I saw another video on youtube in which the creator constructed a similar deep transparent top hat design. He placed the inlet tube directly on the top of the unit, at an angle, but without an elbow. It doesn't enter the chamber at all and although it seems to work, it isn't nearly as smooth as the first video I posted above. So in a deep chamber higher is better for the inlet, but no elbow at all seems to be counter productive.
To me it appears that the elbow helps to create the cyclonic motion and it places the dust at the right location for optimum separation. Without an elbow it appears that the dust enters the chamber unevenly, and it's separation seems to work but not nearly as efficient as other designs. As I have learned in construction and design there are always many different ways to accomplish the same thing, but some are always better than others. I like Phil's original design.
To me it appears that the elbow helps to create the cyclonic motion and it places the dust at the right location for optimum separation. Without an elbow it appears that the dust enters the chamber unevenly, and it's separation seems to work but not nearly as efficient as other designs. As I have learned in construction and design there are always many different ways to accomplish the same thing, but some are always better than others. I like Phil's original design.