I went ahead and machined my cracked and shrunk sheave. To my surprise almost all the crack machined out. I think it is good enough for me to use.
The new one is on the right and the crack is upper right in the photograph.
One more attempt at a sheave. The first attempt was better than the second, so I just hollowed out the flat side in the cope a little to give it shrink material, not liquid to fill the shrinking cavity. If I get internal cracks this is a bad plan, but I've seen no internal cracks in my other attempts.
Made a shallow gate with a little rise in it to make a choke.
Failure! It only took a little metal. I went ahead and melted some more cans while waiting for it to cool.
When I cracked it open I was able to figure out what was wrong. Dummy left the pattern in.
I'm pretty sure I'm not the first to do that, but I also be tit will help me remember to remove it. It was late and I went ahead and salvaged the drag.
Casting turned out OK. A few shrinkage cracks around the hub but I think that's because I have too tight of a radius on the pattern.
I had put a vent in the middle of the flat side and the metal ran right up the vent. I guess that means it was plenty hot and fluid for being can-o-lite.
Please post your comments and observations. I'm here to learn.