Torsional rigidity

Where did I say that? I said it could easily be made better, which is what I am doing to mine thank you.

 

I've been wondering the same thing myself.

I sure wish I'd known what complete POSs these cars are before a buddy & I put well over 10k track miles on his early 348TS (yeah, the bendy version) without any diabolical handling surprises, without the car twisting itself into two pieces (or cracking any paint), and without even a single on-track failure. With no mods other than a single can muffler, track tires, racing brake pads & fluid, and a Challenge alignment (including ride height) that car was bulletproof and spanked a whole lot of more powerful cars because it inspired the confidence to drive it to the limit. But now, years later, thanks to Paul and LDM, I finally find out that the car was actually a lemon. Who knew?

As a counterpoint to all this interwebular postulation, see my recent post of the supercar shootout video for a firsthand example of just how well the "floppy old 355" compared to other cars of its generation.

 

No you did not say that.

What you said is-

Not surprised you changed your point of view as the quote above makes absolutely no sense.

In summary, the car would be stronger if it was made stronger? LMAO, yes I agree.

I'm not a "fan boy" or saying the F355 chassis could not have been improved upon, just need to set the record straight when you are posting information which is completely false.

Really the rear subframe mounting likely has the absolute least to do with the torsional rigidity of the car compared to anything else.

Twisting force is going through the body of the car. Floor pans/rockers, roof (if there is one) and to some extent doors at hinges and latches will resist twisting, but since the body allows a fair amount of flex it really does not matter that it's only bolted in at the top by 1.5x1 square tube.

The flex is due to lack of rigidity of the body not because the attachment points weren't milled out of old anvils.

Fatbillybob's results back that up as the cage (and then again better cage) was stiffening up the unibody, not replacing the subframe attachment points with train rails.

 

You are clearly reading incorrectly what I said. In both instances I have stated the cradle is supported below and that the upper mounting does not add much torsional rigidity, I have not changed my viewpoint one iota, both my statements mean the same thing. How have a changed my tune when my photographs clearly show exactly what I have stated?

Ok lets clear a few things up, the thread is about the torsional rigidity of the 355, I have provided pertinent key photogaphs to show in detail how the engine cradle lacks any significant support in the upper part of the body, I have gone so far as to even provide dimensions of the weakest part of the structure alongside an actual photograph of said section of metal.

Another user has provided a first hand account of how his own car was vastly improved when some of these weaks point were addressed.

Everyone else has just jumped on the defensive bandwagon, on the basis of.... well because they can.

No one is claiming the 355 is a death trap, the figures provided by the OP show the 355 is not that rigid, a user has identified how it can be improved using his own car as an example, and I have provided key photographs to show how the design is not the best, and the reasons why that is, end of.

 

I am clearly reading incorrectly? I'm reading and responding to exactly what you wrote.

You said it needs to be triangulated better, is so flimsy it provides no rigidity whatsoever and "It is all connected down below the engine, very little support above or any significant triangulation of the cradle above the engine into the chassis"

Explain to me how I am reading what you wrote incorrectly.

Even in your own pictures, on the body of the car there is the square tube that the upper subframe bolts attach to. Just forward of the front/upper subframe bolt is a round tube intersected to the upper square tube that goes down and forward to the bulkhead triangulating that mounting point.

Just behind the rear upper subframe mounting point you have square tube intersecting the top square tube dropping down and tying in to the rear of the subframe and forming the rear bumper support frame.

This construction certainly isn't "shocking".

All of this metal however adds no strength because it's not up to your spec and you can buy it at home depot? Makes no sense.

It is there, it is triangulated, and contrary to what you might think, thin wall square tube does have more than just an insignificant amount of strength.

I have continually agreed that anything, including the F355 could be made stronger, of course. You are trying to make it seem that the upper subframe mounting is just flopping around with no thought or reinforcement and that just isn't true.

I'm done with this, I have said all I need to say
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A chain is only as strong as its weakest link, I have shown you an actual cross section of the weakest point of the upper mounting position of the engine cradle into the chassis, either side of that could be made from boat anchors as you state, makes no difference when the intersecting part as photographed in cross section is a bit of flimsy box section.

At the end of the day if you are happy with that, then simply crack on, I am not so will be engineering a far sturdier assembly into my own 355 project to provide it with far superior torsional rigidity than how it left the factory, as proven in the table provided by the OP.

Then again with a 600 bhp plus v12 installed its going to need it!

 

Take away all superfluous bits and bobs and this is what the actual skeletal support work looks like, the circle shows where the bolts go through and the arrow shows where the stresses are being directed to at the weakest point in the structure.

Its at those two points that all the loading of the two suspension corners are being directed under cornering. everything else surrounding all that has no effect on the actual strength of the chassis.

Just presenting the facts gents, it is there for all to see.

However if just aft of the arrow, where the bolt goes through, if you were to take some tubing and cross brace that point back up into the cabin area ala F40 LM below with the x tubes then the forces at that point would be dissipated more evenly through the chassis and reduce flex.

The design of the 355 hood area does not allow that though but the tubing could run through the buttress instead potentially, the cross bracing element is lost but transfer of the corner load would still occur, this is how they dealt with it on the road F40 as seen in the pic below to the left of the x brace

Its not about slating the design as such, its more about how it could have been made better for not a lot of effort.
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