I've been toying with the idea of building a 55 gallon drum tophat separator. I stumbled upon a stupid-cheap Reliant 3hp 2 bagger at the local Habitat Resale store. I'll use 1 drum for the collection and part of another for the tophat. I got started last weekend so here's what I have so far. Some drums have a rib ringed in thirds so the tophat will be 1/3 the height of the collection drum. I did this because the bottom of the rib fits nicely into the open top of the collection drum. All I need to seal it is some foam weather stripping. I think the weight will keep it in place. If not I can easily add clamps. I also used one inlet port from the bag ring of the collector as my side inlet to the tophat. This will make it easy I think for servicing and connection to a hose or pipe system.