Aluminum sand casting for Chenery Gnome Rotary

[albd5a]

That is a very nice casting !

Your riser located on the left has a very small gate into it, and so that gate solidified before the main casting fully solidified, and the remaining molten casting acted as the riser, and caused the shrinkage.

Perhaps use two risers at a 45 degree angle, and make the gate into the bottom of them much larger.
The gate could be perhaps six times larger than what you used.
You will machine that area anyway, so the size of the gate does not matter.

That is a really good casting for a first-time aluminum melt.
I tended to overheat my aluminum when I first started to cast metal, and that caused a very rough surface finish.
Now I use a pyrometer, and pour at approximately 1,350 F, which gives a good surface finish like you have.

Your mold alignment is very good.
This is a most excellent casting effort for sure.
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Thank you for your kind words Green Twin. My miscast defects could probably be repaired but I’ll just likely use this one for machining practice. I won’t stop until I get a couple of good ones. I will definitely use your suggestions. THANK YOU. Norman

 

[Roger Taylor]

I would use a single, large center sprue with three large gates at 120-deg intervals, so the sprue acts as a riser.

 

[GreenTwin]

Another option, especially if you get into using bound sand, is to turn the mold on edge, and then you could use a single larger riser at the top of one cylinder, with the sprue feeding a runner into the bottom of one of the cylinders.
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[Richard Hed]

I decided to split my wood pattern on the bandsaw; I am glad I did. Obtain perfect alignment of the two halves with steel pins references. The difficult part was getting the inside of the crank case hollow rather than one chunk of metal to be bored out later. ( did not use a sand-water glass Core. However, I was able to get enough draw on each half to get a casting. I never melted aluminum before so at least I figured out how to do that now. Sure enough , unfortunately I have a slight miscast - View attachment 161436is the same as a big miscast if you can’t use it. Not sure why it’s deficient on this flat circumferential surface. Any thoughts and why I have the deficiency at the top surface of the pattern? The bottom surface is fine.

That is such a good casting that I would consider filling in the hole with a bit of tigging.

 

[GreenTwin]

That is the beauty of making your own castings.
If it does not turn out exactly like you want, just ram up another mold and pour again.
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[albd5a]

That is the beauty of making your own castings.
If it does not turn out exactly like you want, just ram up another mold and pour again.
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So far my miscast to usable, casting ratio is not very good! I have a feeling maybe it’s a difficult pattern… I do have one crisp completely usable one so far out of about four attempts; a few of my other attempts where porosities or that same shrinkage problem area as before, but they are all very small defects, Really small. I was hoping that somehow they could be just repaired- add on. I don’t have a TIG or a welder but I’m able to braze with MAPP gas if I knew of a solder rod with flux or without flux that would work. Also, this thing is a pretty big heat sink . Would love to repair a couple of them.

 

[albd5a]

So far my miscast to usable, casting ratio is not very good! I have a feeling maybe it’s a difficult pattern… I do have one crisp completely usable one so far out of about four attempts; a few of my other attempts where porosities or that same shrinkage problem area as before, but they are all very small defects, Really small. I was hoping that somehow they could be just repaired- add on. I don’t have a TIG or a welder but I’m able to braze with MAPP gas if I knew of a solder rod with flux or without flux that would work. Also, this thing is a pretty big heat sink . Would love to repair a couple of them.

These photos are in a rather random order, taken during a couple of different casting attempts just thought that some of them were cool looking.

 

[albd5a]

I would use a single, large center sprue with three large gates at 120-deg intervals, so the sprue acts as a riser.

I have a mold, ready to go made up with a large central riser with some spokes going out to the perimeter. However, I kept the other sprue and Riser idea . will try to cast this tomorrow although it’s supposed to rain in the morning. I’m looking for a pattern, sprue riser gate system with a high success rate . right now it’s rather hit or miss. Although, green twins, advice of really enlarging my gates did work. That is my best casting so far; it’s perfect.

 

[Richard Hed]

I have a mold, ready to go made up with a large central riser with some spokes going out to the perimeter. However, I kept the other sprue and Riser idea . will try to cast this tomorrow although it’s supposed to rain in the morning. I’m looking for a pattern, sprue riser gate system with a high success rate . right now it’s rather hit or miss. Although, green twins, advice of really enlarging my gates did work. That is my best casting so far; it’s perfect.

You're int the USA, your friends or neighbors will have a TIG machine.

 

[GreenTwin]

I had all sorts of problems when I first attempted to cast aluminum.
I did not understand the process, and so it was trial and error, with lots of error.
I had flask halves separate because I did not use weights on top, aluminum too hot, too cold, sand and slag inclusions, porosity.
You name it, I had problems with it.

Once I figured out what was happening, mainly by listening to Bob Puhakka's videos, and following John Campbell's 10 rules for good castings, my success rate went from perhaps 10% to basically 100%.

Using bound sand with a ceramic mold coat is a game changer too, especially with iron castings, but bound sand is not really necessary with aluminum castings. Petrobond makes some great castings with aluminum, and it gives an excellent surface finish if you pour at around 1,350 F.
Petrobond can be used with iron, but is subject to mold failures due to the extreme heat, and I don't recommend it.

Your setup is good; you just need to tweek your method, and then I think you will have a very high success rate.

There is nothing quite as fun as pouring molten metal, in my opinion.
It makes my wife a bit nervous, but she has gotten use to the fire show, and she knows I can do it safely.

Edit:
I use a sheet metal heat shield on my pouring shank, and that allows one hand to be within a few inches of the crucible.
Having one hand close to the center of mass of the crucible/molten metal makes it much easier to handle the crucible, and gives a much better fine control over pouring.

Another trick is to use a piece of steel pipe, perhaps 2.5" or 3" diameter, and 1" tall, and place that at the top of the sprue, so that you don't have overflows that can run over and burn the flask.

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