After deciding to build the DD-40, I had to figure out how to do it. I had originally figured on cutting the necessary parts from billet aluminum. I actually started this way and milled one side frame almost completely... before making a mistake that would have scrapped it. In addition to the potential for mistakes, It would not have been cost effective as the material cost would have been outrageous. I finished the part mistakes and all and patched it with an epoxy, this would become the pattern for casting the parts. With the pattern made it was time to make a foundry. This is what drove the project because I would have quickly lost interest if I had no NEED for it. My father and I built a Furnace, Muller, Crucible and Tools and then spent every weekend the summer and fall of 2010 learning how to do it. The process of casting is Faaaaraarrrrr more complex than initially presented. In retrospect it’s the part that caused alot of the pain. The size and shape of the side frame made it extremely prone to shrinkages. The part is big, which made every attempt a real undertaking. The flask is roughly 4 cu.ft., which is alot of sand to pack, alot of sand to mull and alot of weight to carry. We only had enough capacity to melt for one, and only enough sand and flasks to make one. Every attempt was 2 hours from pattern to part. At best we got 10 in a weekend. Learning a little at a time and making slight changes to the pattern or the sand would yield a slightly better part each time. finally the big break came when I at last addressed the obvious The thick middle could not be made without a core to lessen the volume of aluminum. First pour with a core 1/1/11 was a success. the first usable part emerged and it was a firestorm of progress there-after. Originally we set up in my fathers shop, (which is crowded already) and proceded to cover everthing with sand...it didn't bother me but He began to offer complaints after a couple months. He offered up one of his shed's to convert into a dedicated Foundry. It is not big but offers enough room to make things happen.
PHOTO: The furnace running under the vent hood.
We have a large storage chest to kep the sand. Never leave your sand out if theres a cat around, you'll find you need less bentonite .... A ramming bench, very sturdy 6x6 post lagged onto burried concrete blocks. the furnace nested below an exhaust hood; the stink can be pretty bad when fluxing/degassing. Finally the Muller, an absolute necessity if you intend on doing anything other than mixing sand.
PHOTO: a view from the distant corner of the foundry showing the Muller left, sand chest, ramming bench with compressor under.
PHOTO: Built from a carefully selected assortment of whatever we had lying about; the shell is made from an old air compressor and is lined with a castable refractory. The lid swivels open to remove the crucible. The flame is provided by a repurposed oil furnace gun in which we run biodiesel from a boat fuel tank.
This is a real machine made from a junkyard grab-bag. The center rotating mass is mounted on a Ford Ranger 8.8" rearend with the right side cut off and plugged. the bowl is he bottom of a large propane storage tank and the compactor wheels were grinding disks from some sort of concrete resurfacer, then filled with dumbell weights. The motor and gear reducer were purchased new but the gear reducer was a closeout special.
PHOTO: Again from corner, alittle more crap strewn about for good measure