Author Topic: A small foundry setup  (Read 7428 times)

PatJ

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A small foundry setup
« on: November 28, 2013, 06:34:42 PM »
I made this small (small being a relative term I guess, some have said this is what they consider large) furnace to melt iron and aluminum using propane.

These are the insulating type bricks, like the ones from Budget Castings, and they can be cut with a hacksaw easily, and shaped with a wood rasp.

If I had to do over, I would probaby just stand the bricks up vertically, in a circle, but I had to try this method, and wanted a perfectly round interior surface.

There is not much mass to this furnace, and I can pick up up by myself if necessary, or roll it around on a little cart.
The bricks are glued together with 2,700 F (?) furnace cement.

Two layers of ceramic blanket are wrapped around the bricks.

Two wash tubs from the hardware store, one washtub going on inverted after the ceramic blanket wrap.

It works well, and uses a #10 crucible.

Note:
Don't coat the interior with furnace cement, that is not a good idea, it peels off.
If you want a sprayed-on interior top coat, ITC-100.

And wear a good dust mask, don't breathe either the brick dust or the ceramic blanket fibers.
Don't breathe brass fumes either, the zinc in those is toxic.  Most backyard casters use bronze.
« Last Edit: November 29, 2013, 04:09:49 AM by PatJ »

PatJ

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Re: A small foundry setup
« Reply #1 on: November 28, 2013, 06:41:18 PM »
Here are the lifting tongs I made.
I included an adjsutable postive stop to keep from crushing the crucible.


PatJ

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Re: A small foundry setup
« Reply #2 on: November 28, 2013, 06:43:19 PM »
And finally a pouring shank.
The handle works best for me pointing straight down.
There are a lot of variations on pouring shanks.

I need to rework the crucible retainer, it does not work well.
I need to make a variable height retainer.

Offline Don1966

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Re: A small foundry setup
« Reply #3 on: November 28, 2013, 06:44:10 PM »
Nice setup Pat, you know it just occurs to me who you are. Welcome back bud.

Don

PatJ

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Re: A small foundry setup
« Reply #4 on: November 28, 2013, 06:49:32 PM »
Thanks Don.

I read the statement in the introduction section:
Please take the time to introduce yourself when you first register; you are assured of a warm welcome by all.

And so I took that at face value and decided to join up.

It is good to see much of the old group in one place.

PatJ

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Re: A small foundry setup
« Reply #5 on: November 28, 2013, 06:53:40 PM »
Here is the furnace in action, using petrobond (oil-based sand).

The crucible retainer design was not a good one, so the crucible slipped a bit, and sloshed molten metal.

Learning foundry work is trial-by-fire, so to speak.

This arrangement used petrobond (oil-based sand), and it has a distintive reddish color when new, or black when used for a while.
Note: "Petrobond" is a trade name for oil-based foundry sand.

A pyrometer is very useful for measuring brass, bronze and aluminum temperatures, and I don't try and pour these metals without the pyrometer.  It can be critical too good surface finish and pouring a good part that the pour temperature is hot enough to fully fill the mold, but as low as possible for a given metal.  Metal that is too hot can have a poor surface finish, and metal that is overheated can erode the sand mold.
« Last Edit: November 29, 2013, 04:15:02 AM by PatJ »

PatJ

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Re: A small foundry setup
« Reply #6 on: November 28, 2013, 06:55:32 PM »
The wife is dragging me by the ear to dinner.
More later.

Offline peatoluser

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Re: A small foundry setup
« Reply #7 on: November 28, 2013, 08:28:21 PM »
Looking forward to it. and welcome back

peter

Offline swilliams

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Re: A small foundry setup
« Reply #8 on: November 28, 2013, 10:27:35 PM »
Wow, very cool Pat
Just to get an idea, what size flywheel do you anticipate you could cast with this setup? Or is a flywheel too big?

Steve

PatJ

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Re: A small foundry setup
« Reply #9 on: November 29, 2013, 03:43:00 AM »
Thanks Peter/Steve-

A #10 crucible will hold approxiately 22 and 32 lbs. of bronze, or approximately 7-10 lbs. of aluminum, depending on whether you have an "A" shaped crucible or a "bilge" shaped crucible.

I think mine is an "A" shape.

I would think it would be a good idea to assume from a practical standpoint that you can pour at the most 70-80% of the crucible maximum rating.

Below is a 6" diameter flywheel with a 0.75" wide rim.
In aluminum it weighs about 1.06 lbs, and in bronze or cast iron it weighs about 2.86 lbs.
In either metal , it has a volume of 11 cubic inches.

One cubic inch of gray cast iron has a mass of approximately 0.26 lbs.
Once cubic inch of leaded bronze has a mass of approximately 0.31 lbs.
Once cubic inch of aluminum has a mass of approximately 0.0968 lbs.

So theoretically you could pour about 6 flywheels at 6" diameter each.
In reality, metal is required for the sprue, basin, runner, gate(s), riser (when a riser is used), and the weight of these items can weight as much or more than the part itself.

And with machining allowances, the part will actually weigh closer to 4 lbs in cast iron (before it is machined).

So with a #10 crucible, if you are lucky, you could perhaps pour two 6" dia. flywheels, or one larger flywheel, perhaps up to 10" diameter, depending on the size of the rim.
« Last Edit: November 29, 2013, 03:47:24 AM by PatJ »

Offline swilliams

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Re: A small foundry setup
« Reply #10 on: November 29, 2013, 03:54:29 AM »
Nice Pat!

Looks like you can really make some serious engine castings with that setup.

Steve

PatJ

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Re: A small foundry setup
« Reply #11 on: November 29, 2013, 03:57:59 AM »
And here is a second attempt using a white commerical foundry sand and sodium silicate as a binder.
The sodium silicate is a thick liquid that is mixed with the sand and then hardened with carbon dioxide gas.

Since the patterns were fully contained on one side of the flask (the drag or bottom half of the flask), I was able to use a piece of plastic wrap instead of parting compound (parting compound is generally powdered corn starch).
« Last Edit: November 29, 2013, 04:02:32 AM by PatJ »

PatJ

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Re: A small foundry setup
« Reply #12 on: November 29, 2013, 04:00:14 AM »
Nice Pat!

Looks like you can really make some serious engine castings with that setup.

Steve

Thanks Steve-

A #10 crucible is a nice size because it is large enough to make model engine parts for most common model engine sizes, but small enough to be hand lifted and poured.

As you get larger than a #10 crucible, you begin to require cranes and pouring carts.

PatJ

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Re: A small foundry setup
« Reply #13 on: November 29, 2013, 04:07:04 AM »
My first flask had identical alignment pins on either side, and I accidentally rotated the cope (top half of the flask) 180 degrees after pulling the patterns from the sand, and thus had a mismatch out of alignment part, where the two pattern halves were not aligned.

So I studied the commercial flasks, and noticed that one pin was larger diameter than the other, in order to prevent assembling the cope and drag with the wrong pattern alignment.

Below is the hardware for one side of the flask.

 

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