done properly it is very strong, labor intensive to do, the pins are fairly expensive. The sell kits, drill bit tap and pins. looking at those cracks not sure it will work they look like it broke into 2 pieces???
Do you have any local foundries?? I restored a tractor one time and was able to convince the owner to cast me some pieces. I think he found it interesting and something different to do. I made the patterns and he ran them thru for $5 each at the time, I needed 40 pieces. I know he thought he would never see me again being he told me to bring him useable patterns. Little did he know I was a tool maker and had made many patterns. I actually made the patterns so he could cast 4 at a time saving him time. That part is fairly simple, you could probably use it as the pattern for the casting. You would have to drill and tap all the holes after casting.
Lock stitching only works on captive cracks, like a water jacket on a engine. It's a plug basically with no actual joining capability. Try stick welding with nickel rod first and if a no go brazing will probably take. Either way probably better to fish plate it afterwards.
The only fixing I've ever done on cast is JB Weld. It is amazing how many things can be fixed with that junk.
I suppose I should have said it before but that frame would be very easy to fabricate completely from steel. Very few of the dimensions are important and it all could come out of flat plate with no bending.
I'll have to inspect the cracks closer to see if they go all the way through and are held together by the plates.
Brazing is almost as strong as the cast. Those little carbide teeth on a saw blade are brazed on as carbide cannot be welded and they take alot of abuse. If you decide to weld it grind a U shaped grove (not a vee) pre heat to 500°F weld it with the high nickle rods, then peen, then cover it with sand so it cools VERY slow or you will hear a really cool snapping sound. Now all of that said are you sure that it is cast iron or is it cast steel? Do a spark test with a grinder to find out. If it is cast steel weld it as you would any piece of A36.
