DIY - Backyard Metal Casting

[JerryRigg]

That's cool man! I want a cupola furnace but I think I'm better off casting aluminum first with a basic, backyard casting furnace.

Casting steel for exhaust manifolds, parts, etc would be fun.

Steel is out of the range of backyard capabilities... too hot for most combustion based furnaces, or at least totally impractical for usable amounts. Need induction or arc furnaces for that stuff. Castiron melts much lower and can be done in an oil or even gas fired furnace but it takes time.

Cupola... I have one partially built. It needs to be lined with refractory and a mass of molds to pour all that iron into. They're beasts. Iron works fine for exhaust manifolds.

Lots of really good info on alloyavenue.com

In the meantime anyone who is interested in getting things cast feel free to contact me

[ericjon262]

Steel is out of the range of backyard capabilities... too hot for most combustion based furnaces, or at least totally impractical for usable amounts. Need induction or arc furnaces for that stuff. Castiron melts much lower and can be done in an oil or even gas fired furnace but it takes time.

Cupola... I have one partially built. It needs to be lined with refractory and a mass of molds to pour all that iron into. They're beasts. Iron works fine for exhaust manifolds.

Lots of really good info on alloyavenue.com

In the meantime anyone who is interested in getting things cast feel free to contact me

Thanks for chiming in here! I was wondering where to go for a good forum on casting! I really want to do a LIM now!

[Futures Passed]

I watched the first two videos and I already want to make something.

Would drink-can aluminum be too low-grade for something like a throttle body? If so, I know someone that has a massive amount of the can tabs that they're not using; I've heard those are more pure or better in some way.

[ericjon262]

the main problem I see with drink cans is the paint, and the weight. the paint will add to the impurities, and you need a ton of them to cast anything substantial.

[JerryRigg]

The paint just burns off - it does not affect the alloy. There's two problems with pop cans. Well 3 I guess - 1. You need a *massive* amount of them to have a usable amount of metal. 2. Dross. "slag" if you want to call it - the large surface area and thin section of the metal means it oxidizes very rapidly, you only get 40-60% out in metal of what you put in. Save them for the scrap yard. 3. The alloy is almost pure aluminum - which makes it a very poor casting alloy.

Rule of thumb for acquiring scrap:

If it's cast to begin with, it's probably good for backyard casting. Cylinder heads, blocks, older small engines, alloy wheels, transmission cases, gearbox housings are all good. Extruded stuff (cans, window frames, siding, etc) is a different alloy and poor for casting/machining - but pulls in good money at the scrapyards. Take it in for $$$ to fund your adventures!

[pocket-rocket]

Rule of thumb for acquiring scrap:

If it's cast to begin with, it's probably good for backyard casting. Cylinder heads, blocks, older small engines, alloy wheels, transmission cases, gearbox housings are all good. Extruded stuff (cans, window frames, siding, etc) is a different alloy and poor for casting/machining - but pulls in good money at the scrapyards. Take it in for $$$ to fund your adventures!

Very good advice. I've been watching the videos when I find time (on #4) and I'm interested in experimenting in casting this spring/summer.

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[1988GTU]

If anyone is looking to cast something small, let me know please. I have something I'd like to have casted. PM me Thanks!

[unchained01]

Contact jerryrigg , thats his forte

[TGP37]

Making a custom LIM would be the ultimate backyard casting accomplishment. I can see myself spending a LOT of time sculpting the runners from a spare block in my garage. Maybe even build it to accept a supercharger.

Jerryrig, that's good info to know. I can hang with cast iron, make me some thick, high velocity manifolds designed for pulse tuning turbo. Maybe even make a twin setup and hang each little potato charger off each head. Would make for some insanely fast spool with such little exhaust volume between the heads/turbo.

If the manifold was made right, I bet I could fit them. Routing twin 2" downpipes should be easier then one 3" downpipe. Hmmmmmm

[JerryRigg]

I wish it would be that easy, that you could sculpt off of an existing part & cast it to match up. However, from your pattern to the casting, the casting will shrink 1-2% depending on the alloy... so something previously 1 foot long will end up cast ~11 3/4" long. Not as much a big deal with smaller stuff but it gets tricky with larger stuff. Patterns are made oversize to compensate for shrinkage as well as added material to alloy proper cleanup when machining. So if you work directly off the engine, it'll be too small once cast. Measurements have to be taken, scaled up, and then modeled into a pattern.

I'm still toying with LIM ideas but there's not much room to work. I could make a supercharger LIM but it would also require an ultra slim supercharger housing to be cast, something I'd like to play with but that's even more machining intensive than the LIM

The good news is, I've finally purchased a spare engine I can work off. The bad news, my time to do so is severely limited at the moment :/

[ericjon262]

I've started working on my furnace, right now, I'm working on the burner.

started with a propane tank adapter, it appears as though there is a valve of some kind built into it that is restricting flow,you have to knock it out from the threaded end.



i followed the adapter up with a ball valve for fast stopping of flow if necessary.



you can see the pressure regulator in the pictures as well... I was hoping to try and get the burner working this weekend for some odd reason. when I couldn't find a propane regulator that was adjustable, I grabbed this air regulator. I'm going to try it, and if it works, cool. if it doesn't, I'll get something else.



exploded view of the parts for the burner/tube



installed a NPT to flare adapter, and a union



slipped a short piece of 5/8" ID hose over a 3/4 NPT to 3/4 PEX fitting



slipped that over the nipple with the threads pointing away from the union



Drilled and tapped a cap so a MIG contact tip could be threaded in, threads are M6x1.0 BTW. then installed on the other end of the nipple, and installed the tip.



assembled the venturi, top to bottom: 3/4 inch black iron pipe, 1" to 3/4" reducer, 1" close nipple, 1" Tee, and 1" to 3/4" bushing.



then the brass nipple is installed by threading the 3/4 NPT to PEX fitting into the 1" to 3/4" bushing.



completed burner:



one thing that's really nice about my design, is that you can, fairly easily, change the size of the jet. I did it three times tonight, took a couple of minutes each time, but nothing too bad. on another forum, it was suggested that my burner is probably outputting about 150 K btu.

.025 jet, 20 PSI



40 PSI



60 PSI





.030 jet 20 PSI



40 PSI



60 PSI





.035 jet 20 PSI



40 PSI



60 PSI

[ericjon262]

got my crucible today.





it's pretty big...

[Xnke]

I'd think long and hard before I put that burner into a casting furnace. Too much PSI, too much airflow.

Your idea is close though, I'll take some photos of my casting setup for you this weekend.

The problem with too much PSI and too much airflow is that you'll burn a hole clean through the furnace wall, or you will overheat a spot on the crucible and crack it. Also it's nice to be able to choke the airflow down to do a melt in a reducing environment.



Make an investment in Thermal Ceramics K23 ceramic fiber wool for your furnace lining-much faster heat up times and better insulating value than hard firebrick or high-temp castable refractory. For aluminum castings, K23 is fine, for iron castings you'll need to use K28 backed with K23, and you'll want to use a high-temp castable for the working face-Mizzou K3000 is what I use.

[ericjon262]

the burner performs well across a wide range of pressures, the images above show everything from 20-60 PSI, but I can go lower, no problem, I can also restrict the airflow by installing a choke over the air intake. I can also adjust the jet size, and position. right now, I'm in the process of casting my furnace right now. I'm gonna try what I have, and go from there. if it works well, awesome, I'll stick with it, if it sucks, oh well, I'll fix it. won't be the first time I'll have built something twice!

[Xnke]

I normally run mine at 8-12 PSI gas pressure, and would melt 20lbs of aluminum and heat it to 1450F pour temp in 21 minutes from cold, or 11 minutes from hot. At 12PSI on the gas I had problems with burning the furnace up with extended casting days.

What are you using for molding? I used water-bond greensand that I mixed, and sodium silicate for cores. All wood patterns, including the two engine blocks I cast. Neither engine block has been machined yet as the castings still need to season...so I tell myself...in reality I haven't had a need for them yet.

I haven't actually fired up and poured a casting in years now, since I bought the TIG. Very few things I've *had* to cast, and most aluminum castings that come in for repair I weld now instead of re-pour.

Also, heat that crucible very slowly to full pour temp completely empty the first time. They absorb water just sitting around and if you don't fire them regularly they can shatter violently when heated.

Never add cold metal to a melt. Always preheat to 250F before adding to the liquid in the crucible.

Never pour over concrete or asphalt. Concrete spalls off razor shards if you drip metal on it, asphalt catches fire. Do it over bare dirt.

Get some good safety gear, I've poured a quart of liquid aluminum down one of my legs due to a crucible failure 12 years ago. I wouldn't recommend that experience, it kinda sucks. Ruined a good pair of blue jeans and a work boot.