Large Reverberatory Furnace

I'm going to build a large (10x24 target capacity) lathe, I suppose Gingery-inspired but the plans are pretty much my own. The bed I have in mind calls for more than 15 pounds of metal, but I can only do 6 pounds at a time or maybe 12 or 18 if I do a simultaneous melt with the reverb furnace and trashcan on charcoal. But syncing it would suck, and I've never tried such a large can\\\crucible in the furnace anyway. So...

Base Frame

Base frame. Two 4' beams of 1" pipe with 14" tall posts miter-jointed on the far end (to support the furnace itself on the pivots) plus two crossmembers (front and back; middle is a forged flat bar for the hearth handle to rest on) to keep it together and double as feet. The crossmember ends were forged flat in the forge. All joints are brazed, no bolts or welding, not even any oxypropane - I got out the monster burner and blasted the hell out of the joints while inside some firebricks. Two 1/8" brazing rods and a tablespoon of borax later, it's done. Two 1/2" holes in the support members and a 13/64" hole tapped 1/4-20 hold the pivot pegs (clearly, in the out position as pictured) which support the hearth and lid.

Lid Frame

Lid frame. Sheetmetal (old ductwork actually :) cut and folded, nothing to see here... The bars are approx. 3/16 x 3/4" steel with a DAMNED LOT of zinc on them. The first couple brazed joints I made (this time fired with the medium burner as pictured below) didn't work at all and in fact were white colored instead of brassy because they were just that, white brass! (Definition: more than 55% zinc vs. copper.) So I remelted them and pushed a fifth of the 3' rod into each joint and NOW they hold tight. Ack!
The far ends of these bars go down (with a brazed lap joint) and end with 1/2" holes for yup, the pivot pegs. On the left of the photo they meet in a point (just bolted) where some day I'll add a handle for opening the lid.

Brazing Rig

That tank got sweaty down there. Like I said, I must've spent 3 or 4 melts worth of gas on this already. More ack.

The Hearth, Curing

And finally, the hearth. About the same construction as the base frame except the sheetmetal form is bolted to the pipe in 4 places and has only one crossmember brazed on (not worth the bother of another when the hearth will keep it stiff). Also cross-drilled in the vertical sections (front of the pic) for the pegs.

Also pictured are some firebricks drying... So ya, I got the refractory in already.. :D This bag of refractory (the same old LWI 26 from Plibrico) is almost brand new and works tremendously better than the last batch. (I never realized how time-sensitive this stuff is!) It's squishy, needs exactly as much water as indicated (in fact, despite the seeming exactness of my getting the consistency right, it ended up bleeding water as it settled) and holds together at much lower water levels, passing the "toss 1 foot in the air" test with ease. This time I had to ram it like molding sand rather than casting like concrete. Scratched on the top of the curing refractory (which will actually be the bottom and just about out of sight in normal use) is "TMW" "2004".


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