Next Patternmaking Question...

[addo]

Looking at the standard 2V manifold, I have some questions/ideas. Here's the top view:



And the bottom. It's my belief that the centre shape is a mock "Map of Australia".



Mating face (flange):



View towards head (Note angle of carb pad; manifold runners in horizontal plane):



After reading up more about pattern making and casting alloys, I came up with a few questions.

I assume that the mould is stood on edge , flange face down when pouring. Would this be likely? Note the bandsawed patch which would be on the "top" if this were the case. (See view towards head.)

As aluminium shrinks about 2%, do you make the main passages' core mould larger or smaller than desired finish size? Or is it in fact exact?

For the water jacket, following my surmise of the mould-on-edge, would the core for this be supported just in the hole now filled by the allen head plug? (See the flange view.) Or, would it be stabilised by one / both of the water pipe holes?

There are (from memory) three parts visible in the pattern (it's hard to see in the pics). Would this be due to a simple approach, using the one pattern to mould the cores and outside form? Or would there be some higher-tech reasoning in it?

Have I missed anything blindingly obvious?

Adam.

 

[weeds]

Parting line can be seen in picture number 4.

Since these were likely poured in batches, they would have been poured with the parting line horizontal. It is easier to make the mould. The gate(?) would have been to the heaviest part of the casting, and the bandsaw marks would indicate where. There may also have been gates located near cylinders 5 and 6, but I doubt it.

Because the aluminum shrinks, the runner core would be just a touch larger since as the metal shrinks, the circumferance of the runners would shrink. Although, at a shrink rate of only 2%, it may have been cast to near final dimensions.

The water jacket core would have been supported in at least three places. Locates it in XYZ planes and secures it against rotation.

Three parts in the pattern? Florida Phatman may have more and more correct input. I see three pieces to make this casting. The pattern, the core for the runners, and the core for the water jacket.

Afterwards, machining for the carb mount, the water inlet (pressed in pipe), the threaded bosses, and the core plugs.

 

[Anonymous]

Hello Addo and Weeds,

I tried to post yesterday but it wouldn't go.

Weeds your correct in how it was cast. The Stem would have been in the heaviest area with Risers in the outer most areas.
The mold would be horizontal with a slight tilt so that the metal would flow down hill, it tends to pick up less inclusions that way.

The mold is made of sand and sodium silicate (water glass) and set with CO2 gas. The cores are made of the same material but with less sodium silicate or added impurities like fine saw dust. The cores are painted and vented to the out side of the mold to prevent ingassing of the aluminum.

It's really remarkably simple and a lot of fun!

John

 

[addo]

I've lost a lot of time this week waiting for someone to give the "go" on a job that was to be done BC (Before Christmas) - would have been able to hack at some patterns. Nothing this fancy, but still...

 

[addo]

OK, this setting of the moulding medium by fumigation - what are the physical requirements of the patterns? Like if I have a pattern for moulding the cores (as you have suggested prior), does it need to be metal to withstand this process? Ditto for the exterior moulds. You say the cores are then painted. What with? Graphite coating?

Core size - If I make it 2% oversize, won't the casting be under stress as it sets up? Or doesn't this matter? And do you typically turn out (shake out) aluminium manifolds hot or cold?

The box for the pour - looks like everyone uses timber. Is one inch OK? Just some kind of stable timber, or is there a preferred, like oak, pine or something?

Cheers, Adam.

 

[Anonymous]

Hi Adam,

When the molds are fumagated, they are not under any stress at all. I use wood, plastic body filler(bondo), clay, anything that I can shape.

The reason why I paint the core molds is simple.
If I use just sand and sodium silicate for the core it is just to hard to get out of the casting. So I ADD impurities like saw dust. This causes an out gassing problem. So I seal the core with Latex paint and vent it to the out side of the mold. But it allows me to remove the cores much easier. Plastic drinking straws work well for core vents.

Core size does not really have much bearing on the stresses in a casting. I have shaken out both hot and cold and I prefer cold so I can handle the casting easier and I know that it is not stressed.

Box for the Pour
There is no box in Hard Sand Casting. That is Green Sand or Petro Bond Casting. The hard sand is the mold. It is held together with clamps. Apply a bead of calk to prevent leaking of the two mold halves. The little bit of flashing that ends up on the casting is easily removed.
Box for the Cores and Mold sets are made of plywood and steel corner brackets held together with screws. There are hundreds of little holes in these for the CO2 gas to pass through. Then the box is disassembled leaving the hard sand mold.

Pattern Boards
The Pattern Board represents 1/2 of the mold that you are making. It is a flat board with half of the mold permanently attached to it. Maintain a 2% draft angle so it can be removed after gassing. It will be on the bottom of the Mold box.

If you ever saw it done once, you would see just how easy this is.

Take care,
John

 

[addo]

Aha, I'm learning more as we go! The core and venting isue is clear now. Latex paint here would mean just regular water-based house paint. But there is also brushable latex that we use to glue the discs on the big stationary sanders. So you don't pack the mould sand as hard (compared to green sand casting), or do you? What is the real advantage of fumigated moulds over this other process? Can you rework it once it's set?

Can't see the draught issue being a problem with the shapes I'm thinking about. Lots of nice curvy surfaces.

Thanks, Adam.

 

[Anonymous]

John, I'd really like to see a "how to" web site with pics. Know of any good ones?

Thanks for sharing your expertise with us!

 

[Anonymous]

Stan the Man,

For You only the finest will do!

http://www.chiheads.com/articles_06.html
http://www.dmdaustralia.com.au/block1.html Check out the head 3/4 down the page. Looks like a round port Chevy Duggan!

These will show you what this style of casting can do, and where my evil little mind wants to lead you!

John

 

[Anonymous]

Hi Addo,

You don't have to pack the sand tightly just a little firm pressure. You want the casting to vent through the sand as much as possible. It is only the cores that require vent tubes.
There is also resin bonded sands, as you saw in the links above, they perform about the same as the CO2 set sand on smaller sizes and better on larger sizes.
The advantage of CO2 set sand is the speed, since the Sodium Silicate sets instantly and rock hard.
Once it's set there is no going back. But this is when I cut in the gates and risers and the sprue. A dremel tool works well for this. I use a 1/4 long snout die grinder, the same that you would use for porting heads.

You know you want to do this!

John

 

[Anonymous]

Wow! Those are incredible.

Is this the work you do, John? Patternmaking, molding and casting? I have a book on how to cast your own small pieces in simple sand molds, but it doesn't get into anything about pattern making, cores, etc. The book presumes one is making solid pieces.

I quick question about the water jacket core on DMD's website. The core appears in the photo to be some kind of pink foam, perhaps painted. Is that what it is?

Thanks!

 

[Anonymous]

Hi Stan,

I'm a Distiller by trade, I do foundry work as a hobby.

The material that looks like pink foam is resin bonded sand. The dark paint around it seals in the gasses that are produced when it gets heated a lot. You should be able to see the little vent tubes leading from it in the big mold.

I've used Lost Foam a few times, but only when it was a piece that I was going to machine as it is a little on the crude side for hobby use. The factories are better equipt than the average hobbiest.

A lot of very good books on Foundry and Pattern Making can be found on Ebay, one of my favorites is the Navy Foundry Manual.

John

 

[Anonymous]

Thanks, John! Three such books are on auction right now.

 

[addo]

I still can't get over those two sites. They actually make me proud of my country - go figure.

You know you want to do this!

Do I what?!? Hanging out for a chance!!!

 

[Anonymous]

Hey Addo,

There are several Very Good Foundrymen down in your area. Like me, they do it as a hobby. But they are way past me in skills. They could teach you all you need to know to create the castings on those two sites.

They are not into cars, they build perfect scale models of Steam Trains. Real beuties, highly complex and very difficult to produce. The castings are so difficult that a car engine part might bore them, it's to easy.

I know Cameren has a 30 pound tilt furnace. So he could easily cast your intake for you. Or better still teach you how.

If you want his email address, just send me a PM. I'll get it to you.

John

 

[Anonymous]

John,
I have been sitting back reading all of your post. I checked out the two sites you should. You have really fired up an interest that I have had in the back of my mind for many years. My grandfather, and two of my great uncles were patternmakers, and they did small castings as a hobby. I remember my grandfather pouring a few parts for his tractor intake. I was very young at the time, he had passed away long before I got to the age to learn from him.
You have rekindled this interest of mine, I am going to get a few books. Start reading. I may to have a few questions for you in the future.
I do have a question do you know of anyone in the Western Ohio area that are into casting, that would share there knowledge with a new generation?
Thanks for your time!

 

[Anonymous]

Hi Falcon428scj,

Go to http://groups.yahoo.com/group/castinghobby/ and ask that same question.
This is a big group of guys that vary from casual intrest to major professional level. They all share a love of the hobby, and will tell you all that you need to know, and then some.

Ask about the Casting Videos that one of the members made that are for sale. They are great!

Metal Casting is one of the cheapest hobbies that I have found. I have seen guys start casting parts, good ones, for under $50.

Man, I love this stuff!

John

 

[addo]

John, I will get in touch with that chap if you forward me his contact. In the interests of courtesy to him, I'll continue my research by posting a few more pics and questions here first. There is a model steam bunch about a mile from my house, who run trains once a month or so. It looks weird to see grown men sitting on steam trains!

I also remember seeing on the 'net, those 1/8 scale V8 motors which actually ran. Awesome!

Sometimes I wish I had nothing to do except amuse myself... Everyone would enjoy the results. :roll:

Adam.

 

[Anonymous]

John thank you very much for your quick response. I hope to talk to you more in the future. I did go to the site that you suggested, I am waiting to be accepted in to the group.
THank you again!