I broke my homemade handlebar at the base in New Zealand right before Unicon. Anyways, I got around to rebuilding it. Anyone who is interested in DIY stuff can check out my blog with the pictures:
The final result:
corbin
Corbin,
I made my own handle bar (see it at post your homemade handlebars here!) based on your information but I used different tubes as I guess there were big difference in diameter with your design and thinnest tube was the one with highest stress.
My order to Aircraft Spruce (enough to built 3 handle bars) :
1.00 of 03-05400-2 4130 STEEL TUBE 7/8X.049 2FT
1.00 of 03-06200-2 4130 STEEL TUBE 1X.049 2FT
1.00 of 03-07100-3 4130 STEEL TUBE 1-1/8X.058 3FT
1.00 of 03-07810-1 4130 STEEL TUBE 1-1/4X.083 1FT
Cool! I remember seeing yours before. I used:
03-05300-4 4130 STEEL TUBE 7/8X.035
The 0.035 is nice and light, but too thin for the part that attaches to the base; it has too much stress at that point. I think it is fine for the top “T” (mine haven’t bent yet).
Next time I’ll go for .049.
–corbin
The break right above the brazing joint may suggest a change in metal temper during brazing. Perhaps you’d do well to do an afternoon of Googling on materials and heat? I know it’d do me well 
The process of powdercoating is an application of heat as well. You may not get near the point of re-tempering but you may be affecting the strength of some materials in the 10-20% range… which makes a difference when you apply your hard-Corb power to said materials.
I don’t think it broke due to the metal being tempered – it just wasn’t thick enough. I think it was just fatigue and a lot of stress at a large angle.
corbin