Home Foundry

Update:
After 5 years of using this foundry I decided to re-line the inside with some fire mortar. See the videos below

Project:
It all started with inheriting a 1949 Ducati Cucciolo (motorcycle /moped) which in itself deserves its own blog post some day down the road. One of the things I've noticed was that the kick stand was broken. Of course, the first thought I had was gosh, I can fix that. But soon i realized that it was actually cast aluminum which is pretty much impossible to fix so I thought gee, I can MAKE one. That started the long (but rewarding) journey and research into building my own home foundry.

Process:
There are a few things that are needed for a home foundry:

1. Foundry furnace
2. Propane burner
3. Molding sand
4. Molding flasks
5. Crucible & tools

Each of the above deserves a lot of details, but for the sake of brevity (and not to bore people, particularly my wife Melanie) I figured I'd give a brief summary, then the pictures

1. Foundry furnace
I found a 30 gallon steel drum at a scrap yard dealer for 10 bucks, cut it to size and lined it with a 2" layer of cement/vermiculite (1:8 ration by volume) with just enough water to make it workable. After curing the cement for a few days, I added a 3" layer of cement/silica sand/fire clay/water mixture (10:20:20:7 ratio by volume). After covering it with poly and letting it moist cure for a week I removed the poly and it's now drying. By the end of the week I hope it will be cured and dried enough to fire it

2. Propane burner
During our trip to the states I found a 20 buck propane burner that hooks up to a regular BBQ tank which I intend to use to fire the furnace and to use it to melt the aluminum. I will probably have to make some adjustments to it but I won't know until I'm ready to actually use it.

3. Molding sand
After some extensive research, I found out that molding sand is actually simply silica sand mixed with bentonite clay (the stuff well drillers use as lubricant and well sealant) and about 5% water. The clay makes the sand stick together enough to hold a shape and the coarseness of the sand makes it porous enough for the steam to escape when pouring molten aluminum into it.

4. Molding flasks
Simply a frame made out of wood to hold the molding sand

5. Crucible & tools
Although a $200 silicon carbide crucible would have been the cat's miao, I decided to go with the cheaper alternative and pick up a 6" long, 6" diameter 3/16" thick well casing at that same scrap yard for 5 bucks and weld my own crucible. The tools were made using 3/8" square solid iron rod bent into shape and a little hook from a piece of 1/4" round steel rod.

Videos:

Pictures:

1949 Ducati Cucciolo in its glory

Broken kick stand that was fixed by a previous generation

Drying out 40 lbs of bentonite clay

Ball mill used to crush up bentonite clay

Cement, silica sand and fire clay (clockwise from left)

Mixed up refractory (10:20:20:7 ratio by volume of cement, silica sand, fire clay and water)

Top 5" of water barrel with a 2" hole

Mixed up insulation (1:8 ratio by volume of cement and vermiculite)

Bottom 17" of water barrell

Welding 10mm rebar into the lid for reimforcement

After a 2" cement/vermiculite layer of insulation

Adding a 2" cement/vermiculite layer of insulation around the outside as well

Getting ready to place the refractory. I increased the hole to 4"

Lid drying out

Base after a 2" layer of cement/vermiculite insulation

Placing a 9" centre to leave a 3" space for the refractory

Cutting a 2" ABS pipe to create the hole for the propane burner

You can see the refractory is half way done

Almost at the top placing the refractory which was of a model clay consistency

Top-down view of base

Wrapped up in poly to cure for one week

After a week of moist curing, air drying it out for one week

A few 6" diameter well casings (9", 11", 6" high from L to R)

Cutting a base out of 1/4" flat steel

After the bottom was welded and a spout was hot formed

The crucible after welding the hooks on the side and the back

Hooked with the crucible tools

The crucible tools

As a test, I wanted to make a mold of a broken construction lamp

Filling in the green sand

The mold after it was rapped and struck off at the top

The mold was flipped around and the bottom of the construction lamp is now visible

After the construction lamp was pulled out. Normally, there is a second part of the mold, the two parts are put together and the cavity is where the molten aluminum is poured in

UPDATE:
It's been 4 years since I built the home foundry and it is still going strong. The fire clay has developed some cracks but nothing too big; I won't even bother patching it up. The crucible is taking a beating but is still almost 1/4" thick so I don't see it failing anytime soon. Here are some updated pictures of the furnace and crucible:

Tools:
Ball mill, welder, grinder, hammer, drill, hole saw, scale, vacuum, gloves, respirator, eye protection, ear muffs, measuring tape, pencil

Materials:
Vermiculite, silica sand, portland cement, fire clay, 30 gal. steel barrel, 4' of 10mm rebar, ABS pipe, sheet metal for core, 1/2" melamine for core, 6" dia. well casing, 1/4" thick and 8" wide flat steel for crucible bottom, 3/8" square steel rod and 1/4" round steel rod for crucible tools, poly

Cost:
$200.00 so far

Time:
About 40 hours so far, not including time spent for research

Conclusion:
To be determined