I don't know if I'm waisting my time or yours, with this post, but I've got some pictures of my frame connectors.
They're 2"x 3"x 3/16" full length, slip over rear frame member, full welded to the floor pan, not thru the floor pan,if anyone is interested. The only place they're not welded to the floor pan is small kick up for the rear floor pan under drivers seat.
They're on my '65 Coronet.
Max

Max, any and ALL pics are welcome !!! I know your pans are different, but if nothing more, it will give a better idea of different ways to do them. The pics might also be added to a tech article on the subject, and could be used for your year/model vehicle for others to enjoy.
You can post 'em, or send them to me or Rich(Zippy)

My e-mail is belvedere66@hotmail.com the only problem, is the max size I can recieve is 1M at a time. the other option is my work e-mail: todd.desmarais@verizonwireless.com no size limit there, but harder to get on my personal computer.

Tim, where are ya buddy ???

Todd

Trail dust, I'm back at work and pulled some equations. Here goes:

The first two equations are for SOLID pieces, I will post the equation for a HOLLOW piece as well, but the idea will be the same. I wasn't able to find a clear equations for the hollow, but the equations I found lead me to believe the trend will be the same.

The section modulus under torsion (Wt) for a square is:
Wt = 0.208a^3 where a is the length of one side.

The section modulus for a rectangle is:
Wt = x*b^2*h, where x is the ratio between the long/short sides (3/2 for our case), b is the short side, and h is the long side

In our case, we have a 2x2 and a 2x3, the square will have a modulus of 1.664 and the rectangle of 2.772, a 40% increase for the rectangle.

Hope this helps..

Maxwedge, post thos pics, or send them to me!!

Tim, where are you?

Quote:

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Frame connectors should be stood upright in case at some later date you want to ladder bar it. Then you just holesaw holes through the connectors and insert the ladder bar crossmember through it and weld up both sides. I don't like to butt weld ladder bar crossmembers. Have you ever seen one pull loose while under braking at the top end? That is a nasty, nasty handfull!

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That's enough of a reason right there! I wouldn't consider it right now but who knows what I'll try down the road.

I picked up a good supply of 4 1/2" cutoff wheels at the swap meet this weekend, and will hopefully be able to pick up the steel today or tomorrow and get on it.

re: tacking to the floor from underneath: If it is done that way with the 3" section vertical, the connector will hang down below the frame...not really the way I wanted to do it...

Sorry guys... I was away for the weekend...

I will take some pics tonight and post them...

Tim

This seems to be a very hot topic, and lucky for me because I need to install a set of conectors in my 66 belvedere and have not decided just how bad I want to cut the car up, just a 6 cyl. shell but rust free, perfect for a S/S class. Have you guys received your copy of Mopar Collector Guide, and noticed the tubular bolt in connectors made by a company called Magnum Force, these things look like they might have some potential, made from 1 1/4' round tubing, what would the benifits and disadvantages of a bolt in set-up like these be over the traditional 2x3 installations. Giving some serious thought on calling this company and trying them out. Gearbox.

OK guys sent 4 jpegs to 66 Belvedere, who said he'd post them to Moparts.
I've got about 20 total some need a little help from paint sop Pro. Also when we welded them 3 mo ago I did not have enuff paint to paint them completely. That and living near the coast has made them rusty. please try to overlook unsightlyness.
Max

A bump in case someones looking for it

Here is a pic of the pair I made for my Challenger. I used 2x3 tube and cut the rear to fit the contour of the rear frame back to where the frame starts to go up. Everything that touched the floor I cut through. The rear frame rails come up at an angle so I heated the rear of my connectors and tweaked them so they would follow the line of the factory frame but go straight forward to the torsion cross member.

Hey thanks for the ideas, very helpful!

Yesterday I tried to get a head start on the prep work and scraped most of the undercoat off the areas we'll be working on. Now it appears they won't interfere with the ribs in the front floor section once the undercoat is scraped off, and I can live with them running through that short section. That's just a first impression, we'll see if I'm right after we take some measurements and possibly string it/maybe snap some lines.

It also looks like....if a person really wanted to go wild with this idea, 2x4 wouldn't be out of the question it would have to run through the entire floorpan front to rear though. But that's really more work than I want to do, and probably overkill.

Cut it tight Zippy. I had to use my jack to gently reaise the sub-frame while I used a block of wood to tao the floor down around the sub-frame to get it in place. That picture is kind of dark, just about where the picture ends towards the front is where the subs quit going through the floor.

Eric

Well, Rich came over today and we put her in the air (jack) to have a look. I think we've decided to cut the rear pans, and run them upright. We marked the pans and where the connectors will meet the torsion x-member. Now all that needs done is for the brake and fuel lines to be rerouted. We will window the rear rail and slide the sub into it. Also I will punch six or so holes on the sides of the rear rails to weld through to the sub. As for the front, I will be welding a plate to the front of the sub (probably a 3x5) where it will be attaching to the torsion x-member. That should eliminate any possibility of the sub tearing/twisting away from the x-member.
I think I am going to set up the hoist so I don't have to weld on my back.(was waiting to paint the new floor before installing the two post hoist) Did I mention I HATE welding on my back ???
Pics will follow, along with measurements for future projects
Todd

Well................

I started on it today.

The original idea didn't work!

I wanted to run them through the rear footwell only, and it looked as if we could just massage the ribs in the floorpan to get it to clear in front of that.

So I had the rear cut, and everything was looking fine, and I started to flatten out a couple of the ribs ahead of the cut. It turns out that I couldn't flatten them out enough, and the hammer tore holes through the metal where I tried to dolly it . And after tearing through w/the hammer in a couple spots, I gave up on that idea and trimmed it up straight.....but now it is a loose fit in that one area

The back section is a tight/force fit for the first foot or so, and the floor has to be tapped with a hammer to get it to sit flat. So that part went perfect, but the very front part will either need some filler material or additional passes with the mig. You have plenty of wire and gas, don't you Todd???

I should be able to do a better job on the other side now that I know what's going to happen, and am going to get on that tonight/over the next couple days.

Should be pretty beefy when it's done

They're in !! Just a little touch up on a few welds, and all done. I took a decent number of pics, but I haven't the slightest idea how to post 'em. anyone care to advise.
Todd

Now complete with paint+ a little undercoating. Trying to get ready for the track Saturday.

I am glad we did them this way, they're really integrated with the car and are going to act more like double rocker panels.....as opposed to a separate piece.

Todd, you da man, thx again for all the welding

IIRC, on unibody Mopars the actual rocker panels are stressed members of the chassis(note where the LATERAL boxing of the rear subframe is on a Hemi car.) The rockers are not tube steel, but they are rolled, double wall steel which are quite strong unless compromised by a significant side load. If this were not the case, a Mopar would collapse like a beer can if it were hit in the side, no?

Therefore, it is logical that on a unibody the further out you reinforce the perimeter, the more effect you will have on minimizing the torsional, or twisting motion. I suggest that with regard to torsional strength, thinner tubing further out from the center can be more effective than larger tubing closer in. The closer to the center, the less effective it will be. Beaming rigidity and compression forces (certainly the main considerations in a rigid foundation in terms of a roll cage) benefit the mostfrom subframe connectors, torsional rigidity is enhanced with a roll cage primarily through the cross bracing BETWEEN the subframe connectors.

A unibody is just that, it's more likened to a monocoque design. That means the roof and floorpan are also major contributors to the strength. A good basic understanding of these can be found in Herb Adam's 'Chassis Engineering' book.

Roll cage issues aside, I've often reasoned that long-Double heim joint adjustable bars (with anchors welded to the subframes) could be lighter and more effective (by being able to adjust preload side to side) than standard subframe connectors. Never got drunk enough to try it though

Wize

Wize, all of the Mopar rockers I have seen have been two "halves" spotwelded together top and bottom, just like the rest of the car. The one difference I noticed is the thickness of the steel in the rocker sections. and they do crumple like a beer can when hit, more so on new cars. as was the case with the girl who died when she hit the back of my truck

I do agree with the theory of the torsion relative to the placement of the connectors (inboard/outboard), but am totaly cornfused by the idea of a heim joint for torsional control, as a heim joint by design allows for rotation. There are numerous ways to attack this situation, but Rich wanted an easy, economical, and upgradeable (rollcage, ladder bars, etc.)way to acomplish the task.

We welded the connectors as an extension of the rear frame rails, up to the trans x-member. They slip ~6 inches into the rear rail, I then windowed each rear rail in 5 spots on each side (10 per rail)and welded through to the connectors. Up front, I capped the connectors with a 3x5 plate wich in turn is welded to the x-member ~ 2 inches inboard of the front rails. The floor pans were also welded to the conectors. When it was finished, we jacked the car from the front sub, just behind the tire and the whole side of the car lifted with no flex, where there was mucho before !! That's all I needed to see

Thanks for all the great suggestions,opinions,and help as well as the pics. I have many pics of the installation, but no server to host them. If anyone would like to see them, PM, or e-mail me or Rich.

Todd

I figured the Heim joint would get ...uhhh, mis-understood

What they would do is allow the existing frame structure to be pre-loaded and the inherent stresses on the chassis adjusted. This is similar and works along with how we Cross-weight the left front torsion bars and right rear shock. Adding subframe connectors will stiffen the entire chassis (albeit IMO not in the ideal places for up to a ~11.50 car) where as I want to allow the left front to flex a little; but not so much that it rips the welds out of the 1/4 panel-roof joint.
I'm not supplementing the beaming strength of the chassis (as a frame connector does), I submit that fore to aft the chassis is inherently strong. I merely looking for a way to find lateral tuning (the torque reaction of the MoPar chassis is very well understood already) and limiting/adjusting (for track conditions) torsionally what is already there.


The rolled steel rocker panels give adequate beaming strength, but mainly due to them being
"supplemented" by the inner skin of the unibody. The rear channels (parallel to the leaf springs)where the typical subframe connectors are roll/formed as well; they are not tube steel channels as many people might think. Unless they are compromised by external forces (such as a perpendicular side load like a crash), they are quite strong.

Also, something many people mis-conceive about MoPar unibodies is this: The front inner fenderwells are actually stressed/integral components in the sub-frame. They are light and are much stronger than many people realize. When you cut them out and replace them with tube steel welded to the firewall, all the mass of the K-frame, motor and suspension is now directed straight to the firewall. This is preferable in a full cage equipped car (as the roll cage itself cross braces and provides rigidity throughout the chassis)but again in doing so you have altered all of the dynamics of the chassis.

Again, the Herb Adams book, particularly the latter chapters discussing Monocoque (more likened to Uni-CHASSIS than UniBody) is particularly enlightening. In short, converting a unibody into a ladder frame car has some advantages(particularly in beaming strength), but also has disadvantages.

I've always been kind of Out-of the box with regard to chassis design, I've been fascinated ever since I saw the MoPar "wire car" pro-stock back in '74.

Wize

This easily one of the best threads I've seen here! My question... anyone try a triangular section for chassis stiffening? I thought it would be the structure with the highest resistance to flexing. I can see difficulties in welding it to a non-flat surface. Any thoughts?