Tubular Subframe connectors

[WSC-SHO]

So this idea begins late at night, as most of mine do...

Has anyone ever made sub frame connectors out of heavy wall tube? Something like Sch 40? I was thinking if you sectioned it in half where it sat on the front "rails" and where is sat on the rear strut box, it would be as strong if not stronger than the square tube ones currently in use. You could also weld a brace/gusset in where it bends to further prevent twisting. I'm thinking I'm going to fab a set up and wanted to see what the general consensus was..

:wave:

 

[zblackbeast]

Be the test mule?

 

[HotRodKid]

pound for pound, your better off running double small tubes then running one larger thicker tube. Also helps with ground clearance.

Ive played this game already. rolling tube was part of my duties at the fab shop.

 

[WSC-SHO]

Sectioned 1.5" tube would be 3/4 tall where it mounts to the "frame" That's around what people use now with the 1x2 bars. Also, tube is inherently stronger than square, although I'm not sure if torsionally this is true..

 

[firebat45]

Sectioned 1.5" tube would be 3/4 tall where it mounts to the "frame" That's around what people use now with the 1x2 bars. Also, tube is inherently stronger than square, although I'm not sure if torsionally this is true..

Torsionally (round) tube is stronger than (square) tube. But you're cutting the tube in half, which will drastically reduce it's strength. If you take a drinking straw and bend it, it's got a small amount of force resisting you, but if you take a drinking straw that's been split lengthwise, it will have almost no strength at all.

Half a tube is a lot less metal in the vertical plane than double 1x1 tubing. That's where the strength in the SFCs is, and that's why double 1x1 is marginally better than a 1x2 laid flat.

 

[WSC-SHO]

I won't be cutting the whole tube in half, just sectioning it where it welds to the "frame" rails up front and the strut boxes in back.. I'll probably reinforce it with some flat steel as well, something like this..

 

[Off Road SHO]

Then you're good to go, except you need to weld your round tube to the semi-flat frame rails. Of course you could always weld flat stock gussets all along the frame rails and end up with a lot of rounded bottom square tube, but that sure seems like a lot more work.

Tom

 

[HotRodKid]

If your that worried about making these incredibly strong, you need to run another tube down the rocker panel lip with diagonal braces to the SFC's, and the tubes cant just be connected at the front and rear, the have to be skip welded to the sheet metal their entire length

think about it, everything else on a unibody car is welded every inch, your SFC's should be to

 

[whiteguy3]

I did it. I custom made my subframe connectors for about $45. They were a sinch and were made out of square tubing. I also made a custom cross-member bar connecting the two subframe connectors right before the junction boxes.

 

[WSC-SHO]

I did it. I custom made my subframe connectors for about $45. They were a sinch and were made out of square tubing. I also made a custom cross-member bar connecting the two subframe connectors right before the junction boxes.

Do you have any pictures?

And HRK, what do you mean by running another tube? And I was planning on stitch welding them their length down the rails in one to two inch segments to avoid warping.

 

[LJRuddy]

If/when you go to put your connectors on, make sure you have the car off the ground and on jack stands. You want the connectors to be welded to the body without the load on it so that when the car is put back on the ground, the connectors are actually doing something other than being extra added weight.

 

[WSC-SHO]

I understood you wanted to have no weight on the cars wheels, so that that chassis was flexed upward so that the connectors would be pulled tight against the downward force of the body once it was lowered back to the ground.

 

[LJRuddy]

I understood you wanted to have no weight on the cars wheels, so that that chassis was flexed upward so that the connectors would be pulled tight against the downward force of the body once it was lowered back to the ground.

Thats exactly what I was trying to say... I seem to lose my thought when I attempt to type something out.

 

[WSC-SHO]

Thats exactly what I was trying to say... I seem to lose my thought when I attempt to type something out.

I got what you meant, just making sure we're on the same page :wave:

 

[HotRodKid]

And HRK, what do you mean by running another tube? And I was planning on stitch welding them their length down the rails in one to two inch segments to avoid warping.

like this:

and dont bother stitching them solid, run a 1" bead's with 2-3" spaces between. Even our spreader beam at the fab shop was skip welded like that, and we hung 10 tons of steel from it no problem.

 

[WSC-SHO]

Are the outside tubes in that system welded to anything or just hanging out there?

 

[HotRodKid]

Connected to the rocker panel pinch weld / floor area

 

[DJSHO91]

like this:

and dont bother stitching them solid, run a 1" bead's with 2-3" spaces between. Even our spreader beam at the fab shop was skip welded like that, and we hung 10 tons of steel from it no problem.

Sweet set-up! My 1st thoughts are "It's a bit over-engineered for a street car", but definitely give you top marks for ingenuity. How much weight does the whole set-up ad?

 

[HotRodKid]

Sweet set-up! My 1st thoughts are "It's a bit over-engineered for a street car", but definitely give you top marks for ingenuity. How much weight does the whole set-up ad?

Those are just pics i pulled of the net, i didn't make them.

if you made something similar out of 1.5" x 1.5" x 3/16" it would prob work out to 120 lb, maybe a bit more ... and thats probably overkill on material thickness.

 

[WSC-SHO]

schedule 40 works out to being just slightly over 1/8 inch.. 3/16 would be overkill