French Aluminium Alloy Home Foundry

Ron Wallman

I have been asked how I do casting but this is a massive subject and a spin off from Five inch gauge trains. As this could be a thread of book like size I have only put an introduction and very basic kick off information on the forum. I will expand on request but there is going to be an awful lot of text.
I only cast aluminium alloys as they are good enough for what I need. I normally cast in the winter so that waste heat leaks into the house. What I do is potentially extremely dangerous. It works but I am skating on edges based on that I did foundry work professionally and hence know what can go wrong and be standing just out of range or line. It would be dangerous to stray very far from what I do. I will say right away under no circumstances allow red rust to get anywhere near hot aluminium. It will explode if conditions are right. What I do might look care free but it is based on knowing what I can get away with.

What I recount needs to be checked against other sources so that you can find a method that suits.

The kick off information is that:

I use Petrobond sand.

I use 100 mm steel tubes to make casting flasks for most of the models I make.

I use homemade patterns usually made of acrylic plastic.

I use any aluminium scrap I can get hold of although I suspect most of it is Dural.

I use a hand held propane blow torch to heat scrap in a steel ladle.

I prefer bitter beer. Only the insane or drunks would try home casting.

I will wait for someone to ask for an extension of information. This too might stop short to limit text until somebody triggers a response or buys me a beer.

I have added a shot of four castings in the sand as viewed when the flasks were opened and still hot, plus two previous ones that were part of the ore car I made. These are the batch of forty lower hinge castings and I have put the split pattern that was also a casting in the view. The flasks are 100 mm square. The foundry sand is a mixture of my own and has gone nearly black. Usually Petrobond in its fresh state is red. This shot was taken as a personal note as I tend to forget how I made things. This is exactly how it was done complete with all the mess. The flasks are in an up turned strong steel shelf that I use as a moulding board. The edges conveniently retain sand but even so I get sand everywhere when I make the moulds.

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Ron

Jim · Posted: Sun Aug 17, 2008 11:47 pm Post subject:

Thanks Ron for opening up an activity that could be of use to a number of us.

In my case I need for a start, a number of cosmetic cast leaf springs and their hangers. Casting in aluminium, dangers taken into account, could seem to be more achievable within the home workshop than say casting in bronze, or maybe not I don't know hence my interest.

As a starter, for small objects such as leaf springs are there alternatives to casting sand for the moulds?

I'm glad to learn that others also forget how they did things. I'm still trying to work out how exactley I secured a 10" disc for machining in readiness for cutting a 100 tooth final drive for my traction engine. I did take photos but none showing the setup I used.

Jim

Ron Wallman

Hi Jim,
Yes you can use plaster of Paris instead of foundry sand or if you can find an art supplies shop, casting plaster. Plaster can set very quickly and can get hot whilst setting due to chemical reactions. You will need to bake it in the wife’s oven to ensure it is absolutely dry. Usually metal is cast whilst the mould is still very hot. You can slow setting plaster down by er... how can I put this?... you pee into it. The major problem is getting the pattern out as usually this is a lost wax process. The other problem is air bubbles that cling to the pattern and form otherwise beautiful knobs on a casting. Plaster gives a much finer finish than sand.

If you use plaster of Paris or dental plaster you have got to move fast. Use a kids plastic potty to mix (one with a handle), use your hand and you literally throw the stuff onto the pattern. You need plenty of water available to wash off your hand as setting involves heat and you could lose entrapped fingers. Knowing the danger is the way of avoiding it. You need to mix and get the mould made in around four minutes. You get plaster everywhere at these speeds. At seven minutes the plaster would have set. You need to wash off long before this happens.

You could try and get hold of casting wax and open a whole new world of casting in wax and then lost wax casting. As I said this is a whole subject in itself. Casting wax is expensive but less than machinable wax. I still think wax is a great deal of fun but I have a dead hand. I can imitate others but my art work lacks life.

I have used steel tubes as a flask for plaster and a small plank wrapped in wet newspaper that is placed firmly on the very hot and just poured metal header. You need gloves as superheated steam is nasty stuff. The trapped steam then drives the molten metal before it. You have to be very quick. This works for very small castings but it a bit risky. I had the neighbour call the fire brigade when he spotted me doing this as he saw me disappear in steam and smoke. The chief fire officer lived two doors away at the time and was round in a shot only to find me just watching freshly cast flasks cooling down. He stopped his men from arriving.

The still fairly hot flask is then thrown into water. Depending on size we could be talking of half an hour later. The plaster will then react going into the most awful muck but soft so it can be blasted away with a hose and brush. The mess is foul and probably a major polluting agent.

You can add sand to the plaster. In art school we used casting finings and silica flour with plaster as a third each mix but I am going back a bit and even in those days they were difficult to buy.

I found one art supplier in Paris selling casting sand. You need a supplier that deals with sculpture and statue makers. Your best bet is to find either a casting material supplier or slither into a foundry having a sack and a bottle of spirit such as whiskey handy. A swap is not usually a problem. There are recipes published in various home casting books and watching how casting is done in India is an education. If you think what I do is risky you have not seen anything yet. Foundry sand is simply sand, clay and water. Casting can be done in the street. Remember ancient Egypt could make castings in gold and Nile crocodiles are smaller than sea crocs in NSW for those that failed to get it right.

I have attached a shot of the ore car castings that follow on from the previous shot. There were forty to be done so I was busy milling them.

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Ron

Jim · Posted: Sat Aug 23, 2008 12:30 pm Post subject:

Hi Ron,

Sorry for the delay in responding to your very helpful reply but we were away for a few days catching up with our daughter who had driven down from Alice Springs, a distance of 2100 odd kms, not to see us of course Sad

but to take her dogs to a dog show!

Anyway back to the main story. Being a keen '0' gauge modeller (as a break from the 5" gauge) I'm familiar with plaster and all its messy features.

With the helpful information you have supplied I shall have a go at casting some dummy leaf springs. I'll keep the site posted on how I go.

Jim

Ron Wallman · Posted: Sat Aug 23, 2008 1:37 pm Post subject:

Hi Jim,

Of course we have heard of a dreadfully slow train service and a young lady on board getting more and more anxious about her arrival time at Alice. The guard enquired and it turns out she was about to give birth. On being told that she should have never got on the Ghan in that condition she replied that when she joined the train she was not expecting.

I am a little wary of plaster mixes as foundry sand is much faster to use. Are you sure there is not any sand lying around at Alice?

I have attached a shot of the acrylic patterns of dummy springs that I have made. These do not have much or any draft on them. I mean an angle of 1° for external surfaces and 2° for internal surfaces so that the entire pattern is tapered. This will allow the pattern to lift out of the mould easily. Introducing a shock should release the pattern but not enough to break the mould. I would be inclined to spray the pattern with PTFE to ensure that it would release.

The ‘leaf springs’ were made by cutting sheet with a slitting saw putting a small chamfer on the edges and bending them to form a curve whilst the glue was setting on assembly. The more bizarre spring and strange axle box was used on the Playmobil carriage on the forum under Playmobil train. It is a representation of what these gauge one toys have.

I have also attached a shot of the finished but not cleaned up casting awaiting its turn to be finished. I forget what happened. We moved house and ongoing projects went to the wall at the time. It gives you an idea of what can be achieved with oil bonded foundry sand. The spring eyes are about 105 mm apart.

Good Luck.

Ron

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Ron

Jim · Posted: Sun Aug 24, 2008 1:27 pm Post subject:

Ron, that's just the info I was looking for.
I'm sure others will find your detailed photos and text as informative and helpful as I have.
You're a master caster Ron! Rolling Eyes

Regards

Jim

As a footnote the old 'Ghan' and it's slow progress on dubious track has now long gone. The modern standard gauge 'Ghan' is a great way to travel up to Darwin from Adelaide. We hope to make the trip next year to see our daughter in Alice Springs.

Ron Wallman

Hi Jim,

If you have enough information to have a go then I will hold at that point until you have made the patterns.

I try to scan the forum everyday but with three kids there are problems with getting hold of the computer. On principle I am here so if you or anyone else needs advice, I can be called.

Good luck

Ron
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Ron

ilvaporista · Posted: Sun Aug 24, 2008 6:13 pm Post subject:

Good info. Thanks very much for the posts. Another thing I must get round to doing...
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Adrian Parker

Ron Wallman

OK this thread has gone silent for a month so I will add a progress report.

I have just completed another batch of castings needed for the ore cars I am building. Getting hold of small channel section was easy until the garden centres switched from using this form of fence support to a Tee section. I still had a bit so I decided that I would use it as a pattern and cast rather than having to buy section from a stock holder that is quite a way off and does not want to sell to private individuals. As I recycle foundry sand my principle expenditure is propane gas. The price of gas I use is getting on towards the cost of petrol I would need to collect stock especially if I hit traffic.

I used a special long skinny flask because it is easy to make up the mould using a minimum amount of sand hence fast taking about fifteen minutes to make this one up. I have attached a posed shot of the ladle just after I actually poured as I cannot easily pour with one hand and photograph with the other. A further shot shows the flask shortly afterwards clearly showing that the fumes are on fire hence less smoke. The casting weighs 270 grams and I have forty two in the attached shot with one taken with its sprue removed so about 11.3 kg of castings are shown although only 7.1 kg will be used on the wagons. Had I used mild steel then 20 kg of steel would have been needed. This makes my train light for what it is plus ball bearings throughout means I use very little energy to run the train and one reason why I can run for so long on a single battery charge.

Picking an ore car up weighs about what I would expect it to. I think had I used steel then it would weigh about 30 kg and given any one lifting quite a surprise. This amazing weight also tells me why this type of wagon was not common. They must have been quite heavy and they are complicated meaning they were expensive to buy and run. I note that photographs normally show mostly wooden construction for this type.

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Ron