I am really surprised this didn't kick up

-
hasn't been mentioned but would be good for a daily driver' compromised by
frame, body, floor, quarter, rot,rust and damage.
 
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I happen to have a 66 B body and a 74 A body on jack stands right now.
So, I slithered under them and did some quick, dirty measurements if anyone is curious.
I'm sure people could find actual Chrysler drawings somewhere.

The A body measurement from the trans cross member frame to the rear frame rail first point of contact (rear frame rail forward flange) is 36.5 inches.
This would be the area that the rocker panels span.
And it measured 33.5 inches from one rear frame rail to the other across the car.

The B body measurement from the trans cross member frame to the rear frame rail first point of contact (rear frame rail forward flange) is 39 inches.
Again, this would be the area that the rocker panels span.
And it measured 34.5 inches from one rear frame rail to the other across the car.


The rear frame rails on both the A and B appear to be 4.5 inches in height.
The gauge of metal APPEARS to be the same on both cars.
I didn't have time to try and measure that as it would be more difficult.

But what was surprising is that the B body rear frame rail was actually narrower than the A body.
The A body is 2 5/8 inches wide.
The B body is 2 1/4 inches wide.
I had to measure that twice to be sure.


Now admittedly there probably are other factors to consider.
Like is is assumed the B body rear for a given type would weight more.

And the B body is more likely to have a high torque heavy motor twisting the front to rear.
All this points to me sticking with my previous assumptions.


20190715_103945 (Large).jpg
20190715_104226 (Large).jpg



How I measured this.

20190715_104321 (Large).jpg
 
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Interesting that the folks that support 'what is he smoking Tony' could not come up with and write on this forum an explaination of the work hardened welds and how adding sub frame connectors adds stress to the existing unibody chassis.

Since you can't, I can list out a simple visual that shows how inept "what is he smoking Tony's" thought process is on this subject.
1) In your mind visualize a common 2x4, ten feet in length, that has each end of the 2x4 suspended on a cement block.
2) Now in your mind, add a common bathroom scale between the 2x4 and the cement block at each end of the 2x4.
3) Now position the 2x4 so the wide cross section of the 2x4 is horizontal and parallel to the ground that the cement blocks are setting on.
4) Then position your body so you stand on the 2x4 centered between the two cement blocks.
5) The 2X4 will bow down due to your weight.
6) the combined weight on the two scales will be your weight + the weight of the 2x4, regardless of the bow, unless the bow is so large it contacts the ground.
7) Now get off the 2x4 and re position the 2x4 so it has the narrower side horizontal and parallel to the ground.
8) Position your body so it is centered on the 2x4 on the scales on the cement blocks.
9) The same 2x4 will bow less than it did in the previous test, due to the more rigid cross section of the 2x4 bearing your weight.
10) The combined weight on the two scales will be your weight + the weight of the 2x4, the same as the test in #6, even though the deflection
is much less.

The point of this exercise is that, for a given load, reducing deflection does not increase loading at the end points. Deflection and end point loading are two different issues. Reducing deflection is good in that reducing deflection does reduce the possibility of mechanical failure due to bending fatigue.
Visualize , how many times do you think that you can jump up and down on the bowed 2x4, from the first example before it breaks.
And how many times can you jump up on down on the not as bowed 2x4 in the second example before it breaks. The truth is the not as bowed 2x4 will survive a lot more stress cycles than the bowed 2x4, with the same loading.
 
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Connectors help transfer the load over a WIDER area, not a smaller one. Stresses radiate for epicenter, IIRC.
 
2x4 cars.
In days of old when men were bold and ...
Wait.
I better not finish that limerick

How about this instead?
In days gone by men were made of iron and ships were made of wood.
Now , we have ships made of iron and men made of wood.
 
I understand but with my old big block 69 Coronet Rt and various other BB block B bodies that had twisted, I like them better NOT twisted and therefore maybe with sub frame connectors and even torsion boxes.!
 
I had an actual electrician tell me that water doesn't conduct electricity but just the metal pipes it runs through.
Uhh huh, hold this wire.:lol:
We were always taught you are safe with a solid stream hose line with in 10" of a power outlet. But I never tested that theory
 
Concerning where stresses concentrate,,
Will be at a notch, groove, a sharp angle. Definitely not at a circular spot weld.

And the levels of stress transferred are reduced whenever it changes planes. rocker, strut, rail... you have two plane changes minimum. A stress chicane... LOL
 
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Useto be if my car was on jack stands you couldn't open or close the doors.

12 point cage and frame connectors. Now i can lift it from one point anywhere on the frame and the doors open and shut nice as you please.

I want all the force to hit the tire not dispersing through the frame.

I will agree tony is a super smart guy and a pleasure to deal with. Like Rany said, he would be welcome to drive my car and wouldn't have a worry about it.
 
I will agree tony is a super smart guy and a pleasure to deal with. Like Rany said, he would be welcome to drive my car and wouldn't have a worry about it.[/QUOTE]
And I have a brother in law that is a super smart nice guy, but is also a moron when it comes to the real world. I admit that I have only watched 3 of the ‘what is Tony smoking’ videos.
1)The slant six part one where he brags about welding a 7 1/4 spider gear and ends with a weak street burn out. If that appeals to you, ok, but what are you going to do after you graduate from 6th grade?
2) the Slant Six part 2, where he does not have the sense to get out of the rain, and brags out on a primer-faded Dart.
3) the lead off video in this post, where he absolutely endorsed loosely goosey chassis.
So I may be a bit biased, but he comes off to me as someone that sprouts tribal knowledge as his own new enlightenment. And his own lame brand of engineering theory as astute physics.
I ain’t impressed, I know snake oil when I smell it.
 
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Everyone on here is right about what they have posted. The only thing missing is from the engineering aspect of the unibody design. Safety was built into the design, body's were crash tested and studied for collapseing, we got collapsible steering columns and such, these bodies were studied for taking the shock of a crash, its suprising how similar unibodies are today compaired to the early ones. You would think stiffer is better in a crash, but not so when it comes to metal compressing and folding up.
 
I happen to have a 66 B body and a 74 A body on jack stands right now.
So, I slithered under them and did some quick, dirty measurements if anyone is curious.
I'm sure people could find actual Chrysler drawings somewhere.

The A body measurement from the trans cross member frame to the rear frame rail first point of contact (rear frame rail forward flange) is 36.5 inches.
This would be the area that the rocker panels span.
And it measured 33.5 inches from one rear frame rail to the other across the car.

The B body measurement from the trans cross member frame to the rear frame rail first point of contact (rear frame rail forward flange) is 39 inches.
Again, this would be the area that the rocker panels span.
And it measured 34.5 inches from one rear frame rail to the other across the car.


The rear frame rails on both the A and B appear to be 4.5 inches in height.
The gauge of metal APPEARS to be the same on both cars.
I didn't have time to try and measure that as it would be more difficult.

But what was surprising is that the B body rear frame rail was actually narrower than the A body.
The A body is 2 5/8 inches wide.
The B body is 2 1/4 inches wide.
I had to measure that twice to be sure.


Now admittedly there probably are other factors to consider.
Like is is assumed the B body rear for a given type would weight more.

And the B body is more likely to have a high torque heavy motor twisting the front to rear.
All this points to me sticking with my previous assumptions.


View attachment 1715363874 View attachment 1715363875


How I measured this.

View attachment 1715363876

Remember there are 111" and 108" wheel base A-bodies, and the difference is in the floor between the ends of the frame rails. B-bodies are also quite different by year and model. Quite frankly you've made too many assumptions already. The engine thing makes no difference either, remember that A-bodies got Hemi's and at the design stage a big block powerplant would have been considered. The chassis didn't change when they stopped doing factory big blocks.

Honestly I shouldn't have bothered measuring my E-body, it's not a relevant discussion because there are simply too many more variables to consider. The simple fact of the matter is that the number of ribs molded into the floor pan makes a difference in how stiff the car is. The length and height of the roof, the width of the C-pillar, the height of the kick up for the rear axle, the track width and distance between the wheels and the springs, etc, etc, etc.

So, your assumptions are exactly that, assumptions. Your assumptions aren't good ones, because as you put it yourself, there are "other factors to consider". Well, those "other factors to consider" have at least as much of an effect, if not more, on the strength of the chassis as the couple of measurements you took. And that's why this discussion is so silly to begin with. We have a bunch of people, many of whom have no education or training in structural analysis, providing commentary on a subject that is more complicated than they could possibly know. Engineers trained in structural analysis don't make half assed guesses about how strong a structure is, they do a finite element analysis and actually get the facts. The reason for that is that there are plenty of structures that "look good" that fail. Literally every stamped feature in the sheet metal has an effect on how strong the uni-body is overall, even the relatively simple unibody structures of these cars have hundreds of relevant variables.

Everyone on here is right about what they have posted. The only thing missing is from the engineering aspect of the unibody design. Safety was built into the design, body's were crash tested and studied for collapseing, we got collapsible steering columns and such, these bodies were studied for taking the shock of a crash, its suprising how similar unibodies are today compaired to the early ones. You would think stiffer is better in a crash, but not so when it comes to metal compressing and folding up.

The design and construction of these cars is RADICALLY different than a modern unibody. The only real thing they share is the fact that they're both unibodies. The crash performance on these old cars isn't comparable to modern designs, the level of engineering and analysis is on a completely different level now. Even modern unibodies have changed dramatically in recent history, look at the first time that the Insurance Institute for Highway Safety included an 40% offset frontal crash test in 1995. The performance of cars that were considered safe the year before was abysmal. A few years later, many makes and models were performing quite well in the same test. In 2012 they came up with a new 25% offset test, same deal again. Even some cars that performed well in a 40% offset crash did poorly in the new test. But the designs that take that new test into account perform better. And to the untrained eye, those chassis' don't look any different at all.

And as I said before, the safety that was designed into the chassis on these cars was based on how these cars were equipped from the factory. As soon as you start changing things, the amount of power, the amount of traction, the factory design is no longer ideal (assuming it was in the first place, which is a big assumption). I can absolutely guarantee that the factory engineers would not have put out the same design if they had intended these cars to have radial tires. You know why? Because they changed all the designs when radials became factory equipment a few years later.
 
I hate to say it, but every post in this thread except one is off base. Please follow along.

Of all the Uncle Tony videos, this one is the only one that I disagree with.
I seriously doubt that any engineer would purposely design their cars to flex.

It's not so much that they do, but that they try to accommodate what they know will happen anyway. You have to acknowledge it and account for it. Kinda like....the plunge coupling on a steering box.

Oh boy. Well, I'll start off by saying- it's on the internet, so it must be true right?

So, this concept that the factory engineers knew best. First off, they didn't. The greatest engineering minds weren't working in the auto industry in the '60's.

Technically, some of the greatest engineering minds of the '60's were working in the automotive industry; they just weren't working directly on automotive projects. We didn't get to the moon on a Chevrolet rocket....

This guy is only partly right- he needs to go to engineering school. I have been involved with motocross since the '60's. Those who really want to understand chassis stresses and flex and their effect on suspension and handling need to get educated. Beware this guys advise.

Having been through engineering school, I can tell you that 99% of engineers do not understand as much as Tony. He just doesn't do the math problems associated with it. Many engineers can only do the math, and understand very little.

This is like all the arguments about which kind of subframe connectors are best too. Until someone runs a finite element analysis, no one here can actually know.

Run it through FEA and it will correlate with what I explain below.

I guess one clue to this, is what is done to Nascar and the big time drag cars? Rigidity, safety, performance...

Apples and oranges, man.

For those that say ‘What is he smoking Tony’ provides good information,, I want to know more about those spot welds that get work hardened after sub frame connectors are installed.
Walk me through the physics of how a spot weld, that is already harder than the surrounding material gets ‘work hardned’ by removing flex.

See below.

I wonder if maybe he's talking about metal fatigue from the flex. Since the spot welds are already harder....and they are.......good point........maybe he means they get metal fatigue from having to carry more load from the added connectors? I know......I'm reaching here but that's all I can think of.

As usual, this non-engineer (at least to my knowledge) gets it more than most. Say it ain't so.

I had an actual electrician tell me that water doesn't conduct electricity but just the metal pipes it runs through.
Uhh huh, hold this wire.:lol:

Clean, pure water doesn't conduct electricity. Salt water does. When you stick your hand in, the electrolytes from you skin create conductive water, but I digress.

********************

What Tony is trying to say here, but not being concise about, is that subframe connectors DO reduce flex, but that the forces that create that flex don't magically disappear; they are distributed elsewhere.

When we study sheet metal structures, we have to look at what happens when forces are applied. A rectangle is free to become a parallelogram as soon as the material gives at all. This is why a triangle is the strongest shape: It has no sides that are free to move, and only making a side non-linear will create a change in shape. This change in shape is what we are totalling up with the term 'rigidity'.

The key to maximum rigidity in any sheet metal structure is 'boxing'. If it's a cube, but open on two opposite sides, it's still going to fold where the remaining sides meet. Add a sheet to one side, and the other side will still try to fold. Add to the remaining side and you've max'd the strength for that particular shape. This gets into tetrahedrons, four-sided pyramids vs. three-sided pyramids, etc., that I won't get into, but if you picture it in your mind, you should be following along.

Still struggling? Go get a new box of cereal, and try to 'flex' it. Then open it, and try to flex it. Then open the other end, claim the prize, and try to again flex it.

If we look at the basic unibody of a Chrysler muscle-era car, it's a big rectangle and it's open on opposite sides: The passenger compartment. The doors contribute nothing to structure, even when closed, unless the flex is severe enough for the body to hit the door. Onto this rectangle, we have grafted two other rectangles: The front and rear subframes. These sub frames are heavily boxed, quite rigid, and assembled using almost exclusively spotwelds. They're rigid is as rigid does, and they're also where the suspension mounts. Think of the suspension as the 'input' for forces into the structure.

The passenger compartment, along the rockers, has some spotwelds but we're using the rockers to 'box' the floor section. It's still way weaker that the subframe sections, but it's strong enough to carry the load even without the roof, as in a convertible. The factory will still beef it in a convertible through torque boxes (there's that cereal box again), but it'll hold if we cut the roof off.
Proof: http://www.imperialclub.com/Articles/EBerg/EBerg5.jpg

Let's go back to the cereal box. Open the top, and flex. The sides don't move straight. It twists. Remember this.

Remember also that coat hanger that you flex repeatedly. It eventually (work hardens and) breaks.

In your front and rear subframe sections, the body is not fully boxed. It also twists. This twisting is what's stressing the hell out of those spot welds. This is what Tony is referring to in his video. Hit a bump on the front right, and every spot weld in that neighborhood gets twisting force (among others) applied to it. The suspension absorbs some load, but force in equals force out, and the chassis still sees the resultant force.

If you've ever spotwelded, you know it's not hard break them by twisting; that's usually the fastest way to break them.

So, what Chrysler has done is to effectively direct this force to an area where flex is ok: In the middle of the passenger compartment. The center 'box' is flexing to relieve some of the force applied to the subframe body sections. The mid-body cracks cited earlier show this, in all it's glory. You can flex the middle and it's free to twist and flex and there aren't any critical structures there that could catastrophically fail. In fact, the long span means more flex with less force applied to spotwelds in those areas, because the force is distributed in the flexing of the metal as well as being applied to spotwelds.

Stiffen that up, and those suspension loads aren't going away. We know it's stiffer; we can feel it. But the loads are still there, and our fatass torsion bars, mega shocks, and lo-profile badass tires aren't helping. They're transferring more loads to those not-very-well-boxed sub-frame body sections.

In other words, exactly the opposite as Chrysler intended. And exactly as Tony is describing.

TLDR: Chyslers' intent is that the passenger-compartment (Danger: Engineer lingo ahead) becomes a stressed member instead of something that's simply holding the front suspension to rear, as rigidly as possible.

Please note, I make no comparison to modern cars, and I make no comparison as to what's 'better', although I agree with Tony and I still consider subframe connectors on a car I don't drive much.

Edit: the imperial in the link above does not apply, as I just realised it is body on frame. I will update with a photo of a decapitated unibody as I find one.
 
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Without a doubt, new unibody structures are designed completely different, and even the metallurgy in the structural components as well as exterior panels is completely different. Light-weight high-carbon content steel replaced the older conventional stuff, starting in the late '70's-early 80's, and half of the exterior panels are glued on a lot of these modern bodies.............
 
Gosh thanks.......I think? lol

It is a compliment in the highest regard, and also meant to point out that a person's education or employment is not an indicator of intelligence. I don't know your education, but I know you're not an engineer.
 
It is a compliment in the highest regard, and also meant to point out that a person's education or employment is not an indicator of intelligence. I don't know your education, but I know you're not an engineer.

That's very true, I am not. I'm just an old redneck mechanic.
 
I'm reminded of a wrongful death trial that I was on some 25 years ago or so.
I opened my big mouth in deliberations and the ladies made me jury foreman.
By the time of the trial the death car had already been crushed and was not available for examination. It was an older car of some type. Late 70s I think.
Still, the expert witness for the plaintiff made conjecture about what speed the other car was traveling when it hit the death car.
The trial did not end in the plaintiff's favor.
We all make assumptions every day to get through life.
 
Just going to toss this into the discussion... my MP Chassis Manual has a section on structural chassis mods and covers subframe connectors. It's mentioned as something you should do to any Mopar you intend to modify for performance. If the factory engineers didn't think it was necessary or beneficial (or would potentially compromise other parts of the unibody structure) I don't think it would have been published in those books (written by Chrysler engineers) for the past 40-some years.
 
Stiffen that up, and those suspension loads aren't going away. We know it's stiffer; we can feel it. But the loads are still there, and our fatass torsion bars, mega shocks, and lo-profile badass tires aren't helping. They're transferring more loads to those not-very-well-boxed sub-frame body sections.

In other words, exactly the opposite as Chrysler intended. And exactly as Tony is describing.

TLDR: Chyslers' intent is that the passenger-compartment (Danger: Engineer lingo ahead) becomes a stressed member instead of something that's simply holding the front suspension to rear, as rigidly as possible.

Please note, I make no comparison to modern cars, and I make no comparison as to what's 'better', although I agree with Tony and I still consider subframe connectors on a car I don't drive much.

You fell into exactly the same trap as Tony. The factory engineering becomes irrelevant the moment you change the load inputs beyond what the factory intended. If you change the load parameters you can't assume the factory design will work as intended. If you want to run around on bias ply's with /6 torsion bars that's fine, but if you don't you'd better re-evaluate the situation.

The flex allowed by the factory was good for the amount of load these cars were capable of putting through the chassis at the time. Increase the loads, and I mean SUBSTANTIALLY increase the loads, and the resulting flex becomes too much for the materials to handle. The distribution of the forces through the factory structures is no longer enough to keep the spot welds from failing. Which is exactly why you get the mid-body cracks that show up on these cars, as you correctly describe. Because the distribution of those forces is no longer enough to keep all the individual spot welds within their design parameters.

That means something has to change. The chassis must be stiffened to reduce the flex back down to something that can be handled by the spot welds in the body section. Does that increase the stress on other members? Yes. That's why you're adding material too. Subframe connectors don't just connect stuff, they also add more material to further distribute that load. The subframe connectors themselves still flex. They are absorbing load, and that load is in addition to the factory design.

There are certainly engineers out there that lack the hands on experience of someone like Tony. And that can lead them to make inaccurate assumptions on the design end, I've seen it. But Tony doesn't understand the concepts he's trying to explain, it's obvious from his description of work hardening. Too much flex can cause failure just as quickly as not enough, there is more than one mode for failure.

As for this-
, I'm not sure what you think that "proves". Just because it didn't fold in half doesn't mean it's as strong as it was before, it's not. Ask any 'vert owner if their car has more or less flex than a coupe or hardtop. That poor car would have folded right up if it hit anything, and it would have failed had it been driven any number or miles like that. All that's proof of is that less weight means a faster 1/4 mile time. And perhaps that the floor section of the car is stronger than you give it credit for.

I'm not saying I have all the answers, I don't. But I know for a fact that if I ran my car around with 1.12" torsion bars, sway bars, and 275/35/18 and 295/35/18 tires with 400+ hp and no chassis stiffening I would already have issues with cracks forming at the critical body joints- quarters to roof, rockers to subframes, etc. Instead, after almost 20k street miles I have no cracks. Not at the suspension points, not at the body. That's an indication that the subframe connectors, torque boxes, radiator support brace, seam welded and reinforced K frame, and J-bars are doing their job. Have I hit the "sweet spot" for the chassis? I don't know. It could be too stiff, maybe I will see fatigue cracks show up at the suspension mounts as I continue adding miles. It might not be stiff enough, in which case I'll still see cracks form at the body joints. But I know that what I've done so far is better than nothing, ie, depending solely on the factory engineering to carry the input loads that I've increased substantially by adding more grip and more power.

I'm reminded of a wrongful death trial that I was on some 25 years ago or so.
I opened my big mouth in deliberations and the ladies made me jury foreman.
By the time of the trial the death car had already been crushed and was not available for examination. It was an older car of some type. Late 70s I think.
Still, the expert witness for the plaintiff made conjecture about what speed the other car was traveling when it hit the death car.
The trial did not end in the plaintiff's favor.
We all make assumptions every day to get through life.

Which is why everyday people don't design cars, and why not all "experts" are worth their title.

Assumptions are necessary, even at the engineering and design level. But those assumptions have to be based on good information and must be valid for the conditions. If you don't understand the consequences of the assumptions you're making, they can't be good assumptions. Assuming that the span between the frame rails, by itself, determines the overall stiffness of the chassis is a colossal mistake.

Just going to toss this into the discussion... my MP Chassis Manual has a section on structural chassis mods and covers subframe connectors. It's mentioned as something you should do to any Mopar you intend to modify for performance. If the factory engineers didn't think it was necessary or beneficial (or would potentially compromise other parts of the unibody structure) I don't think it would have been published in those books (written by Chrysler engineers) for the past 40-some years.

Exactly.
 
You fell into exactly the same trap as Tony. The factory engineering becomes irrelevant the moment you change the load inputs beyond what the factory intended. If you change the load parameters you can't assume the factory design will work as intended. If you want to run around on bias ply's with /6 torsion bars that's fine, but if you don't you'd better re-evaluate the situation.

My personal point of view is that I'd rather have the car flex where it won't hurt anything instead of risk damage by altering the fundamental design of the vehicle.

That said, I also said I'd still consider subframe connectors for my car.

Why do I ride that fence? Because I feel that the factory engineering for a pass-car of the sixties was suitable for those roads and conditions (as you allude to) at the time. And I'm in agreement with you that inputs have changed, both internal and external to the vehicle. And as always, end use is the primary concern. You're not exactly using your car in a manner that Chrysler engineers of the time would have considered "statistically significant", just like Ricky Roadracer or Davy Dragracer.

Again, I make no comment to suitability. Just an explanation of why the factory did it the way that they did. Obviously, they had their reasons, and we have reasons we don't do it that way now.
 
My personal point of view is that I'd rather have the car flex where it won't hurt anything instead of risk damage by altering the fundamental design of the vehicle.

That said, I also said I'd still consider subframe connectors for my car.

Why do I ride that fence? Because I feel that the factory engineering for a pass-car of the sixties was suitable for those roads and conditions (as you allude to) at the time. And I'm in agreement with you that inputs have changed, both internal and external to the vehicle. And as always, end use is the primary concern. You're not exactly using your car in a manner that Chrysler engineers of the time would have considered "statistically significant", just like Ricky Roadracer or Davy Dragracer.

Again, I make no comment to suitability. Just an explanation of why the factory did it the way that they did. Obviously, they had their reasons, and we have reasons we don't do it that way now.

I think it all boils down to what you're going to do with the car. Most all of the cars I've built in the past have been down the strip a few times with slicks. IMO, if you do "THAT" frame connectors are a good idea.
 
I can't believe the commotion two pices of square tubing can create.
I can't believe i read posts 152 to 174.
This thread can challenge the 6 inch piece of tubing thread....AKA h pipe!
 
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