Both goals were achieved, though the furnace took a bit longer than I had expected. After using the big-ass wrench to remove the compression nut holding the gas assembly together, it took some heat, some liquid wrench, and a different big-ass wrench to remove the suspected solenoid and redundant regulator. Fitting the new gas feed assembly into position wasn't too hard, and now I can feed more gas into the furnace than the fan can provide air for.
Given that I've expanded one parameter of the furnace, I then worked at increasing the air flow by plumbing in an additional blower. This improved things a bit, but it is quite obvious that the motor that the previous owner put onto the blower, an old sewing machine motor, just isn't able to spin fast enough with enough force to do the job, and while the second blower feeding into the first improves things quite a bit, the real answer is going to be to replace that motor with a very fast, fairly powerful replacement. Off to www.sciplus.com!
Once I was sure that I'll be casting on Friday, I took the pattern I made yesterday for the sickle (1/4" hardboard, sanded smooth on the edges) and rammed up a mold using a cast-iron cope and drag and greensand. I had just enough sand to make two sickle molds and one mold for a couple of mace heads I've decided to make. I'd love to cast a bronze sword, but it's too cold to finish glueing up the extra-long and skinny cope and drag (one done, one cut out but needs gluing and suchlike), oh and I don't like the one sword pattern I made, and I'm not sure I have enough bronze on hand to cast a complete sword. Sigh. Next time.
To make sure I'm ready for tomorrow, I've pulled out the protective coverings (silvered leggings, apron, extra-thick gloves, IR and UV protective face shield), the required chemicals (bronze-specific covering flux, degassing flux), packed the silicon carbide crucible with bronze ingots and scrap, made sure the lifting and pouring tongs are in good shape and easily accessible, and cleared a 10' x 10' area of gravel so that my casting area is clear.
Goal for tomorrow is to safely melt the bronze and do the pours. If I can do that without incident I'll be happy and take the rest the day off. One of the problems I've had in the past is that I tend to remove the work from the mold too soon. Not this time -- I'll let it sit in there until it cools down this time. This does tend to degrade the greensand, but greensand is relatively cheap -- budget casting supply sells a 100 lb box for $115.30, and 100 lbs is a lot of green sand (I have only ever bought 75 lbs of greensand, and even after several dozen casting sessions I still have about 50lbs of useable sand.)
I'll need to head off 1st thing tomorrow and get more propane, as I'm almost out. Other than that I think I'm all set to go.