Weights can be a bit variable and I’ve yet to find one anywhere near as nice as GR17 iron bar. Probably OK if you go with fairly chunky spokes, don’t mind plugging the oversize hole in the middle and don’t want to polish up the rim too much.

Have you considered a couple of discs of CI round bar which is what I mostly carve flywheels out of. M-machine would cut a couple of say 0.9″ thick slices.

If you go aluminium spokes and thick wall steel tube rim then make the rim a bit thicker than shown so you regain the weight lost from the spokes

I’ve not had weights that are chilled, it is just the quality of the iron is a lot less being coarse and more granular. They are not the nicest stuff to machine unlike GR17 bar which is a joy to machine and a lot easier to cut than even a free cutting steel.

This is why I said go for a thicker spoke as the weights are not as robust as good iron, here is a bit I broke earlier you can see the very coarse grain and all the little voids on the machined surfaces.

The object of a flywheel is that it will have a latge momentof inertia to carry the engine round on non power strokes

The limit of how heavy it can be is set  the main bearings (I’ve seen a crankshaft broken by fitt ing a flywheel so heavy that it exceeded the maximum overhung load, and failed the crankshaft on fatigue.

To maximise moment of inertia it would be advisable to concentrate as much weight in the rim, being aware of the strength of the spokes, and the centrifugal forces to which they are subjected when the engine runs at above its nornal speed. (A flywheel, even small, failed by overspeed is dangerous!)

So a very dense, but strong, material is indicated. (lead is too weak, and Tungsten tends to be hard to come by), so cast iron tends to be a cost competetive compromise.

Howard