Supercharging a Johnson: (Gas Furnace, that is………..)

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This is one of those projects thats been hanging around forever. I got this Johnson Gas Furnace at the CAMS Yard Sale a couple of years ago; it was lounging on Steve’s front porch- a freebee that someone never picked up. I jumped at the chance to get it; I had been wanting to explore the world of gas forging for a while (didn’t have too much luck with coal). The lid was cracked in about four pieces (the lifting ring had rotted through), and the gas regulator was missing. I looked into getting the gas rig for it, and quickly found out that a replacement would be upwards of a thousand bucks. Time to get inventive.





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OK: that stub sticking out of the left side is not a factory fitting. Its part of the solution to the gas dillemma.


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I pulled the original gas port out, and decided to hot rod this furnace. I have done a little casting with Aluminum, and thought I’d like to try some brass. Given the cost of getting the factory gas set up, I needed to come up with a better arrangement. This involved chiseling out some of the fire brick, and installing a larger fire port for the new “powerplant”.


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This is the new heat source; a Beckett oil furnace burner. I got this from a friend (known good burner), and plan to fire it with Eric’s Bio-Diesel maybe mixed with some waste oil. This should give me enough BTUs to melt brass (and probably anything else I decide to get into).


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Heres another shot of the burner. It was serviced just before I bought it, and came with the filter set up, all I will have to come up with is a fuel tank.

This thing has been sitting around my shop for about two years now, and its time to get it put together.


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I spent a few hours (off and on) enlarging the inlet port for the Beckett burner, and fitting the pipe to the furnace. Tonight I packed the pipe with 2200 degree insulation, and will make a flange to mate the burner to furnace body. I will need to trim the pipe, and mount the flange to the end, so that the burner can be removed for service.


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A while back I fabricated a new lifting ring for the lid; it was broken in four pieces, and the ring (too lightweight) had rotted through. The heavier ring holds the pieces together, with no need for cement to bond them. I have been scraping the ugly off this furnace for a while. I work on it when the spirit moves me, but its still butt ugly. I have some barbeque black paint that will get the job done, but that will wait till the work is done.


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Heres the lid slid over to one side, to remove the crucible. The repair works real nice; its effortless.


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And with the lid on the other side. It will be a couple of weeks before the refractory is dry enough to fire off, but to be honest; it may be a while before I get this one finished.I cleared a big hurdle tonight, but it will be a while before this job is done. I scrape a little ugly off, chip out some loose refractory, make a new bracket……..etc…………..  I’m getting close to mounting the burner, and that will be the big step. Once that is done, I won’t have too many more excuses for not getting the job finished. The biggest problem I have now is waiting till the insulation is dry before I start messing with the burner mount.



More later…………..

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