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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