I call R2D2 because it reminds me the one from "star war".
The problem with those vac's is that from the so called "5 Gallon", half of the space is used by the motor/filter unit.
Because of space problem in my garage, I was looking to make something compact that will include the vac and the container in one portable unit.
One day, I went with my wife to the "Wednesday market" (in Poland we still have this "market day"), I saw a 25 Gallon bucket that they make the pickled cabbage in (very popular here) and said "oh, that's what I need", and the rest is on the pictures.
The filter idea came from my wife's gardening hobby. It's kind of "plastic cloth", very strong (I cannot tear it with my hands) washable and dries very quickly.
Because the unit is portable, I just drag it near the tool (normally TS) and I use very short hose (2" dia - 3 feet) that reduces the "duct losses" and by that, increases the efficiency.