Backyard Foundry

  • Holder

    I am thinking of making a backyard foundry (made of cement/steel mainly to smelt aluminum) and wondering if anyone wants in on it to help or has any advice.

  • Member

    @colin you probably don’t want to use concrete as it doesn’t fully dry for decades and if the water contained within the concrete heats enough you can have an explosion.
    @fullmetalmaker and I were thinking we would make one out of plaster of paris, sand and steel wool (the thicker stuff) similar to the King of Random

    , he has two other videos that are relevant where he converts it to propane and one where he puts steel wool in to make it last longer.
    I am also pretty sure @pierre has a torch available

  • Holder

    Yes, that’s the one I saw but assumed it was concrete. I would like to build this thing and use it to cast some aluminum blocks for machining.

  • Member

    @colin I have sand, a container to make it in and plaster at the space

  • An induction kiln seems like a fun idea. No fire required.

  • Holder

    I can pick up some scrap pvc to make an air intake, and some steel wool to strengthen the cast plaster.

    I kind of want to start with propane and get going faster, without having to design an electrical induction circuit, and also to keep it relatively portable to start. 50 amps is a lot!

  • Holder

    Just picked up two ~4 foot sections of 1 inch steel pipe and a couple packs of steel wool: 1 fine and one coarse to try out.

    Now that I think about it, it makes more sense to use coarse steel wool to increase the plasters durability, like how they use rebar to reinforce concrete and not tiny strands of wire…

  • Another inexpensive way to build a foundry:

  • Fire clay is easy to make. Torch is easy too. I made my crucible from a starter case.

  • Induction circuit is much more expensive to do than a simple resistive one you want to use kanthal rather than nichrome wire for the high temperature rating. I have Dave Gingery’s book on the topic if you want to read it. The Lil’ Bertha electric furnace used an oven control to operate it, which works and is super cheap (and the book was written in 1984…) but I Rick Sparber published an article about adding a PID feedback controller to the Hartman furnace (which was a Gingery furnace built out of soft fire bricks…) In the electronics lab, we have a couple of PID feedback controllers that would push enough power to do this I think.

    I also have my implementation of Lionel Oliver’s upwind propane burner in the metal room. Rigged to take propane from a bbq bottle through an acetylene regulator (better control and higher pressure than a bbq reg.) It is fierce puts out a lot of heat, and if you screw the right bell on it’ll become a small flamethrower.

    Rick’s article on PID feedback:

    Lionel’s article on the burner. It is the simplest high-energy propane burner I’ve ever seen.

  • Holder

    Nice, can I borrow the regulator for the foundry?

    I have implemented a few PID loops for industrial applications, I think it would be easy to do one up in software on a controller to an analog output feeding some FETs, and have some pots to tune the P I and D constants. I didn’t know they made dedicated hardware PIDs. If I move onto an electrical kiln/furnace, I’ll take a look at those loop controllers.

  • @colin : Grab the whole torch. It is in a bucket under the table in the far back left corner. I already swapped out all the fittings to fit the tank… if you want to try different torches, you just make them to fit a standard plumbing pipe thread, and use a bit of teflon tape to screw them on.

  • I brought in some aluminum rims. They’re in the mud room.

    We’ll bring them up to hot-short and break them up to fit a crucible.

    Please don’t cast muffin-tins for ingots. They’re a total waste of fuel and don’t stack efficiently. Much better to cast by hammering different diameters of dowel into a box of sand to make round stock that can be machined directly, or re-melted to cast other things. I’ll try to turn up a few blanks for making step-pulleys too. Blanks for these:

    would be quite useful for hacking up random tools out of motors and parts.

  • Holder

    Not quite ready to smelt yet! We’ve hit a few snags: ran out of plaster on Saturday, but I have picked some more up today, we’re having some trouble drilling the 1 1/4" intake hole into the steel container, and the drill press chuck shook loose when we were about halfway through.

    Also, we can’t find the torch you were talking about in the metal room.

    I will try to finish casting the plaster lining, and maybe try grinding out the hole we managed to make in the steel container (we managed to make ~1/4" before the drill press gave up, but we need 1 1/4").

    Does anyone know how to re fasten the metal shop drill press chuck? From what I can see online, I believe it’s just press fit into the drive “quill”?

  • It is a morse taper chuck. You clean the quill hole and the male taper with alcohol on a paper towel (to remove any grease), and then put in place with a bit of a slapping action. It is friction driven. Do not hammer on the jaws of the chuck. (Some people do that, but it makes the bits wobble.)

  • I’m willing to acquire a different torch for my plasma cutter if that lets us acquire the consumables easily. It’d be nice to be able to laser out a plywood shape, then trace it with the plasma cutter to make a hole.


    I posted this in my foundry thread a year ago. Tons of info. Incase anyone missed it.

  • Holder

    The foundry is ready to smelt, as soon as there is a crucible and a torch, and a couple holes drilled, and some protective clothing, and some scrap aluminum/copper.

    I think a high volume regulator (30-40psi) is needed to make a torch, and a carbon crucible is about $30 online. Anyone have any suggestions or contributions?

    Sorry I left the foundry in the lounge, I’ll take it home before Sunday. Does anyone have any recommendations for where to smelt? Need a spot on dirt or grass, and snow probably isn’t a good idea. Maybe a big backyard or someone’s farm?

  • Design Lab

    Can this be done on the dirt patch behind the Space? I’d buy a tickets for that! And I’d throw in $20 for stuff!

  • Holder

    I can think of a few reasons that may not be a good idea,

    Some people may frown upon pouring molten metal in a parking lot or around a busy location (did you mean outside the fab shop?). Not me though!

    Might be dangerous with the snow/ice out there right now -
    Molten Copper vs Ice Exploding Ice:

    You probably don’t want to be handling molten metal, with the chance you might slip on ice or snow.

    I would rather wait till the snow melts a bit, unless a patch of snow/ice was cleared really well, and use the foundry on a more out of the way location.

  • You really want to put down a pan with about 3" of dry sand to work on. No snow or ice. A large drop of water will empty a crucible of molten aluminum. Vertically. At which point it rains hellfire until the metal has all landed. Concrete will frequently explode as the trapped moisture in it flashes to steam if you spill on it.

    The regulator in the metal shop on my little melting torch is a Victor Acetelyne Reg, it can be dialed in to up to 60PSI as I recall. Look under the table in the back corner of the metal shop. The little 2.5PSI BBQ regulators are useless to melt metal with.

    I really don’t want to answer to the fire marshals when somebody spots us doing an unsecured melt out back and calls the fire dept.

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