Another consideration is the ability of a well-placed bar to provide a convenient and strong place to attach parts. The under-dash bar is mounted high and will be used for holding the steering column, pedals, evaporator, and stereo components securely. The sill and harness bars are intended to provide the proper anchor points for the seats and body restraints.
Finally, something else to remember: Those tubes are hard! It’s important to position the tubes (especially the ones around your head) to give yourself the most clearance so that the thing that is supposed to save your life doesn’t harm you or turn your brain into mashed potatoes.
CCD builds its cages around the main hoop, like nearly every other cage I’ve seen done. Next, though, Tim and Pete put in the back braces. Tim says, The back tubes are hard to get lined up correctly, especially with the package tray and rear firewall already in the car. So I like to do them before moving up front. From there, the main hoop is tied to the subframe connectors, and then to the 4-link brackets.
After that, comes the most difficult partthe side tubes from high on the main hoop to the floor by the passengers’ footwells. Check out the photos to see what it looks like, but Tim has a trick to make it easier to weld and a bit stronger. The brow bar (above the windshield) and under-dash bar follow. Sill bars and finally door bars complete the cabin portion of the cage. The final difficult part is the front J-bars that tie the front suspension and motor mounts into the rest of the cage.
Now follow along as Pete, Tim, and Denny Steward build a world-class rollcage.
In my continual quest to improve my own TIG welding, I pumped Tim for as much information as he’d give me about his welding technique and machine setup. All the welding was done on an ancient Miller machine about the size of a Toyota Prius. The foot pedal is so old it looks like World War II surplus.
There’s nothing magical about the welding machine, to say the least. Tim uses a water-cooled torch, which really helps when you’re trying to run a bead in an awkward spot since the cable is more flexible than an air-cooled torch, but the rest of his setup is decidedly ordinary: standard collet body, 3/32-inch tungsten, 1/4-inch stick-out (except when digging into corners), 22 CFH argon flow, and narrow cup.
His secret is simple: dozens and dozens of cages built. He’s welded in all the uncomfortable positions many, many times. For those impossible spots at the top of the bracing tubes into the main hoop, he can weld it by feel without actually looking at the puddle. I guess that’s something like Jimi Hendrix playing guitar behind his back. I say guess because I’m sure I’ll never have that degree of skill.
There are two other things I noticed: thorough cleanliness and fast puddle movement. The two things work together. A clean puddle with no mill scale or other contaminants will move faster (and penetrate deeper) and that really helps keep the size of the HAZ down, which is vital when welding 4130 steel.
One other thing to mention: Tim uses mild steel rod (ER70S) when welding 4130. That’s the recommended filler according to Lincoln Electric and Miller Welding.