LOL! I can ask can't I?
Actually, I expect that moving the outer pickup rearward, and inputing the lateral force at 12.5 degrees will have a noticeable (I don't know how significant though) effect on the data output from the model.
As long as I'm asking for the moon, I would also love to see the effect of the lateral force by itself, and the torque force by itself.
John, can you explain what calculation is used to produce the rotation numbers in the table? Do you have control over that calculation?

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LOL! I can ask can't I?

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Actually, I expect that moving the outer pickup rearward, and inputing the lateral force at 12.5 degrees will have a noticeable (I don't know how significant though) effect on the data output from the model.

Actually, the front pick-ups are aligned correctly against the body of the arm. The rear hub assembly was not offset by an angle -- so that's the angle that is not reflected. Moving that back by ~6 degrees is not going to make a huge difference since the large diameter tube that the hub is attached to connects to the arm across a wide area.

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As long as I'm asking for the moon, I would also love to see the effect of the lateral force by itself, and the torque force by itself.

How do I say this nicely?.... No.

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John, can you explain what calculation is used to produce the rotation numbers in the table? Do you have control over that calculation?

Dammit Chris! I'm a salesman -- not a mathematician. That means I was smart enough to recruit to my team (aka: marry) an engineer with a master's degree who grunted through 6 years of advanced college level math rather then take the classes myself.

The other thing that I learned in B-School (in addition to strategic acqusitions) is delegation.

I just emailed to you a copy of the software and the base model.

BTW: Grape is Shareware that can be downloaded from the Grape Software web page.

Oh yeah, here's the latest data table. Note that the rough order of incremental improvement for each strategy is consistent even as we change different force strategies. To my simple mind this suggests that the results will be fairly consistent even if you change an angle here or a few pounds there.

Hold a carpenter's square against the inside face of the box section and you will see what I am getting at.

John, for a salesman you make a pretty good engineer. I have been impressed with the depth you go into this sort of analysis. I really appreciate all you have done and I will find a way to repay the favor down the road. 0

I'll see if I can pick up where you left off on the model (unless I can get Tim to do it ).
Thanks!!

Ok -- I've been thinking that we're starting to "lose the forest for the trees". This is going to be a real challenge -- I'm going to try to be brief.

Using FAE to figure out if the answer is 0.00498 versus 0.00484 is most likely not an effective use of the tool. If you want to know the meaning of life -- it's
42. But what is the question???

To answer that I went back 243 posts to look at where we started and found these thoughts:

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How flexible do you think a stock, trailing arm is? -- 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.

and...

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you could take your invesitgation to another level, and find where the trailing arm needs to be reinforced.

and...

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I only want it to limit the flex from cornering loads.

and finally this fairly pithy problem statement:

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A stock trailing arm definitely isn't stiff enough for a competition car running on slicks.

( If you want to jump to my proposal and skip the long winded monologue, it's at the bottom.)

What we've learned along the way since they consisentanly came out in our tests and model -- no matter what we did to them.

1) The stock arm does flex.
2) Adding an internal bulkhead stiffens it some.
3) Adding an external gusset stiffens it more.
4) Combining the two approaches stiffens it even more
5) There are some concentrated stresses in the hub area (where Porsche's designers kindly designed in a fairly massive piece) and where the arm attaches to the outer end of the front pivot tube.

Some things that we already knew
1) Weight is evil
2) Stiffness increases with the cross sectional area and to a lesser degree by filling in internal voids.

Putting these factors all together I modified the spreadsheet to take into account the extra material being added by each solution (assuming it's all 2mm thick steel) and then compared this to the reduction in Y-displacement and Z-Rotation (which both impact toe). I then tried to optomise the solution some based on the earlier approaches and rather then combining the external gusset with an internal "floor", I tried triangulating the top edge of the gusset to the corners of the arm's original box section. The result?

A solution that is stiffer then all of the previous options, but uses less material then the next stiffest option. But even though, the best "stiffness versus weight gain" option remains the original simple external gusset.

My Final Recommendations!
1) For the lightest solution, weld a lengthwise external gusset to the arm.
2) For the strongest solution, weld additional pieces from the exposed edge of the gusset down to the arm, thus creating a "peaked roof" type of structure.

No matter what you do, doubling the thickness of the material in the area near the outer half of the front pivot tube will essentially cut the surface stresses in that area by half (same stress, double the material) which is a good thing.

Now back to my day job!

Here's the overhead view of the gusset with the "peaked roof" results.

A view from the outside of the arm (when mounted) showing the area of highest stresses.

Finally an "edge on" view showing the "peaked roof" structure that I discussed showed the best stiffness improvement.