So, what improvements have I found? Well, there were limits to what could be done. Paul figured that adding tubes in the floor on the driver side would get in the way of his seat and pedals. I agree that it might result in a higher CGH. It's all a compromise and in the end, it is Pauls car and his word is law.
But I did add a brace to the floor on the passenger side. If Paul was to have a passenger with him, the extra weight of the passenger would be more of a problem than the slightly higer CGH anyway.
With the floor brace, the stiffness was now 9811 Nm/deg.
I then looked at further triangulation of the passenger compartment but didn't get higher than 10313 Nm/deg and I considered this to be a pretty small gain. It just didn't seem to be worth it.
Having studied the deformed mesh, I concentrated on the rear end. I added some braces connecting the engine mounts and the square section tubing at the rear. This time, the results were a bit more interesting: 12649 Nm/deg.
Now, while this was a nice improvement, I am aware that these braces could come in conflict with the driveshafts. Unfortunately, Pauls attention has turned towards a different project at the moment, so he hasn't been able to check this yet. Until he has checked this, or come up with another idea on chassis improvements, I guess there's not much more I can do right now.
Here are a couple of pictures of the frame in its current form
Enjoy
PK
