JPN7075U

I'm curious about something I have not seen discussed here. Years ago when the C6 first came out, I read that the Z06's aluminum chassis was 140 or so lbs lighter than the steel chassis in the base C6 but that it flexed a lot more than steel so GM was forced to go with a solid roof on the Z06 to control the flex. On airplanes, aluminum flexing leads to cracks. Do the Z06's have chassis issues?

acrace

GM compensated for the lower material stiffness by increasing the wall thickness of the aluminum frame.

No chassis issues that I'm aware of.

Bill Dearborn

They weren't forced to go with the fixed roof because of the aluminum chassis. The fixed roof increases stiffness but they would have used it even if they would have been able to achieve their weight goals with a steel chassis. The C6Z like the C5Z is meant to be an ultimate performer. You don't get that with removable roofs.

Bill

FrankTank

Comparing the aluminum used on the Z06 and that used on an aircraft are 2 totally different things. The aircraft I bet is subject to much more force and stress than that of a 500HP car.

Different design, application and everything else

JoesC5

2010 & 2011 C6.R race cars have the Z06/ZR1 aluminum frame. Haven't heard of any of them pulling into the pits looking like a pretzel.

JPN7075U

My co-worker had a GoldWing crack an aluminum frame at 60,000 miles. Just curious about fatigue I guess. Airplanes have lots of issues with it as they age. Apparently GoldWings do to. I've found little bits and pieces on it like:
Originally Posted by LTSpeed
The Z06 uses A6063-T5 4mm thick aluminum. As hydroformed, it's about 97% as rigid as the standard C6 steel frame (though yield is higher). It has pretty poor fatigue resistance, but my guess is it'll never see enough lifecycling to cause problems.

Someone earlier mention 7075 as being much stronger. While that's true, it's probably impossible to hydroform--at least as the technology exists today. Plus, there could be corrosion issues with 7075.

Thanx for posting about the fatigue resistance. I wonder if the z06 cars will ever have any high milage owners to prove that out. That would be my biggest concern with aluminum. After yrs of racing bicycles i can tell you that watching kids crash with broken head tubes on aluminum bicycles is heart breaking enough I wonder if the same thing would happen with the aluminum frame over time.I would personally go steel and use a chromoly cage and focus on reducing uneeded Mass like combining brackets to do mutliple jobs instead of making multiple brackets. there are ways to keep the weight down.I don't think aluminum would be a good cage locating material as its so much softer then steel personally i feel that the bolts for mounting plates would be very prone to ripping out of their locating holes in the frame.

JoesC5

The roll cage on the C6.R cars is steel and use a proprietary method of mounting to the aluminum frame. They didn't just drill and tap the frame and bolt the roll cage on. GM's engineer's really are smarter then that.

GS-Zero

No, all of the C6.Rs use a proprietary steel frame with a fixed roof.

EDIT:

GT2 cars use hydroformed aluminum frame, but the GT1 cars (faster) use hydroformed steel.

JoesC5

WRONG...GT-2 class rules state that the cars have to be based on a production car. GM could have elected to race a skinny body C6 with the steel frame or the wide body with the aluminum frame.

Doug Louth, Corvette Racing engineering director: "Early in the design process we had to decide whether to use the base Corvette coupe with its steel chassis and narrow bodywork or the Corvette Z06 or ZR1 models, which have an aluminum chassis and wider bodywork. We ran a number of simulations and CFD studies comparing the wide versus narrow bodies and looked at various track width options. In the end, the data favored the wider car, even at a high-speed, low-drag track like Le Mans. Fortunately that aligned with the marketing objective to showcase the ZR1 as the Corvette that offers the highest level of performance."

ALUMINUM FRAME
The GT2 version of the Corvette C6.R is built on the same aluminum frame that underpins production Corvette Z06 and ZR1 models. In contrast, the GT1 race cars used steel frames from the Corvette coupe and convertible. Both aluminum and steel production Corvette frames are hydroformed, a process that uses high-pressure hydraulics to form complex shapes.

Fehan: "The race team had been exploring the aluminum frame for several years. The traditional methods of connecting a steel roll cage to an aluminum frame simply didn't provide a level of safety that met GM Racing's stringent standards. Consequently we have developed a proprietary installation method that is consistent with GM's commitment to safety."

Louth: "The race car chassis retains all of the elements in the production chassis structure - the windshield frame, the hoop around the rear of the passenger compartment, the door hinge pillars, the drivetrain tunnel, the firewall, the floor pan - they're all there. In the GT1 class, these components could be removed, modified, or trimmed down, but the ACO and FIA rules for GT2 require that we maintain all of the primary production chassis structure in the race car."

GS-Zero

The fact that the faster C6.Rs in the GT1 class use the steel frame still remains.

LFZ

And your point?

slolane

The problem on the Goldwings was bad robotic welds and was fixed by hand welding the area. The problem was on 01 and 02 wings and was fixed under recall. I wonder if your buddy took his in for the recall. How do I know this? Because I have an 02 wing and had the recall done

The Z has been out since 06 I have not heard of any frame failure of any kind.

Gearhead Jim

Steel is also subject to fatigue, and is more likely to develop rust (corrosion) spots which become stress risers and accelerate fatigue.

Also, all Corvettes use aluminum suspension pieces and the fatigue issues with them would probably be similar.

Overall, I would worry a little less about fatigue in the steel frame than in the aluminum one, but there are no guarantees.

Wayne O

True but Corvette Racing using the aluminum chassis is a recent development. For years (even after the C6 Z06 was released into the wild) Corvette Racing opted for the steel chassis. A year or two might be a bit soon for a chassis to show signs of structural fatigue. It's probably irrelevant anyway...comparing a C6 or a Z06 to the C6.R is a huge stretch....a multi-million dollar, world-class racing program devoted to a handful ridiculously modified cars compared to what we drive. Corvette Racing probably changes out a chassis like we change our socks.

JoesC5

One of the reasons for the delay in using the aluminum frame was having to solve the problems of using a steel roll cage mated to the aluminum frame, not because the aluminum frame was weaker. GM could have elected to run GT2 with the steel frame.

30YR W8T

You would think that the design of the Z06 aluminum chassis was geared toward a specific handling goal, possibly the G forces the car is rated for. you would also think the design of the front and rear cradle assembles further support the chassis as does the engine and and other sub assemblies. Considering that most of these cars will not see the maximum rated forces on a daily basis, I would think structural chassis fatigue would not be an issue for a very very long time. I doubt that most frames in day to day use would see much repetitive flexing at any one point on the cars chassis, so the stresses would be no where near what an air plane structural frame work must endure.

Gearhead Jim

Airplanes are stressed for a certain number of G's, but the fatigue life will be used up rapidly if you go out and pull limit loads on every flight.

The airplane designer makes certain assumptions about what the loads will be during a typical flight, usually much less than limit loads when designing most civilian planes.

The car designers probably do the same.

But I'm not losing any sleep over fatigue problems in my C6. If only I should live so long...

foremaw

The aluminum frame has been in use for many years now and there are CF members on here with cars that have over 100,000 miles on them. I have never seen a thread on here or heard of a frame fatigue issue.

Steve Snake Driver

Wasn't one of the reasons for steel frames in GT1 the class rules? FIA is rather screwy about some things (like no carbon brakes on the GT2 cars even though they are stock for the ZR1 based car).

Silver05GTO

Another anti-Z06 myth is born..........along with wondering when the LS7 will grenade itself, now I get to wonder when the frame will collapse as I pick up my Dunkin Donuts iced coffee