This is my qualitative result, and I will share my quantitative (experimental research) later once I collected those data.
I was first inspired by Mike Kojima project Z32, and really motivated by Epstein(Chris) and the SAE paper 1999-01-1785.
Previously, we had serious and detail discussion over the pro and con of chassis foam; there were plenty of successful cases out there, like Kojima's project Z32, Mines, Apexi, and MCR demo R34; and maybe more. And what really get me going is the test results and strong evident from the SAE paper by Daimler Chrysler Corporation, which performed a test on a SUV. So I want to try this first hand.
Before I start describe the qualitative result, i want to share some result that was performed by Daimler Chrysler Corp first, and due to copyright, I can not post the entire article here.
First of all, Vibration 101: Natural Frequency of a body is square root of stiffness of the body over mass of the body.Fn = (K/m)^(1/2)K is the stiffness coefficient of the body, m is the mass, Fn is natural frequency. So the stiffer the body, the higher the natural frequency.
Credit goes to Daimler Chrysler
here is a study of which joint is most sensitive to foam filling
Here is the original Abstract of that SAE paper 1999-01-1785
Quote »Stability and structural integrity are extremely important in the design of a vehicle. Structural foams, when used to fill body cavities and joints, can greatly improve the stiffness of the vehicle, and provide additional acoustical and structural benefits.This study involves modal testing and finite element analysis on a Sport utility vehicle to understand the effect of structural foam on modal behavior. The modal analysis studies are performed on this vehicle to investigate the dynamic characteristics, joint stiffness and overall body behavior. A design of experiments (DOE) study was performed to understand how the foam's density and placement in the body influences vehicle stiffness. Prior to the design of experiments, a design sensitivity analysis (DSA) was done to identify the sensitive joints in the body structure and to minimize the number of design variables in the DOE Study.[/quote]And the Conclusion:
Quote »The most sensitive area of the body were found to be the A-pillar, the D-pillar and their joints. With structural foam injected into this sensitive areas, the vehicle body was significantly stiffened, as shown by the increase in modal frequencies. The 1st torsional mode was most effected with an increase of 29.1% in modal frequency.The design sensitivity analysis and design of experiments described here, can be used to identify the sensitive ares of the body structure. This results are useful in the determining the best application locations for structural foam.[/quote]--------------------------------------Well, enough talking, let's get down to business. First of all I want to thanks God gave us a safe working environment; my boys Ryan and Jason whose came all the way to my house to help me; and my fiancée, Julie who put up with our boys for the entire weekend.
At first we tried to do some physical measurement of the chassis flex, like how much the door gap distort and close up while it was jacked up,
But it was no luck, we ended up having 3 wheels off the ground, and the door still shut perfectly, i was impressed and yet upset.
We should have measured the distance between the frame rail holes as described in the FSM. But we were ready to Git-R-done.
First step is remove both seats, interior trims, and carpet. So the A,B,C pillar and rocker panels are fully exposed.
A pillar (noticed the drain hose)
C pillar (again, another drain hose)
the longest process is the tape everything carefully, since that junk will harden and sticks on the paint if you are not careful. Here is the rocker taped up.... "me love you long time"
Duct tape works wonderful to cover up some big holes.
Handifoam II-22 kit
Have the interior well cover is very important, get duct tape ready to cover the holes after injection
Foam filled rocker panel
as you can see, it was a good, uniform, completed fill...
We found a trick, it is filled the cavities more than enough, and before it expands out of the holes, cover it with duct tape to force the foam to have a tighter fill, result as a slightly higher density.
completed A pillar
completed floor pan cross rail
completed B pillar
B pillar middle
completed C pillar
everything back together
like nothing happened at all
Modified by H8tred at 6:51 AM 8/9/2007