Foundry (DIY flower pot)

Foundry 1.0

• following Lionel Oliver's Flowerpot Crucible Furnace instructions

Materials

• popcorn tin
• blower (24v dc blower running at 18v)
• refractory materials
  • portland cement
  • silica sand
  • clay planter
  • broken clay planter bits
• scrap steel for lid walls (from cubicle wall cut offs)
• wire for lid refractory retension (bicycle spokes from West Town)
• something for a lid handle (3/16 inch round steel hand bent into shape)
• crucible (3.5" pipe with a plate welded over the end)
• air spreader (a folded and drilled piece of scrap sheet steel)
• air intake pipe (Nothing permanently in the tuyere, using some leftover crucible pipe)
• tongs (square tubing with pieces of crucible pipe welded to one end)
• charcoal
• slotted steel spoon for slag removal

Construction

The flowerpot crucible was constructed and the whole process went as expected. The only problems were when we tried to deviate from the instructions. Using PVC pipes for forms for the holes was trouble when we tried to get them out. Apparently concrete doesn't mix by itself if you just stack the cement on top of the sand (silly me) so about an inch of our lid insulator just crumbled off. Our tongs are a little wide and/or our flowerpot is a little narrow so it's impossible to pick up the crucible with them. This wasn't helped by adding little nubs on the edges of the crucible to prevent slipping; the jaws can't get around them.

First Burn (2009-08-01)

We didn't get much melted aluminum. Many cans went into the crucible and crumbled into a powder but only a few bits melted and they solidified in the crucible. The harvested AC blower overheated and died, so it can't handle the duty cycle. The heavy duty blower in the space we tried is too powerful, it eats through charcoal and blows all the heat out the top. The tiny 24v dc blower undervolted to 18v is probably the right size. It may be too small, in which case I'll just get another one and use them both. By the time we realized this we were already too full of ashes to get any airflow. It was also difficult to get the charcoal started. The coals are separated from any fire you put in the tuyere by the air spreader. We finally got it going by starting with oily paper, then the charcoal and crucible. We had to wait for the coals to light each other naturally because the blower was blowing them out. The switch to the smaller blower will probably help with that problem as well.

Next time we'll start with the small blower and a shorter pipe. (a piece of the PVC we used as the form should work and hopefully won't melt.) I'll grind down the edges of the nubs on the crucible and cut off some of the back of the square tubing used for the tongs to make that fit.

Ideas for Moldmaking

Lost Foam

• Carve a block of foam Lost Foam howto
• Cast a styrofoam positive in a plaster die following this information

Greensand

• I have this book [1]