Chassis twist, Weak spots Options

[r_towle]

Hi there,

So over the years I have seen all sorts of ideas, lots of products etc..

Seems like we are chasing our tails.

Here is my dilema, and I would like to get some input.

Take a 34 year old chassis, fix the rust.
Add super stiff suspension.
Bearings, bars etc.
add really sticky rubber.

Now, what gives in the chassis...where is the weak spot.
Say I seam weld the suspension console.
What next...something needs to flex, or it seems to me that something will break instead.
I ahve seen pics from McMark of a cracked long inside, and in the miidle of the span..not a rust issue per se, but a fatigue issue.

So, where can I engineer in flex, so the chassis wont crack, or break a weld.

No Cage allowed.
Just the chassis.
Currently there is not inner long kit, or outer...just good repair work on the rust to date...
Nothing is cracked yet...but something will have to give..
I just put in roller bearings....now its really smooth, but now more of the forces are put directly into the chassis...

Rich

[McMark]

I think you're looking at it wrong. Yes, the flex does 'move around', but each improvement reduces flex. So you're not talking about concentrating flex, so building in 'flex points' would only negate your modifications designed to reduce flex. I think your idea has some merit, but I think that without realistic FEA, you're shooting in the dark while drunk.

[r_towle]

I think you're looking at it wrong. Yes, the flex does 'move around', but each improvement reduces flex. So you're not talking about concentrating flex, so building in 'flex points' would only negate your modifications designed to reduce flex. I think your idea has some merit, but I think that without realistic FEA, you're shooting in the dark while drunk.

Shooting in the dark works sometimes...

I guess my worry is, where is it going.
I know its gotta go somewhere.
So what is next.
I fix the suspension console, done
Inner and outer long, done

Now, where do I watch...
I am guessing that the front fender welds to the front firewall, and the inner and outer fenders are next...something needs to take the force,,,

I would love a detailed FEA, but who has that kind of money and time..

I was thinking more of a rear suspension console that allows for this type of movement. Something predictable.
Something that allows the suspension to absorb the stress, instead of pushing that force into the frame/unibody.

So , instead of a detailed analysis of the frame/body....more of a look at allowing the suspension to absorb more of the twisting force that is applied on a skid pad, in high load , high g-force scenarios.

It seems to me that we have improved lots of the car already.
Look at the issue, or smack me.
If the trailing arm is super rigid, and allows zero twist at all, then its all up to the tires..
We have trailing arms that twist from the factory.
Take out the twist, and the force starts to add more stress to the trailing arm mounting points.
So we have a fix...solid outers, and re-enforced inners.
Ok, now where does it go...up into the long, and applies the side load force to the lovely weld at the shock towers...woohoo..that is a hard one to fix, and fix well enough to keep it from breaking..but it can be done..

If you follow my trend here.
Instead of rebuilding the car entirely,,all new welds, and all new heavier parts, why not figure out a way to control the twist at the trailing arm.
Not only control it, but limit it.
It can twist, but only so far, so you dont make the rear tire patch worse in a turn, but also you let it twist from say 2 degrees to -2 degrees...

This came to me as I watched the speed channel prototypes racing today.
Those wheels move alot...from 3 degrees or more up to almost 0 degrees.
It just looks like it is designed to do that right from the start.

Its just a thought..

Rich

Rich