Sub-frame connectors... Please build them correctly!

-
4mulaSvaliant

4mulaSvaliant

Well-Known Member
Joined
Oct 26, 2006
Messages
1,554
Reaction score
44
Location
Virginia Beach Va.
So, I can help but notice all of the sub-frame connectors that many people build, and do next to nothing for the rigidity of the car.

I have noticed the common thing to do is to weld some form of tube from the front sub-frame to the rear sub-frame with no attachment to the floor pan itself. This method is next to pointless. Im sure Ill fire up some huge differences in opinion here, but it truly comes down to fact and not ones opinion.

Adding tubing from front to rear will keep your car from stretching.... That's about it... As far I I have ever known, its just not an issue! LOL

So to explain this a little better, there are some basics in building strength into anything, whether it be full tube chassis fabrication or shoring up your twisting little a-body.

By welding in the tube and only attaching it at the ends, you have accomplished exactly the same strength as the rocker panels already produce. They are already there, so why add additional weight?

The correct way to do this is with the laser cut sheet metal sub frame connectors that conform to the floor pans and are meant to be fully welded.

With the new material being welded to the floor pan, you have now tied, the floor to a rail, which in turn is tied to the front and read sub frames.

The correct way to build these to the point they actually provide structured support is shown in the pictures below.
Even the pictures which dont have 100% weld along the connector is better than the "floating" connectors.
Though it transfers much of the torque to the area that is not welded. This creates a high stress area in a pretty concentrated area.

The bottom pictures are the type that do next to nothing for the problematic area in these cars which is the nearly flat plane of the floor pans between the sub frame sections from front to rear.

Im sure this will chap a few hides, but I hate to see this mod over and over and done for nearly no gain.

View attachment DSC_1357.jpg

View attachment DSC00317r.jpg

View attachment DSCN1460.jpg

View attachment SubframeConnectors008.jpg

View attachment dcc-4286868.jpg

View attachment MFR161206.jpg
 
I can see your point on the bolt in connectors in the bottom 2 pictures, but weld in 2X3 connectors that go under the floor is a good option too.
Your set up is ideal, but include a properly fitted and installed 10 point cage, now we're talking.
It all depends on what you want, need, and expect out of the car......
Skin the car and put a full tube chassis under it is ideal if you want to really split hairs.
 
Hahaa... Of course.... Thats whole other ball game there. I am strictly speaking of the add in connectors, whether complete custom and made in your garage or purchased, they need to attach to the floor pans to truly accomplish any real strengthening.
 
I have installed the kind you dislike in my 64 Sport Fury. I could feel a definite improvement in the way the car felt and handled. I think there's room for improvement by adding torque boxes front and rear. I wouldn't use the bolt in style, unless they were welded in, but I wouldn't go blasting everyone who did. You must be a liberal. We all hopefully use our own ideas when building our cars, and I don't think I need your approval to do it. Why don't you post pics of your car top and bottom so we can go over it, and tell you all the things we don't like.
 
I have my car on a rotisserie and before I welded my bars is my car would flex like mad when I rotated it . Now it does not flex at all so I have to say I do not agree with you. Your way might be a little better but is more work than it is worth. This actually makes these cares stronger than a full frame car that is not attached to body solid
 
No need to get all upset, its not to blast anyone, its more to point out that it doesnt do nearly what it should. Thats all. I didnt call anyone out for that reason as it is... I know there are many ways to accomplish it. Hell, I have plenty of my own ways of fabrication. This isnt intended to blast anyone. Certainly no reason to start getting feelings hurt.
Just informative is all. :)
 
But you seem to be the only one who thinks it's informative. Just cause it's your way doesn't make it the best way.
 
The strength you gain welding to the floor is minimal, the type and size of the tubing and if it's X or has a cage attaché will make the biggest difference
 
Actually making sure your windows are rolled up tight will do more than welding your frame connectors to the sheetmetal
 
All I know is before welding in Seymour Scamps connectors I bought off him here on FABO, I couldn't jack the car up from the side. It would just droop the front end. After welding them in I can jack it up no prob. It also made a discernible difference in the overall feel of the car. Is integrating into the floor even more beneficial? Probably. But for my street strip Duster these are more than satisfactory at adding rigidity and strength. And yes those are two seperate but equally important functions to be considered when doing any chassis improvements IMO.
 
Yes of course the strength an type of tubing plays a large part as well.

It has to be understood that building one plane in parallel with another plane does nothing for strength.

If that were the case there would be no reason for having structural steel in the shape of I-beams and C-channel guys.

As a matter of fact and I-beam is a perfect example of the entire theory.

If you can imagine an I beam with out the center web, and it is just two planes parallel, both planes would have the ability to flex. Add the web to attach the two and you have a very structurally sound piece of material.

This is exactly why I say, this isnt a matter of my opinion. Its fact.

Now, I have been very intentional to not claim it does absolutely nothing, but rather "This method is NEXT to pointless". I do understand that you will get a little added structure from this, but the amount has to be damn near immeasurable.

However, even a stitched weld across the floor at several points will begin to make matters better if you have connectors that "float" away from the pan.
 
I agree about the I-beam and boxing forsure that all makes good sense. I think maybe that saying the rockers are already doing the job and adding weld in floating connectors is doing next to nothing just isn't that black and white. I'd love to see someone do some stress and load tests on all variations! I think numbers and data are needed to go beyond just saying ones margianally better or way better etc. maybe someone should submit that idea to powerblock it something. I'd love to see back to back to back teats of stock, floaters and floor integrated connectors. I just have a hard time buying that floaters do next to nothing. They've been around forever and lots of guys have been using them for along time. They would have gone the way of alot of other gimmicky improvements loosely based on science (ie the Super Sucker spacer) if so. Again just my opinion
 
What you say is not fact. If it were, why does a house have wall studs? What about a railing? What about frame cross members? According to you, all that's required is to have a perimeter frame without any longitudinal bars. You can keep arguing the point, but your logic is flawed.
 
You have proven exactly the point with your examples. You wouldnt just place a piece of sheetrock and sheathing next to each other, and only attach the top and bottom of the sheet. Its screwed to the studs throughout the entire sheet of material. Both to secure the sheet to keep it flat as well and to add strength.
 
4mulaSvaliant said:
Yes of course the strength an type of tubing plays a large part as well.

It has to be understood that building one plane in parallel with another plane does nothing for strength.

If that were the case there would be no reason for having structural steel in the shape of I-beams and C-channel guys.

As a matter of fact and I-beam is a perfect example of the entire theory.

If you can imagine an I beam with out the center web, and it is just two planes parallel, both planes would have the ability to flex. Add the web to attach the two and you have a very structurally sound piece of material.

This is exactly why I say, this isnt a matter of my opinion. Its fact.

Now, I have been very intentional to not claim it does absolutely nothing, but rather "This method is NEXT to pointless". I do understand that you will get a little added structure from this, but the amount has to be damn near immeasurable.

However, even a stitched weld across the floor at several points will begin to make matters better if you have connectors that "float" away from the pan.
Click to expand...

Not.
Have you ever used good connectors that are not welded to the floor pan?
I Bet not.

Bolted in = NEVER
Frame tied = Pretty good
Frame and floor tied = Best

That's all there is to it, but to say they don't do anything/immeasurable to the car is rediculous.
That's like saying tennis shoes don't make a difference in the desert because they are to thin.:)
 
oh i don't know. i didn't go through the floor with mine and i felt a huge difference after they were installed..


DSCN6195.jpg
 
Beatnik said:
I agree about the I-beam and boxing forsure that all makes good sense. I think maybe that saying the rockers are already doing the job and adding weld in floating connectors is doing next to nothing just isn't that black and white. I'd love to see someone do some stress and load tests on all variations! I think numbers and data are needed to go beyond just saying ones margianally better or way better etc. maybe someone should submit that idea to powerblock it something. I'd love to see back to back to back teats of stock, floaters and floor integrated connectors. I just have a hard time buying that floaters do next to nothing. They've been around forever and lots of guys have been using them for along time. They would have gone the way of alot of other gimmicky improvements if so. Again just my opinion
Click to expand...



ok my opinion time for what ever it's worth. Since I have no factory data to prove it an can't back it up except for pictures:D and the feel of the car, which is subject to different opinions by whoever is in the car.

The factories did research on it. For example one of the members in this thread stated something about parallel planes not being very effective.. umm look at this from the factory and tell me why they did it then, instead of welding a complete laser cut part. yeah I know money was the reason. but humor me and tell me your thin cut channel welded to thin floorboards will stop torsional effects as well as this. Now I will say that the laser cut part will stiffen up the floor pans.... but that's not the Only part I want to stiffen really and in effect you have a stitch welded box that is EXACTLY the same as rectangular tubing but without the fully welded capability. This (factory) part goes from the rear wheel wells right to the front rocker end caps and is welded to the torque boxes. in essence it is a Hidden weld-on unit from the factory. It's a spot welded C channel It does work well since my 40+ year old car did NOT sag more that 1/8th of an inch when it was flipped over on the rotisserie and that was before I put in the weld on inner ones you say are not as good, now I can jack up the car using a bumper jack and the doors open and close just like it was sitting level and that's on a convertible which is weaker than the hardtops/sedans. My opinion is "if you like your and it stiffens up your car" then well and good for you, mine worked using the other type


Welded and floor frame tied might be the stiffest, but just welded is good for a daily cruiser and a lot cheaper than floor and frame tied with almost as much stiffening. AGAIN just my Opinion and everyone has got one:glasses7:

View attachment 049.jpg

View attachment 048.jpg

View attachment 2011_1109workcar0005.jpg
 
4mulaSvaliant said:
On another note I would hope that nobody is really getting "butt hurt" over this. ;)
Click to expand...

I just had to wonder if you are ever going to get to drive that car, or get hung up on so many relatively minor details that it never gets done. :D

I hope you get to drive it some day.
 
4mulaSvaliant said:
So, I can help but notice all of the sub-frame connectors that many people build, and do next to nothing for the rigidity of the car..
Click to expand...

I am not a structural engineer, and I don't even play one on TV. Are you? I'm just asking

What are your credentials for stating these "facts?"

Are you an accomplished chassis builder?

Manufacturer?

Hey, I'm just asking.
 
Do frame connectors add torsional rigidity - Absolutely!

Jack a car up from the front corner and see how high it lifts before the pass side tire leaves the ground. Put on connectors and do the same. The height will be reduced.

Do the same jacking it up the trans x member and see how high it needs to go before the rear tire comes off the ground.

Using the floor pan as a sheer plane is OK. Put lots of power to it and you may end up tearing the floor pan. Mount a rollbar to the connectors with the other points of attachement and this is mostly a moot point
 
You must log in or register to reply here.
-

Back
Top