Things I might have done differently:
This list could easy be a mile long, however I will limit the list so it only pertains to the furnace construction.
-The vertical rails in which the carriage travels upon consist of “built up” members. A compression 1”x2” 14 ga. tube with a 1”x1” 14 ga. tension tube. These tubes are separated with a spacer which is 1”x1” 14 ga. (I TAKE NO RESPONSIBILTY FOR THIS DESIGN!!!). I had this material on hand, which played a big part in utilizing it. It works very well and offers plenty of strength but took longer to built since it had many cuts and welds. If doing over I would use a single larger member for the vertical rails. If you do such make sure they can resist the moment produced by the carriage forces. A smaller member could be used if a tension brace was added from the top of each of the vertical rails to the back (blower end) of the furnace cart. This would limit displacement that would relieve some of the moment. If you do not perform calculations for the moment and forces then use overly large members designed in a non-critical sense. 290 lbs of a 2800 degree F furnace body suspended from above is not something to be performing structural gymnastics with. Design and build it overly strong. Especially if your welding is lacking in integrity.
-The carriage system could be simplified. This is the triangular truss part that has the rollers and attaches to the furnace. I used four trusses with eight rollers. Fewer rollers could be used but I would still use eight since it works so smoothly. Perhaps the carriage assembly could be simplified. It was rather difficult to get all the angles and alignments precise.
-I would purchase a heavier duty winch. The winch I used cost $12.99 and is rated at 1000lbs. I would be scared to put 1000 lbs on it. It might hold the weight but turning the crank would be very difficult. It is harder than I would like to lift the furnace. The single gear on the winch is already showing signs of wear. Harbor Freight Tools offers several higher capacity winches. One is basically the same but with a longer lever arm and double gears. Another is a screw gear, which offers a lower ratio (increased turns). I think either would be worth the few extra bucks.
-Purchase a pre-made blower. I spent way too much time with the blower. By the time it was finished I do not think I saved much if any money. I had to buy sheet metal, rivets, a riveter (a good tool anyway), belt, pulley, bearings, bolt for axle, find a motor, and make two fan rotors before I got it right. This took a lot of time. If the budget allows then purchase one. In the long run it may even be cheaper. Of course you might not be able to find exactly what you want which was one reason I went to built one. I would try GRAINGER ( www.grainger.com ). They have a wide selection of blowers mostly for HVAC units, of which many will work great.
-Cure the refractory quicker. This may vary on your exact product. I waited weeks before I fired the furnace up after casting the refractory. I put an electric heater in it for several days. Then I let it sit. I should have fired it within about 48 hours. It did strange things in those weeks. Crystals grew on the sides and the exposed surfaces and then turned soft which are now flaking. It only flakes to about 1/8 inch. I have cast some crucible blocks and fired them right at 48 hours after cast and they are hard as a rock. Not a total loss but it did shorten the life of the refractory some.
-Allow the entire exhaust to be TEX-KAST 80. In the lid I cast the bottom 3” as the Tex-Kast 80 3200 degree F. Above that is 3” of 1800 degree F insulation. I often choke the exhaust with a block of refractory in order to keep in heat and tune the furnace. This has melted the lid insulation lining since it is in continuous contact with high temperatures. I would put a sleeve of the high temperature stuff all the way out.
-Allow more than 1” of refractory for the gasket to sit on. I used a 4” shelf with 5” of refractory. This puts the refractory overhanging 1”. I would make the shelf 3”.
-Do not wait until spring to purchase the ceramic rope for the gasket. I saw this stuff all winter in home improvement stores for fireplace doors. Came spring nobody had a clue of what I was talking about. I had to go to the refractory supplier. I got a much thicker rope but had to pay more for it. A fireplace seal should work fine. Just make sure it is rated for the approximate temperature.
-Purchase a regulator with the fittings and pressure gauges included. I purchased my regulator from Tractor Supply Company. By the time I purchased the fittings and gauges it would have probably been cheaper and better to purchase one made for a propane-cutting torch. Harbor Freight sells one for what would have been cheaper. However it is for an acetylene setup, which may or may not be compatible depending on the seal and diaphragm material. Use only a propane compatible regulator.
-Do not purchase the garage door pulleys for the cable routing. What was I thinking? If the lifted weight of the furnace is about 290 lbs then the top pulley has a total load of 580 lbs of load. It was crushed quickly. Not a critical failure but it will have to be replaced. The other two pulleys have only about 410 lbs of load since the resultant opposing force is at a 45-degree angle and not 180 degree. They held up a little better but still need to be replaced.
-The winch could be routed in almost any location. I felt that I did not want to be close to the body as I lifted and lowered it. It naturally fell to the present location when routing, mounting, accessibility, and safety was considered. I do think that I would like to have it closer though. It works best to have someone else operate it but that is not always possible. Dale from Hobbicast has suggested using an electric winch. I think this would be really handy to include. I believe Harbor Freight Tools has a nice one for not much money (but considerably more than the manual type). This way the winch could be mounted directly above or routed through pulleys to any location. Accessibility would not be an issue. Just have a wired remote in hand. This may only interest the “extreme builders” or those of use who just like to play with such mechanisms.
-I would mount some handles to push or pull the big lug around with. I like the fact that it is completely mounted on wheels. This enables me to move from where I want to store and work with it. It is very heavy though and is not easily pushed by one person. If there were a good place to push or pull it would be much easier.
For the most part that is it. If I obtain some more I will post them as well.