Your metallurgist friend seems like the kind of expert you'd want and he certainly has the credentials you'd want and I don't, but I'm a little surprised that he would ask if the upright is sand cast.
Here is where I readily admit that my mechanical engineering degree was awarded in 1980 and I only spent a few years as an engineer and none in metallurgy or similar field. I would think the three ways that part was likely be made is from a forging, a sand casting, or a die casting. Unless there is machining or similar operations (and there aren't in this case), die castings have a fine line where the mold pieces join and are very smooth, forgings usually have a rather broad joint mark. Sand castings and forgings generally have a rougher finish, sand castings may or may not have a line from mold joints and if it does, they are generally thin. It's really a bit more complicated than that, but that is generally how I can tell between the manufacturing processes for pieces of that era. Given that, it is obvious to me that the uprights are sand cast and in my experience when I was racing (back in the dark ages), that seemed to be the most common method of making parts like that. I would have thought he would have figured that out for himself.
All I saw was a picture and he saw the part so I'm not trying to say he's wrong, but if it is a cold shut, that would mean that there would be a "crack" between two parts of the upright. Basically, molten aluminum solidified on top of aluminum that had cooled enough so that there was not a continuous flow of aluminum. From your description of it as an "overlap", there is at least superficial evidence of a cold shut. I'm a bit surprised that he's not more curious about what is below that "overlap."
All this is a long way of saying your friend may be of a more theoretical stripe and possibly more concerned with crystal structure, etc. This is not meant to be a criticism of him in the least. PhDs can sometimes be very immersed in the theoretical at the expense of more practical or real life knowledge. On the other hand, he could be right on the money. Like I said, he actually saw the part, he has much more experience with materials, and for all I know, he has substantial real-world practical experience. I'm just a guy who knows a little about a few things (and some of what I actually know may be correct!) and am taking this opportunity to tell you everything I know about a few of them (and I can do that in a few paragraphs!
). I think another opinion or two is called for. It would make for a really bad day if your upright broke while you were in a fast sweeper in a country road in the woods! I know I would feel a lot better if you followed Brian's advice above.
