johnglenntwo

How'Bout!

Base, & Z51; FE

C8R, GS, ZO6, & ZR2; ME

Ultimately!

JoesC5

Because of the angle, it's difficult to assess the width of the center tunnel(it looks like it may be narrower), but it sure has the height. It is the part that has the gold flange at the bottom, the bluish gray vertical stampings, and the purple horizontal cap.




Notice all the different colors. Each color identifies that part as a separate part, and there are a huge number of them that have to be welded together to make the frame.

The C5 and C6 frames were designed to minimize the number of individual metal stampings that had to be welded together by using two 15 foot long pieces of hydroformed tubing(started out being 6" in diameter for the C5 and C6) for the side rails, but with the C7's frame, they went back to a larger number of different metal stampings/castings that have to be welded together vs the C5 and C6. From the leaked CAD drawings(shown above), it appears that GM is continuing with the same idea of having a bunch of individual stampings/castings for the mid engine's frame, as they did with the C7, but even more so.

The C4's frame was designed with a small, non boxed center tunnel but with huge side rails(that gave the frame it's torsional strength and rigidity). They reversed that with the C5's design, and made the center tunnel large but most importantly, boxed the center tunnel with a large plate with 36 bolts, to give it the required torsional strength and rigidity. Have you ever tried to enter/exit a C4, and then compared that to a C5?









Here is the C7's frame. Which frame do you believe has the most individual parts that have to be welded together, the mid engine or the C4 or the C7? Also look at the size of the center tunnel and compare to the size of the center tunnel in the CAD drawing of the mid engine Corvette.




Not shown in the photo of the C7's frame above are the crossmember castings that also serve as the lower suspension mounts and engine cradle in the front, and the lower suspension mounts and transmission cradle in the rear, that are bolted to the frame at the marriage of the unibody and the drivetrain.

Bill Dearborn

The C4 was supposed to be a T Top car until the director of Chevy Engineering at the time decided it needed to be a Targa like the Ferrari 308 shortly before the design was released. The design engineers said the change was too late in the process but that didn't change his mind. Once they removed the T Top style center roof connection the car became very flexible and they had to build up the side rails to keep it from twisting so much. That is why those side rails look like they were an afterthought. They didn't have time to go back and redesign the car.

Bill

stevebz06

My biggest disappointment with what we've been calling the C8 is the continuation of the perimeter frame versus going with a central monocoque like most of the exotics have, if the information I have is correct. The only thing that I didn't like about the C4 entry was the tendency to knock my shin on the hard plastic protrusion of the outboard corner of the dash.

NewYuriCity

You think that would be better with a CF monocoque? Have you seen how big the outer sills are of cars with a CF monocoque chassis? It would be great to keep weight even lower, but I don't think it helps getting in/out any bit.

Alfa 4C:



720S:

elegant

Thank you NewYuriCity. Good piece of information.

patentcad

Potentially somewhat more roomy for the 2 occupants, but nowhere to put your stuff. So you know, you'll buy this cool $80K-$125K sports car and then whack a Thule rack on top. That will be great.

stevebz06

Getting in and out are not my primary concern, but if that becomes a major consideration for designers then you can give up a little rigidity to account for that. They give up considerable rigidity just to have doors, but you pretty much have to have those. Having a separate metal frame is equivalent to having an airplane built with steel tubing and covered with fabric: it works but isn't state of the art.

SBC_and_a_stick

Well worth it. The stiffness of carbon tubs is way too desirable to care about ingress egress.

NewYuriCity

Based on this part of your original quote I thought you were referring to the ingress/egress:

But right now, although it'd be fantastic for the Corvette to have a carbon fiber tub I bet it is a bit too cost prohibitive; perhaps on a Z06/ZR1 model, similar to the aluminum frame used in the C6 Z06.

I never cared about ingress/egress, was just responding to stevebz06. Though I have a feeling some owners would have even more difficulty getting in/out with that much of a door sill, I'm sure when the technology comes down in price the Corvette will one day have a carbon fiber monocoque.

stevebz06

I remember reading about GM's research into reducing the cost of CF parts through automation. Maybe the C9 will finally benefit from this program.

SBC_and_a_stick

As Gordon Murray would say, there are several kinds of carbon tubs. The next step for Corvette would be a hybrid carbon center with aluminum front and rear sections, likely a C9. It will be at least two more generations, likely C11 before Corvette would have a full carbon tub.

AORoads

And I think access/egress and ease of doing so is one of the primary concerns of owners and GM. Maybe not all owners, but enough to count, and be counted for some good reason. Corvette didn't go for three generations and 21 years from a difficult-to-enter C4 to the C5, 6 and 7 gen only to regress---and that is despite whatever exotic, lightweight materials are utilized. It could be possible to combine new design and materials to provide strength, good access and lighter weight. Let's hope so for the future.

Of course, there is a case to be made, however, if you want to downgrade the access/egress and that is if the company wants to sell cars in the hundreds or low thousands. jmo.