What kind of "flex" do subframe connectors prevent?

[O'Neall]

This is going to sound like a dumb question because I'm not sure I can explain just what I mean... but here goes.... :dunno:

By what kind of "flex" I mean... in what direction? It would seem to me that two bars running lengthwise alone the subframe rails and unibody wouldn't really do much for crossflex (if that's a word... what I mean is flex that goes across the width of the car either straight across or diagonally), but would be better suited to prevent flex that wants to "fold" (like into a "V") the car like a hinge at the firewall.

I don't know if that made any sense, but my point is that it seems to me that preventing this up and down flex at the point of contact is all they'd really do directly by adding strength to that connection. Ultimately that strength would translate to added rigidity which would translate to some "crossflex resistance" (sorry for my lame terminology) I suppose, but it just doesn't seem that without "triangulating" them somehow that SFCs would be much good at preventing this "crossflex" in and of themselves.

Forgive my ignorance and inability to express what I'm trying to ask and explain... but does anybody know what I mean? And can somebody explain to me just what direction of flex SFCs help to prevent?:help!:

Thanks!

[Beige]

http://69.94.75.177/forum/showthread.php?t=23278

[O'Neall]

Thanks for the link.

So, just as a sanity check... after reading that whole thread I have concluded that my supposition above about them being "better suited to prevent flex that wants to "fold" (like into a "V") the car like a hinge at the firewall" is correct and that torsional (what I was calling "crossflex") benefits are minimal.

Sound right? :fingersx:

[Beige]

I wouldn't say minimal. But it is a bi-product of the longitudinal stiffening sfc's provide.

[fotoboy]

body flex

[O'Neall]

I wouldn't say minimal. But it is a bi-product of the longitudinal stiffening sfc's provide.

Is that you what gathered from reading that thread, or is that you're take on SFCs?

Here's what I got from reading that thread:

Nobody seemed to argue that there was much more than minor torsional benefit (from an all around stiffer chassis). If they did, I missed it (which is possible). Some even seemed to say there was "little" benefit. Reducing/preventing beam deflection (i.e. the hinge effect at the firewall) seemed to be the real function for SFCs. At least, that's what I got from the reading.

Thanks.

[79T/Aman]

the SFC will help the tendency of the car to flex in a "V" between the rear most body to frame mount and where the rear unibody section starts it will help in tortional ridgidity but only to a certain degree the sure way of fighting diagonal flex is a roll cage.

[Beige]

Reducing/preventing beam deflection (i.e. the hinge effect at the firewall) seemed to be the real function for SFCs. At least, that's what I got from the reading.

Yes, but most 60's unibody cars are weak in this area, and beam deflection can lead to torsional flex. So adding sfc's is a good start.

There's only so much 2 sections of 2"x2" or 2"x3" box tubuing can do, so compared to a full cage or other types of bracing, the effects are minimal.