FRC Chassis stiffness

[Jim Helm]

We all know that the FRC and Z06 are stiffer than the base Vert Chassis, but how much stiffer. I found an artical that listed the C5 Convertable as having a resonant frequency ( a measure of stiffness) of 21 Hertz, which was 61.5% stiffer that the C4 Convertable. But the FRC and the Z06 have a resonate frequency of 23.5 Hertz or almost 12% stiffer than the C5 Vert., and it's about 80 pounds lighter. Thought yuall would like to have this bit of info.:D

Jim Helm

[fatherlarry]

Originally posted by Jim Helm
We all know that the FRC and Z06 are stiffer than the base Vert Chassis, but how much stiffer. I found an artical that listed the C5 Convertable as having a resonant frequency ( a measure of stiffness) of 21 Hertz, which was 61.5% stiffer that the C4 Convertable. But the FRC and the Z06 have a resonate frequency of 23.5 Hertz or almost 12% stiffer than the C5 Vert., and it's about 80 pounds lighter. Thought yuall would like to have this bit of info.:D

Jim Helm

Thanks for the info Jim. Many years ago I did a restoration on a '59 Caddy Convertible. I don't know if you remember, but they referred to the chassis as an hour glass frame. It was X'd in the center. The Buicks and Chevy's had the same basic frame design. They made them that way so the car could have a lower ground clearance. I remember when I was restoring the chassis, I had a chassis from a hardtop coupe, and the only difference between the convertible frame and the hardtop frame is that they welded a 2 in. by 1/2 in. brace, extending from the plate in the center to the four outer rails to give the car more strength when you open the doors, and less flex in the body when driving. It naturally added weight and I imagine helped a bit. When the convertibles used to come off the truck carrier from the factory to the dealer, they used to tie them down on the front and rear rails to secure the car from moving on the carrier. A lot of times when the driver would open the door the rear rails would bend , bringing the quarters down with them, and as a result the quarter would separate from the door and you couldn't close the doors. We'd have to bring it in the shop and jack the rear rails up to be able to close the doors and line it up again. Just thought you might find that interesting.