How flexible do you think a stock, trailing arm is Options

[ChrisFoley]

Specifically I am looking for rotational stiffness (ie. twist) of the trailing arm due to the tire contact patch resisting sideways sliding of the car. I'm only interested in forces greater than 1G during cornering.
I already know what happens but go ahead and take a guess. (IMG:style_emoticons/default/biggrin.gif)
I'll post pictures of my test fixture shortly.

[ChrisFoley]

OK
I did some more experiments this morning.
The first thing I did was to rotate the trailing arm vertical so I could easily apply a load to induce lateral deflection. I was all alone so I couldn't make accurate measurements but the deflection is similar to the twisting deflection under the same loads. If anything it was slightly less. Personally I don't think lateral deflection is a problem as I am pretty sure the force component in that direction is much smaller.
I thought about my setup for a long time before actually assembling anything. Even though it appears to make significant compromises compared to what happens in the real world I am pretty sure it would be tough to make a major qualitative improvement over what I have. However making quantitative improvements wouldn't be too hard. I don't know if the load I am using is correct, and a digital level isn't as accurate as a dial indicator. OTOH, that is the same digital level I use to set up the suspension on the car and I am really only after comparative data, not detailed design analysis.
Since I was working alone I decided to standardize my forces and make it possible to read the level while under load. That meant I replaced my body weight on the lever arm with a stack of steel pieces adding up to about 220 lbs. The only shortcoming to this method is I can't observe the deflection as it occurs. I can only read the level to see the final effect. Good enough for now.
So I repeated yesterday's test with my standardized load and measured a deflection of 1.1 degrees.
Next I replaced the trailing arm with a boxed trailing arm and the deflection was 0.8 degrees under load.
Finally tested my idea for a reinforced trailing arm. Using just on piece of sheet steel that weighed 4 ounces and measured approximately 3x4 inches I was able to make an equivalent improvement to just 0.8 degrees of deflection on the original trailing arm. That compares to about 2 lbs of sheet metal used for a boxed arm, and a corresponding smaller amount of welding which means less distortion of the trailing arm. (IMG:style_emoticons/default/smile.gif)