<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR> Angry Joe: In order to get accurate numbers the chassis should be loaded through the suspension members, with the shocks replaced by rigid links. <HR></BLOCKQUOTE>
<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR> Joseph: The true torsional stiffness must be measured at the wheels and loading the frame at the rockers, a-arms, and shock mounts. <HR></BLOCKQUOTE>
I intend on including the defection of the A-arms and the push rods. I will assume the rockers and the shocks are ridged. I want to find the torsional spring rate of the entire system minus the shock displacement.
Since I cannot create a pivoting link there are two ways to do the preceding analysis.
1. Use a free body diagram to determine the reaction forces at all mounting points. Then add measures to the model to find deflection at each point in the proper direction. Then sum the deflections to find the resulting deflection at the wheels. This could take some time but it could be done.
2. Define the model with all ridged joints. Then modify the beam elements. At the points where you want a pin joint to be simulated define a cross sectional area but set the I value to 0 that way the beam will only transmit compression and tension forces. With I = 0 no bending forces can be transmitted. This would be the easiest way but I don't know if it will work yet.
Joseph
University of Oklahoma