This is what we often call a “BOM” in database land. (Bill of materials). So you might have an “electric motor assembly” and then that goes to a fan assembly and then hat goes into an air condition unit. The ability to “add together” an un-limited amounts of assemblies is thus an often solved and requested problem in database land.
An Access example of such a design can be found here:
The http://access.mvps.org/access/modules/mdl0027.htm
The above is in Access 97, so you have to “import” the example into recent versions of Access before use. You can also do a BinGoogle for “BOM” database examples.