft.uspto.gov/netahtml/search-bool.html )

So, if it happens, I think this is essentially what we'll see:

A hydroformed aluminum frame for C6 would have variable thicknesses
but a mean thickness of about 4 mm. Section widths and heights would
be increased over the steel version by 15mm to 30 mm. The frame will
be made of annealed 5754 aluminum alloy which, after hydroforming
will have yeild and ultimate tnsile strengths of 152MPa and 267 MPa.
The frames stiffness will be maybe 50% better than the C5 frame
and will have numbers like 11,000N/mm and 1050 kN*M/rad for the
bending and torsional stiffnesses. The frame will be designed to
keep local stresses below 135MPa so that the frame may safely withstand
over 10,000,000 cycles before failure. Weight savings over the C5 frame
will be of the order of 25-30% though more would be possible if the
C6 frame were designed to match the C5's stiffness. As the steel frame in
C6 already has some aluminum and magnesium components, I suspect that
the weight loss will be between 20% and 25%. If we take the C5 frame
weight as near 228 kg, then a 22.5% weight loss would be 50 kg or
about 110 pounds.


Add-ons:
========
http://www.cs.virginia.edu/icaa7/trends.pdf
http://www.hazelett.com/what_is_cont...ting/index.php (Patent says AA5754CC)
http://www.aluminum.org/Content/Navi...plications.pdf (Figure 5.8)
http://www.csa.com/hottopics/metals/alum54.html
http://www.eere.energy.gov/evision/p...ns/j_green.pdf (page 7, 16 kwh/kg )
http://www.engin.umd.umich.edu/ceep/...w10/sld001.htm
http://www.i-car.com/pdf/program_sup...7/novdec97.pdf





[Modified by Runge_Kutta, 12:29 PM 5/25/2004]

SWCDuke

Due to the required differences in design that you summarize, an aluminum frame would require a complete re-engineering of the chassis, which essentially means the whole car. Thus, I would not bet that Z06 will have aluminum side rails.

They'll take some weight out of it, but no more than about 100 pounds, which would put curb weight at around 3100.

Duke

Tony.96LT4

Runge_Kutta

I think there are several issues to keep in mind here.

1) If one would like to see the full benefit of moving from
mild steel to AA5754 then the section dimensions must increase.
In the case of the Ford SUV frame, a 44% weight decrease was
deemed possible if section dimensions were allowed to increase
by as much as 30 mm ( ~1.2 inches ). However, if the exterior
dimensions remained the same and only the metal thickness was
increased, the weight savings was 20%.

2) All of this critically depends on what GM planned for as
C6 was designed. The 1996 patent and the 1999 SAE article make
it rather clear that GM was working with aluminum hydroforming.
If the C6 team was fully aware that at some point in the C6
evolution the frame would be aluminum when conditions were
right, I think this could have been factored into the design.
If switching frames was an afterthought ( as both of you implicitly
suggest) then they would either capitulate on weight savings a bunch
or they would need to redesign the whole car.

SteveJ

Anyone who read ACAR knows that the HUD was planned from the beginning and appeared later as an improvement. I don't know whether we will get an aluminum frame or not, but if we do, I'm sure it will have been planned from the outset. Also, if there is aluminum in the future, I'm sure it will be on the normal C6 and XLR as well as the Z06.

Runge_Kutta

By the way, if you look at page 12 in
http://msl1.mit.edu/msl/meeting_0419...onstantine.pdf

you can estimate that the cost differential of the AA5754 frame
(relative to the current mild steel) would be in the neighborhood of

$6.16*50 = $308

To bad there won't be a $308 option that you can check off for the
aluminum frame.

TTRotary

Unfortunately, the $308 is not the whole story. There is the small matter of $50 million up-front cost associated with what I call the "Aluminum Program". GM must spend this money whether it puts 1 Blue Devil on the Road or 10,000 of them. Where are the dollars going?

$5 million for cycle-testing - 100 or so frames must be tested over millions of cycles modeling 20-year vehicle life and 1 million miles each

$5 million for crash testing and government certification of the new frame

$20 million for tooling - needed to produce/assemble the frames. More expensive because it is parallel to existing equipment

$10 million to train and re-certify UAW employees who produce/assemble the frames

$10 million to train and re-certify ASE body shop personnel who must work with/weld the new material

Now let's say the GM bean counters allow Chevrolet to spread that over 30,000 units (and I'm being generous). That's $1,667 per car additional cost, plus $308 /unit materials. Let's just say $2,000 additional cost per unit. Including coporate overhead and the huge cost of financing GM's pension benefit costs, GM must charge a $4,000 retail increment to support the AL blue devil. Sure, it's not that much for a $75,000 car.

But consider this: we're talking about a 3% weight savings and a 3% power/weight benefit. GM could achieve the same result by increasing engine output by 12HP. Which do you think they'll chose?

That's why there is no business case for an AL frame, unless it is part of a total vehicle program. We'll see it in the C7, but not in the C6.

ivan111

I agree i think it won't happen.........

And also the C6 weight is comparable to aluminum cars and not that far also behind Carbon Fiber cars......

Runge_Kutta

I certainly feel much more comfortable with technical discussions on this
forum. I will not even attempt a detailed cost analysis of an aluminum frame.
Rather, I just want to make a few points.

1) By virtue of GMs inclusion of "hydroformed aluminum" in
http://media.gm.com/division/2004_pr...droforming.pdf

at the GM Technology Preview Displays, Milford Proving Grounds, June 23-25, 2003,
I would say that this matter goes far beyond C6. With looming emission and CAFE
requirements on the horizon for the cash cow SUV and truck lines, aluminum frames
will be needed in the coming decade. Just like Gen IV, much of the development
has likely been bankrolled by the truck programs. C6 may serve as a low production
rate place where maturing technologies can be honed. I believe C5 did just this for
hydroformed steel frames. I think there are many parallels between transitioning from
iron to aluminum blocks and transitioning from hydroformed steel to aluminum frames.

2) If the frame does in fact show up on the Z06 and the spirit of the Z06 program
is the same as for C5, the car will sell nearly 8500/year (2003 numbers). Doing that
for 6 model years is 51000 frames. If in model year 2007 ALL C6's use the frame
instead of just the Z06 then it's 8500 + 35000*5 = 183500. That's a bunch of
frames to amortize one time costs like crash testing and the like.

3) As I recall, the budget for the entire C5 development was $250 Million. Your
estimate for mostly the perimeter rails of the frame is 20% of the entire C5
development budget. That is not plausible. If such a process were so expensive
then how can any of these vehicles afford such gold plating
http://www.autoaluminum.org/frame.htm

Obviously not all of those are full frames but your economic assessment would imply
that all of those programs lost money. I may be minimizing things but the primary
changes to an "aluminum C6 frame" would be the two huge side rails and those front
and rear rails that connect them - four really big pieces.

4) Wasn't Dave Hill's metric essentially, "if it costs less than 10$ per pound
saved, it's worth it?" What do think the cost was for the changes that got C6
down to 3179 versus 3246 in spite of extra cabin accoutrements and increased
sound damping. How about that magnesium engine cradle? Were all of those dirt
cheap but the frame rails are $50 million?? Why do people bother moving to aluminum
engine blocks to save 88 pounds? Think of all the tooling and production items
to do that. Why was that done but an aluminum frame is prohibitively expensive?

5) Dr. Constantine's slide show estimates far more than just the material costs.
Did you look at pages 5, 7, and ultimately 12? While it is not the full picture
for GM, it's a rather broad assessment.

Jinx

Speaking of trucks... imagine the production volume, and the fuel efficiency impact (hello, CAFE?) of an aluminum hydroformed front frame on full-size half-ton pickups and full frame on mid-size (!) SUVs. Sure, it's not a simple substitution, but both Ford and Dodge just revamped their half-tonners; GM's dates to 1999, and given the stiff competition (and profits) in trucks I'd be surprised if 2009 was the same vehicle. If aluminum hydroforming got its toe-dip with Z06 in 2006, I think the timing is right for inclusion on the next-generation pickup, and the mid-size SUV after that.

Do we know that Kappa is hydroformed steel? I'd assume so simply because they didn't shout "Hey, it's aluminum!" but there was an awful lot packed into a short presentation.

.Jinx

TTRotary

Yes, Constantine's information includes tooling and labor costs per unit, but this is for a simple forming of minimal complexity. Furthermore, the slides provide no information about the total unit production assumption (the cost amortization basis), nor do we have any other information regarding case assumptions with respect to size of part, complexity of the casting and so on. What I do understand from the slide show is that the modeling appears to be built around the production of a relatively simple part: a hydroformed tubular structure.

The Corvette frame is vastly more complex than that. In fact, the C5 frame has the distinction, 8 years later, of being the largest and most complex hydroforming structure ever produced. After that distinction, it went on to becoming the only structure of its type ever MASS produced. The tooling costs were staggering. This is Guiness world-record stuff, not just a simple hydroforming project involving a single part.

Furthermore, the Constantine study, being solely focused as a materials study, purposely ignores the massive costs automobile manufacturers must associated with testing, testing, and more testing, government certification, assembly line workers, and training tens of thousands of mechanics nationwide who must support that product for many years.

I don't want to belabor the point, but you guys need to appreciate the truly massive proportions of a project like this. This is galaxies away from welding up a couple of tube sections in the corner of a race shop and slapping them on a frame. From a logistics and cost perspective, it's like throwing a paper airplane versus sending men to the moon.

And all the forgoing needs to fit a business case of $10 per pound saved. That is one hell of a hurdle when all the dollars come into focus.

On the $250 million cost of the C5 program: (1) that was 1990 dollars...same cost today would be (1.45x factor) $362 million dollars; (2) from ACAR, we recall that this was merely the development budget. That did not include tooling costs, training costs, and testing costs I outline above. As I recall, total C5 product cost over the life of the platform (6 years) was slightly in excess of $1 Billlion...that's $1.45 Billion in today dollars. In that context, $50 million relating to the frame is peanuts...as long as it is buried within the total cost structure of the project.

So, as per my original point: AL as a frame material from the getgo and applicable to the entire Corvette/XLR product line...fine - they'll do it. But it didn't happen for the C6. As considered for a low-volume C6-based vehicle: not gonna happen - at least not out of Bowling Green. They'll just get the extra 12HP they need for the power goal by advancing the timing a couple of degrees...a software tweak.

If they can justify the application across light trucks, and it fits in that price range, then it's a different story. Again, one really has to appreciate the massive size of such a program.

SteveJ

I think it's starting to make sense that we would see the aluminum frame first in the new Z06. I don't think GM would have put the effort into hydroformed aluminum if it were destined to be a technology just for the Vette and XLR. Given that there is a corporate committment to go with aluminum hydroforming in major vehicle lines, then it makes sense that they would start with the Z06. Pilot production with low quantities, and huge publicity.

Jinx

TTRotary does make a good point. We often think of Corvette as a fertile test bed for GM technology, but in this case the Corvette frame fits the bill only in terms of volume, not in terms of complexity and tooling cost. If GM wished to establish a beachhead with aluminum hydroforming, they might start with a more conservative part than the Corvette frame rails.

On the other hand, maybe today's Z06 frame is tomorrow's coupe/convertible frame, meaning that the cost of the Z06 frame is expected to apply to an early C7 or C6.5?

Forgive my ignorance, but could XLR/C6 frame be built with an incremental-cost tweak of the C5 tooling? Perhaps there's very little cost in the C6 frame and the investment went to Z06's frame with the idea of it being applied in a few years to C6.5/C7, perhaps a car that carries over most parts. Grasping at straws, I know, but it can be fun.

Does anyone know if the XLR/C6 frame rails use variable-thickness steel? That was talked about as the next step in hydroforming; has it been taken yet? Maybe the Z06's new frame simply uses variable-thickness steel for incremental weight savings.

.Jinx

TTRotary

The XLR/C6 frame does indeed use variable-thickness hydroforming. This requires different tooling since the forming bed must be capable of varying pressures in different sectors. So I imagine that tooling is all-new. How extensive tooling changes were beyond this, I don't know, but I imagine they were able to carry over the majority of assembly line tooling from the C5. Maybe someone else with BG connections can fill in here.

Another option, might be for GM to complete all endurance, safety, and federal crash testing, plus training, then have a sub-contractor produce the AL frame and ship to to BG for final assembly. Again, though, I fail to see the business case. Then again, with Lutz there, they might produce a $100K C6 derived supercar to compete against the GT40, Modena Stradale, etc. and incorporate it into the racing program and budget, so they produce C6Rs alongside a homologated street car. Such approach would be a radical departure for GM, but would go to your idea of limited release and high profile.

Scissors

It's already been stated that the C6 Z06 frame requires different tooling than the C6 Coupe and 'Vert frames.

LittleBoyBlu99

TTRotary

Scissors...its a conspiracy...they're Styrofoam frames made to look like AL frames, just to fool me. Trust me...I know this

SteveJ

I just read the article in February C&D on the C6. I was very unimpressed with their treatment; they didn't even highlight the improved runflats which may be a very big deal for those who don't want to switch to high performance tires. In any case, buried in the final remarks they mentioned the Z06 with a rumored 500 hp and aluminum frame.

Runge_Kutta

Since this section is a bit slow these days, I thought I'd
add some links that are relevant to AA5754 in automotive
applications.
http://www.cs.virginia.edu/icaa7/trends.pdf
http://www.hazelett.com/what_is_cont...ting/index.php (Patent says AA5754CC)
http://www.aluminum.org/Content/Navi...plications.pdf (Figure 5.8)
http://www.csa.com/hottopics/metals/alum54.html
http://www.eere.energy.gov/evision/p...ns/j_green.pdf (page 7, 16 kwh/kg )

davidwp97

Today I had a conversation with a GM racing insider and offhand mention was made of "the discussions about whether to use 'an aluminum frame like the production car' as the basis for the C6-R roll cage".

It is a fact that the production C5 steel hydroformed frame rails are used as the basis for the C5-R roll cage.

Therefore, we can speculate that:
1. The C6-R will be based on the Z06.
2. The production Z06 will have an aluminum frame.

Time will tell - until then, ain't this FUN!

David