Hey...

Don't make me kick yur butt again!

I was hoping you'd chime in. I was trying to show you that I'm not the only one that builds a dumb cage.

Seriously, I don't see how can you have any exception to what I've said about that cage? Unless... you think it was GOOD?

 

On the side topic regarding the need to heat treat thin walled chromoly tubing used for roll cages - that is an Rennlist urban legend (we need to come up with a name for info like this that is perpetuated on the Rennlist). As Geo and Fatbillybob pointed out in an earlier post, chromo is used for aircraft fuselages and not required to be heat treated. Here is a pretty good article explaining the welding of 4130.

http://www.eaa1000.av.org/technicl/4130.htm

 

It's not just propagated here! It is in both of my welding books as well. From the link. Well said too. "By letting weld joints air cool, the joint becomes normalized. Further normalizing and evening of the internal stresses can be accomplished by heating the general area of the weld (cluster) to a straw color (light yellow) and letting the area air cool. This is not absolutely necessary (because the internal stresses of the weld are not that much higher) like it would be with a higher carbon content steel, but I was taught to do"

Note that 4130 gets brittle at low temps.

John. Promise to not use any bondo on the cage and I will stay out if it too. BTW i am just getting started caging and framing up a 911 and I will post pix for coment, o my turn under the microscope is coming up.

 

Being t-boned might be a low probablility, but sliding sideways into something is pretty high. Really, when you think about it, you see a lot of damaged cars with issues in the door area....

 

Kurt - do your weld books refer to thin walled tubing or chromoly in general? The rules are different in regards to thin walled tubing versus thicker stock. When welding thicker stock the welds do need to be heat treated, but both ASME and FAA do not require it for thin walled tubing.

 

You have hit the nail on the head I think. both books talk in general but one also does mention that it is not required in thin sheet or wall but can help the weld. Kind of a what the hell, why not to be safe kind of thing.

 

This is why I am shy of FG doors. I know that a well built bar system is a good replacment/ improvment but I keep seeing wreck footage where the door is gone and you are watching the driver as the wreck is still unfolding. Might keep the other car or tires out but what about all the other jusk that is flying around? I fully understand that this might be unfounded and is just my own feeling.