Progress has been somewhat slower than expected on the shop furnace development front, but I wanted to share some little progress updates, a few pics from a local manufacturer that does green sand casting of aluminum, and some neat Google books.
At the open house we successfully did a lost foam casting, but the furnace was far from a reliable piece of shop equipment that we could train up new people to use safely and repeatably. I was basically scurrying around doing a lot of unnecessary work tending the furnace because it was in a perpetual state of near-failure. The goal is to have a sturdy piece of equipment that folks can use for their projects. If the furnace itself remains the focus of the work, then we're missing the point.
Based on the experience from the open house, the main improvement that needs to be made is actually to the cold section. I used one of the coiled fiberglass socks as the base for the hot section to sit on. This allowed an air "dump" or manifold underneath to drop the velocity from the shop vac (without losing too much pressure) before it hit the charcoal (combustion takes time, that's why scramjets take some thoughtful design). The bottom of the manifold was loose sand and clay (as a heat barrier), but I succeeded in blowing that stuff all over the place as the "sock" was really not up to holding much pressure: we can do better. I got an 80lbs bag of fiber reinforced cement and some cardboard for forms, so we can make a concrete base / cold-section. Should be much sturdier in all dimensions: structural, thermal, etc.
I had the great opportunity to tour Hartzell Fan's facility up in Piqua recently. They still cast many of their aluminum fan rotors in green sand. These castings are big. It takes a team of several guys to pick up the crucible out of the furnace and do the pour. Hartzell still finds it cost effective to keep their own foundry in-house. What I find encouraging for us: real manufacturing concerns still find green-sand casting of aluminum to be versatile and affordable. I think this will be a great capability for our space to continue to develop.
|Big Casting Still in Sand|
Here's a couple of neat (free!) books I found recently that I wanted to share. Cutting edge stuff (it was in 1913 anyway). The first one is on Forgecraft, the second on tool making.