Q-talk 102 - Backyard Foundry
- Category: Q-Talk Articles
- Published: Wednesday, 23 December 2009 16:24
- Written by Mike Callahan
- Hits: 3095
I have a backyard foundry I built several years ago. I have actually successfully cast a couple of motorcycle timing covers in green sand. They were not particularly attractive, but they did work nicely. I can melt about 60 lbs. max per run or as little as 3lbs., depending on which furnace and crucible I use. I have been using just junk scrap, mostly VW pistons and broken up water pump housings. Last year a friend gave me a bucketful of scrap 3003 slugs punched out of 1/4" thick angle from one of his projects. This stuff pours like water, no slag, no holes and it welds just like you would expect from 3003. The only drawback is machining. It's a little gummy, so you have to use VERY sharp HSS tools and high speeds to get a decent finish. Carve the patterns out of blue Styrofoam (yup, same stuff we make Qs out of) and make sure to allow for shrinkage. You can only produce one part using this method, but it works absolutely flawlessly. You can also use the foam and double shrink it to make an aluminum master pattern.
Now, do you want your own furnace? Here's a really fast way to build one. You will be able to melt metal in about 3 hrs., including the time spent rounding up all the materials. You probably have most these items in your home right now.
Materials & Tools:
5 gallon metal bucket 2 dog food or bean cans 8" clay flower pot 40 lbs. fine DRY sand Blow dryer (or vacuum cleaner with blower outlet) lOlbs. charcoal briquettes Duct tape Tin snips
Cut the top and bottom out of one bean can making a sleeve shape and the top only of can number two. Cut a hole on the side of can with bottom so other can will slide in to form a "T". Duct tape the joint to seal. Put the T on its side in bottom of 5gal. Bucket. Make sure the open end of can is facing up and can with both ends removed is pointing to side of the bucket. Cut a hole in side of bucket to correspond with open-ended can, center assembly in bucket and seal joint with duct tape. Sit flowerpot on top of open can end (cans and
Cut the top and bottom out of one bean can making a sleeve shape and the top only of can number two. Cut a hole on the side of can with bottom so other can will slide in to form a "T". Duct tape the joint to seal. Put the T on its side in bottom of 5gal. Bucket. Make sure the open end of can is facing up and can with both ends removed is pointing to side of the bucket. Cut a hole in side of bucket to correspond with open-ended can, center assembly in bucket and seal joint with duct tape. Sit flowerpot on top of open can end (cans and hole in flowerpot are air inlets). Fill bucket with sand around flowerpot and cans to hold in place and insulate from heat. Stop about 1/2" below rim of flowerpot (don't sweat it if you get a little sand in the bottom). Voila...FURNACE.
2-3" long section of 2-3" steel water pipe (preferably not galvanized due to zinc) 1/4 "-3/8" steel plate disc to fit pipe 2 large nuts
2 pieces steel rod (rebar works great)
Weld a disc to one end of pipe to form crucible. Weld INSIDE AND OUT THOROUGHLY AND CHECK FOR ANY LEAKS WITH WATER. Once you are sure you have a solid and robust weld, heat an edge of the pipe and bend out (quickly) with pliers to form pouring spout. Weld nuts on one side of pipe, top and bottom, inline with each other. Bend a short crook in the end of rebar to fit into nuts securely. Bars are hooked into nuts and both bars held in one hand for lifting crucible from furnace. Bars are separated and used independently with each hand for pouring.
Put layer of briquettes in bottom of flowerpot. Light the briquettes with charcoal lighter or propane torch (I like oxy-acetylene). When burning, place cmcible about 3/4 full of aluminum in center of pot, fill around with more charcoal, stick blow dryer nozzle near hole in side of bucket and turn on (cool setting works fine). It'll take about 25 minutes to melt. If you wish to add more scrap, do so as the initial charge melts down. Do not exceed 3/4 load in the crucible... too dangerous to handle. You should get two heats out of a 101b. bag of charcoal. Go to a thrift store and buy an old used muffin pan to use for making ingots. Make sure it is uncoated and steel. A Teflon pan will stick and an aluminum pan will make things interesting really quickly. Here are a couple of cautions. Wear leather boots and gloves. Better burn cowhide than your hide. If you can get some fireproof clothing, it's a REALLY good idea. Lots of Volcanolo-gists wear old surplus military flight suits for hot work made with Nomex. You can usually get them at a thrift store for under $15. A friend mixed some coke, found by the railroad near his house, with the charcoal and nearly melted the 3/8" steel bottom out of his crucible! This thing gets HOT! Coke gets hotter. If it is getting too hot back the blower out a few inches.
The flowerpot is GOING to crack after about five minutes of heat. Don't freak out. It's just there to hold the sand back, anyway. Handle it carefully and you will get four or five heats out of it. When it finally collapses, or you just want to fix it back up, pull out the big parts and filter the sand through a wire screen sifter into another container to remove the small fragments. Then go buy another $ 1.50 flowerpot and refill. I use this for my small runs and have gone through about four pots so far. The main thing is to keep the sand DRY!!! WATER IS THE ENEMY OF THE FOUNDRY. I keep my sand in a big Rubbermaid storage tub.
You can order a printed copy of Q-talk #102 by using the Q-talk Back Issue Order Page.