It is never a good idea to straighten an old die casting, so it broke. I made a video about recasting a new part and if you are a beginner there are traps to avoid when sand casting a new part using a die casting as a pattern. They are very thin and most likely it will not fill up the sand mold. There are many deep pockets of sand so some pockets will break so thickening up the casting will give you a 100% success rate. When I was a beginner I would have tried to cast it without modifying it leading to a very high failure rate and then wondering why casting could be so difficult. I know better now.
Stuffing pockets with sand and casting the part solid to avoid having to mold and cast a web of super thin sections and deep pockets on the back side works great for copying certain broken plastic injection molded parts too. Fixed the armrest on my office chair that way. Jeff
It is a great melting stock to use because unlike car rims which do take a lot of effort to break into bit size chunks for melting. Also they are very strong maybe because they are heat treated. One thing to watch for is the bicycle rims has a seam where it joins and two heavy gauge steel wires are used for re-enforcing the join. Just run a magnet along the rim and you will locate it. It is always a bad idea to not separate steel before melting.
First things first, nice job casting a replacement fence. For part like Ironsides' fence, since the webbed side is flat, another option might have been to glue the broken pieces to a piece of plywood and use it like a match plate.
In hindsight I should have done that because the two broken pieces moved out of alignment when the mold was rammed up. After casting the bicycle rims are soft enough to hammer back into alignment and then used a belt sander to finish the casting.
