Is there any guide on how to build your own eldritch machines in some Eberron book? Or should I guide myself with the ones in Rising? Not really; the original 3.5 campaign sourcebook discusses them. But the point of eldritch machines is that they are plot devices; they essentially should do what you need them to do, and there's no specific guidelines or restrictions.

— Keith Baker (@HellcowKeith) March 18, 2021