I am really surprised this didn't kick up

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This stuff is all way over my head but it brings to mind a test i read in the late 90's involving pick up trucks.They put a brick under the right front and left rear of each Ford, GM, Mopar and Toyota.At the time the Toyota was the only one with a boxed frame AND the only one they could open and close the tailgate on. None of the big three had any concerns about frame flexing. You could put a canoe on racks in the box and watch it move independently of you in the cab.Those trucks were overloaded, used and abused many times during their life and probably all fine for years i'm sure.
 
I'm a streeter. The speed limit is 65mph. I have about 437 hp according to the 93mph Eighth mile trapspeed. Yes on 1.03 bars, 1.125 swaybar, HD springs and shocks, and Big N Littles.
But no frame connectors, And since I never had them, I can't miss them. The only body mod is, I got the body guy to continuously weld the front floor to the back floor on both sides.
Could the car be stiffer? sure, but 90/95% of the time I'm behaving myself, so ......... My car won't be getting them anytime soon.
Besides, I've learned to appreciate the flex in certain situations; it's a street car, and was a DD for many years.
 
An A body is built the same way as a B body.
So stretching the B body car doesn't allow "too much" flex in a B body between the front and rear then?
If a car has frame connectors there is more holding the front and rear together than just the rocker panels.
Would I go to the trouble of adding them to my daily A body?
Probably not just because of down time and work.
But if I've already got them in a B body, I'm leaving them in.
The car is almost 50 years old.
It's flexed enough over the years already.
That's the way I'm going to look at it.

You're already making assumptions. You have no idea if an A-body is stiffer than a B-body. Yes, they're both unibodies. But let me ask you, which one has the longer span between the frame rails?

On my '72 Challenger, the length between the frame rails is almost identical to the length on my Duster. And you know what that means? It means that the span on my '71 Dart is longer. That's right, my '71 Dart has longer frame connectors than my '72 Challenger. And even longer frame connectors than a 70-74 Barracuda, because their subframe connectors are even shorter than the Challengers.

And what's the width? Well, the B and E body cars have wider frame rails. Which completely changes the math. The frame rails don't have the same cross sectional areas either. Which changes the math again. You can't say that a B or E body has more flex just because the car was bigger. Roof height and length make a difference too. There are too many variables to make basic assumptions like that.

I'd put subframe connectors in ANY Mopar I intended to drive.

This stuff is all way over my head but it brings to mind a test i read in the late 90's involving pick up trucks.They put a brick under the right front and left rear of each Ford, GM, Mopar and Toyota.At the time the Toyota was the only one with a boxed frame AND the only one they could open and close the tailgate on. None of the big three had any concerns about frame flexing. You could put a canoe on racks in the box and watch it move independently of you in the cab.Those trucks were used and abused and were probably all fine for years i'm sure.

You're right, this is all way over your head.

Even in your own comparison, you don't have nearly enough facts to have an informed opinion. You don't even know that the big three didn't have concerns about frame flex. I'm sure they did. But more than likely, they decided their product would last long enough that they wouldn't get sued to the point of not turning a profit. They figured the truck would last long enough to be replaced by the next one, not necessarily that they made the best product.
 
Thats good info thanks for sharing that!! He convinced me! One step I can skip now. I had planned on doing the frame connections

I'm guessing you got the disagree because of the extras. it wasn't a simple "thanks for sharing". I disagree with most of your post. Starting with "thats good info"

Connectors are a good idea and the car will drive more solid. Your car, your choice.
 
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So let me see if I got this right, "to stop the spot welds from work hardening you want the body to flex." His assumption is (I guess) that flexure stress relieves the weld. I guess I need to take statics, dynamics and strength of materials over again, I must have missed those dissertations regarding weld work hardening. The one thing that flexure will do over time its cause the weld to fail, guaranteed. Flexure will work harden the weld, make it brittle and cause failure. Classically the weld fails at the weld in the heat affected zone if not the weld nugget itself. And I know that because I have actually run those spot weld failure tests in a lab to test spot weld failure in "U channel" sheet metal, which closely approximates floor pan sheet metal spot welds.
I agree with the rest of you who question the validity of the video.
 
So let me see if I got this right, "to stop the spot welds from work hardening you want the body to flex." His assumption is (I guess) that flexure stress relieves the weld. I guess I need to take statics, dynamics and strength of materials over again, I must have missed those dissertations regarding weld work hardening. The one thing that flexure will do over time its cause the weld to fail, guaranteed. Flexure will work harden the weld, make it brittle and cause failure. Classically the weld fails at the weld in the heat affected zone if not the weld nugget itself. And I know that because I have actually run those spot weld failure tests in a lab to test spot weld failure in "U channel" sheet metal, which closely approximates floor pan sheet metal spot welds.
I agree with the rest of you who question the validity of the video.

Only one failure mode is considered in the video and even that isn't addressed properly, I agree.

As you clearly understand there are multiple modes for the failure of a structure, too much flex is just as bad as not enough.
 
You're already making assumptions. You have no idea if an A-body is stiffer than a B-body. Yes, they're both unibodies. But let me ask you, which one has the longer span between the frame rails?

On my '72 Challenger, the length between the frame rails is almost identical to the length on my Duster. And you know what that means? It means that the span on my '71 Dart is longer. That's right, my '71 Dart has longer frame connectors than my '72 Challenger. And even longer frame connectors than a 70-74 Barracuda, because their subframe connectors are even shorter than the Challengers.

And what's the width? Well, the B and E body cars have wider frame rails. Which completely changes the math. The frame rails don't have the same cross sectional areas either. Which changes the math again. You can't say that a B or E body has more flex just because the car was bigger. Roof height and length make a difference too. There are too many variables to make basic assumptions like that.

I'd put subframe connectors in ANY Mopar I intended to drive.



You're right, this is all way over your head.

Even in your own comparison, you don't have nearly enough facts to have an informed opinion. You don't even know that the big three didn't have concerns about frame flex. I'm sure they did. But more than likely, they decided their product would last long enough that they wouldn't get sued to the point of not turning a profit. They figured the truck would last long enough to be replaced by the next one, not necessarily that they made the best product.

You are right
I assumed a B body was longer.
My bad.
 
Its been a long time since I thought about the failure mechanics of steel or sheet metal, but as I remember it, all materials go through the same failure mechanism, (72bluNblu and others, feel free to correct me) material stretch and return to equilibrium with a 2% offset (commonly called relaxation), plastic deformation, some form of hysteresis, work hardening and ultimately failure. All those functions can be diagramed and explained in classic engineering stress strain curves. Some materials such as glass have properties with stress strain cures that are quite short, while materials such as carbon steel have properties that can be manipulated to make the steel ductile, tough, hard, etc.
The strength of the unibody is determined, in part, by the number, size, and placement of the spot welds. In todays cars some spot welds are being replaced by adhesives specifically designed for automotive use which are structural in nature.
 
Why are people putting a red disagree on the first post ?

It's not my video, I am just asking what you guys think. People who disagree with the video are red marking the post not the video.

I posted it because I am not sure what to think on subject and wanted some input
 
Why are people putting a red disagree on the first post ?

It's not my video, I am just asking what you guys think. People who disagree with the video are red marking the post not the video.

I posted it because I am not sure what to think on subject and wanted some input
I think when you asked "what do you guys think?" - they are saying "we disagree" by hitting the disagree button. It's not you they are disagreeing with, but the video.
 
I think when you asked "what do you guys think?" - they are saying "we disagree" by hitting the disagree button. It's not you they are disagreeing with, but the video.

Correct assumption and hypothesis... unlike that video. :thumbsup:
 
Ok ,I'll throw my hat into the ring. I've had 3 street driven cars with subframe connectors.Never once did I see,feel any difference in the ride or whatever.
I've been doing this stuff since 1965. We all have opinions.
I do watch Uncle Tony on You Tube and this one did throw me when I saw it.
 
And why were the early "post" 2 door much more popular among racers.... Yep, that's why... the post created structural rigidity.

Torque boxes are like tits on a boar.... band aid on a cut artery.A cheap, minimally effective, easy to install on the assembly line improvement of the original design. Nothing more. They do the EXACT same thing that a connector does except over a smaller area. They apply load to a greater contact patch.

Even 13-15 second cars can benefit from frame connectors. Just because Mopar didn't do it doesn't discount the benefits of connectors. Drive a car before and after, close the doors before and after (especially if the front rear are on opposing slopes), the cars feel more solid and responsive when driven.

Any potential drawbacks are killed in spades by the benefits. End of story.
So would a 2 door post still need connectors or is it ready for 440 torque as is?

1D8EE846-7AE1-491F-A830-C65575A71094.jpeg
 
I was super confused as well by the "body needs to flex or the spot welds will work-harden" comment by Uncle Tony. Things work harden by moving that's why it's called WORK harden, pretty sure he's got it backwards...

Also I'm a huge fan of UTG but after watching a lot of his videos it's clear he doesn't have a background or interest in making cars handle, just old-school drag racing. Which is fine but not everyone is building their Mopar for that.

So would a 2 door post still need connectors or is it ready for 440 torque as is?

View attachment 1715363288

I would definitely still add subframe connectors. I doubt the posts add as much rigidity as connectors do.
 
I've got subframe connectors on my dart and to my surprise when I jack the car and put it on stands the body still flexes. So what do you suppose is going to happen when you put the loud pedal down with that big, honking, torquey 440? You're going to have more stiffness with that 2 door post (great car, by the way, I like it) but certainly subframe connectors will help. Be sure to weld them to the floor pan, not just the end points.
 
I've got subframe connectors on my dart and to my surprise when I jack the car and put it on stands the body still flexes. So what do you suppose is going to happen when you put the loud pedal down with that big, honking, torquey 440? You're going to have more stiffness with that 2 door post (great car, by the way, I like it) but certainly subframe connectors will help. Be sure to weld them to the floor pan, not just the end points.
I bought this car from a fabo member. He had it for sale for a long time on fabo and fbbo and I can't believe he didn't sell it right away. It's much better in person than in pics. Fabo rocks
 
I put cheap DIY frame connectors on my 65 and I can jack the front from behind the wheel and the back comes up with the front now. Its almost like a full frame...and the door closes fine even when its jacked up. try that on a flexible flyer.
 
Heck the reason the pentastar is only on the passenger side is the bean counters and marketing arguing over the cost to put them on every car. Marketing wanted it on both sides, bean counters didnt want it on there at all. In the end they both conceded. The star would be passenger side only since its curb side, only half the costs.
Yes. Not many people know this.
 
Besides the subframe connectors I ran the forward strut connectors to stiffen the car and they tie everything together chassis wise. Besides, I love the "gee wiz" factor when people look at the engine bay at the car shows!
:lol::thumbsup:

Ov6AnPkuQ9m66yVwLmgr6Q.jpg
 
Hey there are 20ish people that think that video is not good. Can't believe 1300 think it's good.

BTW, I'm a French model! :rofl:

This response to a detractor says it all... and the answer is that you STILL have to put the rocker on anyways.

"Then why was it engineered in, in the first place. The factory could have just as easily taken the extra metal in the rockers and moved it inboard ten inches to complete the frame as single pieces. You clearly don't understand basic car construction."

Smug dickish answer. You're too stupid to understand.... Well done there.

Some of the answers about wings breaking off planes are ridiculous. Why do planes have inspections at flight hours over their useful life? Yeah so those wings, bulkheads or engines don't break off and crash the fricken thing due to FATIGUE!!! Stick to your thesis, no matter the evidence/engineering basics to the contrary.
 
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I watch the "how cars are made" stuff on MT. Intresting. Everything from every foreign exotic to even a Chevy Camaro!!!! Makse a difference if making a $200,000 Porche or a $30,000 Camaro!
I still say domestic makers of run of the mill cars, back in the 60's and beyond, do anything to save a penny and make another buck.

I wonder why pickups an big trucks still use a full frame and not a unibody?
 
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