CG height
Originally Posted by critter
Lots of posts mention CG, but never quantify it. Any guess as to how high the CG is on a 4th gen F-Body?
Carl,
I should have known this would be "yours" (darn engineers)....lol
Hmmm, I've grappled with this one myself for a while. And, my best guess would be somewhere about level with the rear "package shelf" behind the rear seat, maybe a couple inches lower. Since most of your weight is low in the chassis (motor, trans, etc) but the roof is still "so far away" from that point (but much lighter, but still lots of glass). I'd not think it could be much lower in the vehicle than the centerline of the brake booster (where the brake actuator rod runs through the firewall) and not any higher than the rear shelf. That narrows it down (through guestimation only) to a range of only a few inches.
The question is, how accurate is my guestimation?
My thoughts...
Originally Posted by trackbird
Carl,
I should have known this would be "yours" (darn engineers)....lol
I should have known this would be "yours" (darn engineers)....lol
Hmmm, I've grappled with this one myself for a while. And, my best guess would be somewhere about level with the rear "package shelf" behind the rear seat, maybe a couple inches lower. Since most of your weight is low in the chassis (motor, trans, etc) but the roof is still "so far away" from that point (but much lighter, but still lots of glass). I'd not think it could be much lower in the vehicle than the centerline of the brake booster (where the brake actuator rod runs through the firewall) and not any higher than the rear shelf. That narrows it down (through guestimation only) to a range of only a few inches.
The question is, how accurate is my guestimation?
My thoughts...
The question is, how accurate is my guestimation?
My thoughts...
Originally Posted by critter
Inquiring minds, ya know
Thanks! Yeah, I've been trying to guess the masses and guess the location, but all guess work. I came up with a guess of about top of console, not too far from you. But one of my reference books said it is generally 20 to 22 inches in passenger cars. I think it might have been Chassis Engineering by Adams. BTW, I found the first error on page 8. It seems to have some good stuff, but is sloppily edited. Anyway, we know the longitudinal location because of the 56/44% weight distribution. My current plan to find vertical is to find out what 60 ft time it takes to carry the front wheel, convert that to Gs and then to force at the ground, and then the height that would balance at that force. Unfortunately, the answer will be only as good as the input assumptions. If I only had a set of scales ...
Thanks! Yeah, I've been trying to guess the masses and guess the location, but all guess work. I came up with a guess of about top of console, not too far from you. But one of my reference books said it is generally 20 to 22 inches in passenger cars. I think it might have been Chassis Engineering by Adams. BTW, I found the first error on page 8. It seems to have some good stuff, but is sloppily edited. Anyway, we know the longitudinal location because of the 56/44% weight distribution. My current plan to find vertical is to find out what 60 ft time it takes to carry the front wheel, convert that to Gs and then to force at the ground, and then the height that would balance at that force. Unfortunately, the answer will be only as good as the input assumptions. If I only had a set of scales ...
Originally Posted by trackbird
Yea, that 20-22 inches number was sticking in my head from the adams book as well. Are these cars 56/44? The 3rd gens were (as I remember) 53/47%. If that is the case, it seems odd that GM would shift it that far. However, it is possible....
coupe - 55/45
z28 coupe - 56/44
convert - 54/46
z28 convert - 55/45
Must be the Z28 emblems on the front fenders ... However, they are close and all nose heavy compared to your 3rd gen number. That is strange also, given that the motor is aluminum and how far back it seems to sit. They list the CD at 0.33 unless it is Z28, in which case it is 0.34??? Which reminds me, I heard the other day that the 3rd gens take less HP/mph, but I don't know if is was less frontal area or lower CD.
I did the math, using the 60 foot times of a couple cars that can carry the front wheels, and arrived at ~19.5", so I think 20" is a pretty good number. I say go ahead and use it in your calculations
