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Author Topic:   Chassis Stiffness
69-er
Dirt Full Roller

Total posts: 39
posted December 22, 2000 06:56 PM
Do any of you chassis builders know how much a Camaro chassis should flex/twist? Right now, almost of all the tubing I plan to install is in place, but if I lift up on a rear corner at the bumper, it raises about
1/4" just as the other rear corner is coming off its jack stand. At the moment, the car is stripped bare, no roof, the trunk area completely cut out with front loop, main cage, rear kickers, rear loop installed, rear
frame rails tied together, etc. I don't know where to add more tubing to make it stiffer.

It seems to me that once the car is complete, the extra weight and racing stresses will make it twist even more.

Also, if I shake the car up and down at this corner, with the jack stand out of the way, I can set up a vibration/oscillation that lasts for a 1/2 second or so.


HELP!!

Larry

CUSTOMPERFORMANCE
Dirt Freak

Total posts: 213
posted December 22, 2000 07:10 PM
before you can really tell how much flex you have you should have the roof and the entire cage welded up before you can get an accurate idea on flex.

69-er
Dirt Full Roller

Total posts: 39
posted December 22, 2000 07:20 PM
But, in the end, should I be able get zero flex or am I worrying for nothing?

Larry

d4490
Dirt Full Roller

Total posts: 43
posted December 23, 2000 10:26 AM
you should have no flex between your chassis points.
from your back bumper, it sould have some give int it, just in case of a bad crach.

[This message has been edited by d4490 (edited December 23, 2000).]

CUSTOMPERFORMANCE
Dirt Freak

Total posts: 213
posted December 23, 2000 10:05 PM
with the roof on and the entire cage welded up the flex will be at a minimum compared to now, the roof adds a lot of strength to a unibody car, plus the joints that arent welded will flex. the flex will minimise after weldeing. this is just my oppinion, if somebody has different views i would like to here them.

69-er
Dirt Full Roller

Total posts: 39
posted December 24, 2000 10:10 AM
The roof isn't going to help in my case. The inner panel has been removed. It's just a flimsy piece of sheetmetal. The only part of the body that is still somewhat intact is the firewall, floor and rear frame with quarters, everything else has been cut away. The rear bumper is still firmly atached with no visible movement. Most of the rear half of the car appears to be twisting, the front appears very stiff.

Larry

cmiller9x
Dirt Roller

Total posts: 13
posted December 27, 2000 07:38 AM
Have you connected your front stub to the rear with tubing? I always use 2 x 2 square. It works well because it fits inside the front stub and goes right beside the front of the rear stub. I've seen other cars without this perticular connection, but they built their four point chassis with two points on the front stub and two points on the rear stub. Seems to work as well. Make sure when building the chassis that you weld to the frame and NOT just the sheet metal. Hope I helped a little.

widebody
Dirt Full Roller

Total posts: 74
posted December 28, 2000 12:37 PM
Like cmiller9x said, when you add the box tubing from the sub frame to the front spring hanger, it makes a huge difference, even with a full cage already in it.
The front spring hanger buckets can be plated/welded to the box tube for extra strength.
Do your rules allow you to run fabricated rear frame rails?

Strokin3
Dirt Full Roller

Total posts: 68
posted December 29, 2000 06:51 PM
As a rule of thumb you should install the
frame connectors BEFORE doing anything else.
As a previous post stated the roof and front
and rear roof post is a big part of the strength on a unibody car. Also did you replace the front body bushings with steel.
this will help also.

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