[Ron Sutton]

Hey Steve !

Originally Posted by gerno

Ron - another question about the structure, this time the cage.

Based on pics of other builds it seems typically people use 1 piece front pillars that extend from either the main rear hoop or the roof hoop to the floor. In this build the front pillar is a short piece attaching the roof hoop and dash bar. I also notice the dash bar isn't bent but instead welded together. Without having any real knowledge of what works best I always assumed it was better to bend the steel rather than weld it together. This build seems to prove my assumptions wrong and in general this looks a bit easier than bending in tight spots. Is there any difference or benefit in strength when bending vs welding a joint?

What Vince said in a complicated way is correct.

Originally Posted by Vince@Meanstreets

Its all about placement, force direction-continuation-pathways and proper use of nodes. A straight piece of tubing will resist a bending force more so than a bent piece of tubing,even if welded. Its safe to have a bent tube but that depends on force loading, support (nodes) and directions.

I'll clarify a few things ...
A. We do not want to butt weld 2 pieces of tubing together with no support. That would not be as strong as a bend.
B. But if we bring multiple tubes together ... triangulated them ... & weld them, that is stronger than a bend.

Looking at the photo below, if the red tube simply bent into the the tube in blue, and the tube circled green butted into this bent tube ... it would not be as strong as joining all three with welding.

The strength difference is not monsterous, but in the 15%-25% range.

Some bonuses of doing it this way is we can offset the A-pillar tube (red) to better fit the car & keep the firewall bar (green) higher than we could with a bent tube.

And lastly, just as Vince was stating, a bent tube is not nearly as strong as a straight tube. For example, when we make watt's link tubes straight (normal) we can run the 7/8" OD tube with .065" to .095" wall thickness & never have any issue. With our GT Watt's link, the lower passenger side tube is stepped. Meaning it is bent back & then bent again to be parallel. (See HERE). Those stepped tubes need to be .156" to .220" wall ... or they'll bend ... right where we "pre-bent" them.

Same with roll cages. Where you have a bend ... needs to be braced ... or that is your weak link. See how we brace them in the 2nd photo below. (Purple Circles)

Make sense?