Chris, that is an interesting thought. If I may, I'll share my views on the X-brace design.



As far as those "pesky cross braces" go, they will add more chassis stiffness per pound than a straight (2 point) connector.

We have to consider the properties of the material and the nature of the problem.

When a chassis flexes, its size and shape are altered (temporarily). When you drive over a speed bump with only one wheel (we'll use the drivers side front wheel for this example), the chassis stretches. When the driver side front wheel runs over a speed bump, it travels upwards and twists the chassis upwards as well. This increases the distance between the drivers side front sub-frame and the passengers side rear subframe. Simply, it stretches. This is the nature of the problem.

Now, consider kite string. It sure isn't stiff, and it bends easily...but it is strong in the one direction we need help. It's strength is in tension. A thin piece of steel has similar characteristics. It dosen't have to be terribly heavy to offer resistance to a stretching load (we have to worry about ultimate tensile strength and permanent elongation....a much more complicated discussion). So, a couple well placed (reasonably light weight) diagonal bars on a subframe connector will do wonders for eliminating chassis flex. Potentially, a connector design that utilizes a form of diagonal bracing can reduce the size of the "2 point" portion of the connector while giving up no (or nearly no) chassis stiffness. This potentially allows for a connector that is lighter in weight and stronger than a 2 point design.

As a side note. Consider a sway bar (for your suspension). A sway bar is a heavy chunk of steel that is designed to resist "twist". A 2 point subframe connector is asked to deal with this same type of twisting load. Now, we all know that sway bars flex and there is still body roll present (even with that large chunk of steel under the car). This is basically the same thing we have to contend with on a 2 point subframe design. We know it will twist. It is simply a sway bar with longer "arms". The longer the arm on a sway bar (diameter and length being equal), the "softer" the rate of that bar. So, we now have a 2 point sway bar (2 point connector) with the entire width of the chassis for "arms", to offer leverage to try and twist the bar. The cross brace becomes a light weight way to eliminate much of this flex with out resorting to 5 inch diameter tubing to get the necessary torsional rigidity.

Just my thoughts.....


Is everyone still awake?

 

I'm awake.

Trackbird I know your moving but www.arp-bolts.com has information on the bolts they make.
I just read about it CHP September 03 haven't been there yet but it should be enlightening.
Will their bolts compare to others? maybe

Yes I completely agree about the car body being the weakest part of equation.
I make nuts that spread this area out instead of using standard nut and washer arrangement.
These nuts provide 54% more area than the standard nut/washer combination.
It's still a compromise

 

As I remember (from the last time I looked at "ARP vs. Regular bolts"), the ARP will generate signifigantly more clamp load than a standard bolt of the same size at the same torque value. They use special (proprietary) alloys that have specific characteristics needed for each application. I'll see if I can find my ARP catalog and my book anytime soon.

 

Why don't you guys just come up with a new bolt... If you are trying to reduce the slipping of the SFC vs. the mounting points then create a bolt with a ridge all the way around the bottom of the head. Not just a raised portion but an actual 'flange' if you will. This could then fit into a groove mirrored in the SFC. Granted this will not fix the weakness of the uni-body but it will hold everything in place a little better. To fix the uni-body... maybe a weldin backing plate. yeah yeah yeah... I know the purpose of bolt-ons is to actually keep you from having to weld anything to the car and ease of installation but if you are going to make a super stout setup then you will have to strengthen the uni-body, period. Otherwise, as I am reading over the past posts, any SFC will strengthen the uni-body construction. Also, refering back to past posts, the more mounting points the better. So a three point SFC will stiffen the car more than a two point. So the moral of the story is... "If you can afford to do something for your car the best thing to do is to install a good SFC." As for me weight is not an issue. I have no intention of racing my T/A... (except for a red light from time to time... but only to the posted speed limit of course... )

 

I have been reading this and I think an important point has been lost, forgotten or just overlooked.

While honing in on the bolt strength, the strength of what you are bolting too is highly questionable.

As I lay on my back, looking at the potential mounting points for ANY SFC, I don't see any structural part there that could withstand the sheer forces of a grade 5, much less a grade 8 bolt.

I also think that there isn't enough clamping force that can be applied to keep said forces from causing SOME movement.

There has to be enough room to get the bolt through the holes. Those tolerances alone will allow for movement.

Disclaimer for those who are **** retentive:
JMHO

 

Like I've said before a timeless debate.
I think I'll stick with the Grade 8 bolts and large 2 hole nuts I currently supply with my coupe version subframe connectors.
Did I mention that these items are a compromise.
I hope the Gen 5 F-body has a full frame that would solve several problems.

 

Mitch, I glanced on that earlier....but I didn't make much of a point of it....

I think all connector designs are somewhat of a compromise....it simply needs a cage.....

 

I guess the point is that there is really no need for grade 8 bolts when attaching whatever to 12guage stamped metal. The meal will tear long before the bolts give way.

Now, which is an easier repair? a bolt replacement or ripped metal?

 

While you are welding that "tear"....

 

Yes, as I have continued the search for the right suspension subframe connector for my 02 SS A4, I started out with the standard SLP black bolt on subframe connector. Then, I started to look and watch some of the 4th Gen. GM F-body that were involved in T-bone accident, side impacts, and other serious crashes. My family has been in the insurance business combined for over 80 years (all types). What I learned is that a bolt will not hold to the force of the impact. Anytime a weld is added to a body structure, this will surely strength up the compartment area. So, off with the SLP bolt on, and now to find the strongest Subframe connector on the market. Found it.

www.globalwest.net
Part #905
Made out of 2" roll cage .125 wall tubing. And welded in with big thick pockets too.
Excellent protection IMHO

 

Weld your SLP's....

Just my thoughts....

 

I agree... The SLP's are a three point design and have the benifit of the extra support in the middle.

 

Lou, these won't use conventional fastening systems, meaning, no threaded fasteners. They are held in place with a type of gravity locking system developed in the aerospace industry. There will be virtually no flex under load with this system.

 

Kevin, these won't weld in or be fastened in with typical threaded fasteners. The goal was to create design that could be removed in a minimum amount of time with few tools. They will be held in place, with a type of gravity lock. So they won't flex or give, when under stress. I have no problem getting titanium, and it's excellent quality stuff, with the certs that go with it

 

I almost agree...
The coupe version I make have three point attachment and can be welded if you choose. Looks better as well.
Just my thoughts

 

With all this talk of chassis stiffening I am surprised no one has mentioned seam welding.

 

Well it is an option but with everything compromises those damn compromises.

 

I've also heard excellent things about the Global West connectors. Thats what I'm going with when I have the $ to get 'em.

 

Whats the deal with the titanium SFC's? Are they ready yet?

So are the SLP SFC's the "best" right now? (strongest)

 

I ALSO WOULD BE INTERESTED IN THEM AS THEY WOULD BE LIGHT AND STIFF.I WAS CONSIGERING THE GLOBAL WEST SFC's.PLEASE PM ME SAWEDOFF.