Casting tiny(for me) parts

I am making patterns for some steam engine parts I want to cast in aluminum. These patterns have been drawn up in Fusion 360 from plans in old books, magazines, and in one case, from copies of the original blue prints from a 1940’s toy manufacturer. I have split the patterns in what I think is the appropriate parting line , and in one example, added core prints.

Though I have been casting aluminum for several years, albeit not every day, I have never attempted anything this small.

I have both greensand, and some petrobond. I plan to use the petrobond, as it is much finer and should yield good detail. My problem is where do I gate, where to put sprue and risers, and how big should each be? I would like to combine the arts in one mold if possible.

Have a look at the patterns and make any recommendations as necessary.

 

myfordboy uses a single sprue and gates directly from the sprue into the rim of his flywheels, with maybe a riser on the opposite side (check me on the riser), and this works well for him.
I have used his technique, and it does work, however, if you want to go by the book, then use one or more runners with dead ends so that any lose sand gets trapped in the dead ends and does not get carried into the mold cavity.

I will try to dig out one of my flywheel runner/gating examples, not that my method is necessarily correct or better than anyone else's, but it works pretty well for me.
My last flywheel casting had a heavy rim, and the rim ended up with shrinkage (with aluminum), so for a heavy rim, some risers to control shrinkage would be required.

The photos below were a prototype, and thus the use of the temporary painter's tape.
I don't make permanent flask setups until I have proven the sprue/basin/runners/gates will work. I have also transitioned to all 0ne-piece patterns.



I have also tried casting multiple parts in a single mold, and I have seen others do this (maury in TX I think is one guy who does the multi-parts in a single mold, but generally the parts are relatively small).
I had a partial mold fill due to the length of the runner in my multi-part mold, but I think my iron was also not hot enough.

Another method I have seen for multi-parts in a single mold is to arrange the parts/gates in a radial fashion around a large (perhaps 2.5" diameter) central sprue, with very short gates.

For cylinders, I use a gate at each flange (one gate on either end of the cylinder), and that seems to work well.

 

I would probably lay it out like this with the sprue located over the basin.
With the right aluminum pour temperature (I have been using 1350F; may need a little hotter for such small parts), I think this will fill.
1350 F or less will give you the best surface finish.

I vent the high points in the cope mold to allow air to escape, using a fine wire pushed from the inside out through the top of the mold.

Edit:
I generally always gate into a surface that must be machined, thus you can eliminate the gate entry from the part.

 

I would use a good sized riser at the hub of the flywheel, perhaps 1" diameter (or maybe less if that is a small flywheel), to allow for shrinkage there.

Generally I can get a flywheel (or most other parts) to fill with dual gates.