Jordy,
can you tell me a little bit about the welding you had to do between the two metals? I'm not keen to do it myself, just like to learn about welding (I'm an amateur). What did you use, a tig? I have a mig, and have welded plate aluminium together before.. used alushield.. not sure of the wire, it came with the welder - the guy who owned it before me made a boat out of al plate he got cut by laser from a cdrom pattern he bought.
Just after a quick rundown on the different requirements of cast and billet al with a mig... but if you're a tig guy maybe it's totally different?
I'd be prepared to trust your welds. Yeah, there's a bit of stress from the blower being mounted and being pulled by the belt.. but those are some bigass chunky welds, I don't see them going anywhere from the size of the metal and the small stresses we would put on it.
Are you going to weld more, or were you thinking about casting the whole thing? Or cast the bottom and weld a plate on each?