Help building subframe connectors

[Spook50]

At some point this summer (preferably soon after I return home in a month) I want to build a pair of subframe connectors for my Duster. This will be a first for me as far as fabrication and welding, so I'm not ashamed to admit I'm gonna need some help. Anyone live in the Spokane area who's willing to help me out? As said before, I pay in beer 

[super70bird]

Just finished mine, first time for me too as far as welding, etc.  Just take your time and measure everything first (many times!).

[PureGTS]

Looks good. I wish I could train my car to roll over too. 

[bOb shingler]

i don't understand why some of the fellows install subframe connectors sideways or use square tubing, would anyone care to explain?

[Spook50]

i don't understand why some of the fellows install subframe connectors sideways or use square tubing, would anyone care to explain?

My understanding is that it creates a more rigid brace when the assembly is complete, plus it's way easy to get scrap sheet metal. I think aesthetics has something to do with it too. A well built and installed set of square subframe connectors can easily be made to look like the rest of the frame.

[b569rr]

If you were concerned only with loading in the vertical plane, then the section modulus of the tube with the 3" in the veertical position would be greater than if the 3" portion was installed in the horizontal.

But being that the connector is exposed to torsional load, the modulus between the two configurations of 3" x 2" tube would be closer than you would think. But the above stated installation is stronger.

[loiq]

So, if you have 3x2 tubing, is it stronger to install the tubing vertical or horizontal?

[Prodart]

If you were concerned only with loading in the vertical plane, then the section modulus of the tube with the 3" in the veertical position would be greater than if the 3" portion was installed in the horizontal.

But being that the connector is exposed to torsional load, the modulus between the two configurations of 3" x 2" tube would be closer than you would think. But the above stated installation is stronger.

DAMN you're smart   

[Cpt Panzer]

 

If you were concerned only with loading in the vertical plane, then the section modulus of the tube with the 3" in the veertical position would be greater than if the 3" portion was installed in the horizontal.

But being that the connector is exposed to torsional load, the modulus between the two configurations of 3" x 2" tube would be closer than you would think. But the above stated installation is stronger.

[Prodart]

If you were concerned only with loading in the vertical plane, then the section modulus of the tube with the 3" in the veertical position would be greater than if the 3" portion was installed in the horizontal.

But being that the connector is exposed to torsional load, the modulus between the two configurations of 3" x 2" tube would be closer than you would think. But the above stated installation is stronger.

 While you're up can i get a Coke or Pepsi

[Cpt Panzer]

  Dr. Pepper

[b569rr]

Paulaner Salvator 

[codfish]

Well I guess I'm the oddball here.  I used round, .125" tubing for mine.  bent very slightly to follow the contour of the floor.  Cost about $30, and a 12 pack.



codfish

[Spook50]

Paulaner Salvator 

Weak! Stone Brewery's Arrogant Bastard is the only way to go.

Anyhoo, I figure I'll use 1/8" wall 2" x 2" square steel tubing, slide it inside of the "rails" of the rear subframe, then do the slight trimming necessary on my floorpan to fit it. A friend of mine did this on his Duster and the intrusion into the floorpan was pretty minimal. And since it'll be a rare ocassion that anyone sits back there, it works for me.

[bbscamp]

To see what way is stronger, forget the modulus stuff and just think about this example.  Take a 2x4 piece of wood, 8 ft. long and support it on both ends by some sawhorses.  With the long dimension wider....stand on it and see how much it flexes.  Turn it on edge and repeat.  You won't bend it at all.  Frame connectors that are wider than taller are weaker than ones that are taller than wider.  However, that config. makes them harder to fit.   If you runn taller frame connectors, cut the floor and weld the floor to them..that is the strongest way....just happens to be the most work too.    Have fun.   Oh yeah....anything you add will be better than nothing, so you can never really go wrong with what you do!   

[Nitrous340dart]

I built a set over the week wend.  Bought a 10' stick of 2x3 .125 (1/8th") box tubing for $60.  They gave me some 1/4" by 2" wide flat stock for free, I  had asked for 1/8th but he came back with 1/4.... I wasn't going to complain.  Took a couple of hours and was not hard to do. They are 50" long with about 9" notched out in the back.

[Nitrous340dart]

[smallbigblock]

I've got the tubing sit in my garage and I look at it almost everyday, but I'm freaked out about two things that have kept me from building these things.

     1. I hate the thought of cutting my pristine (no rust) floorboards
     2. I don't want to weld-in a twist or bad alignment somehow.  Car is sittin on jack stands with no suspension or anything else on it.

[Nitrous340dart]

That exactly how mine is sitting right now.  The doors open and close fine so I dont think the body it twisting, I just have the grill and one fender on and I can pick the front of the car off the front jack stand.  I was going to weld in the frame connectors as it sits.  I think as long as you have it on a good level ground and not in the dirt or uneven ground it should be ok...... I hope!

[fishy68]

The statement bbscamp made about adding anything is going to help is definitely true. I just have 1x2 1/8 wall tubing under mine and it helped tremendously. To begin with my car was a nearly rust free car but even it was prone to twisting pretty easily as evidenced by when I would jack up one front corner the doors wouldn't open or shut nearly as good. They seemed to hang up. After we welded in the 1x2 tubing I can now jack it up from either corner of the front to the point the other front wheel is coming up and the doors open and close as good as when it's on the ground. Nice thing is they don't hang down and I didn't have to cut up the floorboard to make them fit. I know it would have been stronger welding them to the floor but since it seemed to work real good as it is I just left it.

[guzzimike]

To see what way is stronger, forget the modulus stuff and just think about this example.  Take a 2x4 piece of wood, 8 ft. long and support it on both ends by some sawhorses.  With the long dimension wider....stand on it and see how much it flexes.  Turn it on edge and repeat.  You won't bend it at all.  Frame connectors that are wider than taller are weaker than ones that are taller than wider.  However, that config. makes them harder to fit.   If you runn taller frame connectors, cut the floor and weld the floor to them..that is the strongest way....just happens to be the most work too.    Have fun.   Oh yeah....anything you add will be better than nothing, so you can never really go wrong with what you do!   

Whereas the above is definitelly true, in our specific application you do have to consider the shear modulus of torsional loads, as B569 said..

IOW, take that same 2 X 4 - 8 foot long pice of wood, clamp it solid on one end and start twisting at the other end. Start with the wood flat or on edge and try to twist it..say 10 - 20 degrees from horizontal. Note how much effort it takes to twist the piece of wood.

Then place the wood the other way (flat or on edge) and twist it again. You may find that it will make little noticeable difference in the end how the piece of wood was laid out.

So now other factors come into consideration, such as how important are aesthetics...IOW how much of the Frame Stiffener do you want to have portruding into your floor pans..? In a Race only car, it may not matter much; OTOH, on a daily driver, it may.

With mine (a daily driver), they were going to penetrate either way, so we went with the 3" wide side on the horizontal plane, with a penetration of about 1" at its deepest.. The padding & carpet in the rear compartment camouflaged it nicely.

YMMV.

 

[jackie]

on the wood one's, what size nails would you use?? sorry, had to ask.. no really i agree there are good and better ways to do it, but all of them are better than nothing..

[BIG DOG]

on the wood one's, what size nails would you use?? sorry, had to ask.. no really i agree there are good and better ways to do it, but all of them are better than nothing..

The longest nails and biggest hammer you can find!!
I used 3"X 3"square tubing.And as you can see I didn't have pristine floor boards to worry about!....wish I did though!

[b569rr]

Nice work Big Dog.

[kudah440]

Interesting thread...
I can see how they help it front to rear (my uneven door gap for example), but if they they are installed to nuetralize body twist, isnt it going to be a lot more efficient if they are connected side to side? 

[BigSlim]

Here is some food for thought. Years ago I had store bought bolt in frame connectors in my 67 Cuda. I could really tell the difference in the way the car handled after i put them in. They did a great job of stiffining up the chasis. I have to say that after building this latest set and welding them in on the horozontal that they are far and above better than the bolt ins. I'm not an engineer but I'm willing to bet that by the time you do the sub frame on the horizontal and then add a roll bar that certifies to 8.5 or even 10.0 that an average person is not going to put enough horse power in it, or get it to hook hard enough (especialy a street car)to bend anything. The sub frame that these connectors are welded to is actually just a C channel and not a complete peice of box tubing. I would think that once these things are welded in as described that they are the stong part of the chasis.

[Nitrous340dart]

SMALLBIGBLOCK,
Did you do your subframes yet? with the car torn apart?  Did you weld in a twisted body

[mopar_man72]

SMALLBIGBLOCK,
Did you do your subframes yet? with the car torn apart?  Did you weld in a twisted body

thats a good point.  when you do something like this should you move around w/ your beads so you don't twist the frame?  If you weld in one side completely then go to the other side have you just made 1 side of the frame shorter then the other?  when a weld cools it shrinks, pulling the metal closer together.

[BIG DOG]

Before I welded my car it was leveled front to back and side to side.Very hard to do as the car still had quite a bit of structural strength to it .So if you moved the front it moved the back or vise versa.I ended up using 1/16" and 1/8" shims and about four hours to get it perfect.Then I welded in the connectors .

[kudah440]

Ok on that subject... where should you support the car while you are welding them?
If you put the jackstands under the subframe channel then weld,  the doors may or may not open/close, but if you leave the weight is on the tires, then you may be welding in a permenant sag in the middle...

I sure am glad this thread came up before i started welding mine.