I am really surprised this didn't kick up

[MOPAROFFICIAL]

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.

Exactly.
There's a few vids that have been shared that have a very odd take on it's subjects intended function. With very little understanding...people eat it up... like yeah it makes perfect sense they want the whole car to flex, twist and move around...because shocks,bushings,tires dont already do that right...
New cars, the cheaper line... all unibody...full size, the expensive line, some full frame.. bushings better known as insulators dampen the road noise...and not to help the car move around. The more you spend the quieter it gets.... more cashola more rubber between you and the road. While some flex is engineered... I cant agree with the video , the way its stated and relating it to frame connectors anyways.

 

[retroron]

I'm sure corporate, or at least the engineering dept. knew about chassis flex. It's one thing to know about it, but it's an other to deal with it. No computers in those days, everything was computed with a slide rule and the engineering time and cost to do those calculations was extreme. It is strictly a dollar function. I believe that is why frames were replaced with unibodies and why such things as full perimeter unibody frames were omitted. And what everyone has said on this post is correct, the bean counters ruled the roost. Run it on an app? Nope didn't exist.
Back "in the day" I had a 1950 Olds with a 57 J2 engine. Talk about chassis torque! first thing that would happen on launch is the back end (factory coil springs with truck arms) would go skyward until the shocks reached full upward travel, then the fun stuff would happen, some of you "senior' folks may remember that. You could judge how good your launch was by the front end twist. And yes, you could see and feel it. Dick Landy's '65 Dodge used to launch that way too.

 

[72bluNblu]

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.

Funny, when I installed frame connectors on my Duster it was immediately noticeable. More positive handling response, less creaks and groans, doors that open and shut easily even when the car is up on stands. Sure, most of that is subjective, but an objective analysis of that stuff is not simple.

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

View attachment 1715363288

I would still install subframe connectors! Even assuming the post cars are stiffer is a bit of a mistake. The hardtops have a larger span without support, but that was taken into account with the design of the hardtop structure. Now, are the post cars probably stiffer? Probably, but it's still an assumption. And either way not so much that I wouldn't add subframe connectors.

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.

Yeah it's not like a subframe connector by itself can remove all the flex from the car. It can't, the subframe connector itself will still flex. And just adding stiffening in basically one plane can only improve the rigidity of the entire structure so much.

As for welding to the floor pan, gonna disagree. You can't know that. I don't know that for certain. I run tubular subframe connectors on my Duster that are just welded at the ends. I used large landing plates at both ends to maximize the amount of frame rail and crossmember I grabbed to ensure that the subframe connectors act over a large area, but they're not welded end to end. And there's an argument to be made there. MIG weld is more brittle than the surrounding metal. Only so much flex can be eliminated. It would be a legitimate question to ask if a fully seam welded subframe connector like the US Cartool connector doesn't overstress the area of the floor pan they're welded to. I think that long of a seam weld does introduce the possibility of cracks in the pan along its length. I installed connectors like that on my Dart though, so obviously I'm not too concerned about it. But it's a valid question.

I'm totally happy with the 1.5"x3" tubular subframe connectors on my Duster. I'm also happy with the US Cartool subframe connectors I installed on my Dart. And without a full FEA, I don't think you or I can say which one is actually better. Both are better than nothing IMO.

 

[MOPAROFFICIAL]

Chevy pickups early/mid 80's, frames all cracked.

 

[retroron]

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?

Load carrying capabilities and towing. And the trucks are designed to allow for some frame twist.

 

[barbee6043]

Yes the front end comes up, the front end twists and so does the car at the rear also. Then the car sitting on concrete, one side of the bumper is 2 inches higher than the other! Something must have twisted?

 

[famous bob]

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

View attachment 1715363288

Like others have said, I would put them on any thing above a stock 6 cyl. .. I have twisted a B body pretty bad, had to jack the low corner up to get the door to close right , before welding in a puny 4 point bar, it helped tremendously, but wasn`t enough to completely cure it.
If , u drive around w/ a stock 440 and don't push it , u can probly get by w/o it.
A 2 door post is a little stouter than a hardtop anyway. Me, I`d subframe it anyway ! Level ur jackstands if doing it on the floor , especially if ur doors open and close right when leveled.----------JMO

 

[retroron]

Funny, when I installed frame connectors on my Duster it was immediately noticeable. More positive handling response, less creaks and groans, doors that open and shut easily even when the car is up on stands. Sure, most of that is subjective, but an objective analysis of that stuff is not simple.



I would still install subframe connectors! Even assuming the post cars are stiffer is a bit of a mistake. The hardtops have a larger span without support, but that was taken into account with the design of the hardtop structure. Now, are the post cars probably stiffer? Probably, but it's still an assumption. And either way not so much that I wouldn't add subframe connectors.



Yeah it's not like a subframe connector by itself can remove all the flex from the car. It can't, the subframe connector itself will still flex. And just adding stiffening in basically one plane can only improve the rigidity of the entire structure so much

As for welding to the floor pan, gonna disagree. You can't know that. I don't know that for certain. I run tubular subframe connectors on my Duster that are just welded at the ends. I used large landing plates at both ends to maximize the amount of frame rail and crossmember I grabbed to ensure that the subframe connectors act over a large area, but they're not welded end to end. And there's an argument to be made there. MIG weld is more brittle than the surrounding metal. Only so much flex can be eliminated. It would be a legitimate question to ask if a fully seam welded subframe connector like the US Cartool connector doesn't overstress the area of the floor pan they're welded to. I think that long of a seam weld does introduce the possibility of cracks in the pan along its length. I installed connectors like that on my Dart though, so obviously I'm not too concerned about it. But it's a valid question.

I'm totally happy with the 1.5"x3" tubular subframe connectors on my Duster. I'm also happy with the US Cartool subframe connectors I installed on my Dart. And without a full FEA, I don't think you or I can say which one is actually better. Both are better than nothing IMO.

You're right, I don't know that for certain, I was generalizing, a foolish thing to do. Mine subframe connectors are welded full length, but I also have a lowered floor pan and I understand welding well. I was a welding engineer for more years than I'd like to recall. I ran a welder test qualification shop for number of years. I would disagree with you regarding MIG being more brittle, of course a lot of that depends on wire type, feed rate, amperage, shielding and the welder. I've seen MIG welds that bent like rubber, in fact the standard bend test for plate and pipe require the weld to bend over a prescribed radius, but I'll bet you know that ! And to be fair I've also seen MIG weld that cracked like glass.

 

[retroron]

Some people just aren't flexible.
They are like concrete.
All mixed up and set.

I didn't realize you'd met my ex.

 

[crackedback]

Agree w/ ttat, they weren`t computer designed either, makes a big diff. in the chassis !

Cad/Cam has killed some people... Gordon Smiley in 1982 at Indy as an example. My grandfather fixed the front suspensions on those cars after the CAD/CAM got it wrong. Garbage in/garbage out.

The USCartool uses the floor as a sheer plane to spread loads. Is it the best way, not really. But it does spread the load to a different plane with the welds being an area of concern.

If you ever see someone that wants to form a piece of sheet metal, they anneal the sheet with a oxy torch. The heat changes the hardness and chemical structure of the metal slightly to make it more malleable/workable. Less likely to crack when bent, etc. The same thing happens in the heat affected zone on a spot weld, that small area around the weld is more flexible and easier to work harden/crack. Nothing is the perfect solution, everything has a trade off.

 

[retroron]

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!

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.

I must have missed the part about wings breaking off. Aircraft are inspected for cyclic fatigue so as to preclude material failure. Airplanes normally crash because of terrain interference with the flight path or operator error, hardly ever for material failure.

 

[famous bob]

Cad/Cam has killed some people... Gordon Smiley in 1982 at Indy as an example. My grandfather fixed the front suspensions on those cars after the CAD/CAM got it wrong. Garbage in/garbage out.

I meant uni bodies -----todays uni bodies are way better built than our old ones.
Hey I saw a big lincoln continental being hotrod moded, they said it was a unibody back in 1958 / I think. THAT ONE REALLY CAUGHT ME BY SURPRISE! Wonder if its true !?

 

[moparmat2000]

Lots of debatable info.Flex was definately a part of engineering our vehicles.They used to say a Model A would flex through any rough road of the day and that is why their frames weren't boxed.
Think of a long piece of steel and apply weight to the centre...it will form a smooth gradual bend.Now reinforce the centre 50% and apply the weight again and you will probably break the ends off.
I don't think it will matter for the majority of us one way or the other.

Flex was engineered into model Ts and to a lesser extent on model As simply because the roads were mostly rutted dirt paths and horse trails turned into roads. In the rainy season it was like quagmire, when it dried it sucked bsdly. They needed the twist because the roads were soooo bad.

By the time our stuff was engineered the interstate highway system was built, or close to finished in what places that were unfinished. Chrysler touted their "new" unibody cars of the time 50 years ago as a design as stiff or stiffer as a traditional body on frame car with lighter weight, and less flex than traditional body on frame construction. They were all working towards a tighter and stiffer car. This was a relatively new approach to car building. Chrysler went all in. So did Ford. GM kinda tip toed around it.

 

[retroron]

With respect to Model T's and A's don't forget the body mounts used to take up the twist. I can't think of any Model T or A body that could have withstood the twisting on rutted roads of the early 20th century. Having built a couple A's in my lifetime I can also say the tolerances on the car weren't too terribly tight.

 

[crackedback]

I must have missed the part about wings breaking off. Aircraft are inspected for cyclic fatigue so as to preclude material failure. Airplanes normally crash because of terrain interference with the flight path or operator error, hardly ever for material failure.

Simplest answer as why planes crash... Gravity!

Yes, error is a larger factor in plane crashes.

The other engineering deal with early cars was the huge dive the front end would make when braking to give passengers the sensation of stopping quickly, when they really weren't!

 

[moparmat2000]

I must have missed the part about wings breaking off. Aircraft are inspected for cyclic fatigue so as to preclude material failure. Airplanes normally crash because of terrain interference with the flight path or operator error, hardly ever for material failure.

Yep, you want some flex in an aircraft structure. That is for certain. With x ray inspections performed on critical structural points at certain airframe cycle numbers in an airframes lifespan to detect issues before failure. The reason most of em end up at the scrap yard to be cut up, is they reached their cycle limits for the airframes projected lifespan as set by the manufacturer.

Most crashes are caused by pilot or air traffic controller error, incorrectly packed items in cargo compartments causing a fire, acts of God like lightning strikes, bird strikes etc. and software issues. For awhile though the biggest was CFIT. Controlled Flight Into Terrain. That's because aircraft only had altitude indicator pingers that went straight down. Now they use an antenna pinger that looks fwd and down. I am pretty well versed on airline crashes, and causes. A lot of them could have been prevented. The FAA investigators when they find a cause work to have the U.S. fleets and aircraft manufacturers update the aircraft or change procedures that caused the crashes in the first place.

 

[crackedback]

I meant uni bodies -----todays uni bodies are way better built than our old ones.
Hey I saw a big lincoln continental being hotrod moded, they said it was a unibody back in 1958 / I think. THAT ONE REALLY CAUGHT ME BY SURPRISE! Wonder if its true !?

58's were unibody, first year for that process.

Todays cars are light years better in construction than in the 60, no doubt.

 

[72bluNblu]

You're right, I don't know that for certain, I was generalizing, a foolish thing to do. Mine subframe connectors are welded full length, but I also have a lowered floor pan and I understand welding well. I was a welding engineer for more years than I'd like to recall. I ran a welder test qualification shop for number of years. I would disagree with you regarding MIG being more brittle, of course a lot of that depends on wire type, feed rate, amperage, shielding and the welder. I've seen MIG welds that bent like rubber, in fact the standard bend test for plate and pipe require the weld to bend over a prescribed radius, but I'll bet you know that ! And to be fair I've also seen MIG weld that cracked like glass.

Haha, yeah, you caught me generalizing too! It is a really long length of weld with those subframe connectors, and that definitely can have its own shortcomings. But of course there are a ton of variables just with the weld as you mentioned.

There are pros and cons to both styles, both from an engineering standpoint and a general installation standpoint. I certainly can't say which is better, and I've installed both. But I think either kind is better than nothing at all.

I must have missed the part about wings breaking off. Aircraft are inspected for cyclic fatigue so as to preclude material failure. Airplanes normally crash because of terrain interference with the flight path or operator error, hardly ever for material failure.

That is the truth! That damn ground gets in the way!

Although some of aircraft materials engineering is making sure that when the materials DO fatigue you can catch it on the inspections. Because they do fatigue and parts do have to be replaced over the lifespan of the airframe. A notable exception was that Aloha Airlines flight that had the section of fuselage rip off- catastrophic failure due to rapid crack propagation. Turns out the cracks were being hidden behind the heads of the rivets of the panel, a materials problem because the metal could fracture small enough to be hidden behind the rivets but still achieve enough of a crack that it would propagate. Other part of that issue was all the short hops, the number of pressurizations became more important than the number of flight hours, and the hours were the inspection threshold.

 

[moparmat2000]

Haha, yeah, you caught me generalizing too! It is a really long length of weld with those subframe connectors, and that definitely can have its own shortcomings. But of course there are a ton of variables just with the weld as you mentioned.

There are pros and cons to both styles, both from an engineering standpoint and a general installation standpoint. I certainly can't say which is better, and I've installed both. But I think either kind is better than nothing at all.



That is the truth! That damn ground gets in the way!

Although some of aircraft materials engineering is making sure that when the materials DO fatigue you can catch it on the inspections. Because they do fatigue and parts do have to be replaced over the lifespan of the airframe. A notable exception was that Hawaiian Airlines flight that had the section of fuselage rip off- catastrophic failure due to rapid crack propagation. Turns out the cracks were being hidden behind the heads of the rivets of the panel, a materials problem because the metal could fracture small enough to be hidden behind the rivets but still achieve enough of a crack that it would propagate. Other part of that issue was all the short hops, the number of pressurizations became more important than the number of flight hours, and the hours were the inspection threshold.

I am only disagreeing on one point. A big part of the hawiian air 737 convertible incident was a lot pencil whipped inspections on those aircraft. The employees started pointing fingers to save themselves. The cracks in the fuselage would normally have been found waaay before failure. A lot of folks lost their jobs because of that. A buddy of mine, His dad was a pilot for em at the time. The feds came in, inspected the fleet, marked almost all of em to be cut up for scrap.

 

[ir3333]

Lots of experience talking here.Wonder how many guys have welded as an occupation...and how many have picked up one end of a long piece of square tubing?Mild steel is soft and Even 10 gauge will bend quite easily.The design or geometry is very important and as i stated earlier a triangle or gusset can be very strong.

 

[moparmat2000]

The aircraft I work on are at 50% of their lifespan. I see a lot of fatigue issues when they are just starting. The inspections on the Hawaiian air 737s were not done. If they had been, these issues would have been caught long before the top ripped off one of em.

 

[moparmat2000]

Lots of experience talking here.Wonder how many guys have welded as an occupation...and how many have picked up one end of a long piece of square tubing?Mild steel is soft and Even 10 gauge will bend quite easily.The design or geometry is very important and as i stated earlier a triangle or gusset can be very strong.

You do realize a subframe connector is about 4 foot long right? Are you comparing a 12 ft long span of box steel to a 4ft span. If so the 4 ft span will flex a whole hell of a lot less. I dont believe any of us said subframe connectors completely eliminate flex. It severely limits it.

 

[72bluNblu]

I am only disagreeing on one point. A big part of the hawiian air 737 convertible incident was a lot pencil whipped inspections on those aircraft. The employees started pointing fingers to save themselves. The cracks in the fuselage would normally have been found waaay before failure. A lot of folks lost their jobs because of that. A buddy of mine, His dad was a pilot for em at the time. The feds came in, inspected the fleet, marked almost all of em to be cut up for scrap.

The aircraft I work on are at 50% of their lifespan. I see a lot of fatigue issues when they are just starting. The inspections on the Hawaiian air 737s were not done. If they had been, these issues would have been caught long before the top ripped off one of em.

Oh totally, there was a lot going on there. Boeing and Aloha airlines both had part in it. The 737's were redesigned after that to improve strength in that area and the inspection schedules were modified. There were also claims that the cracks had been visible before the flight and ignored, obviously an inspection issue. It's not usually just the "one thing", but a chain of events.

 

[barbee6043]

I wonder what all Carroll Shelby did to is R model GT 350's, frame , suspension wise, back in their running and winning at LeMans, etc. and beating all the exotics???

 

[retroron]

Haha, yeah, you caught me generalizing too! It is a really long length of weld with those subframe connectors, and that definitely can have its own shortcomings. But of course there are a ton of variables just with the weld as you mentioned.

There are pros and cons to both styles, both from an engineering standpoint and a general installation standpoint. I certainly can't say which is better, and I've installed both. But I think either kind is better than nothing at all.



That is the truth! That damn ground gets in the way!

Although some of aircraft materials engineering is making sure that when the materials DO fatigue you can catch it on the inspections. Because they do fatigue and parts do have to be replaced over the lifespan of the airframe. A notable exception was that Hawaiian Airlines flight that had the section of fuselage rip off- catastrophic failure due to rapid crack propagation. Turns out the cracks were being hidden behind the heads of the rivets of the panel, a materials problem because the metal could fracture small enough to be hidden behind the rivets but still achieve enough of a crack that it would propagate. Other part of that issue was all the short hops, the number of pressurizations became more important than the number of flight hours, and the hours were the inspection threshold.

Local Humor. Fresh out of high school, one step ahead of the police, I joined the USAF and spent 4 years working on mostly B-52's and its fair to say I have a great love for that aircraft. After the USAF I went to college and in what can only be described as strange twist of fate I wound up back in the Navy flying F-4s at the end of Viet Nam. I tell you this only because some truths were told to me, one of which is "beware of the clouds, mountains hide in them". The other one that I remember, when I'm down in the dumps and things aren't necessarily going my way, said by my RIO who was fond of saying (while on deck or land) "it ain't all that bad no-one's trying to kill us today". Kinda puts it in perspective don't ya think! And shoot, look at the pictures of the dart if you need more proof!