Casting Alumineum in the Forge

[IronPuppet]

Hi there,

I have a small casting project I am doing for a friend. I am going to use the lost wax technique. I have done this years ago and my memory is a little fuzzy. Perhaps someone can enlighten me.

I am going to make a crucible out of iron pipe by welding a bottom on it and making a lid and tools to lift and handle it for the pour.

I can't remember if I need flux to clean the aluminum before the pour. I know I will need a ladle to clear off any slag that floats, but what about flux? And if I need it what should I use for flux?

Of course I am going to preheat the mold as hot as I can make it, about 500 degrees in the oven. I think this should work.

Any help will be greatly appreciated.

Christopher

[Glenn]

Dress for the occasion, full leathers - leather chaps, leather spats, leather apron, leather gloves, steel toed boots, long sleeves, long pants, full face shield, eye protection (think shade 3 or shade 5 goggles), ear plugs, fire extinguisher, first aid for burns, cell phone pre-programmed speed dial, etc. Melt more metal than you will use during the pour.

Yes it is a pain, but not near as painful as something going wrong and hot molten metal being splashed all over you AND the work area. Be careful, and play safe.

[chyancarrek]

Hey Ironpuppet,

You can use plain borax (20 Mule team works fine) as a flux but honestly you don't need to do anything other than skim the cruce as you're already planning on doing.

What are you casting? Pre-heating the molds will help particularly if you have some narrow areas in the mold and/or finer detail - if the piece is larger and solid it's not as important.

A steel tube with a welded bottom is fine - don't overheat the aluminum - it doesn't take long to get to temp.

Glenn's right - if you haven't done it in a while, go overboard on the safety prep.

Let us know who it goes!

[IronPuppet]

Thanks for the info and advice.

I'm a model railroader and I love to scratch build stuff. A guy I know has gotten me interested in modeling a pole road. This is a very obscure type of thing to model and there are no wheels available in the current marketplace.

No one makes wheels because the complexities of modeling a pole road are challenging to say the least.

What is a Pole Railroad? Well let me tell you. You see along about 1880 until around 1920, small logging operations were a viable way to make some good money. Some of the smaller operations saved money by having trains that ran on wooden logs instead of iron rails. No cross ties were used. The logs were held in place by long wooden stakes driven through holes drilled in the logs.

So a crew could go into the woods and fell trees to build the pole road as they went. See photo here


This next pic is of the engine my friend is modeling and I am making the wheels for him. I was going to turn them on the lathe, but they have spokes. So I plan to cast them and then turn the concave wheel tread on the lathe. If I get the RTC casting silicone I want then I will just have to clean them up on the lathe and drill the hole for the axle.

As you can see, a lot of these locos were built in the logging company's black smith shop. A real catch-as-catch-can sort of affair. Often built with what was on hand.

My friend models in "O" scale (1-48) and I model in "HO" scale (1-87). I think I have figured out how to supply electrical power to the engine, but this will take some experimentation. No, not with a radio controlled battery powered unit either. That would be too easy and besides, dealing with batteries is a pain for something like this.
He wants 16 wheels for his engine and rolling stock, so the best way is to cast them.

I have done casting before and I think I am up to the challenge.

Christopher

Copyrighted photos removed and replaced with links

[chyancarrek]

Hey IP

Great info - I'd never heard of a Pole Railroad before!

Heating your molds for small scale stuff like that will really help as aluminum can misbehave when you're gravity casting instead of doing it centrifugally.

Look forward to seeing the results!

[IronPuppet]

Yes, I am familiar with centrifugal casting machines. The type used most commonly in the model train industry for casting low temp meal is nothing like the one I used years ago.

Now they use silicone molds that will take the heat and the casings are arranged in a disk-like shape and spin continuously on a turntable, then you pour your melt in the center as it spins. Designed for big volume, but has poor quality (IMO), flash and casting lines. Plus low temp metal is $15 to $20 a pound.

The one I used years ago was a jeweler's style. An articulated arm that is wound on a spring, then you set your hot mold in a clamp on the end of the arm and the gold was melted in a crucible a few inches from the mold and once melted, you close the lid and hit the release and the spring would spin the arm with great force. The molten gold would shoot out the crucible and directly into the mold where the force would push it into every void in the mold.

I'm not sure if I need a centrifugal casting machine for this job, but if I need one I will build it myself. Those commercial units cost real big bucks!

Christopher

Edited May 27, 2008 by IronPuppet
typing with feet.......again

[chyancarrek]

You got it Chris!

My casting machines are the jeweler's type and do give great results.
Yeah, they are real spendy given what a simple machine they are!
Luckily I got mine for free from a sculptor who didn't use them anymore.

Your intended method should work fine for you - let me know how it goes!

[Bentiron1946]

Have you finished your castings yet? If not you may want to try the lost foam method. Instead of wax you use Styrofoam or urethane foam. Then invest it just like the wax but instead of burning it out you direct pour the metal on the foam and have an instant burn out. Stinks like crazy but it works. I have cast some small parts for modelers of ships and planes with this method using pewter and zinc.