Vintage racer build Options

[jhelgesen]

We started cage work for a vintage racer 914-6...

Customer brought in a decent stripped tub, fitted for a complete fiberglass fender setup.

(IMG:http://www.914world.com/bbs2/uploads_offsite/i184.photobucket.com-9299-1274358902.1.jpg)

(IMG:http://www.914world.com/bbs2/uploads_offsite/i184.photobucket.com-9299-1274358902.2.jpg)

We started in with the main hoop

(IMG:http://www.914world.com/bbs2/uploads_offsite/i184.photobucket.com-9299-1274358902.3.jpg)

We'll be tying in all the suspension points.

(IMG:http://www.914world.com/bbs2/uploads_offsite/i184.photobucket.com-9299-1274358902.4.jpg)

Trial fit the door bars last night.

(IMG:http://www.914world.com/bbs2/uploads_offsite/i184.photobucket.com-9299-1274358903.5.jpg)

[sean_v8_914]

OT: I was watching monster truck jam. Blue Thunder hit some jumps and both rear shock consoles came apart. then they showed the carnage...WTF? it all came apart at the welds. can someone with real welding experience explain that? I say cold joints and poor penetration.

[rick 918-S]

OT: I was watching monster truck jam. Blue Thunder hit some jumps and both rear shock consoles came apart. then they showed the carnage...WTF? it all came apart at the welds. can someone with real welding experience explain that? I say cold joints and poor penetration.

If it was 4130 it is likely poor penetration. (monster trucks likely would use light 4130) The other problem with welding 4130 is the rate of cooling. Mig welding 4130 can result in a concentrated local heating of the tubes with a quick flash cooling. This will cause a brittle condition and lock in stress. IIRC Tig welding can even be worse as the heat concentration is even more concentrated with a faster cooling cycle. In welding body panel seams tig is ideal because of the small heating and your ability to concentrate the work to a smaller area minimizing the warp factor.
That's why experimental air frames are gas welded. The molecules expand slower with the torch and further down the tubes. The tubes hold heat longer after the welding process is completed. Cooling is slower allowing the tubes to naturalize (tube and weld metal) restoring the strength.

Mild steel DOM can be mig welded with great success. It's a little heavier.