And then there were two.

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After some more blending of the curvy bits, it will be time to weld in the arch section. The steel used here is 4140 and it has had a post weld, stress relief treatment of 1200 degrees F for two hours, with a nice slow cool down overnight in the furnace after it had been turned off.  Before Tig welding, the components had a preheat of 500 F to eliminate stress cracking in the 4140.  Weld rod was ER70S. Multiple tacks, along with slowly building up the fillet by alternating from one side to the other, was rewarded with no discernible warpage and the tangs fit back into the loops on the field frames pretty near perfectly.  Currently these parts are in the annealed state so they are fairly ductile, at least for 4140.  They will be plenty tough for our purposes just as they are.

And that’s the way we do it in the twenty first century — workaholic electrons and a billion spools of copper wire.

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